Reduction of water consumption in thermal power plants with radiative sky cooling

Evaporative wet cooling and dry cooling are gradually replacing water-intensive, thermally polluting once-through wet cooling in thermal power plants. Widespread adoption of evaporative wet cooling increases water losses to the atmosphere and still requires uninterrupted makeup water. Dry cooling substantially increases auxiliary power consumption and causes plant efficiency penalty. Therefore, efficient water-saving cooling technologies are of great importance. Here, we explore the water saving potential of day-night radiative sky cooling with and without evaporative wet cooling in thermal power plants. With a radiative cooling system size of 0.0055 km(2)/MWth normalized by the condenser thermal load at design, we show that a hybrid evaporative-radiative cooling system yields annual water savings of 30-60% in the dry and hot southwestern United States and 50-90% in other parts of the country without causing efficiency penalty. Furthermore, 100% water saving is achievable if the radiative cooling system functions as a stand-alone cooling system, with a much lower efficiency penalty and auxiliary power consumption than that of stand-alone dry cooling systems.