Does Car-Mounted Solar Make Sense?
Researchers consider plug-in hybrids charged by stationary solar arrays a better bet.
Worth the cost?: The solar roof glued to this Prius combines 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. The panel, which can add five miles to the car’s 50-mile electric-only range, is available for $3,500 from Solar Electrical Vehicles. Something similar could soon be factory-installed by Toyota.
Solar Electrical Vehicles
Last week, the Japanese newspaper Nikkei caused a buzz by reporting that a redesigned Toyota Prius, to be released next year, will come equipped with solar panels. Toyota spokespeople will neither confirm nor deny the report, but several companies already offer solar roof kits for the Prius, and researchers at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL), in Golden, CO, have been testing one on a Prius modified to plug into the electrical grid. Their conclusion: for the time being, plug-in hybrids charged from stationary solar arrays are a more efficient and cheaper option.
The idea of car-mounted solar cells is not new: in the early 1990s, Mazda offered its 929 luxury sedan with optional solar cells in the glass sunroof to drive fans that removed hot air from the car. But most onboard solar systems to date have cost several thousand dollars while generating less than 100 watts of energy, improving a vehicle's fuel efficiency by just a few percent. "I think it's more a marketing gimmick," says Andrew Frank, a plug-in hybrid pioneer at the University of California, Davis, and chief technology officer for UC-Davis hybrid-vehicle spinoff Efficient Drivetrains. "It takes kilowatts to really drive the car."
The limited surface area of the car roof is one constraint on the panels' power production. Another is that they can't be tilted perpendicular to the sun for optimal energy capture, unlike most photovoltaics on buildings or in solar farms, which either track the sun or are installed with a fixed southward tilt.
The NREL researchers tested the extent of these limitations by equipping the plug-in Prius they built earlier this year with the most powerful rooftop solar panel on the market. Assembled by Solar Electrical Vehicles, based in Westlake Village, CA, the panel completely covers the Prius roof, wiring together 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. However, NREL senior engineer Tony Markel says that his group's tests suggest that the output will max out at closer to 165 watts under normal use.
That's a meager improvement compared with the boost that the plug-in Prius gets from its extra lithium-ion battery. Markel says that the six kilowatt-hours of electricity available from the fully charged battery enable NREL's Prius to get about 100 miles per gallon in the first 50 miles of driving--more than double the fuel efficiency of a standard Prius. Put another way, the overnight charging should take the car about 50 miles in light-duty driving. Markel says that NREL has yet to quantify the solar panel's additional impact, but that the five hours of good sunlight the car sees on an average day would give it an electrical output of at most 0.825 kilowatt-hours. The system would probably boost the plug-in's fuel efficiency for the first 50 miles from 100 to 105 miles per gallon, he says.
Solar Cells Use Nanoparticles to Capture More Sunlight
Optical antennas could help solar cells produce more energy.
Solar antenna: The square at the center is an array of test solar cells being used to evaluate a coating that contains metallic nanoantennas tuned to the solar spectrum.
Brongersma lab, Stanford
Inexpensive thin-film solar cells aren't as efficient as conventional solar cells, but a new coating that incorporates nanoscale metallic particles could help close the gap. Broadband Solar, a startup spun out of Stanford University late last year, is developing coatings that increase the amount of light these solar cells absorb.
Based on computer models and initial experiments, an amorphous silicon cell could jump from converting about 8 percent of the energy in light into electricity to converting around 12 percent. That would make such cells competitive with the leading thin-film solar cells produced today, such as those made by First Solar, headquartered in Tempe, AZ, says Cyrus Wadia, codirector of the Cleantech to Market Program in the Haas School of Business at the University of California, Berkeley. Amorphous silicon has the advantage of being much more abundant than the materials used by First Solar. The coatings could also be applied to other types of thin-film solar cells, including First Solar's, to increase their efficiency.
Broadband believes its coatings won't increase the cost of these solar cells because they perform the same function as the transparent conductors used on all thin-film cells and could be deposited using the same equipment.
Broadband's nanoscale metallic particles take incoming light and redirect it along the plane of the solar cell, says Mark Brongersma, professor of materials science and engineering at Stanford and scientific advisor to the company. As a result, each photon takes a longer path through the material, increasing its chances of dislodging an electron before it can reflect back out of the cell. The nanoparticles also increase light absorption by creating strong local electric fields.
The particles, which are essentiallynanoscale antennas, are very similar to radio antennas, says Brongersma. They're much smaller because the wavelengths they interact with are much shorter than radio waves. Just as conventional antennas can convert incoming radio waves into an electrical signal and transmit electrical signals as radio waves, these nanoantennas rely on electrical interactions to receive and transmit light in the optical spectrum.
Their interaction with light is so strong because incoming photons actually couple to the surface of metal nanoparticles in the form of surface waves called plasmons. These so-called plasmonic effects occur in nanostructures made from highly conductive metals such as copper, silver, and gold. Researchers are taking advantage of plasmonic effects to miniaturizeoptical computers, and to create higher-resolution light microscopes and lithography. Broadband is one of the first companies working to commercialize plasmonic solar cells.
Flexible Silicon Solar Cells
Thin but efficient solar cells use one-tenth the silicon of conventional cells.
Flexing silicon’s power: Arrays of tiny silicon solar cells like the one in this photograph are assembled using a transfer-printing technique. These arrays are as efficient as conventional solar cells, which are bulky and rigid. Each microcell in the array is about 1.5 millimeters long and 15 micrometers thick.
John Rogers
Conventional solar cells are bulky and rigid, but building lightweight, flexible cells has come with trade-offs in efficiency and robustness. A new method for making flexible arrays of tiny silicon solar cells could produce devices that don't suffer these trade-offs. Arrays of these microcells are as efficient as conventional solar panels and may be cheaper to manufacture because they use significantly less silicon. The tiny solar cells could be incorporated into, among other applications, window tinting, and they might be used to power a car's air conditioner and GPS.
Researchers led by John Rogers, a professor of materials science and engineering at the University of Illinois in Urbana-Champaign, used a combination of etching and transfer printing to create arrays of silicon cells that are one-tenth the thickness of conventional cells. They demonstrated multiple possible designs for solar panels incorporating the microcells, including dense arrays flexible enough to bend around a pencil. "You could roll them up like a carpet, transport them in a van, and unfurl them onto a rooftop," Rogers says.
