Concentrating solar more cost competitive Part 1
by Ray Block
The accepted view is that wind energy electricity per kWh is almost competitive with natural gas and coal, but solar energy is much more expensive. In turn, concentrating solar (CSP) in utility scale plants, is cheaper than solar PV
However, there is a concerted effort among CSP producers to bring down costs to more competitive levels. The then largest CSP developer in the world, the Israeli company Luz International, founded in 1980 designed and constructed for Southern California Edison (SCE), nine parabolic trough solar systems in the Mojave Desert. The technology consists of rows of curved mirrors focussing heat onto a tube filled with oil, which boils water to make steam for the turbine.
Known as SEGS 1-9, California for the first time had concentrating solar generating capacity of 349 MW, the two final units each of 80 MW being installed in 1990. Although Luz planned more CSP plants, the company was bankrupted mainly because of dwindling levels of subsidies for this pioneering company.
Considerable improvements in design enabled Luz to bring down electricity costs per kilowatt hour (kWh). The first two plants produced electricity at an uneconomic 24cents per kWh. The next five installed plants had reduced electricity costs to 12c per kWh, and the final two plants achieved an electricity cost down to 8c per kWh.
The company aimed to enable new plants to generate electricity at 6c per kWh, which based on the first two plants would have allowed for a 75 per cent cost reduction. Each of the SEGS plants were configured as hybrids to use natural gas on cloudy days, or after dark.
A great deal of ground has been made up in the last two years. At December 2009, there were 25 CSP projects under development in the US. These involved contracts for 6.2 GW, made up of 21 in California, two in Nevada, and one each in Arizona, Florida, New Mexico, and Hawaii.
Today, parabolic trough systems are the most numerous in the CSP market, with the dominant suppliers Solar Millennium of Germany and Abengoa and Acciona of Spain. Solar Millennium’s three 50 MW plants in Andalusia, Spain (the third plant to be completed in 2011) is to be followed by a fourth 50 MW plant in the Spanish Extremadura region.
According to the suppliers, energy efficiency for each of the identical plants peaks at 28 per cent, with an average efficiency of 15 per cent. Each of the plants requires a ground area, equal to 70 soccer playing fields (195 hectares), and uses an immense amount of ground water. Given that CSP is most suitable in arid and desert conditions with large sun cover, the excessive water usage often leads to hostility among local landowners.
Each of the Andasol plants has 209,664 large curved mirrors, each mirror being anchored at four points to a steel structure, with a laser scan checking each mirror’s curve at 1,000 measuring point per mirror. The parabolic trough system is about twice as expensive as other technology platforms on the market.
Solar Millennium’s latest development is a contract of up to 726 MW with SCE in Southern California, with at least two solar trough plants each of 242 MW beginning construction in 2010. A third plant is also contemplated in the future.
A likely solution to the cost of the traditional parabolic trough design comes from SkyFuel of New Mexico. With the collaboration of the National Renewable Energy Lab (NREL),. Skyfuel is demonstrating its SkyTrough, where the traditional glass mirrors are replaced with lightweight glass-free highly reflective polymer mirror film reflectors. This is to be tested out at the site of Luz’s original SEGS 1 and 11 near Daggett, Southern California. Sunray Energy, a division of Cogentrix Energy operates the SEGS plants supplying 43 MW of solar power to SCE.
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Posted under Economies, Global Warming, Low Carbon Economy, Renewable Energies
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