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Tag: Photovoltaics



23 Aug 10

Even clean energy can get dirty

Dust: it’s enemy number one for solar photovoltaic panels (PV) in the sunny, warm areas with the most potential for solar power. That’s because it takes less than a tablespoon of dust per square meter to reduce the electrical output of a typical PV panel by 40 percent.

“In Arizona,” says Professor Malay Mazumder of Boston University, “dust is deposited each month at about four times that amount. Deposition rates are even higher in the Middle East, Australia and India.”

Few home owners in the Southwest want to climb up on their roof several times a month to hose off the light-blocking dust. Utility-sized PV installations are hand-washed or use mechanical sprayers — but either way is costly. In the desert there’s the additional problem of increasing water use in an arid land — one that is likely to grow drier as the climate changes.

The solution to this problem (or at least a solution) comes from the U.S. space program — which is fitting, given that PV panels were pioneered by NASA in the 1960s and ’70s to power satellites and, most recently, rovers on Mars.

At the 240th National Meeting of the American Chemical Society (ACS) last weekend, Dr. Mazumder reported on advances in bringing the same technology used to clean dust from the Mars rovers down to Earth.

The trick to cleaning PV panels without water is to incorporate an Electrodynamic Screen (EDS) like the one on the Mars rovers. An EDS is a thin, electrically sensitive layer on the surface of the panel. When enough dust accumulates on the EDS, a sensor triggers a small electric pulse which repels the dust.

NASA first developed the idea for an “electric curtain” in 1967. In 2003, NASA’s Electrostatics and Surface Physics Laboratory (ESPL) worked with researchers at the University of Arkansas at Little Rock (where Dr. Mazumder then taught) to design and build an EDS for the Mars rovers. (The ESPL website has a short video showing test modules working under space conditions.)

Mazumder reports that the EDS developed by his lab can remove 90 percent of dust particles from a square meter of PV paneling in two minutes using just 10 watts.

Mazunder said the Earth-version of the EDS should be commercially available within a year.

Not all PV panels may require EDS technology, says Alan Bernheimer, a spokesman for First Solar, the world’s largest manufacturer of thin-film PV.

“Theoretically it would be possible to apply this technology to thin film solar modules,” Bernheimer wrote in an Email. “First Solar’s advanced thin film technology, however, is productive in diffuse and lower light conditions, such as those caused by dust.”

While even thin-film panels eventually need to be cleaned, Bernheimer said First Solar has no plans to adopt the EDS technology.

For traditional silicon-based PV manufacturers, however, the development of waterless cleaning technologies is likely to be seen as a milestone on the road to renewable, sustainable, energy.

You can read a 2008 paper about EDS technology co-written by Prof. Mazumder here (PDF).


Filed under: All,Media,Renewables,Solar,Southwest,Video

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3 Jul 10

Energy Independence Day, July 3, 2010

With the economy and job-growth stagnant, oil still spewing from the BP well-head into the Gulf of Mexico as a toxic reminder of our addiction to fossil fuels, President Obama couldn’t have picked a better time to announce a major solar power initiative than today, July 3rd — only hours away from Independence Day.

The president labeled his weekly radio address “A Solar Recovery,” reflecting the emphasis on pocket-book voting in this election year. Personally, I wish Obama would have gone with “Energy Independence Day,” putting the spotlight on the larger, long-term prize. But I guess that explains why I’m a journalist and he’s The President of the United States of America.

“We’re accelerating the transition to a clean energy economy and doubling our use of renewable energy sources like wind and solar power…” the president said and then announced a new commitment to solar power of $2 billion.

Solana Solar Generating Station

The bulk of the money will be used to build the world’s largest solar power plant, a 280-MW station in southwestern Arizona. The Solana generating plant, said Obama, “will be the first large-scale solar plant in the U.S. to actually store the energy it generates for later use — even at night.”

Solana (Spanish for “sunny place”) will be built and operated by Abengoa, headquartered in Seville, Spain. The plant will use concentrating solar power (CSP) technology, which uses heat generated by sunlight to produce electricity. Most Americans are more familiar with photovoltaic (PV) solar panels used mostly on rooftops to generate electricity.

Electricity generated by Solana will be purchased by Arizona Public Service, the state’s largest utility, and used to supply electric power to an estimated 70,000 homes.

“This is very encouraging news,” Pat Dinkel, VP for power marketing and resource planning at APS, told The Sun today. “We know there are a lot of steps remaining before our customers can benefit from Solana’s generation but this action brings that goal a step closer.”

Abengoa’s Fred Morse thanked Arizona Congresswoman Gabrielle Giffords (D-Tucson), a leading solar advocate in Washington.

“Congresswoman Giffords played an instrumental role to make this project a reality,” said Morse. “She understands the importance of creating jobs in Arizona and the ripple effects that this project will create throughout the Arizona economy. Solana will bring Arizona one step closer to becoming the solar capital of the nation.”