The process builds on techniques for making flexible electronics that Rogers has been developing over the past few years. First, the Illinois researchers etch bars about 1.5 millimeters long, 50 micrometers wide, and 15 micrometers thick from a wafer of monocrystalline silicon. They use a stamp made of a soft polymer to pick up the microbars and place them on a substrate, which may be glass or a flexible plastic, and then fabricate interconnects. Rogers found that a cell thickness of 15 to 20 micrometers struck a good balance: thin enough to be flexible, but thick enough to be mechanically stable and efficient. Conventional solar cells use a layer of silicon 150 to 200 micrometers thick.
Arrays of the cells have about a 12 percent efficiency. The Illinois researchers increased the arrays' power output by about two and half times by adding concentrators in the form of a layer of cylindrical microlenses. The best solar cells on the market convert more than 20 percent of the sunlight that falls on them into energy.
"This is a nice start at using silicon wafers more efficiently," says Howard Branz, principal scientist in the silicon materials and devices group at the National Renewable Energy Laboratory, in Golden, CO. With their transfer-printing approach, says Branz, Rogers and his group have for the first time demonstrated how such thin cells could be manufactured on large areas.
Toward Cheaper, Robust Solar Cells
Researchers are working on solar cells that use a novel organic dye.
Making solar cheaper: Dye-sensitized solar cells, which are cheaper than silicon cells, consist of dye-coated titanium dioxide nanoparticles immersed in an electrolyte solution, which is sandwiched between glass plates. A new combination of electrolyte and dye promises to make these solar cells even cheaper and more robust. Key to the innovation is an organic dye molecule.
Alex Agrios, Northwestern University
Cheap and easy-to-make dye-sensitized solar cells are still in the early stages of commercial production. Meanwhile, their inventor, Michael Gratzel, is working on more advanced versions of them. In a paper published in the online edition of Angewandte Chemie, Gratzel, a chemistry professor at the École Polytechnique Fédérale de Lausanne in Switzerland, presents a version of dye-sensitized cells that could be more robust and even cheaper to make than current versions.
Dye-sensitized solar cells consist of titanium oxide nanocrystals that are coated with light-absorbing dye molecules and immersed in an electrolyte solution, which is sandwiched between two glass plates or embedded in plastic. Light striking the dye frees electrons and creates "holes"--the areas of positive charge that result when electrons are lost. The semiconducting titanium dioxide particles collect the electrons and transfer them to an external circuit, producing an electric current.
These solar cells are cheaper to make than conventional silicon photovoltaic panels. In principle, they could be used to make power-generating windows and building facades, and they could even be incorporated into clothing. (See "Window Power" and "Solar Cells for Cheap.") A Lowell, MA-based company called Konarka is manufacturing dye-sensitized solar cells in a limited quantity. But the technology still has room for improvement In existing versions of the solar cells, the electrolyte solution uses organic solvents. When the solar cells reach high temperatures, the solvent can evaporate and start to leak out. Researchers are now looking at a type of material that may make a better electrolyte: ionic liquids, which are currently used as industrial solvents. These liquids do not evaporate at solar-cell operating temperatures. "Ionic liquids are less volatile and more robust," says Bruce Parkinson, a chemistry professor at Colorado State University.
New dyes are also being investigated. In commercial cells, the dyes are made of the precious metal ruthenium. But researchers have recently started to consider organic molecules as an alternative. "Organic dyes will become important because they can be cheaply made," Gratzel says. In the long run, they might also be more abundant than ruthenium
Does Car-Mounted Solar Make Sense?
Researchers consider plug-in hybrids charged by stationary solar arrays a better bet.
Worth the cost?: The solar roof glued to this Prius combines 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. The panel, which can add five miles to the car’s 50-mile electric-only range, is available for $3,500 from Solar Electrical Vehicles. Something similar could soon be factory-installed by Toyota.
Solar Electrical Vehicles
Last week, the Japanese newspaper Nikkei caused a buzz by reporting that a redesigned Toyota Prius, to be released next year, will come equipped with solar panels. Toyota spokespeople will neither confirm nor deny the report, but several companies already offer solar roof kits for the Prius, and researchers at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL), in Golden, CO, have been testing one on a Prius modified to plug into the electrical grid. Their conclusion: for the time being, plug-in hybrids charged from stationary solar arrays are a more efficient and cheaper option.
The idea of car-mounted solar cells is not new: in the early 1990s, Mazda offered its 929 luxury sedan with optional solar cells in the glass sunroof to drive fans that removed hot air from the car. But most onboard solar systems to date have cost several thousand dollars while generating less than 100 watts of energy, improving a vehicle's fuel efficiency by just a few percent. "I think it's more a marketing gimmick," says Andrew Frank, a plug-in hybrid pioneer at the University of California, Davis, and chief technology officer for UC-Davis hybrid-vehicle spinoff Efficient Drivetrains. "It takes kilowatts to really drive the car."
The limited surface area of the car roof is one constraint on the panels' power production. Another is that they can't be tilted perpendicular to the sun for optimal energy capture, unlike most photovoltaics on buildings or in solar farms, which either track the sun or are installed with a fixed southward tilt.
The NREL researchers tested the extent of these limitations by equipping the plug-in Prius they built earlier this year with the most powerful rooftop solar panel on the market. Assembled by Solar Electrical Vehicles, based in Westlake Village, CA, the panel completely covers the Prius roof, wiring together 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. However, NREL senior engineer Tony Markel says that his group's tests suggest that the output will max out at closer to 165 watts under normal use.
That's a meager improvement compared with the boost that the plug-in Prius gets from its extra lithium-ion battery. Markel says that the six kilowatt-hours of electricity available from the fully charged battery enable NREL's Prius to get about 100 miles per gallon in the first 50 miles of driving--more than double the fuel efficiency of a standard Prius. Put another way, the overnight charging should take the car about 50 miles in light-duty driving. Markel says that NREL has yet to quantify the solar panel's additional impact, but that the five hours of good sunlight the car sees on an average day would give it an electrical output of at most 0.825 kilowatt-hours. The system would probably boost the plug-in's fuel efficiency for the first 50 miles from 100 to 105 miles per gallon, he says.
Solar Cells Use Nanoparticles to Capture More Sunlight
Optical antennas could help solar cells produce more energy.
Solar antenna: The square at the center is an array of test solar cells being used to evaluate a coating that contains metallic nanoantennas tuned to the solar spectrum.
Brongersma lab, Stanford
Inexpensive thin-film solar cells aren't as efficient as conventional solar cells, but a new coating that incorporates nanoscale metallic particles could help close the gap. Broadband Solar, a startup spun out of Stanford University late last year, is developing coatings that increase the amount of light these solar cells absorb.
