University of Colorado, Boulder (CU-Boulder)

In thermoelectric power generation, only about 40% of the energy in the fuel is converted into electricity. In other words, the power plant operates at about 40% efficiency. The remainder of the energy is converted to low-grade waste heat that must be removed to maintain the power plant’s efficiency. Most power plants use water from nearby rivers, lakes, or the ocean for cooling. The water may pass directly over tubes containing the plant’s heated condenser water, and then be returned, warmer, to the original source, or it may be evaporated to carry off the heat in water vapor. In areas with limited water or under drought conditions, dry-cooling systems use air to remove heat from the plant’s condenser water. However, present dry-cooling technology reduces the power plant’s efficiency and requires costly equipment. With water supplies becoming increasingly strained in many areas, economical dry-cooling approaches that do not reduce the efficiency of power plans are critically needed. Innovative methods to allow cooling below the daytime ambient air temperature and improve heat exchange between air and the plant’s recirculating condenser water will provide the keys to ensuring the continued efficiency of power generation while decreasing the burden on water supplies.

Researchers from the University of Colorado, Boulder (CU-Boulder) will develop Radicold, a radiative cooling and cold water storage system to enable supplemental cooling for thermoelectric power plants. In the Radicold system, condenser water circulates through a series of pipes and passes under a number of cooling modules before it is sent to the central water storage unit. Each cooling module consists of a novel radiative-cooling surface integrated on top of a thermosiphon, thereby simultaneously cooling the water and eliminating the need for a pump to circulate it. The microstructured polymer film discharges heat from the water by radiating in the infrared through the Earth’s atmosphere into the heat sink of cold, deep space. Below the film, a metal film reflects all incoming sunlight. This results in cooling with a heat flux of more than 100 W/m2 during both day and nighttime operation. CU-Boulder will use roll-to-roll manufacturing, a low-cost manufacturing technique that is capable of high-volume production, to fabricate the microstructured RadiCold film.

If successful, CU-Boulder’s design could provide power plant operators a low-cost way to supplement cooling without consuming additional water.