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Interesting News in Renewable Energy
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Storing Solar Energy May Not Be Such a Problem After All
An article in this week’s Science Times offers an intriguing glimpse of the potential of solar thermal, a form of renewable energy generation that, while not nearly as hyped as PV solar, may ultimately be more feasible for large-scale energy production. One of the biggest issues with photovoltaic (PV) technology (i.e. - solar panels) has been how to store the energy once it’s generated to meet demand during times of low production, such as at night or on cloudy days. Solar thermal systems avoid this problem because they rely on generating energy from the sun’s heat, which can be more easily stored than the sunlight-generated energy of PV systems. At the core of solar thermal is a surprisingly simple concept: the sun’s rays are used to boil water, which then generates steam to power turbines. The energy is then stored in tanks of molten salt, which can reach about 1,000 degrees Fahrenheit without becoming too pressurized. This allows the energy to be stored for hours, even days, until it is needed. Most current systems achieve this by focusing a field of hundreds to thousands of specially designed lenses on a large water tank or pipe system, then pumping the resulting heat through a closed loop consisting of hot and cold salt tanks, a steam generator and a turbine. “Nevada Solar One”, the 64 MW Acciona power plant which opened in Boulder City last year is one such system. The largest solar power plant to be built around the world in the past sixteen years, Nevada Solar One can produce enough energy to power 15,000 households. Now other visionary companies are experimenting with variations of this basic design to further improve efficiency. Proponents of solar thermal boast other benefits, as well, including greater potential at higher latitudes and other places that don’t get much sun and its greater affordability; solar thermal systems based on a parabolic trough design produce energy at a rate that is 50-75% cheaper than its PV equivalent. As these technologies develop further, different niches may emerge for each. While PV panels may ultimately become the industry standard for individual home-owners and relatively small, off-the-grid systems, solar thermal’s double-barreled promise of storage and price make it a strong candidate for that clean, large-scale power source we’ve all been clamoring for. |
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Cheaper Solar Cells in the near future?? Nanosolar, a heavily financed Silicon Valley start-up whose backers include Google’s co-founders, plans to announce Tuesday that it has begun selling its innovative solar panels, which are made using a technique that is being held out as the future of solar power manufacturing. The company, which has raised $150 million and built a 200,000-square-foot factory here, is developing a new manufacturing process that “prints” photovoltaic material on aluminum backing, a process the company says will reduce the manufacturing cost of the basic photovoltaic module by more than 80 percent. Nanosolar, which recently hired a top manufacturing executive from I.B.M., said that it had orders for its first 18 months of manufacturing capacity. The photovoltaic panels will be made in Silicon Valley and in a second plant in Germany. While many photovoltaic start-up companies are concentrating on increasing the efficiency with which their systems convert sunlight, Nanosolar has focused on lowering the manufacturing cost. Its process is akin to a large printing press, rather than the usual semiconductor manufacturing techniques that deposit thin films on silicon wafers. Nanosolar’s founder and chief executive, Martin Roscheisen, claims to be the first solar panel manufacturer to be able to profitably sell solar panels for less than $1 a watt. That is the price at which solar energy becomes less expensive than coal. “With a $1-per-watt panel,” he said, “it is possible to build $2-per-watt systems.” According to the Energy Department, building a new coal plant costs about $2.1 a watt, plus the cost of fuel and emissions, he said. The first Nanosolar panels are destined for a one-megawatt solar plant to be installed in Germany on a former landfill owned by a waste management company. The plant, being developed by Beck Energy, is expected to initially supply electrical power for about 400 homes. The company chose to build its plant in southern San Jose, news that was cheered by local development officials. Much of the microelectronics industry created here has moved to Asia and new factories are a rare commodity in Silicon Valley. |
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Solar Company Says Its Tech Can Power 90 Percent of Grid and Cars
