copypaste mess from the Luminous Green Notes
The objective is to compare the performance of home made natural dye based organic photovoltaic devices with commercial inorganic silicon based photovoltaic devices in sunlight and colored artificial light.
Chlorophyll and anthocyanin organic dyes extracted from citrus leaves, raspberries and blackberries were absorbed onto nano-crystalline titanium dioxide coated on conducting glass slides. Photovoltaic devices were made with an iodide/triodode electrolyte separating a graphite coated conducting glass slide from the dye coated slides. The voltage and current characteristics were measured in sunlight and colored artificial lights and compared to those observed for commercial silicon based photovoltaic devices.
Conclusions Organic dye based photovoltaic cells can be made at home using chlorophyll and anthocyanin dyes. These cells capture energy from sunlight and indoor light of sufficient intensity. Commercial silicon cells are considerably more efficient than the home-made photovoltaic devices. Natural organic dyes can be used to make home made cells for the capture of solar energy. Dr. Greg Smestad, creator of the dye-sensitized solar cell kit, provided tips by e-mail. Mr. M. P. Reidy gave conductive glass plates. Applied Films sent heat shield glass and Drs. Kaustav and Sonali Das gave Triton X 100. Mother took notes during outdoor measurements. Father helped wire the circuit board and
Apart from water nearly all solvents in which dyes are dissolved are flammable, highly toxic (irritants, narcotics and/or anestetics, carcinogen [dioxane]) and some solutions are dangerous by skin contact by expediting the movement of dye through the skin [DMSO]. Solvents Methanol Ethanol Ethylene Glycol DMSO (!) Dioxane (!) Benzyl alcohol (!) Cyclohexane Hexane Toluene Dichloromethane Dichoroethane Create this topic(?)
Ethylene glycol From Wikipedia, the free encyclopedia Properties HYPERLINK “http://en.wikipedia.org/wiki/Image:Ethylene_glycol_chemical_structure.png” \o “Chemical structure of ethylene glycol” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/commons/thumb/2/28/Ethylene_glycol_chemical_structure.png/180px-Ethylene_glycol_chemical_structure.png” \* MERGEFORMATINET HYPERLINK “http://en.wikipedia.org/wiki/Image:Ethylene-glycol-3D-vdW.png” \o “Ethylene glycol” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/commons/thumb/1/16/Ethylene-glycol-3D-vdW.png/180px-Ethylene-glycol-3D-vdW.png” \* MERGEFORMATINET General Name Ethane-1,2-diol HYPERLINK “http://en.wikipedia.org/wiki/Chemical_formula” \o “Chemical formula” Chemical formula HYPERLINK “http://en.wikipedia.org/wiki/Hydroxyl” \o “Hydroxyl” HO HYPERLINK “http://en.wikipedia.org/wiki/Carbon” \o “Carbon” C HYPERLINK “http://en.wikipedia.org/wiki/Hydrogen” \o “Hydrogen” H2 HYPERLINK “http://en.wikipedia.org/wiki/Carbon” \o “Carbon” C HYPERLINK “http://en.wikipedia.org/wiki/Hydrogen” \o “Hydrogen” H2 HYPERLINK “http://en.wikipedia.org/wiki/Hydroxyl” \o “Hydroxyl” OH HYPERLINK “http://en.wikipedia.org/wiki/Atomic_weight” \o “Atomic weight” Formula weight 62.068 HYPERLINK “http://en.wikipedia.org/wiki/Unified_atomic_mass_unit” \o “Unified atomic mass unit” u Synonyms Ethylene glycol Monoethylene glycol MEG 1,2-ethanediol HYPERLINK “http://en.wikipedia.org/wiki/Simplified_molecular_input_line_entry_specification” \o “Simplified molecular input line entry specification” SMILES OCCO HYPERLINK “http://en.wikipedia.org/wiki/CAS_number” \o “CAS number” CAS number 107-21-1 Phase behavior HYPERLINK “http://en.wikipedia.org/wiki/Melting_point” \o “Melting point” Melting point 260.2 HYPERLINK “http://en.wikipedia.org/wiki/Kelvin” \o “Kelvin” K (−12.9 HYPERLINK “http://en.wikipedia.org/wiki/Celsius” \o “Celsius” °C) HYPERLINK “http://en.wikipedia.org/wiki/Boiling_point” \o “Boiling point” Boiling point 470.4 K (197.3 °C) Thermal decomposition ? K (? °C) HYPERLINK “http://en.wikipedia.org/wiki/Triple_point” \o “Triple point” Triple point 256 K (−17 °C) ? kPa HYPERLINK “http://en.wikipedia.org/wiki/Critical_point” \o “Critical point” Critical point 720 K (447°C) 8.2 MPa HYPERLINK “http://en.wikipedia.org/wiki/Heat_of_fusion” \o “Heat of fusion” ΔfusH 9.9 kJ/mol HYPERLINK “http://en.wikipedia.org/wiki/Entropy_of_fusion” \o “Entropy of fusion” ΔfusS 38.2 J/(mol·K) HYPERLINK “http://en.wikipedia.org/wiki/Heat_of_vaporization” \o “Heat of vaporization” ΔvapH 65.6 kJ/mol HYPERLINK “http://en.wikipedia.org/wiki/Solubility” \o “Solubility” Solubility Miscible with water Liquid properties HYPERLINK “http://en.wikipedia.org/wiki/Standard_enthalpy_change_of_formation” \o “Standard enthalpy change of formation” ΔfH0liquid −460 HYPERLINK “http://en.wikipedia.org/wiki/Joule” \o “Joule” kJ/ HYPERLINK “http://en.wikipedia.org/wiki/Mole_%28unit%29” \o “Mole (unit)” mol HYPERLINK “http://en.wikipedia.org/wiki/Standard_molar_entropy” \o “Standard molar entropy” S0liquid 166.9 J/(mol·K) HYPERLINK “http://en.wikipedia.org/wiki/Heat_capacity” \o “Heat capacity” Cp 149.5 J/(mol·K) HYPERLINK “http://en.wikipedia.org/wiki/Density” \o “Density” Density 1.1132 g/cm³ HYPERLINK “http://en.wikipedia.org/wiki/Viscosity” \o “Viscosity” Viscosity 21 HYPERLINK “http://en.wikipedia.org/wiki/Poise” \o “Poise” cP at 20 °C Gas properties HYPERLINK “http://en.wikipedia.org/wiki/Standard_enthalpy_change_of_formation” \o “Standard enthalpy change of formation” ΔfH0gas −394.4 HYPERLINK “http://en.wikipedia.org/wiki/Joule” \o “Joule” kJ/ HYPERLINK “http://en.wikipedia.org/wiki/Mole_%28unit%29” \o “Mole (unit)” mol HYPERLINK “http://en.wikipedia.org/wiki/Standard_molar_entropy” \o “Standard molar entropy” S0gas 311.8 J/(mol·K) HYPERLINK “http://en.wikipedia.org/wiki/Heat_capacity” \o “Heat capacity” Cp 78 J/(mol·K) Safety Acute effects Nausea, vomiting. CNS paralysis. Kidney damage. Chronic effects Kidney damage HYPERLINK “http://en.wikipedia.org/wiki/Flash_point” \o “Flash point” Flash point 111 °C HYPERLINK “http://en.wikipedia.org/wiki/Autoignition_temperature” \o “Autoignition temperature” Autoignition temperature 410 °C HYPERLINK “http://en.wikipedia.org/wiki/Explosive_limit” \o “Explosive limit” Explosive limits 1.8–12.8% More info Properties HYPERLINK “http://webbook.nist.gov/cgi/cbook.cgi?ID=107-21-1&Units=SI” \o “http://webbook.nist.gov/cgi/cbook.cgi?ID=107-21-1&Units=SI” NIST
HYPERLINK “http://en.wikipedia.org/wiki/MSDS” \o “MSDS” MSDS HYPERLINK “http://ull.chemistry.uakron.edu/erd/chemicals/8/7680.html” \o “http://ull.chemistry.uakron.edu/erd/chemicals/8/7680.html” Hazardous Chemical Database HYPERLINK “http://en.wikipedia.org/wiki/SI” \o “SI” SI units were used where possible. Unless otherwise stated, HYPERLINK “http://en.wikipedia.org/wiki/Standard_temperature_and_pressure” \o “Standard temperature and pressure” standard conditions were used. HYPERLINK “http://en.wikipedia.org/wiki/Organic_table_information” \o “Organic table information” Disclaimer and references Ethylene glycol (monoethylene glycol (MEG), HYPERLINK “http://en.wikipedia.org/wiki/IUPAC_nomenclature” \o “IUPAC nomenclature” IUPAC name: ethane-1,2-diol) is an HYPERLINK “http://en.wikipedia.org/wiki/Alcohol” \o “Alcohol” alcohol with two -OH groups (a HYPERLINK “http://en.wikipedia.org/wiki/Diol” \o “Diol” diol), a HYPERLINK “http://en.wikipedia.org/wiki/Chemical_compound” \o “Chemical compound” chemical compound widely used as an HYPERLINK “http://en.wikipedia.org/wiki/Automobile” \o “Automobile” automotive HYPERLINK “http://en.wikipedia.org/wiki/Antifreeze_%28coolant%29” \o “Antifreeze (coolant)” antifreeze. In its pure form, it is an odorless, colorless, syrupy liquid with a sweet taste. Ethylene glycol is toxic, and its accidental ingestion should be considered a medical emergency. Create this topic(?)
History Ethylene glycol was first prepared in HYPERLINK “http://en.wikipedia.org/wiki/1859” \o “1859” 1859 by the HYPERLINK “http://en.wikipedia.org/wiki/France” \o “France” French chemist HYPERLINK “http://en.wikipedia.org/wiki/Charles-Adolphe_Wurtz” \o “Charles-Adolphe Wurtz” Charles-Adolphe Wurtz. It was produced on a small scale during HYPERLINK “http://en.wikipedia.org/wiki/World_War_I” \o “World War I” World War I as a coolant and as an ingredient in HYPERLINK “http://en.wikipedia.org/wiki/Explosive” \o “Explosive” explosives. Widespread industrial production began in HYPERLINK “http://en.wikipedia.org/wiki/1937” \o “1937” 1937 when HYPERLINK “http://en.wikipedia.org/wiki/Ethylene_oxide” \o “Ethylene oxide” ethylene oxide, a component in its synthesis, became cheaply available. When first introduced it created a minor revolution in aircraft design because when used in place of water as an HYPERLINK “http://en.wikipedia.org/wiki/Engine” \o “Engine” engine coolant, its higher HYPERLINK “http://en.wikipedia.org/wiki/Boiling_point” \o “Boiling point” boiling point allowed for smaller radiators operating at higher temperatures. Prior to the widespread availability of ethylene glycol, many aircraft manufacturers tried to use HYPERLINK “http://en.wikipedia.org/wiki/Evaporative_cooling” \o “Evaporative cooling” evaporative cooling systems which used water at high pressure. Invariably, these proved to be rather unreliable and were easily damaged in combat because they took up large amounts of room on the plane, where they were easily hit by gunfire. Production Ethylene glycol is produced from HYPERLINK “http://en.wikipedia.org/wiki/Ethylene” \o “Ethylene” ethylene, via the intermediate HYPERLINK “http://en.wikipedia.org/wiki/Ethylene_oxide” \o “Ethylene oxide” ethylene oxide. Ethylene oxide reacts with HYPERLINK “http://en.wikipedia.org/wiki/Water” \o “Water” water to produce ethylene glycol according to the HYPERLINK “http://en.wikipedia.org/wiki/Chemical_equation” \o “Chemical equation” chemical equation HYPERLINK “http://en.wikipedia.org/wiki/Ethylene_oxide” \o “Ethylene oxide” C2H4O + HYPERLINK “http://en.wikipedia.org/wiki/Water” \o “Water” H2O → HOCH2CH2OH This HYPERLINK “http://en.wikipedia.org/wiki/Chemical_reaction” \o “Chemical reaction” reaction can be HYPERLINK “http://en.wikipedia.org/wiki/Catalyst” \o “Catalyst” catalyzed by either HYPERLINK “http://en.wikipedia.org/wiki/Acid” \o “Acid” acids or HYPERLINK “http://en.wikipedia.org/wiki/Base_%28chemistry%29” \o “Base (chemistry)” bases, or can occur at neutral HYPERLINK “http://en.wikipedia.org/wiki/PH” \o “PH” pH under elevated temperatures. The highest yields of ethylene glycol occur at acidic or neutral pH with a large excess of water. Under these conditions, ethylene glycol yields of 90% can be achieved. The major byproducts are the ethylene glycol HYPERLINK “http://en.wikipedia.org/wiki/Oligomer” \o “Oligomer” oligomers HYPERLINK “http://en.wikipedia.org/wiki/Diethylene_glycol” \o “Diethylene glycol” diethylene glycol, HYPERLINK “http://en.wikipedia.org/wiki/Triethylene_glycol” \o “Triethylene glycol” triethylene glycol, and HYPERLINK “http://en.wikipedia.org/wiki/Tetraethylene_glycol” \o “Tetraethylene glycol” tetraethylene glycol. This molecule has been observed in space by Hollis et al. (The
Journal, 571:L59-L62, 2002 May 20).