Based on computer models and initial experiments, an amorphous silicon cell could jump from converting about 8 percent of the energy in light into electricity to converting around 12 percent. That would make such cells competitive with the leading thin-film solar cells produced today, such as those made by First Solar, headquartered in Tempe, AZ, says Cyrus Wadia, codirector of the Cleantech to Market Program in the Haas School of Business at the University of California, Berkeley. Amorphous silicon has the advantage of being much more abundant than the materials used by First Solar. The coatings could also be applied to other types of thin-film solar cells, including First Solar's, to increase their efficiency.
Broadband believes its coatings won't increase the cost of these solar cells because they perform the same function as the transparent conductors used on all thin-film cells and could be deposited using the same equipment.
Broadband's nanoscale metallic particles take incoming light and redirect it along the plane of the solar cell, says Mark Brongersma, professor of materials science and engineering at Stanford and scientific advisor to the company. As a result, each photon takes a longer path through the material, increasing its chances of dislodging an electron before it can reflect back out of the cell. The nanoparticles also increase light absorption by creating strong local electric fields.
The particles, which are essentiallynanoscale antennas, are very similar to radio antennas, says Brongersma. They're much smaller because the wavelengths they interact with are much shorter than radio waves. Just as conventional antennas can convert incoming radio waves into an electrical signal and transmit electrical signals as radio waves, these nanoantennas rely on electrical interactions to receive and transmit light in the optical spectrum.
Their interaction with light is so strong because incoming photons actually couple to the surface of metal nanoparticles in the form of surface waves called plasmons. These so-called plasmonic effects occur in nanostructures made from highly conductive metals such as copper, silver, and gold. Researchers are taking advantage of plasmonic effects to miniaturizeoptical computers, and to create higher-resolution light microscopes and lithography. Broadband is one of the first companies working to commercialize plasmonic solar cells.
Flexible Silicon Solar Cells
Thin but efficient solar cells use one-tenth the silicon of conventional cells.
Flexing silicon’s power: Arrays of tiny silicon solar cells like the one in this photograph are assembled using a transfer-printing technique. These arrays are as efficient as conventional solar cells, which are bulky and rigid. Each microcell in the array is about 1.5 millimeters long and 15 micrometers thick.
John Rogers
Conventional solar cells are bulky and rigid, but building lightweight, flexible cells has come with trade-offs in efficiency and robustness. A new method for making flexible arrays of tiny silicon solar cells could produce devices that don't suffer these trade-offs. Arrays of these microcells are as efficient as conventional solar panels and may be cheaper to manufacture because they use significantly less silicon. The tiny solar cells could be incorporated into, among other applications, window tinting, and they might be used to power a car's air conditioner and GPS.
Researchers led by John Rogers, a professor of materials science and engineering at the University of Illinois in Urbana-Champaign, used a combination of etching and transfer printing to create arrays of silicon cells that are one-tenth the thickness of conventional cells. They demonstrated multiple possible designs for solar panels incorporating the microcells, including dense arrays flexible enough to bend around a pencil. "You could roll them up like a carpet, transport them in a van, and unfurl them onto a rooftop," Rogers says.
The process builds on techniques for making flexible electronics that Rogers has been developing over the past few years. First, the Illinois researchers etch bars about 1.5 millimeters long, 50 micrometers wide, and 15 micrometers thick from a wafer of monocrystalline silicon. They use a stamp made of a soft polymer to pick up the microbars and place them on a substrate, which may be glass or a flexible plastic, and then fabricate interconnects. Rogers found that a cell thickness of 15 to 20 micrometers struck a good balance: thin enough to be flexible, but thick enough to be mechanically stable and efficient. Conventional solar cells use a layer of silicon 150 to 200 micrometers thick.
Arrays of the cells have about a 12 percent efficiency. The Illinois researchers increased the arrays' power output by about two and half times by adding concentrators in the form of a layer of cylindrical microlenses. The best solar cells on the market convert more than 20 percent of the sunlight that falls on them into energy.
"This is a nice start at using silicon wafers more efficiently," says Howard Branz, principal scientist in the silicon materials and devices group at the National Renewable Energy Laboratory, in Golden, CO. With their transfer-printing approach, says Branz, Rogers and his group have for the first time demonstrated how such thin cells could be manufactured on large areas.
Does Car-Mounted Solar Make Sense?
Researchers consider plug-in hybrids charged by stationary solar arrays a better bet.
Worth the cost?: The solar roof glued to this Prius combines 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. The panel, which can add five miles to the car’s 50-mile electric-only range, is available for $3,500 from Solar Electrical Vehicles. Something similar could soon be factory-installed by Toyota.
Solar Electrical Vehicles
Last week, the Japanese newspaper Nikkei caused a buzz by reporting that a redesigned Toyota Prius, to be released next year, will come equipped with solar panels. Toyota spokespeople will neither confirm nor deny the report, but several companies already offer solar roof kits for the Prius, and researchers at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL), in Golden, CO, have been testing one on a Prius modified to plug into the electrical grid. Their conclusion: for the time being, plug-in hybrids charged from stationary solar arrays are a more efficient and cheaper option.
The idea of car-mounted solar cells is not new: in the early 1990s, Mazda offered its 929 luxury sedan with optional solar cells in the glass sunroof to drive fans that removed hot air from the car. But most onboard solar systems to date have cost several thousand dollars while generating less than 100 watts of energy, improving a vehicle's fuel efficiency by just a few percent. "I think it's more a marketing gimmick," says Andrew Frank, a plug-in hybrid pioneer at the University of California, Davis, and chief technology officer for UC-Davis hybrid-vehicle spinoff Efficient Drivetrains. "It takes kilowatts to really drive the car."
The limited surface area of the car roof is one constraint on the panels' power production. Another is that they can't be tilted perpendicular to the sun for optimal energy capture, unlike most photovoltaics on buildings or in solar farms, which either track the sun or are installed with a fixed southward tilt.
The NREL researchers tested the extent of these limitations by equipping the plug-in Prius they built earlier this year with the most powerful rooftop solar panel on the market. Assembled by Solar Electrical Vehicles, based in Westlake Village, CA, the panel completely covers the Prius roof, wiring together 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. However, NREL senior engineer Tony Markel says that his group's tests suggest that the output will max out at closer to 165 watts under normal use.
That's a meager improvement compared with the boost that the plug-in Prius gets from its extra lithium-ion battery. Markel says that the six kilowatt-hours of electricity available from the fully charged battery enable NREL's Prius to get about 100 miles per gallon in the first 50 miles of driving--more than double the fuel efficiency of a standard Prius. Put another way, the overnight charging should take the car about 50 miles in light-duty driving. Markel says that NREL has yet to quantify the solar panel's additional impact, but that the five hours of good sunlight the car sees on an average day would give it an electrical output of at most 0.825 kilowatt-hours. The system would probably boost the plug-in's fuel efficiency for the first 50 miles from 100 to 105 miles per gallon, he says.
