Friday, March 28, 2008

Solar Thermal: Not as Sexy as PV, But More Ready for Prime Time Energy Production

Solar thermal is the solar sister with less sex appeal, but more maturity. This sister is ready to start putting out power, and over a longer time span.
The ability to utilize solar thermal technology after the sun sets is made possible by a storage system that is up to 93% efficient, according to Ausra’s executive vice president John O’Donnell.

High efficiency is achieved because solar thermal plants do not need to convert energy to another form in order to store it and do not rely on battery technology. Flat moving recflectors or parabolic mirrors focus solar energy to generate heat. This heat generates steam that turns turbines, thus generating an electric current.

If you want to generate electricity-at, say, 3 am-heat from the sun can be stored for later use. This gives solar thermal technology the ability to not just produce peak power, but also generate base load electricity.

“Adding solar plants that reliably generate until 10 pm displaces the highest cost alternative power,” said John O’Donnell. “That is the first wave of solar thermal plants. The daily and seasonal variation in grid load in the United States matches solar availability.”__CleanTechnica

This built-in advantage of solar thermal should exist for at least the next 10 to 20 years. In 20 years or so, utility-scale electric storage should allow photovoltaics to mature, and begin producing at the levels of her older sister.

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Blogger Cyril R said...

It's true.

Thinfilms etc are no doubt going to come down a lot in price, but will they ever be as cheap as bended commodity mirrors?

Unlikely. Sure you need a turbine, but Ausra is going for saturated steam, and those are not that expensive - probably a lot cheaper than the PV inverters would cost.

Will batteries ever be cheaper than simply storing hot pressurized water deep underground - at a cost of about 10USD per kWh?

Unlikely, at least not at the efficiency lever thermal storage is right now. Steam accumulators can be more than 99% efficient due to not needed a heat exchanger.

PV, especially some thinfilms, do produce power more cost effective in small distributed generation, and can capture diffuse sunlight so may operate well in less sunny areas - but that would require a more serious price drop still. However, such distributed PV can compete with retail which is a considerable advantage over competing with wholesale prices.

I think it may prove cheaper to export desert solar to less sunny areas rather than produce it on site. This does require a high upfront investment in transmission.

9:21 AM  
Blogger al fin said...

Excellent point about the efficiency of steam accumulators and other thermal storage, cyril.

Distributed PV, as you say, can be very cost effective.

If they do build some GW scale PV plants in the middle of the desert, they may want to invest in HVDC transmission lines for higher efficiency, and better underground/undersea applications.

2:54 PM  

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