Uses The major use of ethylene glycol is as a coolant or antifreeze in, for example, automobiles and personal computers. Due to its low freezing point, it is also used as a HYPERLINK “http://en.wikipedia.org/wiki/Deicing” \o “Deicing” deicing fluid for HYPERLINK “http://en.wikipedia.org/wiki/Windshield” \o “Windshield” windshields and aircraft. Ethylene glycol has become increasingly important in the HYPERLINK “http://en.wikipedia.org/wiki/Plastic” \o “Plastic” plastics industry for the manufacture of HYPERLINK “http://en.wikipedia.org/wiki/Polyester” \o “Polyester” polyester fibers and HYPERLINK “http://en.wikipedia.org/wiki/Resin” \o “Resin” resins, including HYPERLINK “http://en.wikipedia.org/wiki/Polyethylene_terephthalate” \o “Polyethylene terephthalate” polyethylene terephthalate, which is used to make plastic bottles for HYPERLINK “http://en.wikipedia.org/wiki/Soft_drink” \o “Soft drink” soft drinks. The HYPERLINK “http://en.wikipedia.org/wiki/Antifreeze_%28coolant%29” \o “Antifreeze (coolant)” antifreeze capabilities of ethylene glycol have made it an important component of HYPERLINK “http://en.wikipedia.org/wiki/Vitrification” \o “Vitrification” vitrification mixtures for low-temperature preservation of biological tissues and organs. Minor uses of ethylene glycol include the manufacture of HYPERLINK “http://en.wikipedia.org/wiki/Capacitor” \o “Capacitor” capacitors, as a chemical intermediate in the manufacture of HYPERLINK “http://en.wikipedia.org/wiki/1%2C4-dioxane” \o “1,4-dioxane” 1,4-dioxane and as an additive to prevent the growth of HYPERLINK “http://en.wikipedia.org/wiki/Algae” \o “Algae” algae in liquid cooling systems for HYPERLINK “http://en.wikipedia.org/wiki/Personal_computer” \o “Personal computer” personal computers. Ethylene glycol's high boiling point and affinity for water makes it an ideal HYPERLINK “http://en.wikipedia.org/w/index.php?title=Dehydrator&action=edit” \o “Dehydrator” dehydrator for HYPERLINK “http://en.wikipedia.org/wiki/Natural_gas” \o “Natural gas” natural gas production. In the field, excess water vapor is usually removed by glycol dehydration. Glycol flows down from the top of a tower and meets a rising mixture of water vapor and HYPERLINK “http://en.wikipedia.org/wiki/Hydrocarbon” \o “Hydrocarbon” hydrocarbon gases from the bottom. The glycol chemically removes the water vapor, allowing dry gas to exit from the top of the tower. The glycol and water are separated, and the glycol cycles back through the tower. Ethylene glycol is also used in the manufacture of some HYPERLINK “http://en.wikipedia.org/wiki/Vaccine” \o “Vaccine” vaccines, but it is not itself present in these injections. It is used as a minor (1–2%) ingredient in HYPERLINK “http://en.wikipedia.org/wiki/Shoe_polish” \o “Shoe polish” shoe polish and also in some inks and dyes. Ethylene glycol is commonly used in laboratories to precipitate out proteins in solution. This is often an intermediary step in fractionation, purification and/or crystallization. Ethylene glycol has seen some use as a rot and fungal treatment for wood, both as a preventative and a treatment after the fact. It has been used in a few cases to treat partially rotted wooden objects to be displayed in museums. It is one of only a few treatments that are successful in dealing with rot in wooden boats, and is relatively cheap. [ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Ethylene_glycol&action=edit&section=4” \o “Edit section: Toxicity” edit] Toxicity The major danger from ethylene glycol is following ingestion. Due to its sweet taste, children and animals will sometimes consume large quantities of it if given access to antifreeze. Ethylene glycol may also be found as a contaminant in unlawfully HYPERLINK “http://en.wikipedia.org/wiki/Distillation” \o “Distillation” distilled whiskey ( HYPERLINK “http://en.wikipedia.org/wiki/Moonshine” \o “Moonshine” moonshine) made in a HYPERLINK “http://en.wikipedia.org/wiki/Still” \o “Still” still constructed using an improperly washed car HYPERLINK “http://en.wikipedia.org/wiki/Radiator” \o “Radiator” radiator. In developed countries, a bittering agent called HYPERLINK “http://en.wikipedia.org/wiki/Denatonium” \o “Denatonium” denatonium/denatonium benzoate, is generally added to ethylene glycol preparations as an adversant (to prevent accidental ingestion). Ethylene glycol poisoning is a medical emergency and in all cases a HYPERLINK “http://en.wikipedia.org/wiki/Poison_control_center” \o “Poison control center” poison control center should be contacted or medical attention should be sought. It is highly toxic with an estimated lethal dose of 100% ethylene glycol in humans of approximately 1.4 ml/kg. HYPERLINK “http://en.wikipedia.org/wiki/Ethylene_glycol” \l “_note-Drugs2001-Brent” \o “”  However, as little as 30 milliliters (2 HYPERLINK “http://en.wikipedia.org/wiki/Tablespoon” \o “Tablespoon” tablespoons) can be lethal to adults. HYPERLINK “http://en.wikipedia.org/wiki/Ethylene_glycol” \l “_note-0” \o “”  Symptoms Symptoms of ethylene glycol poisoning usually follow a three-step progression, although poisoned individuals will not always develop each stage or follow a specific time frame. HYPERLINK “http://en.wikipedia.org/wiki/Ethylene_glycol” \l “_note-Drugs2001-Brent” \o “”  Stage 1 consists of HYPERLINK “http://en.wikipedia.org/wiki/Neurological” \o “Neurological” neurological symptoms including victims appearing to be HYPERLINK “http://en.wikipedia.org/wiki/Intoxication” \o “Intoxication” intoxicated, exhibiting symptoms such as dizziness, headaches, slurred speech, and confusion. Over time, the body HYPERLINK “http://en.wikipedia.org/wiki/Metabolism” \o “Metabolism” metabolizes ethylene glycol into other toxins, it is first metabolized to glycoaldehyde, which is then oxidized to HYPERLINK “http://en.wikipedia.org/wiki/Glycolic_acid” \o “Glycolic acid” glycolic acid, HYPERLINK “http://en.wikipedia.org/wiki/Glyoxylic_acid” \o “Glyoxylic acid” glyoxylic acid, and finally HYPERLINK “http://en.wikipedia.org/wiki/Oxalic_acid” \o “Oxalic acid” oxalic acid. Stage 2 is a result of accumulation of these metabolites and consists of HYPERLINK “http://en.wikipedia.org/wiki/Tachycardia” \o “Tachycardia” tachycardia, HYPERLINK “http://en.wikipedia.org/wiki/Hypertension” \o “Hypertension” hypertension, HYPERLINK “http://en.wikipedia.org/wiki/Hyperventilation” \o “Hyperventilation” hyperventilation, and HYPERLINK “http://en.wikipedia.org/wiki/Metabolic_acidosis” \o “Metabolic acidosis” metabolic acidosis. Stage 3 of ethylene glycol poisoning is the result of kidney injury, leading to acute HYPERLINK “http://en.wikipedia.org/wiki/Kidney_failure” \o “Kidney failure” kidney failure. HYPERLINK “http://en.wikipedia.org/wiki/Ethylene_glycol” \l “_note-ClinToxicol1999-Barceloux” \o “”  Oxalic acid reacts with calcium and forms HYPERLINK “http://en.wikipedia.org/wiki/Calcium_oxalate” \o “Calcium oxalate” calcium oxalate crystals in the kidney. Treatment Initial treatment consists of stabilizing the patient and gastric decontamination. As ethylene glycol is rapidly absorbed, gastric decontamination needs to be performed soon after ingestion to be of benefit. HYPERLINK “http://en.wikipedia.org/wiki/Gastric_lavage” \o “Gastric lavage” Gastric lavage or HYPERLINK “http://en.wikipedia.org/wiki/Nasogastric_aspiration” \o “Nasogastric aspiration” nasogastric aspiration of gastric contents are the most common methods employed in ethylene glycol poisoning. HYPERLINK “http://en.wikipedia.org/wiki/Syrup_of_ipecac” \o “Syrup of ipecac” Ipecac induced HYPERLINK “http://en.wikipedia.org/wiki/Emesis” \o “Emesis” emesis or HYPERLINK “http://en.wikipedia.org/wiki/Activated_charcoal” \o “Activated charcoal” activated charcoal (charcoal does not HYPERLINK “http://en.wikipedia.org/wiki/Adsorb” \o “Adsorb” adsorb glycols) are not recommended. HYPERLINK “http://en.wikipedia.org/wiki/Ethylene_glycol” \l “_note-Drugs2001-Brent” \o “”  The HYPERLINK “http://en.wikipedia.org/wiki/Antidote” \o “Antidote” antidotes for ethylene glycol poisoning are HYPERLINK “http://en.wikipedia.org/wiki/Ethanol” \o “Ethanol” ethanol or HYPERLINK “http://en.wikipedia.org/wiki/Fomepizole” \o “Fomepizole” fomepizole; antidotal treatment forms the mainstay of management following ingestion. Ethanol (usually given HYPERLINK “http://en.wikipedia.org/wiki/Intravenous_therapy” \o “Intravenous therapy” IV as a 5 or 10% solution in 5% HYPERLINK “http://en.wikipedia.org/wiki/Dextrose” \o “Dextrose” dextrose and HYPERLINK “http://en.wikipedia.org/wiki/Water” \o “Water” water, but, also sometimes given in the form of a strong spirit such as HYPERLINK “http://en.wikipedia.org/wiki/Whisky” \o “Whisky” whisky, HYPERLINK “http://en.wikipedia.org/wiki/Vodka” \o “Vodka” vodka or HYPERLINK “http://en.wikipedia.org/wiki/Gin” \o “Gin” gin) acts by competing with ethylene glycol for the HYPERLINK “http://en.wikipedia.org/wiki/Enzyme” \o “Enzyme” enzyme HYPERLINK “http://en.wikipedia.org/wiki/Alcohol_dehydrogenase” \o “Alcohol dehydrogenase” alcohol dehydrogenase thus limiting the formation of toxic metabolites. Fomepizole acts by inhibiting HYPERLINK “http://en.wikipedia.org/wiki/Alcohol_dehydrogenase” \o “Alcohol dehydrogenase” alcohol dehydrogenase, thus blocking the formation of the toxic metabolites. HYPERLINK “http://en.wikipedia.org/wiki/Ethylene_glycol” \l “_note-1” \o “”  In addition to antidotes, HYPERLINK “http://en.wikipedia.org/wiki/Hemodialysis” \o “Hemodialysis” hemodialysis can also be used to enhance the removal of unmetabolized ethylene glycol, as well as its metabolites from the body. Hemodialysis also has the added benefit of correcting other metabolic derangements or supporting deteriorating kidney function caused by ethylene glycol ingestion. Often both antidotal treatment and hemodialysis are used together in the treatment of poisoning. Industrial hazards Ethylene glycol can begin to breakdown at 230° – 250°F. Note that breakdown can occur when the system bulk (average) temperature is below these limits because surface temperatures in heat exchangers and boilers can be locally well above these temperatures. The HYPERLINK “http://en.wikipedia.org/wiki/Electrolysis” \o “Electrolysis” electrolysis of ethylene glycol solutions with a HYPERLINK “http://en.wikipedia.org/wiki/Silver” \o “Silver” silver HYPERLINK “http://en.wikipedia.org/wiki/Anode” \o “Anode” anode results in an HYPERLINK “http://en.wikipedia.org/wiki/Exothermic_reaction” \o “Exothermic reaction” exothermic reaction. The HYPERLINK “http://en.wikipedia.org/wiki/Apollo_1” \lAs oil prices hit a new all-time high and fossil fuels continue to increase global warming, the quest to find a suitable renewable energy source is becoming increasingly urgent. Yet wind power is unreliable, hydroelectric systems spoil natural landscapes and nuclear power has associated heath risks. In central Australia greater than 24MJ/m2 day of solar energy is received (fig 1) and attention is now being directed at how we can use it . The basis for all photovoltaic devices is the separation of charge at an interface of two materials that have different conduction methods (Grätzel M., 2000). In conventional cells, this is between n- and p- type semiconductor: although reasonable efficiencies of over 30% have been achieved in the laboratory (Cotal et al., 2000), typically the conversion rate is around 15-20% (Bignozzi, et al., 2000, Zweibel, 1993, 1990). However the widespread use of silicon and compound semiconductor solar cells is impracticable due to their expensive and complex manufacturing process. Toxic chemicals are used during manufacture, and they show a decrease of approximately 20% in the conversion of incident photons to electrons over 20-60°C temperature range (Nazeeruddin et al., 1993). The dye-sensitised solar cell (DYSC) was developed by Gratzel and coworkers (O’Regan & Gratzel, 1991) and uses the principle of photosynthesis to generate power; the boundary in a DYSC is between a wide band gap semiconductor and electrolyte solution. In solid-state devices light absorption and charge movement both occur on the semiconductor, whereas the two functions are performed by different materials in the DYSC (Späth et al., 2003); this has opened up a new mechanism for capturing solar energy.
In a conventional solar cell, electron-hole pairs must travel a considerable distance without recombining to contribute to the current in the external circuit. As a result, expensive high-purity materials must be used to avoid premature recombination (Hart, J. 2003). Conversely, a DYSC alters the wide band gap semiconductors by chemically attaching a redox dye. This dye absorbs light, and positive and negative charge separation occurs across the dye/semiconductor interface; confined within these materials, the charge carriers are transported. Hence cheaper, lower purity materials can be used and the conflicting requirements for the semiconductor band gap are avoided: an optimum band gap must be obtained – a narrow band gap often indicates relatively weak chemical bonding resulting in a solar cell with only a short lifetime that easily photocorrodes, whereas a large band can only absorb high-energy ultra-violet (UV) photons (Grätzel M., 2000). With these limitations in mind, research has turned to the nature for inspiration: the DYSC mimics photosynthesis. DYSCs have achieved greater than 9% sunlight to electrical power conversion efficiencies and greater than 16 mA/cm2 photocurrents (Smestad et al., 1994, Nazeeruddin et al., 1993), which is a remarkable achievement compared to 1% for tropical rainforest flora (Smil, 1992) and 13% for the calculated upper limit of natural photosynthesis (Bolton, 1991). Over the past ten years conversion efficiencies have risen to 11.5% (Green, 2002), and efficiencies can be expected to increase with continued research. The DYSC is a serious competitor to solid-state devices and is a commercially realistic option for using solar energy.
Using a photosynthetic mechanism, a plant converts the Sun’s radiant energy into the chemical into carbohydrates (Knox et al., 2005), by directing an electron through a transport system and extracting useful energy as the electron falls from an excited state back to ground. Despite its complexity, photosynthesis can be summarised by the following equation: 6H2O + 6CO2 + light → C6H12O6 (glucose) + 6O2 (BIOL1101 Lab Notes, 2005). A photosynthetic pigment absorbs a specific wavelength of light and uses this energy to excite an electron. In turn these electrons synthesise dihydro-nicotinamide-adenine-dinucleotide phosphate (NADPH), a molecule that eventually produces a carbohydrate (fig 2). To regenerate the pigment to its original state, an electron is donated in the oxidation of water to produce oxygen (Bering, 1985).
Essentially a DYSC is photoelectrochemical cell containing an electrolyte and two electrodes that produce electrical current by redox reactions that are driven by light. The operating principles of the DYSC in some respects parallel those of photosynthesis: both form a regenerative cycle that converts light into useful energy forms, and use a multilayer structure (similar to the thylakoid membrane) to enhance both the light absorption and electron collection efficiency. In the DYSC, the organic dye replaces light absorbing pigments; the wide band gap semi-conductor replaces oxidised NADPH and carbon dioxide as the electron acceptor; and the electrolyte replaces the water and oxygen as the electron donor and oxidation product, respectively (Smestad & Gratzel, 1998). However, the key difference between the DYSC and plants is that plants store the energy in the form of starch for later use, whereas the DYSC cannot store energy. Currently research is being directed at inventing a device that incorporates both photoelectric and storage functions in a single cell structure or photocapacitor (Miyasaka & Murakami, 2004).
