mirrors, and they focus light onto tubes filled with water, thus directly producing steam. Ausra's collectors produce less power, but that power costs less to produce.
Ausra is initially planning a 177 MW plant in California, and has committed to supply 1,500 MW of power to Californian utilities PG&E and FPL. They are also rumoured to be moving in to Texas as well.
PG&E have also signed a 25-year deal with Ausra competitor Solel Solar Systems of Israel to buy power from a 553 MW solar thermal plant that Solel is developing in California's Mojave Desert. FPL has also hired Solel to upgrade the SEGS solar-thermal plants it operates in the Mojave.
Another PG&E contract is with BrightSource to supply between 500 MW and 900 MW of power per year from solar tower plants in California, beginning in 2011, with the first of a number of 100 MW facilities being built in Ivanpah.
Other companies active in the US include eSolar (linked to Google's energy initiatives), RocketDyne and SkyFuel.
Abu Dhabi's Masdar Initiative and Spain's Sener are have formed a joint venture to build and operate concentrating solar power plants across the world's sunbelt regions called Torresol Energy.
Independently of Torresol, Masdar is developing its 100 MW "Shams 1" CSP plant in Abu Dhabi.
Algeria and Germany have signed a a joint research agreement for the development of a new generation of large-scale, low-cost solar thermal power plants (which could contribute to the Desert-TREC vision of large scale CSP in North Africa powering Europe).
More new plants are being planned in :
* Algeria - 20 MW Abengoa's plant in Hassi-R'Mel
* Australia - 10 MW Queensland State Government facility in Cloncurry
* Australia - 154 MW Solar Systems and TRUEnergy's plant in Mildura
* Egypt - 70 MW plant in Kuraymat
* Iran - 17 MW plant in Yazd
* Israel - 250 MW plant in Ashalim
* Morocco - 20 MW Abengoa's plant in Ain-Ben-Mathar
* US (Arizona) - 280 MW Abengoa and Arizona Public Service's plant in Gila Bend
* US (California) - 50 MW Inland Energy's plant in Victorville
* US (California) - 250 MW FPL Energy's Beacon Solar Energy Project
Feasibility studies are also being done in Oman, China and Mexico.
One of the key differentiating factors between solar thermal power and solar PV is that heat energy is more easily (and efficiently) stored than electricity, with solar thermal plants often combining energy storage into the design to enable around-the-clock, dispatchable electricity generation.
Most solar thermal plants are looking to use molten salt for storing energy - other alternatives being developed are graphite (in the Cloncurry development), heated water / steam (for the Ausra plants) and heat-transfer oil such as therminol (for the Abengoa plant in Arizona).
The existing plants prove that concentrated solar power is practical, but costs must decrease. Electricity from solar thermal plants currently costs between US$0.13 per kilowatt hour (kWh) and US$0.17 per kWh, depending on the location of the plant and the amount of sunshine it receives. Conventional power plants generate electricity for between US$0.05 and US$0.15 per kilowatt hour (not including any carbon taxes or cap and trade related costs) but in most places it's below US$0.10 (wind power generally costs around US$0.08 per kWh).
An economic analysis released last month by Severin Borenstein (pdf), director of the University of California's Energy Institute, notes that solar thermal power will become cost competitive with other forms of power generation decades before photovoltaics will, even if greenhouse-gas emissions are not taxed aggressively.
In 2006 a report by the Solar Task Force (pdf) of the Western Governors’ Association concluded that CSP could provide electricity at US$0.10 per kWh or less by 2015 if 4 GW of plants were constructed.
According to Bernhard Milow from the German Aerospace Center (DLR) electricity from solar thermal plants could cost as little as €0.04 per kWh [US $0.06/kWh] by 2020, with well sited plants potentially generating power at lower prices than coal.
The US DOE began supp