The third-largest solar thermal plant in the world, Nevada Solar One, is set to go on-line in June 2007 with a 64 megawatt all-renewable peak power capacity. According to Gilbert Cohen of Acciona Solar Power, which owns the plant, Nevada Solar One could provide power for about a half-million people.
An informative short movie highlighting the plant and including interviews with engineers who designed and built it can be viewed at http://www.youtube.com/watch?v=cgCJB9mu5CI. This video also includes some stunning images of the plant, which sits on over 300 acres of desert south of Las Vegas, NV.
While solar photovoltaic (PV) is the sun power most people recognize, there are key technical differences between PV and solar thermal systems, as outlined in “Full steam ahead for Nevada solar project”, posted on CNET’s News.com. However, the gist of it is that PV transforms solar photons directly into electrons, most often utilizing a semiconductor-industry-derived p-n junction in silicon. In general, conventional PV panels have an energy conversion efficiency of about 15 percent. In contrast, solar thermal plants convert the sun’s energy to heat using parabolic solar concentrators, which usually track the sun. The heat energy is used in a conventional steam-fired power plant to generate electricity with conversation efficacy limited by the Carnot efficiency. Efficiencies ranging from 20 percent to 40 percent are possible in large-scale solar thermal power plants.
Solar photovoltaic (PV) technology is well-suited to smaller, distributed installations in the kilowatt range, such as residential and commercial roof-tops. Solar thermal is better for large-scale, centralized energy generation in the megawatt range. So, the two approaches should be considered complimentary (not competitive) technologies.
Despite its larger scale, solar thermal has some additional advantages over PV. Thermal energy storage (TES) in the form of molten salt vats can be used to stockpile excess thermal energy as a buffer against cloudy days. In addition, low-grade waste heat rejected from the steam power plant could be utilized as a hot water supply. In hot, dry climates, for which solar thermal is ideally-suited, waste heat could be harnessed for combined cooling and power in nearby buildings or facilities.
In a recent http://www.renewableenergyaccess.com/ article, “A New Chapter Begins for Concentrated Solar Power”, Gilbert Cohen speculated that the U.S. Southwest may ultimately produce up to 40,000 megawatts of solar thermal power, enough for 10 million consumers. While 10 million people using solar-thermal-generated electrons represents only about 3.3% of the total U.S. population, this technology certainly has promise to make a substantial dent the fossil fuel energy demands of the Southwest’s rapidly growing cities: Phoenix, Las Vegas, Albuquerque, etc.