HOW THE DYSC WORKS: blueberry electricity
A redox dye is chemically attached to the surface of the DYSC (fig 3), and the absorption of incident light is determined by the number of dye molecules attached per unit volume of the semiconductor. If the dye is attached to a flat surface less than 1% of incident light is absorbed, and the conversion efficiency of light into useful energy is low (Sommeling et al.,, 2000). Light absorption is maximised by the use of sintered nanometre-sized anatase titanium dioxide; the surface area is increased by two or three orders of magnitude above the projected area of the film (Heij, 2002). This structure has pores in the range 20-500Å in diameter, and provides a huge surface area where absorption processes and electronic conduction can occur (fig 4). It is advantageous to use titanium dioxide because it is abundant, cheap, biocompatible and non-toxic (Gratzel & Hagfeldt, 2000). The anatase phase of titanium dioxide is used because it has a suitably wide band gap that it is transparent to visible light – this ensures that light is only absorbed by the dye – and can provide a useful cell voltage (Hagfeldt & Grätzel, 1995). The ideal titanium dioxide film thickness is between 5 µm and 20 µm (Grätzel, 2000): this is a compromise between maximizing surface area, and minimizing recombination losses. A larger film thickness means that the electrons must travel a greater distance before transferring to the conductive layer of the titanium dioxide. On the other hand, the film must be thick enough to give a sufficient surface area for good light absorption. A photo-induced electron from the dye is injected into the semiconductor conduction band; this induces a charge separation. The electrons travel in this conduction band, via an external circuit (where they can do work) to the electrolyte solution or ‘charge collector’ (fig 5). To restore the original state of the dye, and prevent the electron recapture by the oxidized dye, an electron is donated by the electrolyte solution: 3I-+◊I3-+e-. Often this solution consists of an organic solvent containing a redox system, such as the iodide/triiodide couple. In turn, the iodide is restored by the reduction of triiodide at the counterelectrode (made from conductive glass coated with a catalyst-usually platinum), by an electron that has completed a circuit via the external load: I3-+e-◊3I-.
DYSC DYES: a healthy alternative Create this topic(?)
Commercially produced DYSC use ruthenium bipyridyl–based dyes (N3 dyes) and typically achieve conversion efficiencies of 10% (Nazerruddin, et al.,, 1993); they achieve excellent conversion of incident light photons to conduction band electrons in the titanium dioxide for wavelengths in the range of 510 nm to 570 nm (Nazeeruddin et al.,, 1993), and adequate conversion between 450-650 nm. This absorption spectrum of the dye overlaps well with the diffuse sunlight spectrum, which means that DYSC can be used indoors and in poor weather conditions. However, such dyes are hard to synthesise and are expensive (Cherepy et al., 1997). It is also possible, and significantly cheaper, to generate a significant photocurrent using natural anthocyanin dyes that are extracted from berries as natural water-based substitutes (Tennakone, 1995, 1997a, 1997b). Such dyes are responsible for the red and purple colours of fruit, and biologically serve to attract insects and protect leaves from UV damage (Martin, 1995). The adsorption of cyanin to the surface of
is a rapid reaction; an OH- counterion is displaced from the Ti(IV) site that combines a proton donated by the anthocyanin molecule (fig 6). This strong chemical affinity is one reason that the fruit dyes work effectively in the DYSC.
METHODS AND RESULTS: DYSC construction
A commercially bought titanium dioxide coated glass slide was stained with a berry dye (e.g. raspberries, blueberries, beetroot); the dye was made by crushing the fruit (or leaves) and purifying them in a solution of methanol, acetic acid and water (see Smestad & Gratzel (1998) for methods). This slide was washed with water, and dried with propanol, and a transparent conducting glass slide (tin dioxide coated) was secured over it using metal clips. The electrolyte solution (0.5M potassium iodide and 0.05M iodine in ethylene glycol) was drawn up into the porous titanium dioxide structure (see fig 7). Raspberry, blueberry, beetroot and orange leaf cells were constructed. All cells produced a photocurrent when a voltage was applied (fig 8), but its magnitude varied between the dyes; the region of negative current and positive voltage represents photocurrent activity. It was found that blueberries were most efficient –they produced a photocurrent of 0.2mA (~0.02% efficiency) - followed by raspberries, then beetroot. The orange leaf dyed cells produced virtually no current. Initially the blueberries, raspberries and beetroot showed improvement, whereas there was none in the orange leaf dye. Figure 9 shows short circuit current verses time; there was significant improvement over the first 9 hours, before degradation began. There was improved photocurrent as the concentration of electrolyte solution was increased for raspberries, blueberries and beetroot, but not for the orange leaf cell.
DISCUSSION: what’s going on?
The 2nd half of figure 9 – the degradation process – is hard to predict since many factors such as electrolyte degradation, oxidation of fruit and fruit decomposition by bacteria are contributing. However, it is likely that the improvement process is independent to the ruin degradation process, and the only reason a decrease in efficiency is observed is because this degradation becomes the dominant process (fig 10). The improvement process can be explained by looking at the energy levels associated with the titanium dioxide, the dye and the electrolyte solution (fig 11). Consider the blueberry cell: the ease with which an electron moves through the system is determined by the energy barriers, or band gaps that must be overcome (fig 12). The electron must have a significant energy to transfer from the electrolyte to the dye. As the cell is exposed to the light from the lamp the cell heats up, causing evaporation of the electrolyte solution. This increases the concentration of KI and I2, and the energy level of the valence band is raised, making the transfer of electrons to the dye a far more favourable process. This explains why the photocurrent improved when placed underneath the light. Notice that the conduction band of the blueberry dye lies above that of the titanium dioxide conduction band. Hence it is energetically favourable for the electrons excited from the valence band into the conduction band of the dye to be transferred to the conduction band of the titanium dioxide. Turning to the orange cell, the conduction band of the orange cell lies beneath that of the titanium dioxide (fig 13). Few electrons can transfer to the titanium dioxide, and a small photocurrent is produced. Even when placed underneath light, and the concentration of the electrolyte increases, this has no effect since the electrons still cannot make the transfer from the dye to the titanium dioxide.
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CONCLUSION: moving towards the light
In choosing materials to construct a solar cell it is important to consider the energy levels of such components. A cell that produces a large photocurrent has a dye that is energetically well suited to the titanium dioxide with a conduction band energy level that is slightly higher than the titanium dioxide conduction band level. Similarly, the concentration of the electrolyte solution is energetically well suited to the dye (Bisquert et al., 2004). For future work on anthocyanin dyes such as raspberries, blueberries, beetroot, the optimal electrolyte concentration of electrolyte needs to be established quantitatively by varying the concentration of potassium iodide or iodine and observing the changes in photocurrent. Also, to further confirm the band-gap model, it must be proved that temperature does not influence the improvement process in any other way than increasing the electrolyte concentration.
A significant shortcoming of the DYSC is leakage of the electrolyte, which reduces the lifespan of the cell, and technological problems associated with devices sealing up and long-term stability (Man Gu Kang, et al., 2003). Although a solid electrolyte replacement such as XXX is possible, where (on absorption of light) the dye would inject an electron into the titanium dioxide and a hole into the solid electrolyte, the efficiency has been very low. This is due to poor penetration of the solid into the pores of the titanium dioxide (Spiekermann, et al.,, 2001), allowing only a small surface area contact for electron transport. Currently there is research into the use of polymer gel to quasi-solidify the liquid electrolytes (Ren et al.,, 2001; Kubo et al., 2001; Nogueira et al., 2001). The addition of Poly(viny1idene fluoride-co-hexafluoropropylene) to the KI/I2 electrolyte has improved the fill factors and the energy conversion efficiency of the DYSC by about 17 % (Man Gu Kang, et al.,, 2003).
The DYSC has the potential to become an economically viable method of using solar energy commercially. Advantages of the DYSC over conventional solar cells include that it: does not need ultra-pure substances; uses low-cost materials and processes that have little environmental impact; achieves reasonable efficiencies which are expected to improve with more research; long-term stability of 10-20 years (Grätzel, 2000, Grätzel, 2001). There is flexibility in the choice of material for each component, allowing the properties to be adjusted and optimised for particular applications. As fossil fuel resources dwindle, other methods such as solar energy must be considered: with improvements to increase their efficiency, extend their lifetime and reduce costs, the DYSC provides an economically viable solution, and could direct us to using solar power regularly.
Special recognition must go Dr Nicholas Ekins-Daukes, my supervisor, for all his efforts, support and patience throughout my project. I’d also like to thank Dr Mathew Boreland, George Brawley, David Young and Professor Dick Hunstead.
Bignozzi, C.A., Argazzi, R., Kleverlaam, C.J., 2000. Molecular and supramolecular sensitization of nanocrystalline wide band-gap semiconductors with mononuclear and polynuclear metal complexes. Chem. Soc. Rev., 29, 87-96.
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Blueberry Power; Photosynthetic Electricity
Photovoltaics (technology that produces electric power directly from sunlight), once dominated by solid-state junction devices is now being revolutionised by the dye-sensitized solar cell (DYSC). Based on nanocrystalline materials and conducting polymer films, it is the only serious alternative concept (both technically and economically) to p-n junction photovoltaic devices. Not only are such cells cheap to produce, but they have little environmental impact. Already these cells produce 11% conversion efficiencies, and with further research could overtake conventional solid-state devices. Here, I will compare the DYSC to natural photosynthesis, present our existing understanding of the field, and assess the potential for widespread use of the DYSC in our society.
Blueberry Power; Photosynthetic Electricity
By Helen Smith
Figure 1: Australian Government, Bureau of Meteorology: Australia’s Daily exposure to solar energy
Figure 9: Short circuit Current vs. Time for a typical blueberry cell
Figure 8: Short circuit Current vs. Voltage for a typical raspberry cell
Figure 7: A blueberry DYSC
Figure 6: Chelation process of dye to Titanium dioxide
Figure 5: How the DYSC works
Figure 4: Electron micrograph of Titanium dioxide in the nanocrystalline form
Figure 3: DYSC construction
Figure 2: Photosynthesis
NADP+ ADP + Pi
Figure 10: Model to predict improvement and degradation of DYSC. In red is the predicted improvement if degradation was absent
Figure 11: Energy levels associated with the different components of the DYSC
Dye Create this topic(?)
Figure 12: Energy levels in a blueberry DYSC
Dye Create this topic(?)
Figure 13: Energy levels in an orange DYSC
INTRODUCTION: Shonky Solid-State Solar Cells
Kang, M.G., Park, N-G., Kim, K-M., Ryu, K.S., Chang S.H., Kim, K.J., 2003. Highyl efficient polymer gel electrolytes for fye-sensitized solar cells. 3rd World Conference on Phorovolroic Emru Conversion . May 11-18, 2003 Osnh, Japan
Miyasaka, T., Murakami, T.N., 2004. The photocapacitor: An efficient self-charging capacitor for direct storage of solar energy. Applied Physics Letters, 85, number 17. Create this topic(?)
O'Regan, B., and M. Gratzel, 1991. A low-cost, high efficiency solar cell based upon dye-sensitized colloidal
films. Nature 353, 737-740
Smestad, G., Bignozzi, C., Argazzi, R, 1994. Sol. Energy Mater. Sol. Cells, 32, 259.
Smestad G.P., Gratzel. M., 1998. Demonstrating Electron Transfer and Nanotechnology: A Natural Dye–Sensitized Nanocrystalline Energy Converter. Journal of Chemical Education, 75 (6).
THE DYE SENSITISED SOLAR CELL (DYSC): a fruitful future?
PHOTOSYNTHESIS: power to the plants
HOW THE DYSC WORKS: blueberry electricity
DYSC DYES: a healthy alternative
METHODS AND RESULTS: DYSC construction
DISCUSSION: what’s going on?
