Why Concentrated Solar Power

Two of the widely used alternatives for collecting the suns energy are the concentrated solar power (CSP) plant where sunlight is focussed on a receiver in which a circulating working fluid is heated and used as the heating media for a conventional power station and the photo voltaic (PV) plant where sunlight is converted directly into electrical energy.

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The new technology could be attractive in land-rich areas, and it may also have some application for introducing sustainable energy to more densely developed areas, since its use of high efficiency solar cells enables it to pack more generating capacity into less space.  It also may prompt some new exploration of the opportunity to double up solar energy generation with other operations, such as fish farming.

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Aora-Solar, an Israeli company, has constructed, licensed and launched the first solar thermal energy (STE) natural gas hybrid electric generator (June 2009). At the time of this post, it is being tested in Kibbutz Samar in southern Israel. Such hybrids can lower the carbon footprint of existing natural gas power plants. The Israeli design is modular and permits small plants that can serve communities without long distance line losses. Florida Power and Light is scheduled to launch their first hybrid in 2010.

As I discussed in a previous post, electricity can be generated by high temperature or concentrated solar power (Solar Thermal: The Other Solar Energy). Basically, solar rays are concentrated and directed to a heat collector that transfers their heat to a heat engine (usually a closed circuit steam engine) that drives an electric generator.

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It’s not diamonds.  Nor is it gold.  But it might be just as lucrative. European firms this time have their eyes on North African deserts as the location of a giant network of solar thermal plants to provide low-carbon energy for Europe.

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“At noon on a typical workday, technicians in a two-story control room monitor a dozen screens showing the heat generated by each array of mirrors. As temperatures creep past 700 degrees, icons blink to red from green, indicating the center is ready to feed electricity to the California grid.”

The resulting steam turns turbines that generate electricity — enough to power 112,55 L.A.-area homes. Concentrated solar thermal’s potential has not escaped the attention of forward-thinking investors with big money:

“Chevron, Goldman Sachs, FPL, PG&E and other companies have filed more than 50 applications with the Bureau of Land Management to lease government-owned desert property for solar power systems. Google’s philantropic division put $10 million into eSolar, a start-up in Pasadena, California.” –Greg Chang, Bloomberg.com

Second, one of the biggest advantages of renewable energy is it reduces dependence on unstable nations and authoritarian oil regimes. But in this case, those benefits might not exist, or might not in the future.  North African nations aren’t exactly representative of stable democracies.  In fact, Germany’s largest solar company, SolarWorld, has said that North Africa is too risky a location. “Building solar power plants in politically unstable countries opens you to the same kind of dependency as the situation with oil,” said Frank Asbeck, the firm’s managing director.  Granted, as a producer of Photovoltaic-style solar power, SolarWorld has a vested interest in nay-saying solar-thermal power, but the issue is certainly one to consider.  Could trans-continental cables be easily cut or dismantled, posing a serious energy security risk?

Third, is mega-project power production from abroad the future of our renewable energy grid? Should billions be spent on energy production thousands of miles away, when it is increasingly cost effective to have domestically produced, locally-owned and operated solar, wind, and hydro-power production?

Finally, does Desertec smack too much of a new type of resource colonialism? Granted there is a difference: sunlight, unlike diamonds or gold, is infinite.  Indeed, can sunlight even be called a resource in the traditional sense?  Nonetheless, the projects will be built in the Sahara and would presumably be controlled and managed by international banks and corporations for the overwhelming benefit of European citizens and businesses.  Would the project create a deeper foothold for multinationals to control other aspects of North African development, such as desalination plants or water and mineral resources?

Gerhard Knies, chairman of Desertec’s supervisory board, has dismissed these concerns, saying that local needs would come first and local jobs and income would be created.  “It creates win-win situations for the participating sides,” he told the NYT Green Inc. columnist Tom Zeller.

But haven’t we heard this before?

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Las Vegas, Nevada - The current period of sustained growth in the American Southwest is putting tremendous demands on important resources like water, wildlife habitat, and, with the light beaming from the top of Las Vegas’ Luxor Hotel as a reminder, electricity. Nevada currently gets about 90% of its electricity from fossil fuels, and the majority source fuel is natural gas.

As natural gas prices are predicted to rise, a debate is stirring about whether the state needs to build new coal-fire power plants to meet current needs, or whether it should tap its renewable resource potential. For that reason, Acciona Energy could not have picked a better time than today to dedicate their new 64 MW concentrating solar power plant (CSP) in Boulder City, Nevada, less than thirty miles from the Las Vegas strip. And with a star-studded collection of speakers like Ed Begley Jr., NASA astronaut Dr. Sally Ride, and Apple co-founder and tech whiz Steve Wozniak, the Spanish-based Acciona dedicated the facility in true Las Vegas style.

The 300-acre site in Boulder City uses parabolic trough collectors to generate electricity. The 760 mirrored troughs track the movement of the sun’s path, and their 184,000 mirrors face the sky and concentrate the sunlight to a large metal and glass receiver in the middle of the trough that holds circulating oil. The oil travels to heat exchangers, which heat water and create steam that spins a turbine. Seems simple enough, right? Continued…

At 64 megawatts (MW) of generation capacity, Nevada Solar One is the largest CSP plant to be built in 16 years and it makes Nevada the largest per capita producer of solar power in the country. After roughly a decade of little growth for the industry, CSP is coming back strong, as is further evidenced by today’s announcement by Abengoa Solar that they will be building a 280 MW concentrating solar facility in Arizona.

The absence of any new CSP over the last 16 years leaves many people scratching their heads and asking themselves, why? There were some 354 MW of parabolic trough collectors installed in California’s Mojave Desert between 1984 and 1990. And those plants are still in operation, currently producing energy at around $0.12-$0.14/ per kilowatt-hour (kWh). The Nevada Solar One plant will produce electricity at around $0.15-$0.17/kWh.

Just by looking at the National Renewable Energy Labs CSP solar resource map, you might surmise that the US desert southwest has the potential to be the Saudi Arabia of solar resources (although I suppose Saudi Arabia could also be considered the Saudi Arabia of solar resources). However, the federal government must take the lead and adopt policies and incentives that can provide the necessary investment security for companies like Acciona, and Abengoa, to continue their renewable energy development in the American Southwest. And who knows, maybe even an American company or two can get in on a little of this some day. Wouldn’t that be something?

Photo: Tinou Bau via flickr

Map: National Renewable Energy Laboratory’s TroughNet

Technology

The American Southwest would be the home of massive amounts of solar power needed for this clean energy conversion. Specifically, two types of solar power would be employed: Photovoltaic (PV) cells and concentrated solar power.

According to the solar grand plan, 30,000 square miles of PV cells would provide 3,000 gigawatts (GW) of energy. The “30,000 square miles” part made me flinch, but already existing solar installations indicate that the land needed for each gigawatt-hour of solar energy in the Southwest is less that the amount of land needed to run a coal plant and mine the fossil fuel for it.

Concentrated solar power would supply about one-fifth of the solar energy in the plan. Concentrated solar power uses long metallic mirrors that focus the sun’s rays onto a pipe filled with fluid. The fluid is heated and runs through a heat exchanger that produces steam that turns a turbine. Nine plants like this already exist in the in U.S.

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