The key to the scenario, however, is developing the ability to store energy for 16 hours, thus creating a stable power source through cloudy periods and the night, a feat that has so far eluded engineers. "If we can do storage," Ausra CEO Bob Fishman said, "We can take on coal." The paper says Ausra expects to commercialize its energy-storage technology within two years. A prototype of the system will go into a model plant the company plans to finish this summer in Bakersfield, California, the company's founder, David Mills, told Wired.com. Solar-thermal power is gaining adherents, including Google.org, which cut a deal with another player, eSolar, as a way to cleanly generate cost-competitive, city-scale amounts of power. Unlike traditional photovoltaics, which use panels to convert sunlight into electricity, solar-thermal plants focus the sun's rays on liquids to make steam that powers turbines. Solar-thermal is flat-out more efficient -- at 20 to 40 percent -- than photovoltaics, which in the field convert sunlight to electricity at about 15 to 22 percent. And solar-thermal fits into the industrial model of power production, meaning that it works in big plants, not distributed across a bunch of houses and buildings. Mills' paper reveals some interesting statistics about the construction cost of solar-thermal technologies: $3,000 per kilowatt of capacity, but estimated to drop to $1,500 per kW over the next "several" years. The New York Times last year quoted GE Energy executives giving construction costs for coal plants at $2,000 to $3,000 per kilowatt. Ausra says it can generate electricity for 10 cents a kilowatt hour, which is close to the cost of natural gas, and it expects the price to drop even further. The company has received a lot of attention because of its compact linear Fresnel-reflector technology, and because it lined up two big-name VCs early: Vinod Khosla and Kleiner Perkins, where Al Gore is a partner. It's received $43 million in venture capital, and an additional $30 million at least in venture debt. It's planning a $100 million-to-150 million funding round later this year. Ausra, for now, sells power to utilities. In total, it's announced a real commitment for 1,500 177 megawatts of solar power deployments from California's Pacific Gas & Electric, and Fishman says the company has several thousand more megawatts of deals in the pipeline. A recent deal between a different solar player, Abengoa, and Arizona Public Services, for a 280-megawatt plant had the following terms: 30 years, $4 billion. Still, there are reasons to be skeptical. For one, companies have been piling into the solar-concentrating space. Stirling Energy Systems, SkyFuel, Solel, BrightSource, Rocketdyne, Abengoa and the aforementioned eSolar are all working on using mirrors to concentrate the sun's energy in one way or another. That's a lot of competition for a still-small chunk of the energy business. Perhaps a more fundamental question is: Can all these prospective plants actually get built? Conceptually, solar thermal is a real bright spot in an otherwise depressing renewable-energy landscape, but until there are dozens of functional plants, it will be hard to know what kind of engineering costs these facilities are going to run into. And that's assuming that the storage technologies being discussed turn out to work. There's a long road from a prototype plant in Bakersfield to providing 90 percent of the nation's electric needs. For one, the nation's electricity-transmission infrastructure would have to change considerably as well, but that's a topic for another post. Jeremy Carl, a research fellow in Stanford's Program on Energy and Sustainable Development, and a noted sane proponent of cleanish coal, saw scaling up the solar thermal plants as the major problem. "In the time frame we have it is incredibly difficult to scale these sorts of new technologies up to the point where it becomes meaningful to the global energy system," Carl wrote in an e-mail to Wired.com. "There are always shortages of engineers who understand the technology, systems integrators, people to build components, etc." Other environmental groups, however, level the same criticism at carbon capture and sequestration, which aims to trap carbon dioxide emissions from coal burning and bury them underground. Carl also questioned whether or not the solar-thermal plants could approach the 100 percent reliability that grid-electricity users have come to expect. "The Tesla guys are finding out the hard way that 99 percent reliability is not acceptable in a consumer mass-market product like a car," Carl said. "The same is even more true for power sources." In the near term, these companies will be feeding off states in the southwestern United States that have built solar requirements into their renewable energy dictums. Nevada, Arizona, New Mexico and Colorado all require between 15 and 20 percent of their power to come from solar sources. Solar-thermal is the only technology that could realistically deliver that type of power. Any sort of system that puts a price on emitting carbon dioxide -- either a carbon tax or a cap-and-trade framework -- would be helpful because it would penalize coal and aid cleaner technologies. Ultimately, though, these companies want to dominate the grid. As Mills wrote in the paper, solar-thermal "is probably the only currently available technology which can be considered for a globally dominant role in the electricity sector over the next 40 years." To achieve a dominant role globally, including China and India in the picture, they'll have to fulfill Google's dream of making RE < C, i.e., making renewable energy less expensive than coal.
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