CONCLUSION: moving towards the light
“Cause” \o “Apollo 1” Apollo 1 fire catastrophe was caused by this reaction. The ethylene glycol–water mixture was ignited and was able to burn in the atmosphere of pure low pressure oxygen. [ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Ethylene_glycol&action=edit&section=8” \o “Edit section: Carbonyl chemistry” edit] Carbonyl chemistry Ethylene glycol may also be used as a protecting group for carbonyls during synthesis. Acid catalysis, and a ketone or aldehyde with ethylene glycol will form a cyclic structure at the carbonyl. Other chemistry can then be done to the molecule before more acid will break open the protecting ring and restore the carbonyl. Work procedureTuesday, September 12, 2006 Solar Cells for Cheap Not everyone gets a solar cell named after them: but Michael Gratzel did. He says his novel technology, which promises electricity-generating windows and low manufacturing costs, is ready for the market. By Kevin Bullis
Michael Grätzel, chemistry professor at the Ecoles Polytechniques Fédérales de Lausanne in Switzerland, is most famous for inventing a new type of solar cell that could cost much less than conventional photovoltaics. Now, 15 years after the first prototypes, what he calls the dye-sensitized cell (and everyone else calls the Grätzel cell) is in limited production by Konarka, a company based in Lowell, MA, and will soon be more widely available. Grätzel is now working on taking advantage of the ability of nanocrystals to dramatically increase the efficiency of solar cells. Technology Review asked him about the challenges to making cheap solar cells, and why new technologies like his, which take much less energy to manufacture than conventional solar cells, are so important. Technology Review: Why has it been so difficult to make efficient, yet inexpensive solar cells that could compete with fossil fuels as sources of electricity? Michael Grätzel: It's perhaps just the way things evolved. Silicon cells were first made for [outer] space, and there was a lot of money available so the technology that was first developed was an expensive technology. The cell we have been developing on the other hand is closer to photosynthesis. TR: What is its similarity to photosynthesis? MG: That has to do with the absorption of light. Light generates electrons and positive carriers and they have to be transported. In a semiconductor silicon cell, silicon material absorbs light, but it also conducts the negative and positive charge carriers. An electric field has to be there to separate those charges. All of this has to be done by one material–silicon has to perform at least three functions. To do that, you need very pure materials, and that brings the price up. On the other hand, the dye cell uses a molecule to absorb light. It's like chlorophyll in photosynthesis, a molecule that absorbs light. But the chlorophyll's not involved in charge transport. It just absorbs light and generates a charge, and then those charges are conducted by some well-established mechanisms. That's exactly what our system does. The real breakthrough came with the nanoscopic particles. You have hundreds of particles stacked on top of each other in our light harvesting system. TR: So we have a stack of nanosized particles… MG: …covered with dye. TR: The dye absorbs the light, and the electron is transferred to the nanoparticles? MG: Yes. TR: The image of solar cells is changing. They used to be ugly boxes added to roofs as an afterthought. But now we are starting to see more attractive packaging, and even solar shingles (see “ HYPERLINK “http://www.technologyreview.com/read_article.aspx?id=17129&ch=biztech” Beyond the Solar Panel”). Will dye-sensitized cells contribute to this evolution? MG: Actually, that's one of our main advantages. It's a commonly accepted fact that the photovoltaic community thinks that the “building integrated” photovoltaics, that's where we have to go. Putting, as you say, those “ugly” scaffolds on the roof–this is not going to be appealing, and it's also expensive. That support structure costs a lot of money in addition to the cells, and so it's absolutely essential to make cells that are an integral part. [With our cells] the normal configuration has glass on both sides, and can be made to look like a colored glass. This could be used as a power-producing window or skylights or building facades. The wall or window itself is photovoltaicly active. The cells can also be made on a flexible foil. Could we see them on tents, or built into clothing to charge iPods? MG: Absolutely. Konarka has a program with the military to have cells built into uniforms. You can imagine why. The soldier has so much electrical gear and so they want to boost their batteries. Batteries are a huge problem–the weight–and batteries cost a huge amount of money. Konarka has just HYPERLINK “http://renewableenergyaccess.com/rea/news/story?id=45733” announced a 20-megawatt facility for a foil-backed, dye-sensitized solar cell. This would still be for roofs. But there is a military application for tents, and Konarka is participating in that program. TR: When are we going to be able to buy your cells? MG: I expect in the next couple of years. The production equipment is already there. Konarka has a production line that can make up to one megawatt [of photovoltaic capacity per year]. TR: How does the efficiency of these production cells compare with conventional silicon? MG: With regard to the dye-cells, silicon has a much higher efficiency; it's about twice [as much]. But when it comes to real pickup of solar power, our cell has two advantages: it picks up [light] earlier in the morning and later in the evening. And also the temperature effect isn't there–our cell is as efficient at 65 degrees [Celsius] as it is at 25 degrees, and silicon loses about 20 percent, at least. If you put all of this together, silicon still has an advantage, but maybe a 20 or 30 percent advantage, not a factor of two. TR: The main advantage of your cells is cost? MG: A factor of 4 or 5 [lower cost than silicon] is realistic. If it's building integrated, you get additional advantages because, say you have glass, and replace it [with our cells], you would have had the glass cost anyway. TR: How close is that to being competitive with electricity from fossil fuels? MG: People say you should be down to 50 cents per peak watt. Our cost could be a little bit less than one dollar manufactured in China. But it depends on where you put your solar cells. If you put them in regions where you have a lot of sunshine, then the equation becomes different: you get faster payback. TR: Silicon cells have a head-start ramping up production levels. This continues to raise the bar for new technologies, which don't yet have economies of scale. Can a brand-new type of cell catch up to silicon? MG: A very reputable journal [Photon Consulting] just HYPERLINK “http://www.photon-consulting.com/executive_summary.htm” published predictions for module prices for silicon for the next 10 years, and they go up the first few years. In 10 years, they still will be above three dollars, and that's not competitive. Yes, people are trying to make silicon in a different way, but there's another issue: energy payback. It takes a lot of energy to make silicon out of sand, because sand is very stable. If you want to sustain growth at 40-50 percent, and it takes four or five years to pay all of the energy back [from the solar cells], then all of the energy the silicon cells produce, and more, will be used to fuel the growth. And mankind doesn't gain anything. Actually, there's a negative balance. If the technology needs a long payback, then it will deplete the world of energy resources. Unless you can bring that payback time down to where it is with dye-cells and thin-film cells, then you cannot sustain that big growth. And if you cannot sustain that growth, then the whole technology cannot make a contribution. TR: Why does producing your technology require less energy? MG: The silicon people need to make silicon out of silicon oxide. We use an oxide that is already existing: titanium oxide. We don't need to make titanium out of titanium oxide. TR: An exciting area of basic research now is using nanocrystals, also called quantum dots, to help get past theoretical limits to solar-cell efficiency. Can dye-sensitized cells play a role in the development of this approach? MG: When you go to quantum dots, you get a chance to actually harvest several electrons with one photon. So how do you collect those? The quantum dots could be used instead of a [dye] sensitizer in solar cells. When you put those on the titanium dioxide support, the quantum dot transfers an electron very rapidly. And we have shown that to happen. TR: You are campaigning for increased solar-cell research funding, and not just for Grätzel cells. MG: There's room for everybody. I am excited that the United States is taking a genuine interest in solar right now, after the complete neglect for 20 years. The Carter administration supported solar, but then during the Reagan administration, it all dropped down by a factor of 10. And labs like NREL [National Renewable Energy Laboratory in Golden, CO] had a hard time surviving. But I think there is going to be more funding. Friday, July 07, 2006
Beyond the Solar Panel The U.S. government plans to produce a buyer's guide to power-converting roofing materials.- By Lamont Wood
INCLUDEPICTURE “http://www.technologyreview.com/files/874/Wood%20070706%20sunshingle.jpg” \* MERGEFORMATINET Photovoltaic shingles (in blue) can be installed in the same way as conventional shingles. About 500 square feet of them produce three kilowatts during peak sunlight, enough for most residences. Currently, they're still darker than conventional roofing materials. (Courtesy of United Solar Ovonic.) Create this topic(?)http://peswiki.com/energy/Main_Page
The government tests cars for gas mileage. Now it's testing roof tiles for wattage. Homeowners have long been able to partially power their homes with sunlight, but it meant clumsily mounting photovoltaic (PV) panels on the roof. Now the latest generation of PV panels look and act much like ordinary roofing tiles or shingles. And the National Institute of Standards and Technology (NIST) is HYPERLINK “http://www.bfrl.nist.gov/863/bipv/roof.htm” evaluating nine of these commercial PV roofing products in hopes of providing an easy way for consumers to judge the panels' power potential. “A lot of people are considering the use of PV products on their homes and businesses, and in order to make decisions on whether it's a worthwhile investment you need to predict their performance,” says Hunter Fanney, head of NIST's Heat Transfer and Alternative Energy Systems Group in Gaithersburg, MD. “We are collecting detailed performance data to validate those models.” The roofing materials, which use various types of solar-to-electricity conversion, are being tested for 15 months. Fanney hopes to use the data to build a computer program and database with, among other things, average flat-surface solar radiation readings for neighborhoods across the United States (as measured by the weather service at the nearest airport). Punch in the performance characteristics of the roofing product you want to use, plus your location, roof orientation and slope, and other data, and – bingo – you'll know what kind of wattage you can expect from your roof. According to Fanney, roofing tiles and shingles with embedded solar converters have been on the market for about three years. They look like regular roofing materials, keep out the sun and rain, and can be installed in much the same way. But by generating electricity, these tiles and shingles save consumers money. Around 500 square feet of PV tiles can produce three kilowatts of electricity, according to Subhendu Guha, president and chief operating officer of HYPERLINK “http://www.uni-solar.com/” United Solar Ovonic, a maker of PV shingles in Auburn Hills, MI – and most roofs are several times that size. His company's version is dark blue and can blend with ordinary shingles of a similar shade. Or a builder might devote an entire sunny section to PV materials. “A south-facing roof on a three-bedroom home could supply 20 to 30 percent of the home's electrical needs,” says Paul Maycock, a consultant and head of PV Energy Systems in Williamsburg, VA. Without subsidies and incentives, such as those in California, PV power costs about twice as much as utility power, says Thomas Leyden, vice president of east coast operations for HYPERLINK “http://www.powerlight.com/” , a PV systems integrator in Berkeley, CA. That difference, however, is shrinking. “PV hardware prices have gone down tenfold in the last 15 years, thanks to new technologies, better manufacturing techniques, and more efficient use of materials,” Leyden says. Prices are currently falling by about 5.5 percent yearly, he says, so they should come down another 50 percent in a little more than a decade – and become fully competitive with utility power. Maycock is even more optimistic, projecting that the installed price will fall from today's $8 or so per watt to $4 by 2014. That would make solar power “fully economic in the Sunbelt,” he notes. Meanwhile, Guha maintains that PV roofing is already economical at certain times of the day, in places where utilities charge extra for peak daytime usage. There, he says, it can be used to avoid paying those surcharges, a practice called “peak shaving.” Historically, the biggest market for residential PV roofing has been in Japan, which gets about half the sunlight that California does and the average residential user derives only a kilowatt. But government incentives, low mortgage interest rates, and high utility power rates have made residential PV popular there, says Maycock. I would think there is data from current installations in Europe and Japan?? Also, I understand the top surface may be a fluoropolymer film, maybe that would help to reduce adhesion of city grime? Or perchance create a new industry (chimney sweeps to roofing sweeps)? Suppose for a moment that you treat these panels just like a car - say wash them once in a while with soap and water. Then rinse. With newer nano surfaces that repel water they may even be semi-self cleaning. GE has a new plastic that has this capability. As you clea your eves, you can hose your PV's now and then. As for slope: for best results you want to have the sun light coming perpendicular to your panels. Sloped roofs work better than flat roofs (get more light). And this changes with latitude. If builders start including this in their desings, house orientation and roof shapes and slopes will be designe for the local condition to optimally make use of the sun in each particular location. One company makes both solar roofing tiles and PV panels. The efficiency is up to 20%. I hope they get included in the testing. site is www.openenergycorp.com . There is some other interesting things there as well. do these shingles hold up well in the deep south of the east and coast areas, is humidity an issue? they do, if i understand you right. as a matter of fact, normally coastlines have more sunhours that on the land, so for solar coast is perfect. it depends a little whether you place the panels very near by the sea or not. very near means a salty film on the panels which should be affoided to my believe.
PV solarpanels are good to use anywhere, don't understand me wrong. even in canada or norway. i live in the netherlands where we have very diffuse light now and then, but no problem for solar, using poly-crystalline solar modules. these are perfect for that kind of conditions.
a rule of thumb is; the hotter (not about light) a climate is the better you should use thermal-electro solar power, since PV panels don't like their working surface very (VERY) hot. at the end, its all about efficiency and how much you want to matter with that, because we are talking about percents power more or less… writing this, i think i wouldn't care about it too much. just put the panels there and shout it out! so that others hear it and do the same! Solar power for our homes sounds great…until you start to add all the other expensive items. It would be helpful to know the full expense plus all the maintenance needs and failure rates. Also, in the tropics (like Guam), air conditioning is the real energy hog. A solar system for this might be unaffordable for most people. And then there are the typhoons…. concerning solar-energy in the tropics; it is known that photo-voltaic solar panels (PV) are less efficient when the working temperature is high (that is the temp on/in the panel itself). for tropical conditions it is, efficiency-wise, better to invest in thermo-electro solar energy. here the sun heats oil in pipes that runs a generator. the efficency is very high. don't know whether this is technique ready to use on home-roofs, though. You have mentioned temperature being a factor on the use of solar shingles for electricity. What are the specs? I live in TX and we see 20-40 100 degree F days per year in addition to hail storms usually once per year. I love the idea for weening my corner of the world off petrol, but these questions concern me. for anyone interested in new energytech, including foil-solar and stuff, but also many different other projects and ideas, go to; HYPERLINK “http://peswiki.com/energy/Main_Page” http://peswiki.com/energy/Main_Page
Tuesday, April 25, 2006 Holographic Solar A novel approach to concentrating sunlight could cut solar panel costs. By Prachi Patel-Predd
INCLUDEPICTURE “http://www.technologyreview.com/files/760/042506cut.jpg” \* MERGEFORMATINET Rows of silicon solar cells alternate with rows of transparent holograms in Prism Solar's concentrators. (Courtesy of Prism Solar) Other readers liked: • HYPERLINK “http://www.technologyreview.com/Energy/17169/” How To Build a Solar Generator 7/14/2006
• HYPERLINK “http://www.technologyreview.com/Energy/17490/” Solar Cells for Cheap 9/12/2006
• HYPERLINK “http://www.technologyreview.com/Energy/17774/” Cheap, Superefficient Solar 11/9/2006
• HYPERLINK “http://www.technologyreview.com/Energy/17129/” Beyond the Solar Panel 7/7/2006
• HYPERLINK “http://www.technologyreview.com/Energy/17025/” Large-Scale, Cheap Solar Electricity 6/23/2006
The main limitation of solar power right now is cost, because the crystalline silicon used to make most solar photovoltaic (PV) cells is very expensive. One approach to overcoming this cost factor is to concentrate light from the sun using mirrors or lenses, thereby reducing the total area of silicon needed to produce a given amount of electricity. But traditional light concentrators are bulky and unattractive – less than ideal for use on suburban rooftops. Now Prism Solar Technologies of Stone Ridge, NY, has developed a proof-of-concept solar module that uses holograms to concentrate light, possibly cutting the cost of solar modules by as much as 75 percent, making them competitive with electricity generated from fossil fuels. The new technology replaces unsightly concentrators with sleek flat panels laminated with holograms. The panels, says Rick Lewandowski, the company's president and CEO, are a “more elegant solution” to traditional concentrators, and can be installed on rooftops – or even incorporated into windows and glass doors. The system needs 25 to 85 percent less silicon than a crystalline silicon panel of comparable wattage, Lewandowski says, because the photovoltaic material need not cover the entire surface of a solar panel. Instead, the PV material is arranged in several rows. A layer of holograms – laser-created patterns that diffract light – directs light into a layer of glass where it continues to reflect off the inside surface of the glass until it finds its way to one of the strips of PV silicon. Reducing the PV material needed could bring down costs from about $4 per watt to $1.50 for crystalline silicon panels, he says. The company is expecting to pull in another $6 million from interested venture capitalists and start manufacturing its first-generation modules by the end of the year, selling them at about $2.40 per watt. Next-generation modules with more advanced technology should bring down the cost further. In their ability to concentrate light, holograms are not as powerful as conventional concentrators. They can multiply the amount of light falling on the cells only by as much as a factor of 10, whereas lens-based systems can increase light by a factor of 100, and some even up to 1,000. ut traditional concentrators are complicated. Since the lenses or mirrors that focus light need to face the sun directly, they have to mechanically track the sun. They also heat up the solar cells, and so require a cooling system. As a result, although they redirect light with more intensity than the hologram device, “they're unwieldy…and not as practical for residential uses,” says National Renewable Energy Laboratory spokesperson George Douglas. Holograms have advantages that make up for their relatively weak concentration power. They can select certain frequencies and focus them on solar cells that work best at those frequencies, converting the maximum possible light into electricity. They also can be made to direct heat-generating frequencies away from the cells, so the system does not need to be cooled. “In this way, you are efficiently using only that part of the sunlight that really matters,” says HYPERLINK “http://lapt.ece.northwestern.edu/people/selim.html” Selim Shahriar, director of the atomic and photonic technology laboratory at Northwestern University in Evanston, IL. Also, different holograms in a concentrator module can be designed to focus light from different angles – so they don't need moving parts to track the sun. Prism Solar's system incorporates these advantages. Nevertheless, to be competitive with other solar technologies available today, the company might need to reduce its price below $2.40 a watt, says Christo Stojanoff, professor emeritus of engineering at the Aachen University of Technology in Germany. CEO Lewandowski says the holographic modules will cost about $1.50 per watt in a few years, using their second-generation technology, which will have solar cells sandwiched between two glass panels containing holograms. At that price, they'll start to compete with fossil fuel-generated electricity, which now costs almost three times less than conventional solar electricity, according to San Francisco, CA-based research and consulting company HYPERLINK “http://www.solarbuzz.com/” Solarbuzz. The modules' intensive use of glass could be adding to their cost, says Douglas. Still, such a novel idea for a concentrator, using holograms, could be a lucrative investment because it needs less silicon than flat-panel modules and therefore saves money. The high demand for solar cells in Germany and other European countries “has now outstripped the supply, which has [led to] a silicon shortage and a shortage of manufacturing in the photovoltaic world,” he says. Although the idea of holographic solar concentrators has been around since the early 1980s, no one has developed them commercially yet, according to Professor Stojanoff, who has investigated the technique extensively. His company, Holotec
in Aachen, Germany, researches and manufactures holographic materials. Also, Northeast Photosciences, a Hollis, NH-based company, came close to manufacture, before it went defunct for reasons unrelated to the technology or to finance, he says.
So, if all goes according to plan, Prism Solar could be the first company to manufacture and sell holographic solar concentrator modules.
