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Solar Thermal Electricity


Solar thermal electricity (STE) generates electricity from sunlight using standard steam generators (turbines).

Large-scale STE production with solar trough collectors can meet all national and global electricity demand.

Trough Collectors

American engineer Frank Shuman proposed and built a solar trough collector plant that powered a steam engine in Egypt in 1913 (Figure 1). Originally planned to generate electricity with a generator (dynamo), a water pump was used instead, for agricultural irrigation. The plant generated 35 kilowatts (kW) of mechanical energy, with 1233 square meters (m²) of collector aperture area:

Figure 1.1  Shuman solar trough collectors in Meadi, Egypt, 1913, near the Nile River.

In the Shuman design above, the parabolic reflectors are on rollers and rotate around the receiver fluid pipe axis. Modern trough collectors move the receiver pipe along with the reflectors, on tracking stands with flexible/jointed pipes at the ends of the trough collectors:

Figure 1.2  Flexible pipe at end of collector (SEGS, Kramer Junction, California).

“Parabolic trough collectors have been used in the Mojave Desert in California since 1984. The power plants of the Solar Energy Generating Systems (SEGS) have a combined generating capacity of 354 MW. Despite the harsh conditions, the reflector arrays continue to function perfectly to the present day.”

Land that is very dry, very hot, and with at least 6.5 kWh/m² per day direct normal irradiance (DNI) is suitable for generating solar thermal electricity.

Solar trough technology does not require special materials. Standard metals and mirrors are used (e.g., steel and glass). No special elements need to be mined. Recycled materials can be used.

Adjacent solar trough plants could each power a steam turbine hundreds of Megawatts MW per turbine. Energy storage for peak demand extending into night (time-spread base load) will be with molten salt tank storage (to efficiently generate electricity at night):

Figure 1.3  Solar thermal electricity power plant with thermal oil as heat transfer medium and molten salt as storage medium (red: thermal oil, blue: water/steam, green: molten salt). [DLR]

Solar thermal electricity generation is especially productive in hotter regions that are not suitable for other uses. The efficiency of these power plants increases sharply with higher temperatures. Such land is ample and far exceeds the land area that is required to meet U.S. and global electricity needs. Research studies that do not use the hottest and driest land for STE are not indicative of STE capability.

“The only technology presently available for [load follow over a large range of power output] is conventional coal power plants, which are the main tool for dispatchers to control the grid. ST (solar thermal) has here a potential edge, and such plants are the most attractive application of ST today, as they are already cost competitive.”
Shinnar & Citro, Technology in Society, 29(2007):265
“The dry tropics and subtropics receive more global radiation annually than any other zone, including those at a similar latitude or closer to the equator… The total area of the ecozone is 31 million km² or 20.8 percent of the world landmass.”
Jurgen Schultz, Ecozones of the World, 2/e:170,169
“Well-meaning scientists, engineers, economists and politicians have proposed various steps that could slightly reduce fossil-fuel use and emissions. These steps are not enough … Solar energy's potential is off the chart.”
Scientific American, Jan. 2008

References for this page:

 1.  Franz Trieb, et al., Concentrating Solar Power for Seawater Desalination, DLR (German Aerospace Center), November 2007. [ pdf 7.6 MB ]

 2.  Palenzuela, Padilla, Zaragoza, Concentrating Solar Power and Desalination Plants, Springer 2015. [ Worldcat ]

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