The compound annual growth rate of the CSP market is expected to be 42.1 percent from 2010 to 2017.37

The most common available form of CSP is the parabolic trough concentrator, as seen in Figure 5.10. These systems are usually set up on one-axis tracking systems, which track the Sun over the course of the day. This type of plant consists of a parabolic mirror focusing sunlight onto a tube of heat-transfer medium, usually oil, which is then heated and used to create steam, which can drive an electric generator. The maximum temperature is limited by the oil-based heat-transfer medium and the lower concentration required with single-axis tracking, limiting the efficiency of these systems to approximately 15 percent.38

As of 2009, parabolic trough concentrators accounted for more than 83 percent of installed CSP capacity.39 The oil intermediate is difficult to store efficiently for use during off-peak hours. Hence it is possible that trough technology with oil intermediates might lose market share and will have a harder time reaching grid parity.40

The solar tower is a relatively recent incarnation of CSP, using a large field of flat mirrors called heliostats to direct incident sunlight to a focal point in a central tower, as shown in Figure 5.11. A heat-exchange medium, usually a molten salt, absorbs the energy and is heated to temperatures up to 1000°C, which can then be used to generate electricity. This larger temperature difference allows more efficient electricity generation than the common trough technology, with conversion efficiencies in the range of 20 to 35 percent.41

Power tower systems offer a much more efficient alternative to the parabolic troughs that currently dominate the CSP landscape. In addition to the greater conversion efficiency, the power towers make more efficient use of the land, and the heliostats are less expensive to manufacture and maintain than the parabolic

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37 Frost and Sullivan Research Service. 2011. Global Solar Power Market.

38 Acciona Energy. Technology and Experience in Concentrating Solar Power. Available at http://www.acciona-energia.com/media/315798/Technology%20and%20experience%20in%20concentrating%20solar%20power.pdf. Accessed October 25, 2011.

39 Greenpeace International. 2009. Global Concentrating Solar Power Outlook 09: Why Renewable Energy Is Hot. Amsterdam, The Netherlands: Greenpeace International. Available at http://www.greenpeace.org/international/en/publications/reports/concentrating-solar-power-2009/. Accessed July 24, 2012.

40 Feldhoff, J.F., D. Benitez, M. Eck, and K.-J. Riffelmann. 2010. Economic potential of solar thermal power plants with direct steam generation compared with HTF plants. Journal of Solar Energy Engineering 32:1001-1009.

41 Hinkley, J., B. Curtin, J. Hayward, A. Wonhas, R. Boyd, C.C. Grima, A. Tadros, R. Hall, K. Naicker, and A. Mikhail. 2011. Concentrating Solar Power—Drivers and Opportunities for Cost-Competitive Electricity. Melbourne, Victoria, Australia: CSIRO Energy Transformed. Available at http://www.garnautreview.org.au/update-2011/commissioned-work/concentrating-solar-power-drivers-opportunities-cost-competitive-electricity.pdf. Accessed July 24, 2012.



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