Friday, July 14, 2006 How To Build a Solar Generator Affordable solar power using auto parts could make this electricity source far more available. By Kevin Bullis
HYPERLINK “http://www.technologyreview.com/Energy/17169/” INCLUDEPICTURE “http://www.technologyreview.com/images/icon_small.gif” \* MERGEFORMATINET HYPERLINK “http://www.technologyreview.com/Energy/17169/” INCLUDEPICTURE “http://www.technologyreview.com/images/icon_medium.gif” \* MERGEFORMATINET HYPERLINK “http://www.technologyreview.com/Energy/17169/” INCLUDEPICTURE “http://www.technologyreview.com/images/icon_large.gif” \* MERGEFORMATINET
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Demand for solar power is rapidly heating up (see “ HYPERLINK “http://www.technologyreview.com/read_article.aspx?id=17104&ch=biztech” New Solar Technologies Fueled by Hot Markets”). But constructing and deploying large photovoltaic panels to generate electricity remains expensive. Now two groups at MIT are working on alternative approaches to solar-based electricity that could significantly cut costs – and put the ability to harvest electricity from the sun into the hands of villagers in poor countries and backyard tinkerers alike. During a stint in the Peace Corps in Lesotho in southern Africa, Matthew Orosz, an MIT graduate student advised by Harold Hemond, professor of civil and environmental engineering, learned that reflective parabolic troughs can bake bread. Now he plans to use these same contraptions to bring power to parts of Africa baked in sun but starved for electricity. His solar generators, cobbled together from auto parts and plumbing supplies, can easily be built in a backyard. The basic design of Orosz's solar generator system is simple: a parabolic trough (taking up 15 square meters in this case) focuses light on a pipe containing motor oil. The oil circulates through a heat exchanger, turning a refrigerant into steam, which drives a turbine that, in turn, drives a generator. The refrigerant is then cooled in two stages. The first stage recovers heat to make hot water or, in one design, to power an absorption process chiller, like the propane-powered refrigerators in RVs. The solar-generated heat would replace or augment the propane flame used in these devices. The second stage cools the refrigerant further, which improves the efficiency of the system, Orosz says. This stage will probably use cool groundwater pumped to the surface using power from the generator. The water can then be stored in a reservoir for drinking water. The design uses readily available parts and tools. For example, both the feed pump and steam turbine are actually power-steering pumps used in cars and trucks. To generate electricity, the team uses an alternator, which is not as efficient as an ordinary generator, but comes already designed to charge a battery, which reduces some of the complexity of the system. And, like power-steering pumps, alternators, including less-expensive reconditioned ones, are easy to come by. As a result, the complete system for generating one kilowatt of electricity and 10 kilowatts of heat, including a battery for storing the power generated, can be built for a couple thousand dollars, Orosz says, which is less than half the cost of one kilowatt of photovoltaic panels. “You can't afford something that's designed for solar. You have to buy something that's mass-produced for something else – that way the cost is reasonable,” says Duane Johnson, owner of Red Rock Energy, in White Bear Lake, MN, who developed and sells thousands of the inexpensive LED-based sun-tracking devices Orosz uses to orient the solar concentrators. Most of the devices are used to position photovoltaic panels, he says, but some people are using them with old satellite dishes to concentrate heat and make steam. Sales of his devices have been growing 25 percent a year, a rate similar to that of the solar photovoltaics industry. Repurposed auto parts aren't the only way to go. Amy Sun, a graduate student in MIT's Media Lab, has designed an inexpensive system that uses heat from a solar concentrator to drive a type of turbine originally patented by Nicola Tesla. Rather than making complex, difficult-to-manufacture bladed turbines, Sun turned to the Tesla turbine, which consists of simpler flat disks stacked like records on a central shaft. The disks are carefully spaced to allow steam to flow between them. As the steam flows, friction between the steam and the surface of the disks causes them to rotate. “Once I have rotational shaft work, I can couple it to almost anything – an air pump, compressor, fan, mixer, grinder, sewing machine, refrigeration compressor, and, to power those very few things that are truly electric in nature, an electric generator.” She calculates that this system, which she says is simple enough for an eight-year old to make, can produce cheap power. Of course the overall economics of these solar generator systems depend on how long they will last and how much maintenance they will require. The lifetime for Orosz's system could be quite good, since it uses parts designed for rugged service in vehicles. It also works at relatively low temperatures that, in addition to making it safer and easier to work with, won't strain the performance limits of the plumbing used. Having already built a working prototype, Orosz's next step, which he hopes to accomplish starting this September in Lesotho, is to optimize manufacturing and set up a financing system, drawing on a recent $100,000 World Bank grant, to make the system affordable to villagers who would likely use the generator in a community center and as a battery-charging station. Although their system was originally designed for Lesotho, Orosz and his colleagues believe it might appeal to amateurs elsewhere. “Backyard tinkerers could build it themselves. No doubt about it,” says Amy Mueller, an MIT graduate student who's taken on a leading role in Orosz's project. “Matt's dad has one of these that we built to heat his Jacuzzi.”
I'm now standing in IRL's Christchurch laboratories looking at their prototype wave energy device, which has been dubbed the 'Wave Wobbler'. There are two different parts to this device. One part is a large rectangular block about 6 metres long welded together out of steel sheets. It's rather dense and heavy-looking, and it reminds me a little of the monolith from 2001: A Space Odyssey except that it's painted bright yellow. A swing-arm protrudes from the top of this monolith, and is attached to a large rectangular float – which is slightly smaller and much lighter-looking.
Alister, can you explain how this device generates electricity from ocean waves?
Well this, of course, is an experimental device – but basically it's quite simple. The large monolithic hull you mentioned [floats] vertically in the water just below the waterline. The float sits horizontally on top of the water, and the motion of the waves oscillates the float up and down.
Okay, so the monolith is sitting in the water [and] effectively it hardly moves at all. But the float follows the surface of the waves, and the difference in the motion enables you to generate electricity [via a suitable mechanism].
Fundamentally, yes. Although, of course, it's not quite as simple as that. There's some quite complex maths around getting the two parts to move together in a synergistic way.
And you've obviously done quite a lot of modelling to explore that?
Yes, we spent two years developing some complex [mathematical] engineering models to develop the whole concept and come up with an optimized [design].
So I know you've had this prototype in Lyttelton harbour, which only has tiny waves. In your further testing – when you actually get it out into the real ocean – what sort of power output do you expect from it?
With the larger scale version which we'll be heading towards commercialization we're expecting round about 100 kilowatts. Which is enough power to keep round about a hundred houses going.
Okay, right, it wouldn't just be one [machine] by itself – you might have a hundred or more all moored together in a sort of a 'field' of wave generators?
Yes, that's right. And we estimate from our modelling that we'd probably get each individual device up to around about a megawatt ultimately. But they will even be larger still.
So what sort of size are you expecting for that in terms of length and mass?
Well the 100 kilowatt version, which is really our first commercial focus, may weigh between 30 and 100 tonnes in total. So it's quite a substantial device – although, of course, you only see a small portion of it above the surface.
How long [i.e. the length of the device] would that be underneath the water?
It could be up to ten to 15 metres long.
And so would you be using water as ballast – or would it be made out of concrete, or steel, or something [equally] heavy to provide all that mass?
Yes, that's one of the secrets in fact. Most of the mass is taken up by water. So you don't have to actually tow it out [to the desired location]; you simply flood it when you get it there.
On land it's actually quite a light-weight device, it's only when you put it into the sea that it [fills up with water and] becomes this very heavy machine?
Yes, you might argue that it's a submerged yacht with a small float sitting at the top of it. * * * Voiceover:
Naturally enough, IRL aren't the only company who are looking into wave energy devices. Research teams are working on a variety of different systems in countries all around the world.
The United Kingdom are investing hundred of millions of New Zealand dollars on their marine energy program, and British company Ocean Power Delivery are definitely leading the field in terms of development.
Their 'Pelamis' wave energy device is a truly huge machine. It measures 120 metres long, and floats on the surface of the sea like a gigantic snake.
It couldn't be more different from IRL's 'Wave Wobbler' device, and – when we'd returned to his office – I asked Alister Gardiner why the research team at IRL had chosen to take such a different path. * * * Alister Gardiner:
There's no question that Pelamis is the benchmark at the moment. But we feel that our concept of going for a point-absorber gives us more flexibility – and, in theory, should provide a more cost-efficient device because of the lower use of materials. It's more flexible because we think we can make smaller devices, [which] could be used off-shore on remote islands at a lower cost.
What are the comparative efficiencies of the devices – do you have any sort of feel for that?
One can look at the Pelamis data sheets, and work out pretty quickly that their efficiency is relatively low – perhaps just a few per cent. That has it's disadvantages in terms of the size of the device. We feel from our modelling that we can achieve a much higher efficiency than that. And so we've started with an inherent design that we think is cost efficient.
Another point, I guess, is that if a large portion of the device is below the water – beneath the surface of the waves – then there's better chance of it remaining viable and surviving storm conditions.
Which is important when at least some of New Zealand's in the roaring forties, and it's really subject to some pretty horrific waves.
Exactly, yes. New Zealand is very fortunate in its wave energy resource.
We're fortunate in wind, too. And we've seen recently a little bit of wind coming on to the market – there are wind farms generating a very small amount of New Zealand's electricity. How long do you think it's going to be before we see something equivalent to that beginning to happen with wave energy?
We think it will happen a lot quicker.
I would expect that by 2010 there will be a number of commercial (or pre-commercial) devices in the water from various suppliers. And, by 2015… maybe 2020… we'll certainly see quite substantial uptake of marine energy of various sorts.
So that's actually really quickly.
You've only got to look at the energy crisis in the 80s, and so on, to see the massive involvement in wind energy. Now when the fuel prices came down that more or less stopped, which is the only reason it took maybe twenty years for wind energy to get to where it is today. If that research effort had continued we would have seen wind turbines and wind farms much earlier…
That brings me to something else, which is whether rising energy prices are a threat to New Zealand or also something of an opportunity as well? What I'm thinking here is of Denmark. You talked about the oil crisis in the 70s, and [Denmark] responded by investing heavily in wind energy technology. And they've now become – as a country – the world's leading exporter of wind turbines. Is there a similar opportunity for New Zealand here in terms of marine energy?
There's no reason at all why we can't produce a technology that's competitive globally. And, as I've mentioned, we think that basic concepts that we're putting together are potentially globally competitive.
However New Zealand does need a supportive environment and an enthusiasm to capture this [opportunity]. And this is, of course, what happened in Denmark. There was a strong government support for a particular type of energy technology.
We certainly need that sort of involvement (I think) within New Zealand. Both from the energy companies – who are obviously very keen on these technologies – and probably government leadership [as well], and obviously the manufacturing companies that will benefit down the track. * * * Voiceover:
IRL have clearly come a very long way with their 'Wave Wobbler' device, but only time will tell whether New Zealand has the political and economic will to develop a domestic wave energy industry – or whether, as with so many of our other innovative technologies, we'll be content to let the opportunity slip through our fingers.
Theme music… * * * Further information on wave energy devices: Read more about the HYPERLINK “http://www.wavenergy.co.nz/” WET-NZ wave energy converter. Read more about the Britain's HYPERLINK “http://www.oceanpd.com/” Pelamis wave energy converter. Read more about HYPERLINK “http://en.wikipedia.org/wiki/Wave_energy” wave energy in general in HYPERLINK “http://en.wikipedia.org” Wikipedia. What on earth is a Grätzel solar cell, and why is it so important? | Jan 01, 1900 00:04 HYPERLINK “http://www.publicaddress.net/assets/upload/14039/673072625/PAS_GratzelSolarCells.mp3” Play the audio for this post MP3, 5.1 MB This is a transcript of an episode of Public Address Science which was originally broadcast on HYPERLINK “http://www.radiolive.co.nz” Radio Live, 21st April 2007, 2 pm - 3 pm. You can listen to the original audio version of the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page. * * * Theme music…
Solar energy… in theory, it should be the answer to all our energy problems. Properly managed, more than enough solar energy falls on the roofs of New Zealand houses to provide all our domestic electricity needs.
So why don't we make use of it?
One problem is that – fairly obviously – the sun only shines during the day, which means that storage batteries [or similar] are required to provide energy for use at night. The other problem is that the solar cells used to generate electricity from sunlight are incredibly expensive.
That's because the raw silicon ingots used for solar cell manufacture require production technology that is astonishingly high-tech, enormously energy-intensive, and therefore mind-bogglingly costly. As a result, a 60 watt solar panel (enough to power a single dim incandescent light bulb) will set you back by around $850 dollars.
And why would you pay that sort of money when you get virtually unlimited electricity out of the power lines at a fraction of the cost and effort?
But the price of solar generated electricity is actually coming down. For each doubling of production capacity in the factories that manufacture solar cells, the price has fallen by around 20 per cent. In recent years, that's equated to a price drop of around 5 per cent per annum.
So do we all just have to wait for a few decades until we can afford those shiny solar-electricity panels on our roof?
Well, not necessarily. A new type of solar cell technology has emerged which looks set to change everything. Grätzel solar cells seem likely to slash the cost of solar generated electricity. They've actually been around since the early 1990s, but it's only comparatively recently that scientists have been able to get them work in a reliable manner.
One of the research teams at the forefront of Grätzel solar cell technology is the Nanomaterials Research Centre at Massey University. I talked to Dr Wayne Campbell about what the future might hold for solar energy.
I asked him to start by explaining how conventional silicon solar cells are made.
Dr Wayne Campbell:
The common silicon solar cell [which] you can buy is basically made from pure silicon ingots. It's… sliced up into little slices, and then doped with a n-type or a p-type dopant to make the actual solar cell. It forms what they call a p-n junction. When light shines over that junction you get electron transfer.
So putting it in very simplistic terms: the energy in the photons of sunlight knocks loose electrons from the doped silicon material, which produces an electric current. In contrast, how do Grätzel cells work – and how are they made?
Dr Wayne Campbell:
It's a photoelectochemical cell. It works completely differently really. In a simple sense you have a dye, which absorbs light [and] excites an electron up to a higher energy part of the molecule. From there that energy transfers to a semi-conductor – in this case it's usually Titanium dioxide – and from there it's collected on a transparent conducting surface. It's basically photoexcitation followed by charge separation… and then you get the loop of the electron back to the dye again.
So the energy from the sunlight is first absorbed into a dye, and then there's a second step where the energy is transferred from the dye into a semiconductor material. And, in this case, the semi-conductor material is titanium dioxide, which is presumably cheaper to produce than the silicon crystals in conventional solar cells?
Dr Wayne Campbell:
It's a very thin layer, so it's very cheap.
And is the manufacture of Grätzel cells a simpler production process than for conventional silicon cells?
Dr Wayne Campbell:
Yeah, basically [either] it's screen printing, or simple pyrolysis, or plasma deposition.
So I know that your research group have been collaborating with Professor Grätzel who invented these Grätzel cells in Switzerland. What aspect of the technology are you actually looking at?
Dr Wayne Campbell:
Our main area [is] not so much developing the cell anymore – it's just developing a better dye for these cells. The current dyes that are used are quite expensive because they're Ruthenium-based. So they're based on a fairly rare metal which would have limited supplies if it was used in large quantities.
So you've had quite a bit of success with your research. What are the advantages of the new Grätzel cell dyes that your team has developed.
Dr Wayne Campbell:
It's a lot cheaper to make than the Ruthenium dyes – basically because it doesn't have any rare metals.
It's based on a chlorophyll molecule, which is the porphyrin haem group in blood (the red molecule in blood). [So] there's no reason for [the Grätzel solar cells] to be toxic – or anything like that – [when they are disposed of] afterwards either.