The Solana project has been in the works for at least three years. With the federal loan guarantee, construction on the plant may begin yet this year.

Secretary Chu: U.S. leadership in the global green economy

Abound Solar's PV Panel

Secretary of Energy Steven Chu touted the second part of today’s announcement — $400 million to Abound Solar Manufacturing to produce a new form of PV cells. Plants in Longmont, Colorado, and Tipton, Indiana will manufacture Cadmium-Telluride panels, a technology developed at Colorado State University, the National Renewable Energy Laboratory (NREL) and the National Science Foundation.

The Indiana plant was originally built for a Chrysler auto parts supplier, but because of the recession, it had never been occupied. By 2013, Abound hopes to be manufacturing 840 MW worth of solar panels a year at the two plants.

“By supporting new cutting-edge solar manufacturing technologies,” said Chu, “we are advancing a diverse renewable energy portfolio while helping to position the U.S. at the forefront of the global green economy.”

Jobs for Arizona & New Mexico, too

The Solana plant will need nearly a million specially-made mirrors to reflect and concentrate the Arizona sunlight, and miles of tubing to carry the super-heated liquid used in the CSP process. A mirror factory is planned for the Phoenix area, and the tubes will come from neighboring New Mexico, where a factory owned by Schott Solar is currently operating well-below capacity.

Solana Solar Generating Station

The Solana plant will cover 3,000 acres of former farmland. While CSP that uses water for cooling is controversial, especially in the desert, the power plant will use less water than the farm that had been at the same location. According to Rep. Gabrielle Giffords office, Solana will use slightly more than 10 percent of the water drawn by the farm.

Solana generates electricity without producing greenhouse gasses — eliminating an estimated 470,000 tons of GHG a year.

Some 3,200 giant parabolic collectors will track the sun throughout the day at Solana. Each collector is 25-feet wide, 20-feet high and the length of 1.5 football fields. Some of the heat generated by the collectors will be stored as molten salt, allowing the plant to generate electricity for six hours after sunset.


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21 Jan 10

Kyocera's employee parking lot, San Diego. The solar panels on the roofs generates power to charge plug-in cars during the work day. Photo by Envision Solar.


A new study by Environment America finds that electric vehicles (EVs) could do a lot to fight global warming and clean up the urban smog that contributes to respiratory and heart problems. But, the report concludes, changes in public policy are needed to make the switch from internal combustion to all electric vehicles on a mass scale.

Environment America is a national coalition of environmental groups in 25 states.

To download the full report, click on the graphic at the bottom of this page.

Executive Summary

America’s current fleet of gasoline-powered cars and trucks leaves us dependent on oil, contributes to air pollution problems that threaten our health, and produces large amounts of global warming pollution. “Plug-in” cars are emerging as an effective way to lower global warming emissions, oil use, and smog. A “plug-in” car is one that can be recharged from the electric grid. Some plug-in cars run on electricity alone, while others are paired with small gasoline engines to create plug-in hybrids. Many plug-in hybrids can get over 100 miles per gallon, while plug-in electric vehicles consume no gasoline at all.

As automakers race to become the first to introduce a mass production plug-in vehicle to American consumers, citizens and decision-makers are grappling to understand the implications of switching to a vehicle fleet fueled primarily by electricity for our environment, for consumers, and for the nation as a whole.

Plug-in vehicles show great promise for addressing the nation’s environmental and energy challenges. But it will take strong public policy action to help plug-in vehicles make the leap from promising technology to everyday reality for Americans.

Plug-in cars can make a major contribution to America’s efforts to reduce global warming pollution.

Public charging station, San Francisco. Photo by Siena Kaplan.

• More than 40 recent studies show that plug-in cars produce lower carbon dioxide than traditional gasoline-powered cars. One study by the Department of Energy’s Pacific Northwest National Laboratory (PNNL) found that a car fueled by unused capacity in the current electric system would emit 27 percent less global warming pollution than a car fueled by gasoline.

• Studies also found that plug-in cars reduce global warming emissions even when electricity comes primarily from coal, because plug-in cars use energy more efficiently than conventional cars. The PNNL study found that plug-in cars would produce lower global warming emissions than conventional cars in almost every area of the country, using the current electric system.

• America can reduce emissions even further by making its electricity supply cleaner. A study by the Electric Power Research Institute and the Natural Resources Defense Council found that a plug-in hybrid with a 20 mile electric range running on completely clean electricity would emit less than half the global warming emissions of a plug-in hybrid running on electricity from coal-fired power plants.

Switching to plug-in cars will improve our air quality for most Americans.

• Replacing gasoline with electricity will reduce the smog found in our cities and other densely populated areas dramatically. The PNNL study found that powering cars on electricity instead of gasoline would reduce smog-forming volatile organic compounds (VOCs) and nitrogen oxides (NOx) by 93 percent and 31 percent, respectively.

