SRI International

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.

SRI International and PPG Industries are integrating SRI’s proprietary Spectrally Tuned All-Polymer Technology for Inducing Cooling (STATIC) technology into a novel structure for use as a radiative cooling system that can provide supplemental cooling for power plant water during the daytime or nighttime. The two-layer polymer structure covers a pool holding power plant condenser discharge water. The cover prevents sunlight from penetrating it and warming the water, while allowing thermal energy to radiate to the sky, even during the day. The STATIC structure provides an insulating air gap to prevent conductive and convective heating, and both layers work in concert to reject solar energy. Specifically, the bottom layer acts as an emitter at the water temperature and radiates heat to the sky, while the top layer and key component, produced using STATIC technology, enables transmittance of the thermal radiation. The cooling power can achieve greater than 100 W/m2 without evaporation. All materials are inexpensive and amenable to scalable manufacturing techniques, which could lower the cost of the system.

If successful, SRI’s technology could provide power plant operators a low-cost way to supplement power plant cooling without consuming additional water resources.