Solar Thermal’s Rise to Power (get it?)

With Professor Jaluria’s upcoming lecture on solar thermal power, i figured it would be nice to have some background and context. While photovoltaic systems are what most people associate with solar-derived electrical power, thermal systems are, at this point, the most efficient method for generating electricity from solar energy.

Solar thermal power generation was first looked at in the 1970’s during the oil crisis. This research resulted in the SEGS (solar energy generating systems) commercial project, which consisted of 9 different solar plant’s in California’s Mojave Desert (constructed between 1984-1989). Total capacity of the plants, which are still in operation today, is 354 MW. By comparison, the largest PV system currently operational in the world is a 20 MW facility in Spain. This, however, was the only real solar thermal electrical generation facility in the US until 2005.

2005 saw a revival of solar thermal. A company by the name of Stirling Energy Systems emerged with economically sound proposals for new solar thermal facilities. Named Top 25 Breakout Companies of 2005 by Fortune magazine, they signed contracts with Southern California Edison to develop more solar thermal facilities (500MW) in the Mojave Desert.

Most recently, California Utility PG&E signed a contract to develop 900 MW of solar thermal power over the next couple of years from Brightsource Energy.

These are not the only companies trying to get set up in the Mojave.

It seems like solar thermal is really making a splash. Some questions to think about going into Professor Jaluria’s lecture on 4/21 (for those of you in Professor Muller’s Energy Seminar):

How far can electricity be transmitted from desert areas without significant tranmission losses? Can superconductivity be viable in such a hot environment?

Stirling Energy Systems is using Stirling Engine technology (hence the name) to generate electricity from a thermal gradient. How do these engines work? Why do they have higher efficiency than, say, a steam engine?

Thermal energy storage is a key component to any solar thermal installation. I believe they are using molten salts to store their energy. How efficient can an energy storage system like this be?


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5 Responses

  1. Here’s an interesting situation. Stirling Energy has just had their product proven on the testing grounds by demonstrating six fully operational Stirling engines with mirrors. However, I’m not sure of their business smarts. While admitting they still have to get these things produced on an assembly line, they signed a contract with California to have two operational large scale facilities producing a total of 1.75 Gigawatts of peak power. This would require a minimum of 70,000 operational engines between the two facilities. This also assumes that the mass produced versions will produce the same power as the prototypes. If I read this and other websites correctly, which I might not have, then a failure to meet this contract within a few year period will effectively bankrupt the company.

    So it looks like theres going to be a showdown in California between Brightsource, which produces large scale facilities using the rankine cycle and mirrors to focus the light on one central tower rather than parabolic mirrors for use in solar troughs, and Stirling Energy. Both have large scale contracts. Brightsource’s product is a proven tech while Stirling’s has yet to be proven, though that hasn’t stopped California from investing heavily in it.

    According to Stirling’s press releases though, it seems they are heavily emphasizing their tech’s scalability, and seem to imply possible future applications as smaller power plants possibly in conjunction with the “microgrids” approach we’ve heard about. Brightsource’s is not so scalable. In light of the recent presentation on grid ownership and blackout propagation, however, I’m not so sure of Stirling’s ability to break into this market. What are your takes on this?

    Also, Stirling emphasizes they use hydrogen as their working fluid and I can’t figure out why. Does anyone know what its advantages are over other working fluids?

  2. I think the question here is what you mean by scalability. From what I understand, Brightsource’s technology is more economically scalable in the direction of larger plants in hot areas. Since it utilizes a standard Rankine cycle, it needs high-grade heat in order to produce high temperature, high pressure steam. It is more proven because other than the solar concentrating mirrors, the plant would work identical to a standard combustion power plant. I doubt, however, that you’ll see a plant like this outside of desert areas.

    The Stirling Energy technology is “scalable” because the heat needed to run a stirling engine can be low-grade heat. This means that if effective, its more realistic to set up one of these plants on a smaller scale, and not necesarrily in a desert.

    My guess would be that Brightsource produces a more economically attractive plant in the Mojave, but if Stirling can produce a viable alternative, it would be a better option for smaller installations in non-desert areas.

    Brightsource and Stirling are FAR from the only companies trying to make something happen in the Mojave. Here’s a nice overview of the companies vying for plants. Capitalism at its best.

  3. Solar eneragy is the future for the world.
    solar water pump

  4. I read this piece of writing fully about the comparison of most recent and preceding technologies, it’s remarkable article.

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