Solar Cells Use Nanoparticles to Capture More Sunlight
Optical antennas could help solar cells produce more energy.
Solar antenna: The square at the center is an array of test solar cells being used to evaluate a coating that contains metallic nanoantennas tuned to the solar spectrum.
Brongersma lab, Stanford
Inexpensive thin-film solar cells aren't as efficient as conventional solar cells, but a new coating that incorporates nanoscale metallic particles could help close the gap. Broadband Solar, a startup spun out of Stanford University late last year, is developing coatings that increase the amount of light these solar cells absorb.
Based on computer models and initial experiments, an amorphous silicon cell could jump from converting about 8 percent of the energy in light into electricity to converting around 12 percent. That would make such cells competitive with the leading thin-film solar cells produced today, such as those made by First Solar, headquartered in Tempe, AZ, says Cyrus Wadia, codirector of the Cleantech to Market Program in the Haas School of Business at the University of California, Berkeley. Amorphous silicon has the advantage of being much more abundant than the materials used by First Solar. The coatings could also be applied to other types of thin-film solar cells, including First Solar's, to increase their efficiency.
Broadband believes its coatings won't increase the cost of these solar cells because they perform the same function as the transparent conductors used on all thin-film cells and could be deposited using the same equipment.
Broadband's nanoscale metallic particles take incoming light and redirect it along the plane of the solar cell, says Mark Brongersma, professor of materials science and engineering at Stanford and scientific advisor to the company. As a result, each photon takes a longer path through the material, increasing its chances of dislodging an electron before it can reflect back out of the cell. The nanoparticles also increase light absorption by creating strong local electric fields.
The particles, which are essentiallynanoscale antennas, are very similar to radio antennas, says Brongersma. They're much smaller because the wavelengths they interact with are much shorter than radio waves. Just as conventional antennas can convert incoming radio waves into an electrical signal and transmit electrical signals as radio waves, these nanoantennas rely on electrical interactions to receive and transmit light in the optical spectrum.
Their interaction with light is so strong because incoming photons actually couple to the surface of metal nanoparticles in the form of surface waves called plasmons. These so-called plasmonic effects occur in nanostructures made from highly conductive metals such as copper, silver, and gold. Researchers are taking advantage of plasmonic effects to miniaturizeoptical computers, and to create higher-resolution light microscopes and lithography. Broadband is one of the first companies working to commercialize plasmonic solar cells.
Researchers consider plug-in hybrids charged by stationary solar arrays a better bet.
Worth the cost?: The solar roof glued to this Prius combines 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. The panel, which can add five miles to the car’s 50-mile electric-only range, is available for $3,500 from Solar Electrical Vehicles. Something similar could soon be factory-installed by Toyota.
Solar Electrical Vehicles
Last week, the Japanese newspaper Nikkei caused a buzz by reporting that a redesigned Toyota Prius, to be released next year, will come equipped with solar panels. Toyota spokespeople will neither confirm nor deny the report, but several companies already offer solar roof kits for the Prius, and researchers at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL), in Golden, CO, have been testing one on a Prius modified to plug into the electrical grid. Their conclusion: for the time being, plug-in hybrids charged from stationary solar arrays are a more efficient and cheaper option.
The idea of car-mounted solar cells is not new: in the early 1990s, Mazda offered its 929 luxury sedan with optional solar cells in the glass sunroof to drive fans that removed hot air from the car. But most onboard solar systems to date have cost several thousand dollars while generating less than 100 watts of energy, improving a vehicle's fuel efficiency by just a few percent. "I think it's more a marketing gimmick," says Andrew Frank, a plug-in hybrid pioneer at the University of California, Davis, and chief technology officer for UC-Davis hybrid-vehicle spinoff Efficient Drivetrains. "It takes kilowatts to really drive the car."
The limited surface area of the car roof is one constraint on the panels' power production. Another is that they can't be tilted perpendicular to the sun for optimal energy capture, unlike most photovoltaics on buildings or in solar farms, which either track the sun or are installed with a fixed southward tilt.
Researchers consider plug-in hybrids charged by stationary solar arrays a better bet.
Worth the cost?: The solar roof glued to this Prius combines 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. The panel, which can add five miles to the car’s 50-mile electric-only range, is available for $3,500 from Solar Electrical Vehicles. Something similar could soon be factory-installed by Toyota.
Solar Electrical Vehicles
Solar Electrical Vehicles
Last week, the Japanese newspaper Nikkei caused a buzz by reporting that a redesigned Toyota Prius, to be released next year, will come equipped with solar panels. Toyota spokespeople will neither confirm nor deny the report, but several companies already offer solar roof kits for the Prius, and researchers at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL), in Golden, CO, have been testing one on a Prius modified to plug into the electrical grid. Their conclusion: for the time being, plug-in hybrids charged from stationary solar arrays are a more efficient and cheaper option.
The idea of car-mounted solar cells is not new: in the early 1990s, Mazda offered its 929 luxury sedan with optional solar cells in the glass sunroof to drive fans that removed hot air from the car. But most onboard solar systems to date have cost several thousand dollars while generating less than 100 watts of energy, improving a vehicle's fuel efficiency by just a few percent. "I think it's more a marketing gimmick," says Andrew Frank, a plug-in hybrid pioneer at the University of California, Davis, and chief technology officer for UC-Davis hybrid-vehicle spinoff Efficient Drivetrains. "It takes kilowatts to really drive the car."
The limited surface area of the car roof is one constraint on the panels' power production. Another is that they can't be tilted perpendicular to the sun for optimal energy capture, unlike most photovoltaics on buildings or in solar farms, which either track the sun or are installed with a fixed southward tilt.
The NREL researchers tested the extent of these limitations by equipping the plug-in Prius they built earlier this year with the most powerful rooftop solar panel on the market. Assembled by Solar Electrical Vehicles, based in Westlake Village, CA, the panel completely covers the Prius roof, wiring together 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. However, NREL senior engineer Tony Markel says that his group's tests suggest that the output will max out at closer to 165 watts under normal use.
