Water needs in thermoelectric power production:

Water needs in a thermoelectric power plant include water for cooling, water for operation of pollution control devices, such as flue gas desulfurization (FGD), as well as for ash handling, wastewater treatment, and wash water. Cooling is the largest source of water demand in a power plant.

The usage of freshwater in thermoelectric power generation cooling water systems plays an important role in the water shortage problem. In the U.S., thermoelectric power generation consumed 3.3 BGD of freshwater in 1995 (USGS, 1998). With the overall projected growth of electric power demand in the U.S. at a rate of 1.5% per year through 2030, (USEIA, 2008), freshwater consumption for electric power production has been predicted to increase to 5.2 – 6.0 BGD in 2030 (Shuster et al., 2007). It has been projected that cooling water supply is likely to be constrained in Arizona, Utah, Texas, Louisiana, Georgia, Alabama, Florida, Washington, Oregon, and California (Roy et al., 2003).

Cooling tower operation is based on evaporative condensation and exchange of sensible heat. Depending on the technology used for cooling, the amount of water usage can be quite different. The following figure shows the once-through and recirculating cooling tower system.

(a) (b)

Figure: (a) Once-through Cooling tower system, (b) Recirculating Cooling tower system.

For a once-through cooling tower, 20–50 gallons of water are required to generate each kW-hour of electricity. On the other hand, modern recirculating cooling towers need 0.2 to 0.6 gallons of water to generate each kW-hour electricity (Veil, 2007).









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