photo: Tessera Solar
Another day, another Big Solar deal.
Tessera Solar on Wednesday said it will build a 1.5 megawatt Stirling solar dish power plant outside Phoenix to supply electricity to utility Salt River Project.
The announcement follows Tuesday’s spate of solar power plant deals. As I wrote in The New York Times, utility Southern California Edison (EIX) agreed to buy 550 megwatts of solar electricity that will be generated by two massive thin-film photovoltaic power plants to be built by First Solar (FSLR). Later in the day on Tuesday, First Solar said that it had struck a deal with the Los Angeles Department of Water and Power to supply 55 megawatts from a PV farm to be constructed in Southern California’s Imperial Valley.
Tessera Solar is the development arm for Stirling Energy Systems, the maker of the SunCatcher solar dish. The company is developing two huge California projects — a 850-megawatt, 34,000-dish solar farm to be built on 8,230 acres to supply power to Southern California Edison and a 750-megawatt power plant complex for San Diego Gas & Electric (SRE).
The 60-dish Salt River Project solar farm is but a fraction of the California solar farms’ size but will serve as a demonstration project for Tessera’s technology.
Most notable, given the years-long licensing process for big solar power projects in places like California, Tessera plans to break ground next month and bring what it calls the Maricopa Solar plant online in January 2010.
Tessera will lease the project site from Salt River Project and sell the electricity to the utility under a 10-year power purchase agreement.
Green Wombat 
Energy density = 100kw/acre is relatively poor compared to PV and potentially CPV, if it can ever get commercialized. Both Esolar and Stirling structures look expensive relative to fixed tilt array structures. Private land doesn’t mean no environmental review or potentially showstopping permit process. On the contrary, the local permitting jurisdiction is required to ensure project complies with CEQA in CA, not sure about AZ. Those reviews are very rigorous.
Actually by my calculations the Stirling Dishes are about the same as PV. Remember when they talk about the amount of land it is not all covered with dishes. Some will be office space, warehouses, shops and sub-stations. The Stirling Dishes are approximately ten acres per MW. Optisolar’s (now First Solar’s) 550 MW PV plant is supposed to be on about 5700 acres of land for a little over 10 acres per MW. Solar thermal is claiming between 4 and 8 acres per MW.
I don’t claim to be an expert on PV but I see some real problems with it. First off with flat plate technology you only get your rated capacity for a very short period of time. As sun angle increases your efficiency decreases. You have no way of adjusting for daily or seasonal sun angles. The Stirling Dishes will be able to do both of these. My problem with both the Stirling Dishes and PV is they have no way of storing energy. When the sun goes away, your power goes away. Not really a problem if you have a few scattered panels on houses but if you have 500 MW field it could cause some real problems. It is very common, especially in the summer, for a couple of large clouds to come over your field and wipe it out. Then 10 minutes later for them to be gone. For PV and Dishes this is basically the equivalent of tripping a power plant and then have it suddenly come back on. Again it is not a problem if you have a few scattered ones but in a large field this could be a sudden two or three hundred MW swing. Not exactly what the grid likes. Remember electricity is not stored.
Now solar-thermal plants have a natural stored energy in the system. When clouds come over they slowly loose power and then slowly gain it when the sun comes back out. Many of the designs also have future plans for energy storage in the form of molten salt or steam. While these designs will not be able to run 24/7 year around they will allow the load to be adjusted to when it is most needed.