That's a meager improvement compared with the boost that the plug-in Prius gets from its extra lithium-ion battery. Markel says that the six kilowatt-hours of electricity available from the fully charged battery enable NREL's Prius to get about 100 miles per gallon in the first 50 miles of driving--more than double the fuel efficiency of a standard Prius. Put another way, the overnight charging should take the car about 50 miles in light-duty driving. Markel says that NREL has yet to quantify the solar panel's additional impact, but that the five hours of good sunlight the car sees on an average day would give it an electrical output of at most 0.825 kilowatt-hours. The system would probably boost the plug-in's fuel efficiency for the first 50 miles from 100 to 105 miles per gallon, he says.
The NREL researchers tested the extent of these limitations by equipping the plug-in Prius they built earlier this year with the most powerful rooftop solar panel on the market. Assembled by Solar Electrical Vehicles, based in Westlake Village, CA, the panel completely covers the Prius roof, wiring together 146 four-inch-square crystalline-silicon cells capable of generating a total of 215 watts. However, NREL senior engineer Tony Markel says that his group's tests suggest that the output will max out at closer to 165 watts under normal use.
That's a meager improvement compared with the boost that the plug-in Prius gets from its extra lithium-ion battery. Markel says that the six kilowatt-hours of electricity available from the fully charged battery enable NREL's Prius to get about 100 miles per gallon in the first 50 miles of driving--more than double the fuel efficiency of a standard Prius. Put another way, the overnight charging should take the car about 50 miles in light-duty driving. Markel says that NREL has yet to quantify the solar panel's additional impact, but that the five hours of good sunlight the car sees on an average day would give it an electrical output of at most 0.825 kilowatt-hours. The system would probably boost the plug-in's fuel efficiency for the first 50 miles from 100 to 105 miles per gallon, he says.
Solar Cells Use Nanoparticles to Capture More Sunlight
Optical antennas could help solar cells produce more energy.
Solar antenna: The square at the center is an array of test solar cells being used to evaluate a coating that contains metallic nanoantennas tuned to the solar spectrum.
Brongersma lab, Stanford
Brongersma lab, Stanford
Inexpensive thin-film solar cells aren't as efficient as conventional solar cells, but a new coating that incorporates nanoscale metallic particles could help close the gap. Broadband Solar, a startup spun out of Stanford University late last year, is developing coatings that increase the amount of light these solar cells absorb.
Based on computer models and initial experiments, an amorphous silicon cell could jump from converting about 8 percent of the energy in light into electricity to converting around 12 percent. That would make such cells competitive with the leading thin-film solar cells produced today, such as those made by First Solar, headquartered in Tempe, AZ, says Cyrus Wadia, codirector of the Cleantech to Market Program in the Haas School of Business at the University of California, Berkeley. Amorphous silicon has the advantage of being much more abundant than the materials used by First Solar. The coatings could also be applied to other types of thin-film solar cells, including First Solar's, to increase their efficiency.
Broadband believes its coatings won't increase the cost of these solar cells because they perform the same function as the transparent conductors used on all thin-film cells and could be deposited using the same equipment.
Broadband's nanoscale metallic particles take incoming light and redirect it along the plane of the solar cell, says Mark Brongersma, professor of materials science and engineering at Stanford and scientific advisor to the company. As a result, each photon takes a longer path through the material, increasing its chances of dislodging an electron before it can reflect back out of the cell. The nanoparticles also increase light absorption by creating strong local electric fields.
The particles, which are essentiallynanoscale antennas, are very similar to radio antennas, says Brongersma. They're much smaller because the wavelengths they interact with are much shorter than radio waves. Just as conventional antennas can convert incoming radio waves into an electrical signal and transmit electrical signals as radio waves, these nanoantennas rely on electrical interactions to receive and transmit light in the optical spectrum.
Their interaction with light is so strong because incoming photons actually couple to the surface of metal nanoparticles in the form of surface waves called plasmons. These so-called plasmonic effects occur in nanostructures made from highly conductive metals such as copper, silver, and gold. Researchers are taking advantage of plasmonic effects to miniaturizeoptical computers, and to create higher-resolution light microscopes and lithography. Broadband is one of the first companies working to commercialize plasmonic solar cells.
Flexible Silicon Solar Cells
Thin but efficient solar cells use one-tenth the silicon of conventional cells.
Flexing silicon’s power: Arrays of tiny silicon solar cells like the one in this photograph are assembled using a transfer-printing technique. These arrays are as efficient as conventional solar cells, which are bulky and rigid. Each microcell in the array is about 1.5 millimeters long and 15 micrometers thick.
John Rogers
John Rogers
Conventional solar cells are bulky and rigid, but building lightweight, flexible cells has come with trade-offs in efficiency and robustness. A new method for making flexible arrays of tiny silicon solar cells could produce devices that don't suffer these trade-offs. Arrays of these microcells are as efficient as conventional solar panels and may be cheaper to manufacture because they use significantly less silicon. The tiny solar cells could be incorporated into, among other applications, window tinting, and they might be used to power a car's air conditioner and GPS.
Researchers led by John Rogers, a professor of materials science and engineering at the University of Illinois in Urbana-Champaign, used a combination of etching and transfer printing to create arrays of silicon cells that are one-tenth the thickness of conventional cells. They demonstrated multiple possible designs for solar panels incorporating the microcells, including dense arrays flexible enough to bend around a pencil. "You could roll them up like a carpet, transport them in a van, and unfurl them onto a rooftop," Rogers says.
The process builds on techniques for making flexible electronics that Rogers has been developing over the past few years. First, the Illinois researchers etch bars about 1.5 millimeters long, 50 micrometers wide, and 15 micrometers thick from a wafer of monocrystalline silicon. They use a stamp made of a soft polymer to pick up the microbars and place them on a substrate, which may be glass or a flexible plastic, and then fabricate interconnects. Rogers found that a cell thickness of 15 to 20 micrometers struck a good balance: thin enough to be flexible, but thick enough to be mechanically stable and efficient. Conventional solar cells use a layer of silicon 150 to 200 micrometers thick.
Arrays of the cells have about a 12 percent efficiency. The Illinois researchers increased the arrays' power output by about two and half times by adding concentrators in the form of a layer of cylindrical microlenses. The best solar cells on the market convert more than 20 percent of the sunlight that falls on them into energy.
"This is a nice start at using silicon wafers more efficiently," says Howard Branz, principal scientist in the silicon materials and devices group at the National Renewable Energy Laboratory, in Golden, CO. With their transfer-printing approach, says Branz, Rogers and his group have for the first time demonstrated how such thin cells could be manufactured on large areas.
Toward Cheaper, Robust Solar Cells
Researchers are working on solar cells that use a novel organic dye.
