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Parabolic Trough FAQs

Find answers to frequently asked questions about parabolic trough solar technology. Question topics include:

Some of the following documents are available as Adobe Acrobat PDFs.

How much does a parabolic trough power plant cost?

The cost of a parabolic trough power plant depends on many factors such as plant size, whether thermal energy storage is included, and whether the solar field has been enlarged to increase the annual plant capacity factor. Based on these considerations the current capital cost for large ~100-MWe-sized systems are on the order of $3-6/W for plants that produce 25-50% annual capacity factors.

For more information, see parabolic trough market and economic assessment.

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What is the cost of electricity from a parabolic trough power plant?

Electricity costs will vary from plant to plant, area to area. For a 100-MWe parabolic trough plant the nominal levelized cost of electricity is expected to be approximately 13/kWh assuming a 30% Investment Tax Credit (ITC) and a solar property tax exemption (CA). This equates to a real cost of electricity of 9/kWh.

For more information, see parabolic trough market and economic assessment.

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What is the potential for parabolic trough technology in the United States and the World?

Recent siting studies for parabolic trough technology show that sites in the southwestern United States have a high direct normal solar resource potential and low slope (<1%). And exclusions for environmentally sensitive lands and urban areas sufficiently provide the total U.S. electric power generation several times over.

Realistically, the potential of concentrating solar power in the Southwest could reach hundreds of gigawatts or greater than 10% of U.S. electric supply. By 2015, the Western Governors' Association estimates that 4 GWe of new concentrating solar power plants could be built in the United States.

Worldwide potential for concentrating solar power also could reach hundreds of gigawatts by 2040. For more information, read Greenpeace's Concentrated Solar Thermal Power — Now! (PDF 1.3 MB).

Also see our information on parabolic trough power plant solar resource assessment.

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What are the benefits of a parabolic trough power plant?

See our information on parabolic trough economic and environmental benefits.

Also read NREL's subcontract report, Economic, Energy, and Environmental Benefits of Concentrating Solar Power in California (PDF 1.5 MB).

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Where can you build a parabolic trough power plant?

See our information on parabolic trough power plant siting.

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How much land does a parabolic trough power plant use?

In general a parabolic trough power plant uses about 5 to 10 acres land per megawatt of electric capacity depending on whether or not the solar field has been oversized to take advantage of thermal energy storage.

One concern often raised about large, central solar power plants is the amount of land required and the potential destruction of pristine desert lands. Solar plants need to be built on flat areas in the best solar regions (such as the Mojave Desert or the Imperial Valley in California). Therefore, they likely compete with agriculture for land availability. The following case study compares land and water use for agriculture and parabolic trough solar power plants in the Imperial Valley in California.

Imperial Valley Case Study

During 2001, 522,000 acres of land were used for growing crops in the Imperial Valley Irrigation District. An additional 278,000 acres of land was undeveloped. A 100-MW solar plant uses approximately 500 to 1000 acres depending on whether the solar field is oversized for use with thermal energy storage. Approximately 1% of the undeveloped land would be sufficient for approximately 2 GWe of solar capacity.

The primary crop in the Imperial Valley Irrigation District is alfalfa. On average, alfalfa uses 5.5 acre-feet per year per acre of cropland. A parabolic trough plant with wet cooling uses 1.3 acre-foot/year per acre of solar field land use. Water use from a solar plant is approximately one quarter that of alfalfa. In addition, the Imperial Valley water district charges industrial customers five times the agriculture rate. Therefore, a solar power plant would generate more revenues for the district.

One acre of alfalfa crop land generates 7.2 tons of alfalfa per acre per year. The gross revenue for alfalfa farming is approximately $600-900/year/acre. Gross income (before expenses) from a 100-MWe solar power plant (at 10¢/kWh) is approximately $42,000/year/acre. Operation and maintenance (O&M) expenses are approximately $9000/acre/year. Most of this O&M cost is for labor or local goods and services.

Solar plants use less water than most agriculture in the imperial valley. They also can generate more revenue for the local community, and offer more and higher-paying jobs.

More Information

See parabolic trough power plant siting.

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How much water does a parabolic trough power plant use?

It usually depends on what type of technology a parabolic trough power plant uses to cool its condenser.

Table 1. shows water use with wet and dry cooling for conventional steam, combined-cycle, gas turbine, and parabolic trough solar power plants. The water use for conventional plants is based on a California Energy Commission report. The water use for the parabolic trough plants is based on data from the SEGS (solar electric generating station) plants operating in the Mojave Desert.

Table 1. Water Requirements for Power Generation (in Gallons per MWh of Plant Output)
Plant Type Steam Condensing Auxiliary Cooling and Hotel Load Total
Stand-alone steam plant 720(1) 30(2) 750
Simple-cycle gas turbine 0 150(3) 150
Combined-cycle plant
(2/3 CT + 1/3 steam)
(1/3 x 720)
(2/3 x 150 + 1/3 x 30)
Combined-cycle plant with dry cooling 0 110 110
Stand-alone steam plant with dry cooling 0 30 30
Parabolic Trough with wet cooling 920(4) 80(5) 1000
Parabolic Trough with dry cooling 0 80 80

(1) evaporation + blowdown = 12 gpm/MW
(2) estimated at ~5% of evaporation + blowdown
(3) mid-range of 75-200 gal/MWh for turbine cooling, emissions control and hotel load.
(4) based on historical data from SEGS (higher than conventional because of lower net steam cycle efficiency of SEGS, in part due to HTF pumping and night time parasitics.
(5) Includes make-up water requirements for steam cycle (60 gal/MWh) and solar field mirror wash (20 gal/MWh) data from KJCOC.

For more information, see parabolic trough power plant wet and dry cooling.

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What are the benefits of central station solar?

According to the Western Governors' Association Solar Task Force, 4 gigawatts (GW) of central station solar power deployment in the southwestern United States would:

  • Reduce electricity costs for large-scale solar power plants
  • Create thousands of jobs and generate millions of revenue dollars
  • Provide a hedge against fuel price volatility
  • Produce societal and environmental benefits.

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What's the difference between large-scale and distributed solar power?

Parabolic trough solar power systems are well suited for central, large-scale generation plants that connect to the electric transmission systems. These large-scale systems typically offer the least-cost solar option.

For a large-scale system, the increased cost for transmission—including losses in the transmission and distribution system— is small compared to the cost savings of building a large plant and the performance improvement of siting a plant in the best resources locations.

While large-scale solar power plants serve many customers, distributed solar power provides small, modular systems for on-site delivery of electricity. Because it's on the customer side of the meter, a modular solar system in many cases offers a higher value and reduces demand charges The system also can take advantage of net metering.

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How does parabolic trough technology compare to other solar technologies?

In desert climates like the southwestern United States, parabolic trough technology offers the lowest cost solar electric option for large-scale power plants.

Electricity from large-scale parabolic trough power plants is 50% to 75% cheaper than electricity from photovoltaic systems. However, photovoltaics can be more cost effective for small, modular solar electric applications.

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Why were no parabolic trough power plants built in the United States between 1990 and 2005?

A number of factors contributed to the lack of any new parabolic trough power plants construction during this period. Because of declining federal and state incentives combined with declining energy prices, parabolic trough power plants were no longer economically competitive with conventional power plants.

These factors combined with a general move to deregulation of the power industry, which focused on least-cost power options, precluded any new large solar plant developments.

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How and where can I obtain what's needed to install and operate a parabolic trough power plant?

Some companies in the solar energy industry work on parabolic trough technology research and development efforts. See information about our industry partners.

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