So basing your dyes on chlorophyll, the chemical that plants use to absorb sunlight, and blood, an energy carrier in animals, that's really a case of science imitating nature. What efficiency are you getting out of the Grätzel solar cells?
Dr Wayne Campbell:
The best for the Grätzel cell was with the Ruthenium dye – and that's quoted at 10.1 per cent.
Okay, and with the new dye that you've developed?
Dr Wayne Campbell:
The latest report from Grätzel's lab is for 7.1 per cent, so we're quite happy with that. [And] it seems to be very reproducible, [whereas] some of these other dyes don't always seem to be reproducible.
The dye itself hasn't actually been optimised properly in the cell either. [Grätzel's laboratory tested it with] the electrolytes and stuff that they normally would use with their Ruthenium dyes.
By modifying things like [the electrolytes] you can actually get a lot more performance out of the cell. We expect even better than 7 per cent, definitely.
So you've got good efficiency – but not quite as good as normal silicon solar cells, which are around the 9 to 15 per cent range, but of course your Grätzel cells would end up being much cheaper, wouldn't they? Do you have any feel for the cost reduction?
Dr Wayne Campbell:
Probably it's going to be [about] one-tenth the cost – but we don't have any exact figures really, at the moment.
Wow, that would be a significant cost reduction compared to the comparatively slow rate that the price of conventional solar cells is dropping. So even if the Grätzel cells stay at their current efficiency you're still cutting something like four-fifths off the price on a per watt basis (in comparison to silicon-based cells).
Dr Wayne Campbell:
Yeah… [the Grätzel cells will only be] a fraction of the [current] cost. * * * Voiceover:
Despite a somewhat lower efficiency, the much lower cost of Grätzel solar cells is certain to bring about a dramatic sea-change in the amount of solar-derived electricity in our society's energy mix.
Dr Campbell expects to see Grätzel cells based on the more expensive Ruthenium dyes in shops within the next few years. Although it may take a while longer before cells with the cheaper chlorophyll-based dyes make an appearance.
Either way, the Grätzel solar cells are another important part of the jigsaw of technologies that will be needed to ensure a secure energy future.
Theme music… * * * Further information on Grätzel solar cells: Read more about HYPERLINK “http://en.wikipedia.org/wiki/Gratzel_cell” Grätzel solar cells in HYPERLINK “http://en.wikipedia.org” Wikipedia. Read more about HYPERLINK “http://en.wikipedia.org/wiki/Photovoltaic_cell” solar cells in general in HYPERLINK “http://en.wikipedia.org” Wikipedia. Read more about the HYPERLINK “http://nrc.massey.ac.nz/” Nanomaterials Research Centre at HYPERLINK “http://www.massey.ac.nz/” Massey University. Read about HYPERLINK “http://www.dyesol.com/” Dyesol and HYPERLINK “http://www.konarka.com/” Konarka, two companies who have already begun to manufacture Grätzel solar cells (using HYPERLINK “http://en.wikipedia.org/wiki/Ruthenium” Ruthenium-based dyes) in small quantities. HYPERLINK “http://www.publicaddress.net/assets/upload/14039/673072625/PAS_GratzelSolarCells.mp3” \o “Play Audio (MP3, 5.1 MB)” INCLUDEPICTURE “http://www.publicaddress.net/img/southerly/btn_audio.gif” \* MERGEFORMATINET HYPERLINK “http://www.publicaddress.net/print,4117.sm” \o “View as Printable” INCLUDEPICTURE “http://www.publicaddress.net/img/btn_print.gif” \* MERGEFORMATINET HYPERLINK “http://www.publicaddress.net/default,4117.sm” \o “Link to this Post” INCLUDEPICTURE “http://www.publicaddress.net/img/btn_link.gif” \* MERGEFORMATINET HYPERLINK “http://www.publicaddress.net/contact,southerly.sm” \o “Send Feedback to Author” INCLUDEPICTURE “http://www.publicaddress.net/img/btn_reply.gif” \* MERGEFORMATINET HYPERLINK “http://www.publicaddress.net/system/topic,362,southerly_what_on_earth_is_a_gr%E4tzel_solar_cell_and_why_is_it_so_important.sm;jsessionid=6B5765F38A2C2B96CD4E84287DFF952E” \o “Discuss this Post” INCLUDEPICTURE “http://www.publicaddress.net/img/btn_discuss.gif” \* MERGEFORMATINET (9 responses) HYPERLINK “http://digg.com/submit?phase=2&url=http%3A%2F%2Fwww.publicaddress.net%2Fdefault%2C4117%2Cwhat_on_earth_is_a_gr%25E4tzel_solar_cell_and_why_is_it_so_important.sm&title=What+on+earth+is+a+Gr%E4tzel+solar+cell%2C+and+why+is+it+so+important%3F&bodytext=This+is+a+transcript+of+an+episode+of+Public+Address+Science+which+was+originally+broadcast+on+Radio+Live%2C+21st+April+2007%2C+2+pm+-+3+pm.%0A%0AYou+can+listen+to+the+original+audio+version+of+the+programme+by+clicking+on+the+%27Play+the+audio+for+this+post%27+link+at+the+top+of+this+page+or+the+%27Audio%27+button+at+the+bottom+of+this+page.%0A%0A*+*+*Theme+music…” Digg this HYPERLINK “http://www.scoopit.co.nz/submit.php?url=http%3A%2F%2Fwww.publicaddress.net%2Fdefault%2C4117%2Cwhat_on_earth_is_a_gr%25E4tzel_solar_cell_and_why_is_it_so_important.sm” Scoopit!
Will the Pulse Detonation Engine Help to Address New Zealand's 'Air Mile' Issues? | Jan 01, 1900 00:03 HYPERLINK “http://www.publicaddress.net/assets/upload/13073/224975781/PAS_PulseDetonationEngines.mp3” Play the audio for this post MP3, 6.0 MB This is a transcript of an episode of Public Address Science which was originally broadcast on HYPERLINK “http://www.radiolive.co.nz” Radio Live, 14th April 2007, 2 pm - 3 pm. You can listen to the original audio version of the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page. * * * Theme music…
[Sound of a blackbird singing]
For some people the song of a blackbird is the most beautiful sound in the world. Other people's favourite sound might be Beethoven or Jimi Hendrix. But for me this is one of the most fantastic noises that I've ever heard…
[Sound of a pulsejet flyby]
It's the sound of a pulsejet engine. And if you lived in London from 1944 to 1945 you might not be quite so enthusiastic about hearing it. Pulsejets powered the 10,000 Nazi V1 missiles that rained down upon England during World War II.
I've got the engineering drawings of the V1 pulsejet engine sitting in front of me. It's pretty much the simplest machine imaginable. It's literally just an empty tube with one end blocked off by a bank of one-way reed valves.
[A pulsejet] works just like a two-stroke lawnmower motor – but without the piston. Air is drawn in through the reed valves, fuel is injected, and then the fuel is exploded. But rather than the explosion pushing on a piston, it pushes hot gas out the back of the engine at high speed… thus producing thrust.
It couldn't be simpler, or cheaper to make. And it's long been the dream of aircraft engine manufacturers to use low cost pulse-jets on commercial aeroplanes.
So why don't they? Well, the answer is efficiency. Basically a pulsejet engine doesn't have any [efficiency]. The Nazi V1 missile used nearly 600 litres of fuel just to travel a few dozen kilometres across the English channel.
A pulsejet engine is inefficient because the fuel is combusted in a subsonic explosion. This means that the pulsejet operates with a very low compression ratio. An efficient diesel car engine might operate with a compression ratio of 20:1, whereas the pistonless pulsejet engine can only achieve compression ratios of around 2:1.
But what if the explosion were like this…?
[Sound of a detonation explosion]
My ears are slightly ringing. That's the sort of supersonic detonation combustion that you can achieve if you get just the right conditions.
In this type of detonation explosion the compression ratio can reach 100:1, [which is] much higher than a normal jet engine. A pulsejet with this sort of compression ratio is called a pulse detonation engine. If such an engine could be successfully developed then it would be a breakthrough in aircraft efficiency and cost.
And that [could have] important implications for New Zealand. It would allow the air-transportation of goods and tourists (to and from) New Zealand at much lower cost, and using much less carbon dioxide-producing fuel. [In other words, reducing the energy consumption and greenhouse gas emissions for each 'air mile'.]
Dr John Hoke works for the United States Air Force Research Laboratory in Dayton, Ohio. He's the head researcher on their pulse detonation engine development programme. His research team have been testing their newly designed pulse detonation engine on a Rutan Long-EZ aircraft. I asked Dr Hoke how things have been going…
Dr John Hoke:
Well, we're doing basic and applied research here. We're able to detonate most practical fuels, [and] we've done high speed taxi tests with [the Rutan Long-EZ] aircraft with a pulse detonation engine attached. We've not flown that aircraft yet with a pulse detonation engine. We have every intent to do that, but at this point we're still doing research.
So you've successfully managed to achieve detonation combustion in your engine – and therefore a much higher compression ratio than in a pulsejet. What sort of improvement in efficiency has this translated into?
Dr John Hoke:
When you detonate a fuel-air mixture, you're going to get about three to four times improvement in efficiency over what the pulsejets are getting. You also have much higher exhaust gas velocities. So where the pulsejet typically operated at about Mach 0.6 or [Mach] 0.8, the pulse detonation engine is thought to be able to run very efficiently at Mach 2 to [Mach] 4.
Okay… Mach 2 to [Mach] 4 – in other words between two and four times the speed of sound – that's a much faster speed than passenger aircraft operate at today. So would the pulse detonation engine actually be a suitable replacement for the ordinary turbofan jet engines on commercial aircraft?
Dr John Hoke:
The turbofan [engine] is made for lower speed. You wouldn't put a pulse detonation engine on a commercial aircraft because typically they don't go Mach 2 to [Mach] 4. However, when you look at these things, the pulse detonation engine is a constant volume process, and the efficiency of that is inherently higher than a constant pressure process…
… which is the combustion process you'd have in a normal jet aircraft engine…
Dr John Hoke (cont):
… yes. And what's thought for commercial application would be to take this constant volume combustor, and stick it in the middle of one of your turbofans. And then you're talking about potentially a 5 to 27 per cent increase in efficiency of fuel economy.
So by sticking a pulse detonation engine inside a normal jet engine – to replace the combustor – you can get up to a 27 per cent increase in fuel efficiency. In aircraft terms, that's huge!
But what about the case where you actually want to operate a commercial airliner at, say, two or three times the speed of sound, maybe as a replacement for Concorde? Would a straight pulse detonation engine – the sort you're working on now – have an application in this context?
Dr John Hoke:
Potentially, yes. The one thing people point out is the noise. High noise-levels can have an impact on structures and what-not, but to our experience the noise [of our pulse detonation engine] is not a whole lot different than an aircraft on afterburner. I've stood right next to the thing when it's running, and it's loud, but it's acceptable.
Okay, that's quite surprising. I've heard a pulsejet engine, and they are really loud. But you're saying a pulse detonation engine isn't actually that bad?
Dr John Hoke:
Well, you're definitely wearing hearing protection. The sound levels coming out the back of the pulse detonation engine are very directional – so if you're standing down behind the engine you're gonna see some pretty loud noise levels, I think. At the exit of the pulse detonation engine you're talking about 190 to 210 decibels, and I believe your ears start to bleed around 160 [decibels]. But when you're travelling Mach 2 [or] Mach 3 the sound is behind you. I think you have more serious [noise] issues with the aircraft sonic boom.
So talking about a pulse detonation engine in the context of a potential high-speed application [such as] a Concorde replacement – it's so mechanically simple compared to a conventional supersonic aircraft engine – have you got any feel for how much that might reduce cost?
Dr John Hoke:
Our best guess is about one hundred times cheaper. It could potentially be huge.
A hundred times cheaper really would be huge…
So coming back to something you mentioned earlier about running your pulse detonation engine on a variety of fuels – I was wondering if you'd tried it on bioethanol or biodiesel?
Dr John Hoke:
We've almost detonated everything, I'd say. We've done ethanol, we've done gasoline, we've done propane, we've done ethylene… hydrogen is one of my favourite fuels.
We've done aviation gasoline, [and] the jet fuels work fine. The one thing was biodiesel – we haven't done that. But I wouldn't foresee any big issues with that because I don't think the combustion properties differ too much from regular jet fuel.
So when do you see pulse detonation engines being commercialized, and in what initial applications?
Dr John Hoke:
Theoretically the pulse detonation cycle [or] constant volume combustion cycle – however you want to put it – I think has a lot potential. As far as making it practical we still have yet to see how that's gonna all pan out. The thermodynamics says it should be more efficient than the constant pressure combustion [which is intrinsic to] the pulsejet and the gas turbine engine. So I'm very hopeful there.
As far as where it would first be used: it would probably be a pure pulse detonation engine, and it will be probably used for a drone or a missile-type of application – where… it's un-manned and you're looking for a cheap engine and you're looking for fast flight.
Commercially – and this may take off really quickly – it depends on the engine companies and their research budgets. If the hybrid-turbine engine (using our constant volume [pulse detonation engine] combustor)… starts to pan out, that's gonna be a huge cost-saver for the airlines, and that could go very, very quickly. * * * Voiceover:
So Pulse Detonation Engines offer the possibility of significantly reduced fuel consumption for normal sub-sonic commercial aircraft – and even the option of running on biofuels.
But also, perhaps, they may usher in a new generation of lower-cost and more fuel-efficient supersonic aircraft. All of which is good news for a country as dependent on air transport as New Zealand.
Theme music… * * * Further information on pulse detonation engines: Read more about Dr John Hoke's research work into pulse detonation engines on the HYPERLINK “http://www.innssi.com” ISSI website (ISSI are civilian contractors to the HYPERLINK “http://www.wpafb.af.mil/AFRL/” United States Air Force Research Laboratory). Some interesting photographs of the prototype pulse detonation engines can be seen in their HYPERLINK “http://www.innssi.com/pde04.htm” image gallery. Read more about the working principles of the United States Air Force Research Laboratory's pulse detonation engines in the ISSI HYPERLINK “http://www.innssi.com/pde01.htm” FAQ section. Read more about HYPERLINK “http://en.wikipedia.org/wiki/Pulse_detonation_engine” pulse detonation engines (in general) in HYPERLINK “http://en.wikipedia.org” Wikipedia. Read more about Dr Hoke's test-bed aircraft: the HYPERLINK “http://en.wikipedia.org/wiki/Long-EZ” Rutan Long-EZ. Read about HYPERLINK “http://aardvark.co.nz/pjet/howtheywork.shtml” How Pulsejets Work on HYPERLINK “http://en.wikipedia.org/wiki/Bruce_Simpson” Bruce Simpson's excellent HYPERLINK “http://aardvark.co.nz/pjet/” Pulsejet website. Read more about the HYPERLINK “http://en.wikipedia.org/wiki/V-1_flying_bomb” V1 missile in HYPERLINK “http://en.wikipedia.org” Wikipedia.
