An advanced system for power plant cooling, consisting of an ''interstellar radiator'' and a pair of thermal storage ponds, is described and analyzed. Performance and economic comparisons with conventional cooling ponds and natural draft wet cooling towers are made at Birmingham, Alabama; Philadelphia, Pennsylvania; Portland, Oregon; and Phoenix, Arizona. Results show that, for systems of the same capital cost, the natural draft wet cooling tower achieves a condensing pressure which is lower by 0.5 mm Hga than the phased-radiator concept at design conditions. The phased-radiator provides slightly higher sensible-to-latent heat ratios resulting in a 5 percent reduction in evaporative water consumption for the same thermal loading at the Philadelphia and Birmingham sites, but increased evaporation rates are predicted for Phoenix and Portland. In addition, the use of phased cooling in conjunction with a dry tower was analyzed, and the performance compared to a conventional dry cooling tower. The thermal capacitance of the two storage ponds permits a shifting of the heat rejection load to the cooler nighttime hours, resulting in an increase in plant output during the peak demand period of more than 2 percent.