Flowing water is the main source of electricity generation in hydropower plants; if it is boiled and transformed to steam, it becomes the source of thermal power. Water is also used as a cooling material in thermal power plants. The volume of consumed water for producing a unit of energy is termed water intensity and is expressed in units of m3/MWh. In a thermal power plant, the water intensity is calculated from the volume of water consumed and lost during the cooling process, while the intensity for a hydropower plant is commonly measured by the amount of evaporation in the reservoir because the water only passes through the turbine without being consumed (Lamberton et al., 2010). Biofuel from agriculture as an alternative energy source does not always consume less water than conventional methods. The production of one litre of ethanol from irrigated corn consumes 190 to 2,260 litres of water, while a litre of biodiesel produced from soybeans consumes 9,040 litres of water. The water intensity for generating energy from different sources is summarized in Table 1 based on Lamberton et al. (2010) and Desai (2013).

Table 1.

Water intensity for energy production (Lamberton et al., 2010; Desai, 2013).

Energy processUnitsaAverage water intensity
Hydropower Gal/MWh 1,430 (variable)
Thermal power
Geothermal Gal/MWh 2,900
Nuclear Gal/MWh 400–720
Coal Gal/MWh 200–480 (390)
Biomass Gal/MWh 390
Natural gas Gal/MWh 100–180 (140)
Solar (photovoltaic)b Gal/MWh 30
Windb Gal/MWh
Crude oil production Gal. water/Gal. crude oil 350
Energy processUnitsaAverage water intensity
Hydropower Gal/MWh 1,430 (variable)
Thermal power
Geothermal Gal/MWh 2,900
Nuclear Gal/MWh 400–720
Coal Gal/MWh 200–480 (390)
Biomass Gal/MWh 390
Natural gas Gal/MWh 100–180 (140)
Solar (photovoltaic)b Gal/MWh 30
Windb Gal/MWh
Crude oil production Gal. water/Gal. crude oil 350

a1 gallon = 3.7854 litres.

bThe water in solar and wind power plants is only used for cleaning the panel or blade.

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