• A study by the Electric Power Research Institute and the Natural Resources Defense Council found that if current emissions standards for power plants are enforced, converting 40 percent of U.S. cars to plug-in hybrids by 2030 would decrease smog for 61 percent of Americans, and increase it for 1 percent of Americans. Soot would decrease for 82 percent of the population, and increase for 3 percent of the population.

• Powering cars on clean electricity such as wind and solar power, either directly or via the electric grid, would eliminate smog in cities and highways with no increased power plant pollution.

Switching to plug-in cars will reduce oil consumption

• If three-fourths of the cars, pick-up trucks, SUVs and vans in the United States were powered by electricity, oil use would be reduced by the equivalent of 52 percent of U.S. oil imports.

Plug-in cars have many benefits and are quickly becoming practical for an increasing number of drivers

• Plug-in hybrids that have been converted from conventional hybrids already exist that achieve 100 miles per gallon or more.

Tesla Roadster

• Electric cars that can go over 200 miles on one charge are being sold in the United States today.

• Most plug-in cars can charge in a normal wall outlet found in many home garages, and rapid chargers have been developed that can fill a 100-mile battery in 10-15 minutes.

• Fueling plug-in cars costs two to five cents per mile, or the equivalent of $0.50 to $1.25 a gallon of gasoline.

• Fuel savings over a ten year period, compared with fuel costs for a conventional car, combined with a federal incentive, can reduce the lifetime cost of a plug-in car as much as $17,000.

• Electric cars are much simpler to maintain than conventional cars, with one moving part compared with the hundreds of moving parts required for an internal combustion engine. Electric cars have no oil changes, and require far fewer repairs.

• Plug-in hybrids are more expensive than conventional vehicles, but will become cheaper over time as battery technology improves and mass production is achieved.

America’s electric system has the capacity to fuel most of our cars today, and plug-in cars could make our grid more reliable and cleaner

• America’s electric system could fuel 73 percent of U.S. cars, pickup-up trucks, SUVs and vans without building another power plant, by charging vehicles at night.

Easy on the grid

• One million plug-in cars charging simultaneously would only use about 0.16 percent of America’s current electric capacity.

• Plug-in cars could help stabilize the electric grid and provide emergency backup power – reducing the cost of electricity for all consumers.

• If half our cars were plug-in hybrids whose batteries were available to utilities, wind power in the U.S. would double by 2050 through market forces alone, according to a study by the National Renewable Energy Laboratory. This is because parked plug-in cars would provide electric storage capacity that could displace the backup generation capacity utilities would otherwise need to purchase to provide power when the wind isn’t blowing, lowering wind power’s cost.

There are still barriers to the widespread adoption of plug-in cars, but public policies can help to overcome those barriers.

• Despite rapid advances in battery technology over the past decade, automakers and battery developers still have strides to make in arriving at battery designs that deliver the range and affordability American consumers are looking for. Continued funding for research and development of advanced batteries can help.

• The cost of plug-in car prices will be high until they are mass produced. Consumer incentives for plug-in cars and government and fleet purchases can help spur the market for plug-ins, enabling them to achieve mass production more quickly.

• Plug-ins have the potential to deliver many economic benefits – from reducing the cost of electricity to curbing global warming pollution. State and federal governments should adopt policies – ranging from investments in “smart grid” technology to a cap on global warming pollution – that would unlock these benefits, and ensure that purchasers of plug-in vehicles are compensated for the benefits their choice delivers to society.

• The lack of public charging infrastructure – while not a deal-breaker for plug-in vehicle owners who can charge their cars at home – could limit the willingness of some consumers to buy or use plug-in vehicles. Local, state and federal governments should jump-start the creation of charging infrastructure by installing chargers at publicly owned facilities, developing procedures for the installation of chargers on city streets, and encouraging private development of charging infrastructure.

Governments should ensure that the electricity fueling plug-ins is increasingly clean and renewable.

The Sun's "green screen" test drive of the Nissan Leaf, before the real one.

• States and the federal government should enforce a low-carbon fuel standard, requiring that transportation fuels be 10 percent less carbon-intensive by 2020. When calculating global warming emissions, full lifecycle emissions such as indirect land use impacts should be included. This would encourage a switch to electricity as a fuel.

• States and the federal government should require that at least 25 percent of our electricity comes from clean and renewable sources like wind and solar by 2025.

• The federal government and states should strictly enforce current power plant emissions regulations, and fill any gaps in regulation, so that our air quality will continue to improve regardless of the amount of electricity produced.

• The nation should adopt a cap on global warming pollution that reduces emissions to 35 percent below 2005 levels by 2020 and to 80 percent below 2005 levels by 2050.

Click on image to download full report.













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