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Is Body Hacking as Thoroughly Distasteful as it Sounds? | Jan 01, 1900 00:02 HYPERLINK “http://www.publicaddress.net/assets/upload/12413/549886639/PAS_Bodyhacking.mp3” Play the audio for this post MP3, 4.4 MB This episode of Public Address Science was originally broadcast on HYPERLINK “http://www.radiolive.co.nz” Radio Live, 7th April 2007, 2 pm - 3 pm. You can listen to the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page. Further information on body hacking: Read more about body hacking (and body modification in general) in the HYPERLINK “http://wiki.bmezine.com” Body Modification Encyclopaedia. Read more about Quinn Norton, a journalist and body hacking enthusiast, in HYPERLINK “http://www.ambiguous.org” her blog. Quinn has an interesting (and slightly disturbing) slide show on body hacking HYPERLINK “http://www.ambiguous.org/quinn/bodyhacking.html” available here. HYPERLINK “http://www.publicaddress.net/assets/upload/12413/549886639/PAS_Bodyhacking.mp3” \o “Play Audio (MP3, 4.4 MB)” INCLUDEPICTURE “http://www.publicaddress.net/img/southerly/btn_audio.gif” \* MERGEFORMATINET HYPERLINK “http://www.publicaddress.net/print,4115.sm” \o “View as Printable” INCLUDEPICTURE “http://www.publicaddress.net/img/btn_print.gif” \* MERGEFORMATINET HYPERLINK “http://www.publicaddress.net/default,4115.sm” \o “Link to this Post” INCLUDEPICTURE “http://www.publicaddress.net/img/btn_link.gif” \* MERGEFORMATINET HYPERLINK “http://www.publicaddress.net/contact,southerly.sm” \o “Send Feedback to Author” INCLUDEPICTURE “http://www.publicaddress.net/img/btn_reply.gif” \* MERGEFORMATINET HYPERLINK “http://digg.com/submit?phase=2&url=http%3A%2F%2Fwww.publicaddress.net%2Fdefault%2C4115%2Cis_body_hacking_as_thoroughly_distasteful_as_it_sounds.sm&title=Is+Body+Hacking+as+Thoroughly+Distasteful+as+it+Sounds%3F&bodytext=This+episode+of+Public+Address+Science+was+originally+broadcast+on+Radio+Live%2C+7th+April+2007%2C+2+pm+-+3+pm.%0A%0AYou+can+listen+to+the+programme+by+clicking+on+the+%27Play+the+audio+for+this+post%27+link+at+the+top+of+this+page+or+the+%27Audio%27+button+at+the+bottom+of+this+page.” Digg this HYPERLINK “http://www.scoopit.co.nz/submit.php?url=http%3A%2F%2Fwww.publicaddress.net%2Fdefault%2C4115%2Cis_body_hacking_as_thoroughly_distasteful_as_it_sounds.sm” Scoopit! Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)Create this topic(?)http://www.evidenttech.com/applications/quantum-dot-fluor-label.phphttp://www.sciencealert.com.au/news/20070604-14870-2.htmlhttp://www.howstuffworks.com/solar-cell.htmhttp://www.angelfire.com/ak/egel/flatcell.html
Can Thorium Reactors Solve the World's Energy Problems? | Jan 01, 1900 00:01 HYPERLINK “http://www.publicaddress.net/assets/audio/PAS_Thorium_PODCAST_MIX.mp3” Play the audio for this post MP3, 4.8 MB This episode of Public Address Science was originally broadcast on HYPERLINK “http://www.radiolive.co.nz” Radio Live, 31st March 2007, 2 pm - 3 pm. You can listen to the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page. Further information on Thorium reactors: Read more about Thorium reactors in HYPERLINK “http://www.cavendishscience.org/bks/nuc/thrupdat.htm” this addendum to HYPERLINK “http://www.cavendishscience.org/bks/nuc/nuchm2.htm” Walter Scheider's “A serious but not ponderous book about Nuclear Energy”. Quantum Dots - Versatile, Longer Lasting Fluorescent Tags for Biology Research Shortcomings in Traditional Biological Taggants It is of great benefit in many types of biological research and industry to mark microscopic structures (cells, bacteria, etc) with fluorescent materials in order to track their movements and activities within an organism or other medium. Traditionally the favored materials for such applications have been organic dyes, which can be chemically engineered to adhere to a diverse variety of cellular structures. After the dye comes into contact with the proper cellular structure, technicians may use light of a certain wavelength to excite the dye into fluorescence, whereby it emits radiation at a peak wavelength controlled by the chemical nature of the organic dye being used. Limited absorptive and emissive capabilities of organic dyes Unfortunately, many shortcomings exist with this technique, most of them a result of the extremely limited absorptive and emissive capabilities of organic dyes. The first shortcoming is that the peak emission of organic dyes cannot be altered - each dye corresponds to a different molecule with a different pre-set emission wavelength (color) that is set by nature. Therefore, applications that make use of light frequencies that do not correspond to the emission peaks of preexisting organic dyes cannot be performed. The second shortcoming is the narrow absorption pattern of organic dyes. Dyes tend to display absorption peaks that are not always in convenient regions of the spectrum, making the excitation of various organic dyes challenging and costly. The third shortcoming is that of uneven absorption and emission peaks. Organic dyes have a tendency to produce 'shoulders' in the geometry of their emission and absorption peaks, which is a major disadvantage in applications that require Gaussian type emission patterns to work correctly. The last shortcoming is that of stability. The lifetime of organic dyes varies but is generally low relative to that of other tagging mechanisms. Quantum Dots - superior fluorescent properties Evident Technologies is the world's leading producer of quantum dots, which are nanometer sized semiconductor nanocrystals with superior fluorescent properties. Whereas the light emission ranges and possible forms of organic dyes are very limited, quantum dots can be made to emit light at any wavelength in the visible and infrared ranges, and can be inserted almost anywhere, including liquid solution, dyes, paints, epoxies, and sol-gels. Quantum dots can be attached to a variety of surface ligands, and inserted into a variety of organisms for in vivo research. Evident's unique technical capabilities enable all new standards for fluorescent tagging. Quantum Dots - A Superior Biological Taggant Organic Dyes - fixed emissions Organic dye fluorescence is controlled entirely by the molecular bonding properties of each individual dye. Incident radiation absorbed by an organic dye molecule moves electrons into excited states, whereupon they decay and release light radiation. This emission cannot be altered because it corresponds to pre-set excited states of the dye molecule that are inherent to every molecule of that type. Quantum Dots from Evident - tuned to absorb or emit any visible or IR wavelength Evident's special line of quantum dot semiconductors represent a marked increase in performance over standard organic dyes, because they can be tuned to absorb or emit at any visible or infrared wavelength and can be fabricated into a great variety of forms and media, eliminating completely the shortcomings of dyes. These unique abilities of quantum dots are due to their very small size (2-10 nm). At these sizes, quantum mechanics allow semiconductor materials to take on all new traits, including that of a bandgap that can be tuned with the addition or subtraction of only a few atoms to the quantum dot. The small size also allows for incredible flexibility of form, letting phosphors match whatever shape their underlying LED needs to assume. By controlling quantum dots' size, Evident can control their color, allowing our customers to overcome nature's limits. Quantum Dots from Evident - How They Do More Evident's quantum dots operate similarly to traditional semiconductors, but with much greater versatility. When light impinges on quantum dots, it encounters discretized energy bands specific to quantum dots. The discretized nature of quantum dot bands means that the energy separation between the valence and conduction bands (the bandgap) can be altered with the addition or the subtraction of just one atom - making for a size dependent bandgap. Predetermining the size of the QLED's dots would fix the emitted photon wavelength at the appropriate customer-specified color, even if it is not naturally occurring - an ability limited only to dots. In addition, the extremely small size and versatility of form for quantum dots would allow them to be inserted into any medium necessary to accommodate research. Quantum Dot Optical and Spectral Properties The underlying quantum dots within Evident's
have distinctive optical and spectral properties that provide unique properties and benefits for a rich variety of life science applications:
Fluorescence Tunable emission -
have a peak emission wavelengths dependent upon the composition and size of the underlying quantum dots. Currently, peak emission wavelengths are available from 490-620nm in 20nm increments. Peak emission wavelengths from 350nm-480nm, 640nm-720nm, and 800nm-2300nm have been demonstrated.
Narrow bandwidth (Full Width Half Max. e.g. FWHM <30nm) -
emit light within a narrow bell-shaped (Gaussian) spectrum without any shoulders and centered at the peak wavelength. In the visible portion of the spectrum the FWHM is less than 30nm.
Absorption Broadband absorption - In contrast to organic fluorophores that have a narrow absorption spectra,
have the unique property that all light that has a shorter wavelength than the emission wavelength can be absorbed with increasing strength at shorter wavelengths.
Stokes shift - In the visible portion of the spectrum, the peak emission wavelength is shifted from the absorption onset by 15nm. Additionally an excitation source shorter than the emission wavelength can be used. Therefore the peak emission wavelength is effectively independent of the excitation source and the effective stoke shift can be tens to hundreds of nanometers. Brightness
are incredibly bright with large quantum yields, large absorption cross section over a wide bandwidth, and offer the possibility of longer integration times.
Lifetime characteristics/ photo bleaching
are based on inorganic particles that are inherently more photos stable than organic molecules and as such they can survive orders of magnitudes longer than organic fluorescent dyes under intense illumination. have been shown no photodegradation after more than 2 hours of constant illumination.
Fluorescence lifetime The fluorescent lifetime (electronic lifetime) of visibly emitting
have been measured to be 15-20ns independent of the emission wavelength. The fluorescence lifetime is orders of magnitude longer than typical autofluoresence lifetimes and many multiples of typical organic dye lifetimes.
Two photon absorption/ up-conversion Quantum dots have large two photon absorption cross sections that allow for narrowband visible light to be emitted when long wavelength IR lasers are focused on the . Electron microscopy Because
are composed of inorganic semiconductor nanocrystal particles, they can be also be visualized with electron microscopes.
Quantum Dots - A Versatile Research Tool in Life Science Quantum dots offer the advantage of superior absorption/emission characteristics, in addition to flexible form and long lifetime. Evident Technologies offers many advantages to the biological research community towards enabling new and less costly techniques in fluorescent tagging. HYPERLINK “http://www.evidenttech.com/applications/quantum-dot-in-life-sciences.php” \o “Quantum Dots” Quantum Dots - In Life Science Applications [Page 1] HYPERLINK “http://www.evidenttech.com/applications/quantum-dot-biotech-applications.php” \o “Quantum Dots” Quantum Dots - Biotechnology Applications [Page 3] For More Information: HYPERLINK “http://www.evidenttech.com/life_sciences/evitags/quantum-dot-evitag-introduction.php” \o “Quantum Dot ™” - Water Stable Quantum Dots HYPERLINK “http://www.evidenttech.com/life_sciences/protocols/” \o “Quantum Dot
Protocols" Quantum Dot Conjugation Protocols
HYPERLINK “http://www.evidenttech.com/applications/quantum-dot-fluor-label.php” http://www.evidenttech.com/applications/quantum-dot-fluor-label.php Cheaper solar cells HYPERLINK “http://digg.com/submit?phase=2&url=http%3A%2F%2Fwww.sciencealert.com.au%2Fnews%2F20070604-14870-2.html&title=Cheaper%20solar%20cells&topic=general_sciences&bodytext=%3Cblockquote%3E%3Cbr%20/%3ESolar%20cell%20technology%20developed%20by%20the%20Massey%20University%20will%20enable%20New%20Zealanders%20to%20generate%20electricity%20from%20sunlight%20at%20a%2010th%20of%20the%20cost%20of%20current%20silicon-based%20photo-electric%20solar%20cells.%20%3C/blockquote%3E” \t “_blank” INCLUDEPICTURE “http://www.sciencealert.com.au/images/M_images/diggit-icon.jpg” \* MERGEFORMATINET HYPERLINK “http://www.sciencealert.com.au/index2.php?option=com_content&task=emailform&id=14870&itemid=263” \o “E-mail” \t “_blank” INCLUDEPICTURE “http://www.sciencealert.com.au/templates/js_simplicity_sciencealert/images/emailButton.png” \* MERGEFORMATINET Friday, 06 April 2007 HYPERLINK “http://www.massey.ac.nz/” Massey University Solar cell technology developed by the University’s Nanomaterials Research Centre will enable New Zealanders to generate electricity from sunlight at a 10th of the cost of current silicon-based photo-electric solar cells. Dr Wayne Campbell and researchers in the centre have developed a range of coloured dyes for use in dye-sensitised solar cells. The synthetic dyes are made from simple organic compounds closely related to those found in nature. The green dye Dr Campbell (pictured) is synthetic chlorophyll derived from the light-harvesting pigment plants use for photosynthesis. Other dyes being tested in the cells are based on haemoglobin, the compound that give blood its colour. Dr Campbell says that unlike the silicon-based solar cells currently on the market, the 10x10cm green demonstration cells generate enough electricity to run a small fan in low-light conditions – making them ideal for cloudy climates. The dyes can also be incorporated into tinted windows that trap to generate electricity. He says the green solar cells are more environmentally friendly than silicon-based cells as they are made from titanium dioxide – a plentiful, renewable and non-toxic white mineral obtained from New Zealand’s black sand. Titanium dioxide is already used in consumer products such as toothpaste, white paints and cosmetics. “The refining of pure silicon, although a very abundant mineral, is energy-hungry and very expensive. And whereas silicon cells need direct sunlight to operate efficiently, these cells will work efficiently in low diffuse light conditions,” Dr Campbell says. “The expected cost is one 10th of the price of a silicon-based solar panel, making them more attractive and accessible to home-owners.” The Centre’s new director, Professor Ashton Partridge, says they now have the most efficient porphyrin dye in the world and aim to optimise and improve the cell construction and performance before developing the cells commercially. “The next step is to take these dyes and incorporate them into roofing materials or wall panels. We have had many expressions of interest from New Zealand companies,” Professor Partridge says. He says the ultimate aim of using nanotechnology to develop a better solar cell is to convert as much sunlight to electricity as possible. “The energy that reaches earth from sunlight in one hour is more than that used by all human activities in one year”. The solar cells are the product of more than 10 years research funded by the Foundation for Research, Science and Technology. HYPERLINK “http://www.sciencealert.com.au/news/20070604-14870-2.html” http://www.sciencealert.com.au/news/20070604-14870-2.html Photo-Voltaic (PV) - PV panels convert sunlight into electricity. You've probably seen calculators that have solar cells - calculators that never need batteries, and in some cases don't even have an off button. As long as you have enough light, they seem to work forever. You may have seen larger solar panels - on emergency road signs or call boxes, on buoys, even in parking lots to power lights. Although these larger panels aren't as common as solar powered calculators, they're out there, and not that hard to spot if you know where to look. You have also seen solar cell arrays on satellites, where they are used to power the electrical systems. You have probably also been hearing about the “solar revolution” for the last 20 years - the idea that one day we will all use free electricity from the sun. This is a seductive promise - on a bright, sunny day the sun shines approximately 1,000 watts of energy per square meter of the planet's surface, and if we could collect all of that energy we could easily power our homes and offices for free. HYPERLINK “http://www.howstuffworks.com/solar-cell.htm” http://www.howstuffworks.com/solar-cell.htm Residential solar electric power systems offer an excellent alternative for people who are looking for back-up power or stand alone power systems. Solar electric systems are ideal for those who choose to live beyond the reach of conventional electric power. Solar electric power is clean, affordable and requires very little maintenance. More than 50,000 families in the U.S. have chosen solar power for their electric systems. Throughout the world, many thousands of people depend on solar electricity as their primary source of power. If you choose to live more than a third of a mile from power, photovoltaic's can be a cost effective alternative for you. when you factor in the cost of line extensions and monthly electric bills, solar electricity is often the preferred alternative. Other options are wind, hydro, or gas generators or some combination of the above. Home Made PV Cells - HYPERLINK “http://www.angelfire.com/ak/egel/flatcell.html” http://www.angelfire.com/ak/egel/flatcell.html An Experts View: I found my views on this subject to be extremely controversial. My response to the government solar energy subsidies proposal is the view that the solar energy market needs to mature naturally, without subsidies, to make the technology a cost effective and viable energy solution for the future. My recollection and experience with the solar energy rebates and initiatives that ended in the mid 1980's remains clear. When 50% of the solar energy systems were subsidized, unethical players entered the solar energy field. Sales were easy and substandard installations become commonplace. Keep in mind that many holes are required to be drilled into a homeowner’s roof to properly and structurally attach solar panels. Long term post installation support and warranties need to be secure. When the solar business marketing relied solely on rebate programs, the market crashed when funds were no longer available. This hurt the manufacturers, suppliers and the consumers as well as giving solar energy a black eye. The highest quality manufacturers of solar panels in the 1980’s, Grumman and Colt, went out of the solar business. The boom was over and few businesses remained to provide for service and repair.
