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Atmospheric 'Sunshade' Could Reduce Solar Power Generation
 The world's largest solar power facility, located near Kramer Junction, Calif., consists of five Solar Electric Generating Stations and covers more than 1,000 acres. (Credit: Department of Energy/National Renewable Energy Laboratory)
ScienceDaily (Mar. 16, 2009)
— The concept of delaying global warming by adding particles into the upper atmosphere to cool the climate could unintentionally reduce peak electricity generated by large solar power plants by as much as one-fifth, according to a new NOAA study.
“Injecting particles into the stratosphere could have unintended consequences for one alternative energy source expected to play a role in the transition away from fossil fuels,” said author Daniel Murphy, a scientist at NOAA’s Earth System Research Laboratory in Boulder, Colo.
The Earth is heating up as fossil-fuel burning produces carbon dioxide, the primary heat-trapping gas responsible for man-made climate change. To counteract the effect, some geoengineering proposals are designed to slow global warming by shading the Earth from sunlight.
Among the ideas being explored is injecting small particles into the upper atmosphere to produce a climate cooling similar to that of large volcanic eruptions, such as Mt. Pinatubo’s in 1991. Airborne sulfur hovering in the stratosphere cooled the Earth for about two years following that eruption.
Murphy found that particles in the stratosphere reduce the amount and change the nature of the sunlight that strikes the Earth. Though a fraction of the incoming sunlight bounces back to space (the cooling effect), a much larger amount becomes diffuse, or scattered, light.
On average, for every watt of sunlight the particles reflect away from the Earth, another three watts of direct sunlight are converted to diffuse sunlight. Large power-generating solar plants that concentrate sunlight for maximum efficiency depend solely on direct sunlight and cannot use diffuse light.
Murphy verified his calculations using long-term NOAA observations of direct and diffuse sunlight before and after the 1991 eruption.
After the eruption of Mt. Pinatubo, peak power output of Solar Electric Generating Stations in California, the largest collective of solar power plants in the world, fell by up to 20 percent, even though the stratospheric particles from the eruption reduced total sunlight that year by less than 3 percent.
“The sensitivity of concentrating solar systems to stratospheric particles may seem surprising,” said Murphy. “But because these systems use only direct sunlight, increasing stratospheric particles has a disproportionately large effect on them.”
Nine Solar Electric Generating Stations operate in California and more are running or are under construction elsewhere in the world. In sunny locations such systems, which use curved mirrors or other concentrating devices, generate electricity at a lower cost than conventional photovoltaic, or solar, cells.
Flat photovoltaic and hot water panels, commonly seen on household roofs, use both diffuse and direct sunlight. Their energy output would decline much less than that from concentrating systems.
Even low-tech measures to balance a home’s energy, such as south-facing windows for winter heat and overhangs for summer shade, would be less effective if direct sunlight is reduced.
The findings recently appeared in the journal Environmental Science and Technology.
Journal reference: Daniel M. Murphy. Effect of Stratospheric Aerosols on Direct Sunlight and Implications for Concentrating Solar Power. Environmental Science & Technology, 2009; 090311080700076 DOI: 10.1021/es802206b
Adapted from materials provided by National Oceanic And Atmospheric Administration.
January 24, 2008
Energy Department Selects Student Teams to Compete in 2009 Solar Decathlon
 WASHINGTON, DC – The U.S. Department of Energy (DOE) today announced the 20 university-led teams selected to compete in the Department's fourth Solar Decathlon, which will be held on the National Mall in Washington, DC, in the fall of 2009. This year’s teams have been selected from universities in the United States, Canada, and Germany and each team will receive $100,000 from DOE to uniquely design, build and operate an energy efficient, fully solar-powered home for this unique competition. Each home will utilize energy efficient technology and demonstrate that homes powered entirely by the sun do not have to sacrifice all the modern comforts and aesthetics Americans are accustomed to. The Department's Solar Decathlon complements the President's Solar America Initiative, which seeks to make solar power cost-competitive with conventional forms of electricity by 2015.
“The Department of Energy’s Solar Decathlon is more than a student project. These creative teams will develop livable, working, energy efficient, and marketable home designs powered by cutting edge, currently available solar energy technology,” U.S. Secretary of Energy Samuel W. Bodman said. “The caliber of this year’s proposals was outstanding and we were thrilled with the significant increase in the number of applicants. It will be exciting to watch as the students work over the next year-and-a-half to design, build, test, and showcase their homes.”
The Decathlon gets its name from the 10 specific areas of competition: architecture, engineering, market viability, communications, comfort, appliances, hot water, lighting, energy balance, and transportation. In addition to producing enough electricity and hot water to perform all the functions of a home, from powering lights and electronics to cooking, washing clothes and dishes, each home must produce surplus energy sufficient to power an electric car. The team that finishes the week of competition with the most points wins.
Selected design concepts represent a range of building technologies from diverse geographic locations, including those targeted for low-income gulf-state rebuilding, affordable urban renewal, and mass-producible habitats for suburban America. Applications for the competition were evaluated by a panel made up of engineers, scientists and other experts from DOE and its National Renewable Energy Laboratory. Teams were required to meet specific criteria, demonstrating their ability to design and build an innovative, entirely solar-powered, 800-square-foot home from scratch, including the ability to raise additional funds and assemble a team necessary to carry the project through to completion.