Making solar cheaper: Dye-sensitized solar cells, which are cheaper than silicon cells, consist of dye-coated titanium dioxide nanoparticles immersed in an electrolyte solution, which is sandwiched between glass plates. A new combination of electrolyte and dye promises to make these solar cells even cheaper and more robust. Key to the innovation is an organic dye molecule.
Alex Agrios, Northwestern University
Alex Agrios, Northwestern University
Cheap and easy-to-make dye-sensitized solar cells are still in the early stages of commercial production. Meanwhile, their inventor, Michael Gratzel, is working on more advanced versions of them. In a paper published in the online edition of Angewandte Chemie, Gratzel, a chemistry professor at the École Polytechnique Fédérale de Lausanne in Switzerland, presents a version of dye-sensitized cells that could be more robust and even cheaper to make than current versions.
Dye-sensitized solar cells consist of titanium oxide nanocrystals that are coated with light-absorbing dye molecules and immersed in an electrolyte solution, which is sandwiched between two glass plates or embedded in plastic. Light striking the dye frees electrons and creates "holes"--the areas of positive charge that result when electrons are lost. The semiconducting titanium dioxide particles collect the electrons and transfer them to an external circuit, producing an electric current.
These solar cells are cheaper to make than conventional silicon photovoltaic panels. In principle, they could be used to make power-generating windows and building facades, and they could even be incorporated into clothing. (See "Window Power" and "Solar Cells for Cheap.") A Lowell, MA-based company called Konarka is manufacturing dye-sensitized solar cells in a limited quantity. But the technology still has room for improvement In existing versions of the solar cells, the electrolyte solution uses organic solvents. When the solar cells reach high temperatures, the solvent can evaporate and start to leak out. Researchers are now looking at a type of material that may make a better electrolyte: ionic liquids, which are currently used as industrial solvents. These liquids do not evaporate at solar-cell operating temperatures. "Ionic liquids are less volatile and more robust," says Bruce Parkinson, a chemistry professor at Colorado State University.
New dyes are also being investigated. In commercial cells, the dyes are made of the precious metal ruthenium. But researchers have recently started to consider organic molecules as an alternative. "Organic dyes will become important because they can be cheaply made," Gratzel says. In the long run, they might also be more abundant than ruthenium
Intensifying the Sun
A new way to concentrate sunlight could make solar power competitive with fossil fuels.
Marc Baldo poses with a collection of glass sheets coated with light-emitting organic dyes. The dyes absorb light and reëmit it into the glass, which channels it to the edges of the sheets. Baldo uses the devices to concentrate sunlight, making solar power cheaper.
In his darkened lab at MIT, Marc Baldo shines an ultraviolet lamp on a 10-centimeter square of glass. He has coated the surfaces of the glass with dyes that glow faintly orange under the light. Yet the uncoated edges of the glass are shining more brightly--four neat, thin strips of luminescent orange.
The sheet of glass is a new kind of solar concentrator, a device that gathers diffuse light and focuses it onto a relatively small solar cell. Solar cells, multilayered electronic devices made of highly refined silicon, are expensive to manufacture, and the bigger they are, the more they cost. Solar concentrators can lower the overall cost of solar power by making it possible to use much smaller cells. But the concentrators are typically made of curved mirrors or lenses, which are bulky and require costly mechanical systems that help them track the sun.
Unlike the mirrors and lenses in conventional solar concentrators, Baldo's glass sheets act as waveguides, channeling light in the same way that fiber-optic cables transmit optical signals over long distances. The dyes coating the surfaces of the glass absorb sunlight; different dyes can be used to absorb different wavelengths of light. Then the dyes reëmit the light into the glass, which channels it to the edges. Solar-cell strips attached to the edges absorb the light and generate electricity. The larger the surface of the glass compared with the thickness of the edges, the more the light is concentrated and, to a point, the less the power costs.
Baldo, an associate professor of electrical engineering, published his findings recently inScience. On their basis, he projects that his solar concentrators could be made big enough for the electricity they help generate to compete with electricity from fossil fuels. Indeed, says Baldo, panels equipped with the concentrators "could be the cheapest solar technology."
Secret Ingredient
The process for making Baldo's solar concentrators begins down the hall in another lab. A postdoctoral researcher, Shalom Goffri, takes several bottles filled with colorful dye powders from a cabinet and measures the powders into small vials. Some of the dyes were developed for use in car paints; others have been used in organic light-emitting diodes. Both types of dyes can last for years in the sun, a quality essential for solar concentrators. Once he has measured out the powders, Goffri adds a solvent to each to make a liquid ink.
The next steps take place inside a sealed box, so that Goffri doesn't inhale the solvents used to make the dye. He reaches into the box, using thick black gloves mounted in its glass front, and carefully mixes together different inks. Determining the right combination of inks solved a fundamental problem that researchers have encountered with this type of solar concentrator. If the glass sheet is coated with a dye that absorbs sunlight in, say, the green-to-blue range of the solar spectrum and emits light of the same wavelength, the emitted light will be quickly reabsorbed by the dye, and little of it will ever reach the edge of the glass. The problem has limited the size of these solar concentrators, since the further the light needs to travel to the edges, the less of the light will make it.
By using certain combinations of dyes interspersed with other light-absorbing molecules, Baldo makes coatings that absorb one color but emit another. The emitted light is not quickly reabsorbed by the coatings, so more of it reaches the edges of the glass sheet.
The coatings that Goffri is making absorb ultraviolet through green light and emit orange light. Once Goffri has prepared the final mixture, he pours a small amount on a 10-centimeter-wide glass square--the largest that can fit inside a device that spins the glass at 2,000 revolutions per minute to spread the ink evenly. Within a minute or two, the solvent has evaporated and the process is finished. The solar concentrator, with its coating of orange dye, is complete.
The process for making Baldo's solar concentrators begins down the hall in another lab. A postdoctoral researcher, Shalom Goffri, takes several bottles filled with colorful dye powders from a cabinet and measures the powders into small vials. Some of the dyes were developed for use in car paints; others have been used in organic light-emitting diodes. Both types of dyes can last for years in the sun, a quality essential for solar concentrators. Once he has measured out the powders, Goffri adds a solvent to each to make a liquid ink.
Sun + Water = Fuel
With catalysts created by an MIT chemist, sunlight can turn water into hydrogen. If the process can scale up, it could make solar power a dominant source of energy.
"I'm going to show you something I haven't showed anybody yet," said Daniel Nocera, a professor of chemistry at MIT, speaking this May to an auditorium filled with scientists and U.S. government energy officials. He asked the house manager to lower the lights. Then he started a video. "Can you see that?" he asked excitedly, pointing to the bubbles rising from a strip of material immersed in water. "Oxygen is pouring off of this electrode." Then he added, somewhat cryptically, "This is the future. We've got the leaf."
