Natural gas electric power plants

There are primarily three types of natural gas-fired electric power plants: natural gas combined cycle (NGCC) power plants, gas combustion turbines and gas-fired steam turbines. While gas turbines are directly driven by hot combustion gases, an NGCC plant first uses a gas combustion turbine to generate electricity and then uses the waste heat to create steam to generate more electricity in a steam turbine. Because gas combustion turbines require no cooling, as there is no steam to be condensed, the overall combined cycle system requires much less water for cooling than traditional steam turbine technologies. According to Macknick et al. (2012), water use values (median) of natural gas-fired power plants are shown in Table 2.3.

According to the US Energy Information Administration (2012), more than 80% of natural gas-fired power plants in the US are NGCC plants. Gas turbine and steam turbine power plants account for less than 10% each.

Table 2.3 Water use at natural gas-fired power plants

Source: Macknick et al., 2012.

Concentrated solar power (CSP) plants

Concentrated solar power (CSP) requires larger amounts of water at the operational stage compared to other commonly used renewable energies (i.e. solar PV and wind). Both CSP and solar photovoltaic (solar PV) require water to clean the mirrors and panels, as dust can reduce the system efficiency. Water intensity for mirror and panel washing ranges from 0.08 to 0.15 m³ MWlr¹ (Bracken et al., 2015). Such variation depends on the frequency of cleaning, which is decided by the site conditions, such as soil and dust properties, vegetation, air pollution, wind speed and direction, humidity and temperature, as well as precipitation characteristics (i.e. intensity, frequency and duration). Other factors are panel/mirrors orientation and angle of tilt; glazing properties also have impacts on the cleaning frequency (Sarver, Al-Qaraghuli and Kazmerski. 2013).

Apart from cleaning needs, the thermal cycle of parabolic trough, linear Fresnel and power tower CSP technologies are essentially the same as those used in coal and nuclear power plants and therefore require water for cooling purposes as well as boiler makeup, as in a coal-fired power plant.

Dish systems do not generally require water for cooling, nor for steam cycle operations, but do require a small amount to wash the concentrators.

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