Sun brings water to desert crops

Ashley N. Paddock, ashley.paddock@photonics.com

In the hot, arid climate of the Egyptian desert, crop growth has proved difficult because of the limited water supply found deep in underground wells. With only a few resources available, farmers in Upper Egypt have turned to harvesting energy from the plentiful sunshine for irrigation.

The dry-climate fruits and vegetables grown in Wadi El Natrun must be irrigated regularly. Farmers use diesel generators to pump water to their fields, a costly endeavor to tap water stored deep underground. But now, a self-contained concentrated photovoltaic (CPV) system developed at Fraunhofer Institute for Solar Energy Systems ISE, has been used to control and manage the irrigation of a wheat field.

Concentrated photovoltaic modules in Egypt are precisely aligned to the sun, supplying solar power to irrigate wheat fields. Courtesy of Fraunhofer ISE.

Requiring far less space than traditional PV modules, the CPV solar panels supply the energy for the system, while Fresnel lenses concentrate the rays of the sun onto pinhead-size multijunction solar cells. The CPV system tracks the sun to ensure optimal solar yield, and it supplies enough energy for a submersible pump that draws water from a well 105 ft deep and for a small desalination unit. The cells also power the PV module trackers, the monitoring and control system, and an air-conditioning unit that cools the utility room.

“Our idea was to develop an energy management system, making a universal, easily expandable photovoltaic pumping system possible,” said Alexander Schies of Fraunhofer ISE.

“By using the PV energy directly and only [storing] a minimum of energy for the measurement and control system, the battery storage is very small and, therefore, the system is getting cheaper and also more energy efficient, since no losses within the storage occur,” he said.

A sophisticated computer system monitors the generation and use of solar energy efficiently, optimizing usage so that energy immediately goes to where it is needed; for example, to the submersible pump to fill the water reservoir or to the irrigation pump.

“The next step is to integrate not only a load management into the energy management, but also a generation management so wind generators or hydrogenerators can easily be integrated into the overall system … by the energy management system,” Schies said. “With implementing weather forecasts, the overall system can be further optimized.”