What Nocera was demonstrating was a reaction that generates oxygen from water much as green plants do during photosynthesis--an achievement that could have profound implications for the energy debate. Carried out with the help of a catalyst he developed, the reaction is the first and most difficult step in splitting water to make hydrogen gas. And efficiently generating hydrogen from water, Nocera believes, will help surmount one of the main obstacles preventing solar power from becoming a dominant source of electricity: there's no cost-effective way to store the energy collected by solar panels so that it can be used at night or during cloudy days.
Solar power has a unique potential to generate vast amounts of clean energy that doesn't contribute to global warming. But without a cheap means to store this energy, solar power can't replace fossil fuels on a large scale. In Nocera's scenario, sunlight would split water to produce versatile, easy-to-store hydrogen fuel that could later be burned in an internal-combustion generator or recombined with oxygen in a fuel cell. Even more ambitious, the reaction could be used to split seawater; in that case, running the hydrogen through a fuel cell would yield fresh water as well as electricity.
Storing energy from the sun by mimicking photosynthesis is something scientists have been trying to do since the early 1970s. In particular, they have tried to replicate the way green plants break down water. Chemists, of course, can already split water. But the process has required high temperatures, harsh alkaline solutions, or rare and expensive catalysts such as platinum. What Nocera has devised is an inexpensive catalyst that produces oxygen from water at room temperature and without caustic chemicals--the same benign conditions found in plants. Several other promising catalysts, including another that Nocera developed, could be used to complete the process and produce hydrogen gas.
Nocera sees two ways to take advantage of his breakthrough. In the first, a conventional solar panel would capture sunlight to produce electricity; in turn, that electricity would power a device called an electrolyzer, which would use his catalysts to split water. The second approach would employ a system that more closely mimics the structure of a leaf. The catalysts would be deployed side by side with special dye molecules designed to absorb sunlight; the energy captured by the dyes would drive the water-splitting reaction. Either way, solar energy would be converted into hydrogen fuel that could be easily stored and used at night--or whenever it's needed.
Nocera's audacious claims for the importance of his advance are the kind that academic chemists are usually loath to make in front of their peers. Indeed, a number of experts have questioned how well his system can be scaled up and how economical it will be. But Nocera shows no signs of backing down. "With this discovery, I totally change the dialogue," he told the audience in May. "All of the old arguments go out the window."
Storing energy from the sun by mimicking photosynthesis is something scientists have been trying to do since the early 1970s. In particular, they have tried to replicate the way green plants break down water. Chemists, of course, can already split water. But the process has required high temperatures, harsh alkaline solutions, or rare and expensive catalysts such as platinum. What Nocera has devised is an inexpensive catalyst that produces oxygen from water at room temperature and without caustic chemicals--the same benign conditions found in plants. Several other promising catalysts, including another that Nocera developed, could be used to complete the process and produce hydrogen gas.
Nocera sees two ways to take advantage of his breakthrough. In the first, a conventional solar panel would capture sunlight to produce electricity; in turn, that electricity would power a device called an electrolyzer, which would use his catalysts to split water. The second approach would employ a system that more closely mimics the structure of a leaf. The catalysts would be deployed side by side with special dye molecules designed to absorb sunlight; the energy captured by the dyes would drive the water-splitting reaction. Either way, solar energy would be converted into hydrogen fuel that could be easily stored and used at night--or whenever it's needed.
Nocera's audacious claims for the importance of his advance are the kind that academic chemists are usually loath to make in front of their peers. Indeed, a number of experts have questioned how well his system can be scaled up and how economical it will be. But Nocera shows no signs of backing down. "With this discovery, I totally change the dialogue," he told the audience in May. "All of the old arguments go out the window."
Nanopillars that Trap More Light
The new design could lead to cheaper solar cells
Thick and thin: A scanning electron microscope image shows dual-diameter light-trapping germanium nanopillars.
A material with a novel nanostructure developed by researchers at the University of California, Berkeley could lead to lower-cost solar cells and light detectors. It absorbs light just as well as commercial thin-film solar cells but uses much less semiconductor material.
The new material consists of an array of nanopillars that are narrow at the top and thicker at the bottom. The narrow tops allow light to penetrate the array without reflecting off. The thicker bottom absorbs light so that it can be converted into electricity. The design absorbs 99 percent of visible light, compared to the 85 percent absorbed by an earlier design in which the nanopillars were the same thickness along their entire length. An ordinary flat film of the material would absorb only 15 percent of the light.
Structures such as nanowires, microwires, and nanopillars are excellent at trapping light, reducing the amount of semiconductor material needed, says Erik Garnett, a research fellow at Stanford University. Nanowires and nanopillars use half to a third as much of the semiconductor material required by thin-film solar cells made of materials such as cadmium telluride, and as little as 1 percent of the material used in crystalline silicon cells, he says. These structures also make it easier to extract charge from the material. Overall, these improvements could make solar cheaper. "Reducing material costs while achieving the same amount of light absorption and hence efficiency is very important for solar cells," says Shanhui Fan, an electrical engineering professor at Stanford.
Many nanostructrued materials have complex designs and require cumbersome fabrication methods to deposit multiple layers, says Ali Javey, an electrical engineering and computer science professor at UC Berkeley who is leading the new work, which is posted in the journal Nano Letters. He says the technique to grow the nanopillars is relatively simple and low-cost.
The researchers make nanopillars two micrometers high, with bases that are 130 nanometers in diameter and tips that are 60 nanometers in diameter. They start by creating a mold for the pores in a 2.5-millimeter-thick aluminum foil. First they anodize the film to create an arrangement of pores that are 60 nanometers wide and one micrometer deep long. They then expose the foil to phosphoric acid to broaden the pores to 130 nanometers--the longer the foil is exposed to the acid, the broader the pores get. Anodizing the film again makes the existing pores one micrometer deeper, and this additional length has the original 60-nanometer diameter. Trace amounts of gold are then deposited in these pores as a catalyst to grow crystals of semiconductor material--in this case germanium, which is good for photo detectors--inside each pore. Finally, some of the aluminum is etched away, leaving behind an array of germanium nanopillars embedded in an aluminum oxide membrane
Javey says that this method of making nanopillars of varying diameters and shapes is simple compared to other approaches, which involve a complicated layer-by-layer assembly of materials, and complex materials that combine wires with metal nanoparticles.
Garnett agrees that Javey's method could be cheap, but says it's still too early to know if the method can translate to a large-scale manufacturing process. "The most exciting thing is proof that nanostructuring can dramatically increase absorption," he says.