http://www.redrok.com/electron.htm#led3http://sorrel.humboldt.edu/~serc/facilities.htmlhttp://www.clean-power.com/research/microgrids/HistoricOpportunity.pdfCreate this topic(?)http://www.attra.org/attra-pub/solar-gh.html
GO Solar Company is one of the few businesses that remains in the field to this time. We have watched the resurgence of the market as solar panels become more efficient and less expensive. The challenging process has been to find practical applications for solar energy that are viable and cost effective. GO Solar Company is currently installing solar powered landscape lighting for the City of Santa Monica. We are using solar power to illuminate palm trees on Wilshire Blvd. and large ficus trees on 5th St. GO Solar Company feels these types of solar installations benefit the public and are a good use of solar power. Utilizing solar power to illuminate government buildings, city properties, bus stop shelters, highway signs and call boxes are practical and truly cost effective. The public will become aware of the positive aspects of solar power and will become receptive to its use. Manufacturers will spend money on research and development to further the efficiencies of solar components rather than promoting expensive marketing programs aimed at collecting subsidies. Perhaps grants and monetary incentives to manufacturers for research and development to produce a more efficient panel may be a more meaningful alternative to promoting solar energy. When solar panels become less costly and more efficient the use of solar energy will proliferate without the constant lobbying to keep the subsidies in place.
Graham F. Owen President GO Solar Company ph: INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/cb_transparent_l.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/famfamfam/us.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/arrow.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET 818-566-6870 INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/cb_transparent_r.gif” \* MERGEFORMATINET fx: INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/cb_transparent_l.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/famfamfam/us.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/arrow.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/space.gif” \* MERGEFORMATINET 818-566-6879 INCLUDEPICTURE “chrome:skype_ff_toolbar_win/content/cb_transparent_r.gif” \* MERGEFORMATINET email: HYPERLINK “mailto:email@example.com” firstname.lastname@example.org website: HYPERLINK “http://www.solarexpert.com” www.solarexpert.com LED Solar Tracker Duane C. Johnson < HYPERLINK “mailto:email@example.com” firstname.lastname@example.org> has been working on a simplified solar tracker. It uses LEDs as photo sensors. See: HYPERLINK “http://www.redrok.com/electron.htm” \l “led3” http://www.redrok.com/electron.htm#led3 HYPERLINK “http://www.redrok.com/images/ledshex3.jpg” INCLUDEPICTURE “http://www.green-trust.org/ledshex3_small.jpg” \* MERGEFORMATINET Info: The Schatz Solar Hydrogen Project The Schatz solar hydrogen project was initiated in the fall of 1989 with the goal of demonstrating that solar hydrogen is a reliable and abundant energy source that is ready for use today. This full-time, automatic standalone energy system takes advantage of the solar hydrogen cycle to power the air compressor that aerates the aquarium at Humboldt State University's Telonicher Marine lab in Trinidad, California. How it works This is how the system works: sunlight hits the photovoltaic panels, which convert solar energy into electricity. This electricity is used in two ways: it powers the air compressor directly, and it powers an electrolyzer. In the electrolyzer the electricity splits water into hydrogen and oxygen. The oxygen gas is vented to the atmosphere and the hydrogen gas is stored in tanks behind the lab. At night or when the clouds are thick, the system automatically shifts to fuel cell operation. The fuel cell directly converts chemical energy into electricity by combining the stored hydrogen with oxygen from the air. This shortcuts the usual way of obtaining electricity from a fuel, which involves burning the fuel, using the heat to boil water, using the steam to turn a turbine, and using the turbine to turn a generator. The direct conversion process of a fuel cell is quiet and efficient and its only byproduct is pure water. In this way, water and sunlight, both natural and abundant, are used in a cycle to produce power. No fossil fuels are used; no pollution is created. And because hydrogen stores solar energy, the fish in the marine lab enjoy solar air bubbles twenty-four hours a day. HYPERLINK “http://sorrel.humboldt.edu/%7Eserc/facilities.html” http://sorrel.humboldt.edu/~serc/facilities.html Research: “The Potential Market for Photovoltaics and Other Distributed Resources in Rural Electric Cooperatives,” by Tom Hoff (Clean Power Research) and Matt Cheney (Utility Photovoltaic Group), forthcoming in Energy Journal, 2000. See prepublication draft online at HYPERLINK “http://www.clean-power.com/research/microgrids/HistoricOpportunity.pdf” http://www.clean-power.com/research/microgrids/HistoricOpportunity.pdf
” Agricultural Applications of Photovoltaic Systems,“ chapter in analytic series “Solar Energy in Agriculture,” edited by Blaine F. Parker. Appeared in Energy in World Agriculture, Amsterdam : Elsevier. 1991. v. 4 p. 115-155.
Applications for Photovoltaic Power for Rural Electric Systems, by Jerry L. Anderson, Rollan G. Skinner, and
E. Stetson. Paper presented before
the American Society of Agricultural Engineers, Summer 1991. Abstract: Previous applications of solar energy for water pumping are briefly reviewed. Photovoltaics [PV's] have been most successful in installations for small loads (1 kW or less). Costs for PV arrays are now abut $6.00 per watt. Electric utilities serving small, remote rural loads are providing PV's as a cost effective energy source. As more applications are used, the cost is expected to decrease and the reliability to increase.
Solar Greenhouses Horticulture Resource List, by Lane Greer, Appropriate Technology Transfer for Rural Areas (ATTRA) March 1999. See HYPERLINK “http://www.attra.org/attra-pub/solar-gh.html” http://www.attra.org/attra-pub/solar-gh.html .
Designing and Implementing a Photovoltaic Tariff for a Rural Electric Cooperative, by Paul Bony. Paper presented at Solar '94, conference of the American Solar Energy Society.
Rural Energy Alternatives Project, by Lloyd Hoffstatter, et al, New York State Energy Office. Paper presented at Solar '93, conference of the American Solar Energy Society.
R&C Solar/Wind Powered House Contact Wayne and Barbara at HYPERLINK “mailto:email@example.com” firstname.lastname@example.org INCLUDEPICTURE “http://www.green-trust.org/house.JPG” \* MERGEFORMATINET Introduction This web site describes all the fun my wife and I have had building a solar-powered home on remote property. Before embarking on this adventure, we found it really helpful to read the stories of others, and to learn from their experience. So we wanted to return the favor. The goal is not to dwell on the technical stuff, but to give you a feel for planning, building, and living in this home. We hope that some readers will find that useful. Be warned, there’s some straight talk, and some of it isn't politically correct. If there’s positive feedback, we’ll improve the site as time allows. The site is about 20 pages of text, includes many links, and some photos where appropriate (click on the thumbnail photos to see a larger version, and then use your browser's back button to return). There’s a little advice and editorializing mixed in. The information is detailed enough for beginners, and it's arranged roughly in the order of construction. The links at the top are for sections, some of which have multiple pages. The links at the bottom will advance you to the next page. There is a single page version if you want the whole site on one long page. HYPERLINK “http://users.rraz.net/wmbjk/” http://users.rraz.net/wmbjk/)
Chicago School Enters New Era In Energy And Education Chicago, Illinois . . . 3 March 2000 . . . The City of Chicago, Commonwealth Edison, the Chicago Public Schools, the United States Department of Energy, the International Brotherhood of Electrical Workers (Local #134), and the Illinois Department of Commerce and Community Affairs announced today that they have collaborated in providing Chicago’s Reilly Elementary School with a 10 kilowatt solar (photovoltaic or PV) electric rooftop system. The system was provided by Spire Solar Chicago, a PV module manufacturing and systems business that recently located in Chicago as a result of collaboration between Spire Corporation of Bedford, Massachusetts, the City of Chicago, and . HYPERLINK “http://www.spirecorp.com/” http://www.spirecorp.com/)
Grid Connected PV… What's It Worth? by James R. Udall HYPERLINK “http://www.aspencore.org/Solar/grid.htm” http://www.aspencore.org/Solar/grid.htm HYPERLINK “http://www.electricboat.com/” Electric Boat Association of the Americas The Electric Boat Association of the Americas is an organization of individuals with an interest in electric-powered boating. Most EBAA members reside in the United States and Canada, but the membership includes a few individuals in the Caribbean, Central and South America. We even have members in Australia and Africa. We welcome new members from anywhere in the world Since electrically propelled vessels do not put hydrocarbons in the air, do not put oil and other pollutants in the water and don't make loud noises, many EBAA members have a keen interest in the positive environmental aspects of electric propulsion. Other members simply like the idea of clean, silent, inexpensive boating. Low maintenance and reliability are appealing to all the members. HYPERLINK “http://www.solarhome.org/pv.htm” http://www.solarhome.org/pv.htm Solar photovoltaic cells can generate electricity from the sun's rays. The HYPERLINK “http://www.nrel.gov/research/pv/tapsun.html” National Renewable Energy Laboratory describes many possible uses for photovoltaic electrical generation, including powering one's home. Solar electric houses today are designed for three types of operation: Stand alone or ” HYPERLINK “http://www.green-trust.org/pv.htm” \l “offgrid” Off grid“, HYPERLINK “http://www.green-trust.org/pv.htm” \l “interactive” Grid interactive with stand alone capability, and HYPERLINK “http://www.green-trust.org/pv.htm” \l “fully” Fully utility interactive. HYPERLINK “http://www.solideas.com/” http://www.solideas.com/ Our latest development is a solar cell kit which is used for instructional purposes in universities and classrooms. We are presently highlighting the release of the HYPERLINK “http://www.solideas.com/solrcell/cellkit.html” Nanocrystalline Solar Cell Kit: Re-creating Photosynthesis. The solar cell kit is a teaching tool which uses natural dyes extracted from berries (anthocyanins) and non-toxic materials to create a solar cell that lasts only a few months, but can teach students about sustainable energy production. HYPERLINK “http://www.cnn.com/NATURE/9910/27/solar.cells.enn/index.html” http://www.cnn.com/NATURE/9910/27/solar.cells.enn/index.html Terrestrial solar cell efficiency has taken another leap forward, converting a record 32.3 percent of the sun's energy into useable power — more than doubling current efficiency ratings. HYPERLINK “http://www.geocities.com/solarliving/” Solar Living Web Pictures and Bio's of off-gridders HYPERLINK “http://rredc.nrel.gov/solar/codes_algs/PVWATTS/pvwatts_index.html” A Performance Calculator for Grid-Connected PV Systems PVWATTS calculates electrical energy produced by a grid-connected photovoltaic (PV) system. Currently, PVWATTS can be used for locations within the United States and its territories, which are accessible through links on the HYPERLINK “http://www.green-trust.org/pv.htm” \l “map” U.S. map located below. Researchers at the National Renewable Energy Laboratory developed PVWATTS to permit non-experts to quickly obtain performance estimates for grid-connected PV systems. Viva Solar Inc. is a Canadian incorporated company with head offices in Toronto and production facilities in Krasnodon, a city in Southern Russia where major developments in solar science were made. The company has been manufacturing under Canadian supervision monocrystal Silicon solar photovoltaic cells and modules since 1990. The production facility has an annual capacity of 800 KWp and employs more than 70 skilled workers. The important feature of this production facility lies in its versatility and flexibility allowing for rapid change of the product. Therefore this production approach is particularly attractive for small series manufacturing. Numerous patents and know-how are used in Viva Solar production technology. Viva Solar PV cells and modules are known for high durability, stable power output and an elegant appearance which does not degrade with time. The research and development department of the company is constantly improving the PV cells and the modules technical parameters. The minimum commercial guaranteed efficiency of Viva Solar' cells is currently 13% with majority of the cells having 14-16% efficiency. Another feature of R&D is a further development of double-sided cells and modules able to produce power from both sides thereby enhancing overall power output. The company employs world class scientists, highly qualified engineers, technicians and workers with extensive experience in the solar industry of 10 to 35 years. We are proud that our staff members are amongst the pioneers of world and Russian solar industry. The company has export solar cells and modules for 10 years through an extended network of distributors in many countries under our own and OEM trade marks. We strongly believe in the bright prospects of the solar industry . Our mission is to bring solar energy to the world marketplace and to make life sustainable for all people. HYPERLINK “http://www.vivasolar.com” http://www.vivasolar.com)
Dealers: HYPERLINK “http://www.solarexpert.com” http://www.solarexpert.com HYPERLINK “http://www.backwoodssolar.com/” http://www.backwoodssolar.com/ HYPERLINK “http://www.windsun.com/” http://www.windsun.com/ Solar electric power is an alternative energy source that is cleaner, more reliable, longer lasting and environmentally safer than nuclear and fossil fuels. Solar power systems are practical and available now. Get renewable energy equipment through the PV Bulk Buy and save money. SOLutions in Solar Electricity offers PV modules and inverters at “better than best prices” for your solar electricity needs. HYPERLINK “http://www.solarsolar.com/” http://www.solarsolar.com/ HYPERLINK “http://rredc.nrel.gov/solar/codes_algs/PVWATTS/” http://mhs-solar.com/
Take care of personal protection (fine dusk mask, safety glasses, laboratory coat, gloves). Keep the work area where dyes are used clean ! Clean up (well !) after preparing a solution. When dye is spilled (both powder and solution) clean up immediately. Keep containers of solvents and dye solutions closed. Label containers clearly with the name of the dye and solvent and its concentration. Wash hands after handling laser dyes/solutions. Do not eat, drink, smoke or store food or beverages in work areas where dyes are in use. Personal protective equipment Use a fine dusk mask. Use a laboratory fume hood or glove box. Use safety eye wear. Use a laboratory coat. Use impervious (butyl) gloves when handling dye solutions.