One of the problems with the last generation of solar power technology is that it really only worked — that is, generated power — when the sun was shining. But the new generation of solar power technology can store heat that can be used to generate power around the clock, and perhaps one day can even be used in heat-intensive manufacturing. John Mathews explains.
Spain and the southwestern states in the United States (California, Nevada and Arizona) are making big bets on concentrated solar power (CSP). When combined with a molten salt heat transfer fluid, CSP can store heat for several hours, allowing power to be generated night and day, at utility scale.
So let's put an end to all the talk about solar (and renewables generally) presenting problems because its supply fluctuates and is not backed by storage. On the contrary, the solar era has finally arrived.
Many U.S. companies involved in CSP are doing well and have been featured in recent articles by major media outlets. One of them is SolarReserve, which utilizes a field of computer-controlled mirrors (heliostats) and a power tower, where the sun's rays are concentrated.
SolarReserve has the go-ahead to build its CSP plant with molten salt storage in the Nevada desert next year. It has already reached power purchasing agreements with utilities, making it easier to raise additional capital. It also has a $737 million loan guarantee from the U.S. Department of Energy.
Another power-tower player is BrightSource, which is building CSP plants in California that are slated to begin operating in 2016 and 2017. The BrightSource technology heats water to superheated steam, which is then fed to a turbine to generate electricity (similar to what happens thermal power stations). The steam can also be used to heat molten salt, which acts as a storage medium.
And just last month it was announced that a new industry association, the Concentrating Solar Power Alliance (CSPA), has been founded by three companies, BrightSource, Abengoa and Torresol Energy. The group will help raise the visibility of CPS in the United States and complement the global industry association, the World Solar Thermal Electrical Association (STELA World).
Insofar as the U.S. federal government is banking on CSP, through loan guarantees and tax breaks, as a reliable technology for the future energy system, it is doing the right thing in helping renewables get to the point where expanding demand will drive down costs to well below those of thermal power.
But the country that really promises to benefit enormously from CSP — and could become the world leader — is India. Recent articles in the New York Times and The Economist explain why.
Vikas Bajaj described in appalling detail how India's power problems are bad and getting worse, because of the mistakes it made in exploiting domestic coal reserves. India's economic growth has slowed from 10% a year in 2010 to 7% last year, in part due to problems in its power sector.
But a problem for coal-fired electricity generation creates an opportunity for an alternative — and solar is stepping in to that breach. The Economist's April 28 article describes India's many solar initiatives, including the Jawaharlal Nehru National Solar Mission, which has the ambitious goal of raising India's solar power capacity to 22 gigawatts by 2022, up from two gigawatts.
India missed the wind and solar photovoltaic waves, but now seems determined to use its latecomer status to catch up and forge ahead in the relatively new field of CSP. Several companies have already emerged and are receiving solid backing from the government's Ministry of New and Renewable Energy.
In October 2011, the world's first commercial-scale molten salt CSP facility came on line in Seville, Spain. The Torresol Gemasolar plant covers 185 hectares and can produce 19.9 megawatts of power. The plant is anticipated to operate with a 75% capacity factor, meaning it comes close to coal, nuclear and natural gas facilities.
This technology is rapidly spreading to other parts of the world. The North African Desertec project promises to transform the energy prospects of countries like Morocco and provide them with non-oil exports to Europe. Desertec is backed by German engineering giants Siemens and E.On.
Concentrating solar thermal energy and storing it with molten salt technology answers many of the criticisms leveled at solar power — that it is fluctuating, cannot meet baseload, and is too diffuse and resource intensive. It is revealing to see how CSP with molten salt technology meets these charges head-on — and triumphs.
CSP with molten salt technology delivers baseload, dispatchable, regular power. The key fluctuation with solar power has always been that it is available only during the day, and thus requires some kind of storage system to carry through to other times. But CSP with molten salt technology produces heat that can be stored for 15 hours or beyond.
CSP can be used to generate electric power or industrial heat continuously — and at industrial-scale levels of 100 megawatts to one gigawatt that, when aggregated, is more than enough for baseload power. Thus, all the talk of needing gas-fired turbines as back-up can be dismissed as so much "hot air."
There is the distinct possibility that CSP could eventually generate sufficient heat that it can be used directly for industrial processes. Indeed, the heat could potentially be used to produce the aluminum and glass needed for the CSP mirror arrays.
This might be a small step as far as the industry is concerned — but it would be a giant step for humankind. Because it would mean that the industrial process for producing CSP equipment would be completely self-sustaining and independent of fossil fuels.
Think about that. Renewable energy equipment would be produced utilizing renewable sources (for heat and power), and this in turn would generate renewable heat and power, which again could be utilized to produce more equipment — and so on, around and around.
Moreover, it is certain that the materials themselves would be almost 100% recirculated (such as steel, now over 90% recycled), and so the resource impact of a large-scale (giga-scale) CSP program would be minimal.
This will be a renewable, circular economy — and it will help make a sustainable future that much more of a reality.