Atmospheric 'Sunshade' Could Reduce Solar Power Generation
The world's largest solar power facility, located near Kramer Junction, Calif., consists of five Solar Electric Generating Stations and covers more than 1,000 acres. (Credit: Department of Energy/National Renewable Energy Laboratory)
ScienceDaily (Mar. 16, 2009)
— The concept of delaying global warming by adding particles into the upper atmosphere to cool the climate could unintentionally reduce peak electricity generated by large solar power plants by as much as one-fifth, according to a new NOAA study.
“Injecting particles into the stratosphere could have unintended consequences for one alternative energy source expected to play a role in the transition away from fossil fuels,” said author Daniel Murphy, a scientist at NOAA’s Earth System Research Laboratory in Boulder, Colo.
The Earth is heating up as fossil-fuel burning produces carbon dioxide, the primary heat-trapping gas responsible for man-made climate change. To counteract the effect, some geoengineering proposals are designed to slow global warming by shading the Earth from sunlight.
Among the ideas being explored is injecting small particles into the upper atmosphere to produce a climate cooling similar to that of large volcanic eruptions, such as Mt. Pinatubo’s in 1991. Airborne sulfur hovering in the stratosphere cooled the Earth for about two years following that eruption.
Murphy found that particles in the stratosphere reduce the amount and change the nature of the sunlight that strikes the Earth. Though a fraction of the incoming sunlight bounces back to space (the cooling effect), a much larger amount becomes diffuse, or scattered, light.
On average, for every watt of sunlight the particles reflect away from the Earth, another three watts of direct sunlight are converted to diffuse sunlight. Large power-generating solar plants that concentrate sunlight for maximum efficiency depend solely on direct sunlight and cannot use diffuse light.
Murphy verified his calculations using long-term NOAA observations of direct and diffuse sunlight before and after the 1991 eruption.
After the eruption of Mt. Pinatubo, peak power output of Solar Electric Generating Stations in California, the largest collective of solar power plants in the world, fell by up to 20 percent, even though the stratospheric particles from the eruption reduced total sunlight that year by less than 3 percent.
“The sensitivity of concentrating solar systems to stratospheric particles may seem surprising,” said Murphy. “But because these systems use only direct sunlight, increasing stratospheric particles has a disproportionately large effect on them.”
Nine Solar Electric Generating Stations operate in California and more are running or are under construction elsewhere in the world. In sunny locations such systems, which use curved mirrors or other concentrating devices, generate electricity at a lower cost than conventional photovoltaic, or solar, cells.
Flat photovoltaic and hot water panels, commonly seen on household roofs, use both diffuse and direct sunlight. Their energy output would decline much less than that from concentrating systems.
Even low-tech measures to balance a home’s energy, such as south-facing windows for winter heat and overhangs for summer shade, would be less effective if direct sunlight is reduced.
The findings recently appeared in the journal Environmental Science and Technology.
Journal reference: Daniel M. Murphy. Effect of Stratospheric Aerosols on Direct Sunlight and Implications for Concentrating Solar Power. Environmental Science & Technology, 2009; 090311080700076 DOI: 10.1021/es802206b
Adapted from materials provided by National Oceanic And Atmospheric Administration.
January 24, 2008
Energy Department Selects Student Teams to Compete in 2009 Solar Decathlon
WASHINGTON, DC – The U.S. Department of Energy (DOE) today announced the 20 university-led teams selected to compete in the Department's fourth Solar Decathlon, which will be held on the National Mall in Washington, DC, in the fall of 2009. This year’s teams have been selected from universities in the United States, Canada, and Germany and each team will receive $100,000 from DOE to uniquely design, build and operate an energy efficient, fully solar-powered home for this unique competition. Each home will utilize energy efficient technology and demonstrate that homes powered entirely by the sun do not have to sacrifice all the modern comforts and aesthetics Americans are accustomed to. The Department's Solar Decathlon complements the President's Solar America Initiative, which seeks to make solar power cost-competitive with conventional forms of electricity by 2015.
“The Department of Energy’s Solar Decathlon is more than a student project. These creative teams will develop livable, working, energy efficient, and marketable home designs powered by cutting edge, currently available solar energy technology,” U.S. Secretary of Energy Samuel W. Bodman said. “The caliber of this year’s proposals was outstanding and we were thrilled with the significant increase in the number of applicants. It will be exciting to watch as the students work over the next year-and-a-half to design, build, test, and showcase their homes.”
The Decathlon gets its name from the 10 specific areas of competition: architecture, engineering, market viability, communications, comfort, appliances, hot water, lighting, energy balance, and transportation. In addition to producing enough electricity and hot water to perform all the functions of a home, from powering lights and electronics to cooking, washing clothes and dishes, each home must produce surplus energy sufficient to power an electric car. The team that finishes the week of competition with the most points wins.
Selected design concepts represent a range of building technologies from diverse geographic locations, including those targeted for low-income gulf-state rebuilding, affordable urban renewal, and mass-producible habitats for suburban America. Applications for the competition were evaluated by a panel made up of engineers, scientists and other experts from DOE and its National Renewable Energy Laboratory. Teams were required to meet specific criteria, demonstrating their ability to design and build an innovative, entirely solar-powered, 800-square-foot home from scratch, including the ability to raise additional funds and assemble a team necessary to carry the project through to completion.
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