Photovoltaic-powered reverse osmosis (PV/RO) is a practical method for desalinating water, especially for many small, remote, off-grid communities. It is shown here that thermal control can increase its productivity, making it more economically attractive. A solar panel produces more power at lower cell temperatures and an RO unit produces more fresh water for a given power with increasing water temperature. These complementary behaviors are exploited by cooling the solar panel using the RO feed water, which warms the water. Cooling the solar panel also permits the use of concentrating mirrors, which further increases system production. The control must also prevent overheating of the panel and the RO unit, and to balance the pressures in the system. Here, a controller is designed to meet these objectives. The effectiveness of controller design is verified in simulation and experiment. (C) 2012 Elsevier B.V. All rights reserved.