Location must be in the desert Southwest

Unlike solar PV, CSP can’t cope with humidity or cloud cover, so it is limited to the southwest were the solar irradiation is high and there is no dust, haze, or smog.  Solar thermal power production is particularly sensitive to cloud cover relative to photovoltaic technologies because scattered light cannot be effectively concentrated by solar thermal collectors.

The lower the latitude is to 10 degrees north (or south), and the higher the altitude the better.  But the Southwest is 30-40 degrees north and rarely high altitude.  Latitude affects the angle and intensity of incoming sunlight.

Restricted to level land, ideally with a slope of 1% or less.

The best solar thermal resources are located in areas that are distant from existing population centers. New transmission is expensive and difficult to permit. Most sites are far from a connection to existing transmission lines. Like other renewables, such as wind, geothermal, and hydropower, achieving reasonable access to potential sites and connecting to existing transmission lines are major barriers to the implementation of additional solar thermal capacity. As a result, many high quality solar thermal resources in the southwest are expected to remain untapped for the foreseeable future, for the simple reason that new transmission facilities are (1) expensive to construct and (2) difficult to permit (Smith).

The average solar radiation (insolation) of a solar thermal power plant in the Southwest U.S. is 8.054 kWh/m2/day. In terms of power per unit area, this insolation is equivalent to 3.36E-04 MW/m2. The solar-to-electric efficiency of a solar thermal system is 14.3 percent, with low and high bounds of 10.6 and 17.0 percent, respectively (Sagent).

Water

Since the best solar thermal facility sites are located in the desert, the acquisition of sufficient volumes of water is a problem.

Blythe Solar Power Plant, located in the Mojave Desert of southeastern California, has a nameplate generation capacity of 1,000 MW. During operations, the project would require approximately 600 acre-feet (195 million gallons) of water per year for cooling. An additional 4,100 acre- feet (1.3 billion gallons) of water would be required in support of project construction (BLM). An acre-foot of water is equal to 1,234,000 kg of water.

The availability of water in order to support cooling during power generation is also a resource issue. Similar to fossil power plants, solar thermal plants must include a cooling system in order to support steam condensation and effective power production. Evaporative (water-based) cooling of power plants is generally much more effective and efficient than dry (air-based) cooling, because evaporative cooling has lower capital costs, higher thermal efficiency, and supports consistent efficiency levels year round. However, evaporative cooling also requires water – up to approximately 650 gallons/MWh – that might not be available in many portions of the Desert Southwest. Air cooling, in contrast, is less effective during high temperatures because it results in lower net efficiency and is more costly to install and operate (DOE, 2009). However, the best available solar resources are located in the Desert Southwest, where water supplies are severely limited. While dry cooling reduces water consumption by about 90 percent, it also reduces net power generation by approximately 5 percent (WorleyParsons), and may increase generated electricity cost by approximately 2 to 9 percent (DOE, 2009).

Dry cooling avoids the need for water, but results in lower net power production and lower net efficiency, especially during the hottest periods (often when solar resources are best for generating power).

Ecological Impact

Habitat loss can be substantial for large solar thermal projects, such as the Blythe Solar Power Project, which has been approved and is expected to have a generation capacity of around 1,000 MW, would result in disturbance to approximately 7,025 acres of land area, equivalent to nearly 11 square miles of land area. Most of this land area would be used for the solar field, but other uses would include generation facilities, transmission lines, and various appurtenances. The facility would be stripped of existing desert vegetation and fenced, resulting in the loss of vegetative habitat within these areas. Other effects include loss of desert tortoise habitat and migration corridors, and loss of habitat for other desert wildlife. Key concerns included potential for interference with Colorado River flows and the consumption of water that could otherwise be utilized for agricultural, residential, or other purposes (BLM).

High water consumption (competes with agriculture)

Interference with geologic or geomorphic processes, such as sand migration and erosion

Flooding associated with desert washes and interference with natural drainage patterns. Most of the time there is no surface water in the vicinity. However, the southwest is subject to infrequent but very high-intensity monsoonal events when flash flooding can occur, which inundates desert washes. To protect solar facilities from floods, many projects have proposed installation of riprap- and levee-like features, flood control channels, and other modifications to re-route existing drainages around project sites. These structures can result in changes downstream, including changes in the distribution of vegetation, as well as altered erosional and sediment transport processes.

Airborne emissions (primarily dust but also other air pollutants)

Concerns regarding GHG emissions during construction

Potential to exacerbate secondary effects of climate change, such as heat waves

Cost

CSP plants with thermal storage are very expensive.

Decommissioning of solar thermal power plants are 10 percent of the capital costs of initial construction (DOE/NETL).

EROI

DOE calculated the EROI for solar thermal power generation as 8.2 to 1, but they didn’t subtract the EROI of energy storage (DOE/NETL). But at least they calculated it – 99.99% of government, university, and peer-reviewed research looks only at greenhouse gas emissions and how much more of whatever-is-being-studied needs to be built for growth rather than energy efficiency and conservation of resources.  There is no document I know of that discusses how to cope with shrinking once oil production declines and shortages occur.

References

BLM. 2010. Plan Amendment/Final EIS for the Blythe Solar Power Project. Palm Springs, CA: U.S. Bureau of Land Management  http://www.blm.gov/ca/st/en/fo/palmsprings/Solar_Projects/Blythe_Solar_Power_Project.html

DOE. 2009. Concentrating Solar Power Commercial Application Study: Reducing Water Consumption of Concentrating Solar Power Electricity Generation. U.S. Department of Energy  http://www1.eere.energy.gov/solar/pdfs/csp_water_study.pdf

DOE/NETL. August 28, 2012. Role of Alternative Energy Sources: Solar Thermal Technology Assessment. Department of Energy, National Energy Technology Laboratory.

Sagent & Lundy LLC Consulting Group. 2003. Assessment of Parabolic Trough and Power Tower Solar Technology Cost and Performance Forecasts. http://www.nrel.gov/docs/fy04osti/34440.pdf

Smith, M. et al. 2010. Permitting and Environmental Challenges for Wind Energy Conversion Facilities and Transmission Facilities.

WorleyParsons. 2008. FPLE – Beacon Solar Energy Project: Dry Cooling Evaluation: WorleyParsons.