By tweaking the arrangement of the pillars, it could be possible to make materials that absorb longer infrared wavelengths of light, which would be useful for making efficient, cheap infrared light detectors. Since submitting the Nano Letters paper, the researchers have also used the technique to make nanopillars of cadmium telluride, a material better suited for solar cells than germanium.
Latest Invention: Tea Bag that Uses Nanotechnology to Clean Drinking Water
It would be interesting to note that the "tea bag" is made of the same material that is used to make the actual tea bags. The only difference is that in the Stellenbosch researchers' invention the ingredients are nanoscale fibers and grains of carbon, reports io9.
Both fibers and grains of carbon filter water from all hazardous contaminants. In order to purify the water, the user needs to place the tea bag in the neck of a water bottle. The tea bag filters the water when the person drinks from the bottle.
One bag can be used to filter up to 1 liter of water and it costs less than a half of an American cent.
Nanotech tea bag creates safe drinking water instantly, for less than a penny
Alasdair Wilkins — Nanotech tea bag creates safe drinking water instantly, for less than a pennyA new "tea bag" uses nano-fibers to suck contaminants and bacteria out of water, providing a desperately-needed, cheap solution for the billions of people without clean drinking water.
Researchers at South Africa's Stellenbosch University made the device from the same material used for the bags of the country's popular rooibos tea. Inside the sachets are two tiny destroyers of all things unsafe: ultra-thin nanoscale fibers, which filter harmful contaminants, and bacteria-killing grains of carbon.
To use the device, a person simply has to place the bag in the neck of a water bottle, and the bag cleans the water as he or she drinks. A single bag can filter up to a liter of even the most heavily polluted water. The bags are thrown away once used.
Stellenbosch microbiology researcher Marelize Botes explained what sets this water-cleaning device apart from its predecessors:
"What is new about this idea is the combination of inexpensive raw materials, namely activated carbon and antimicrobial nanofibres, in point-of-use water filter systems. The nanofibres will disintegrate in liquids after a few days and will have no environmental impact. The raw materials of the tea-bag filter are not toxic to humans."
The device isn't quite ready for mass production, but tests of the filter on nearby rivers have been successful. Clean water experts say this filter, which is applied just before people drink, is preferable to systems that clean water before it's distributed, because it eliminates the risk of recontamination.
Latest Invention: Synthetic Tree to Collect Huge Amounts of CO2
Scientists will use their latest invention to trap greenhouse gas emitted by vehicles or airplanes. The synthetic tree, which resembles a cylinder, will not require direct sunlight, water of branches to work properly. According to Lackner, the tree is flexible in size and can be placed almost anywhere.
Here's how it works: the synthetic tree gathers the greenhouse gas on a sorbent, cleans and pressures the carbon dioxide and then releases it. The technique of gas absorption resembles that of a sponge that collects water.
During a whole day one artificial tree will be able to collect one ton of CO2, which equals to the amount of carbon dioxide emitted by 20 cars. The technology is currently in the development stage at Global Research Technologies, a company based in Tucson, Arizona, co-founded by Lackner, who at the moment is its chairman. Such invention might serve well for the environment by it is quite costly - each synthetic tree requires $30,000 to make, reports CNN.
Data presented by the U.S. Department of Transportation shows that currently in the United States there are about 135,932,930 vehicles, which means that in order to absorb the amount of carbon emitted by these cars, the country would need to "plant" 6.8 million synthetic trees (that's $204 billion). With the current global economic crisis the project will probably remain in the development stage for some time. Still, Lackner and his team look forward to push their latest invention full-force. The researcher managed to arrange a meeting with U.S. Energy Secretary Steven Chu to talk about the concept.
According to GreenSun Energy, their latest invention has its glass made with fluorescent dyes and nanoparticle metals. Besides being more efficient, the new solar cells could also have a lower cost compared to traditional solar cells. Another advantage of the new solar cells is that they require 80 percent less silicon than the traditional ones (less silicon means a lower cost of production). When sunlight (be it direct or indirect) touches the panels, it disperses across and the metal nanoparticles bring the sunlight to the edges where the silicon is placed.
The company's latest invention costs $2.10/W and is 12 percent more efficient than the traditional solar cell, which costs around $4.54/W. In addition, the conventional solar cells have efficiency loss because of the heat that doesn't turn into energy, informs CleanTechnica. In the new solar panels, the sunlight is diffused across the entire panel, thus nanoparticles are able to bring light to the edges of the panel where the light is transformed into energy. You can read more about various green technologies and eco-friendly developments here at www.InfoNIAC.com - please check the links at the bottom of the article. Currently the Tel Aviv-based company is working on making its latest invention even more efficient.
Engineers at GreenSun look forward towards increasing the efficiency of their new solar cell from 12 percent to 20 percent. They also hope to reduce the costs of producing the new panels to $0,94/W.
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Disco pub gets electricity produced by people dancing at specially modified dance floor ...All the flashing strobes and pounding speakers at the dance club are massive consumers of electrical power. So Bar Surya, in London, re-outfitted its floor with springs that, when compressed by dancers, could produce electrical current that would be stored in batteries and used to offset some of the club's electrical burden. The club's owner, Andrew Charalambous, said the dance floor can now power 60 percent of the club's energy needs...
Designer creates a shower that forces you to leave when you've wasted too much water..20% of our total domestic energy usage is from hot water for showering and bathing. That's over 6 times the energy usage of domestic lighting. So designer Tommaso Colia came up with his eco-friendly shower design that will force you to get out when you take too long and waste much water. The eco_drop shower features beautiful concentric circles that will rise to force you to stop showering when you take too long, and accordingly save water.
8.Environmental company creates a staple-free stapler to avoid staple pollution...Staples are supposed to be so bad to the environment that a company decided to create a staple-free stapler. This product promises to make collation eco-friendly. Instead of using those thin metal planet-killers, the staple-free stapler "cuts out tiny strips of paper and uses the strips to stitch up to five pieces of paper together." You can even order them customized with your corporate logo so you can, you know, brag about what your company is doing to stop the staple epidemic.
Environmental company creates a staple-free stapler to avoid staple pollution...Staples are supposed to be so bad to the environment that a company decided to create a staple-free stapler. This product promises to make collation eco-friendly. Instead of using those thin metal planet-killers, the staple-free stapler "cuts out tiny strips of paper and uses the strips to stitch up to five pieces of paper together." You can even order them customized with your corporate logo so you can, you know, brag about what your company is doing to stop the staple epidemic.
