Dry Cooling System for Steam Power Plant, Solar Power Plant

Because enormous amounts of heat must be removed to condense the steam required to drive turbine generators, cooling systems are typically the main supply of water for power plants. Originally, this cooling was provided by water sources such as rivers and lakes, but in recent years, the number of power plants using dry cooling has increased (a cooling system that uses little to no water). Dry cooling systems are more expensive to install and use more energy to operate. These variables contribute to power plants' overall inefficiency, however dry cooling systems consume 95% less water than wet cooling systems.

Many power plants produce electricity by boiling water to create steam, which is subsequently passed via turbines. This type of system is used in coal and biomass power plants, nuclear power plants, some natural gas plants, and even some solar facilities. After passing through the turbines of these facilities, the steam must be cooled to condense back into liquid before being sent to the boiler or steam generator.

Water is used in most steam power plants to cool and condense the steam. According to the US Geological Survey, power generation accounts for over 40% of total water withdrawals in the United States, the majority of which is used for cooling.

Recirculating cooling systems that recirculate cooling water are used by more than 61% of the thermoelectric generating capacity in the United States. These systems maintain the water in closed-loop pipelines, allowing it to be reused. DC cooling power plants account for 36% of US thermoelectric capacity. Large amounts of water are drawn from adjacent bodies of water to cool the condenser, and the warmer water is sent back to the original source.

Dry and hybrid cooling provides for 3% of cogeneration capacity in the United States, the majority of which has been operational since 2000. Dry cooling systems chill and condense steam using ambient air. These systems are classified into two types: direct systems and indirect systems. Because ambient air is used to condense steam in direct dry cooling systems, no water is consumed. The steam is condensed in a normal water-cooled condenser in indirect dry cooling systems, but the cooling water stays in the closed system. As a result, no water evaporates, implying that very little water is consumed.

Hybrid cooling systems combine dry and wet cooling and may condense steam using both water and air. These systems are often designed to function as dry cooling systems during the cooler seasons and as wet cooling systems during the hotter seasons when dry systems are inefficient.

In the United States, 83 facilities use dry and hybrid cooling systems to sustain roughly 20 gigatonnes (GW) of steam production capacity. Although California has the most dry cooling systems (13), Texas has the biggest dry cooling capacity (2.8 GW), closely followed by Virginia (2.4 GW).

Natural gas combined cycle (NGCC) is the most popular generation technology, accounting for more than 83% of dry and hybrid cooling operating capacity. Dry cooling systems are more cost effective for natural gas combined cycle facilities since they require significantly less cooling per MWh than coal or nuclear plants. Dry cooling technology is used in more than 15% of the operating generation capacity of natural gas combined cycle facilities in the United States.

Dry cooling is an appealing solution for concentrating solar power systems as well. Many new concentrating solar power systems use dry cooling because they are located in places where solar resources are generally abundant but water resources are relatively scarce, such as the Southwest of the United States.