The sun is a mass of incandescent gas, a gigantic nuclear furnace where hydrogen is built into helium at a temperature of millions of degrees. But despite its intense heat, it’s being used to do something paradoxical: provide refrigeration (apologies to They Might Be Giants). A winery in Tunisia and a dairy in Morocco are among the sites using a technology deployed by EU scientists to cool food and other sensitive goods by harnessing the power of the sun.
The solar cooling concept absorbs solar radiation to heat water above 200 degrees F, then uses the heat to drive a compressor that lowers the temperature of a refrigerant, explains Tomas Núñez, a scientist at the German Fraunhofer Institute for Solar Energy Systems. It’s a process similar to that used for propane refrigerators, but the sun–not gas or fossil fuels–is the heat source.
“Our method is ideal for countries which have many days of sunshine and in remote areas where there are no conventional means of refrigeration owing to a lack of water and non-existent or unreliable energy sources,” says Núñez . “It is environmentally friendly and reduces the use of expensive electricity for conventional refrigerators to a minimum. Refrigeration is always available when the sun shines, which means that it is produced at the times when demand is at its highest.”
The MEDISCO project (short for Mediterranean food and agriculture industry applications of solar cooling technologies) has built several of these solar refrigeration plants in Mediterranean countries with plenty of sunshine, but not much infrastructure. Engineers are using concentrating collectors to direct the sunlight onto an absorber that heats water.
Although the concept of using a heat source to cool is not novel, MEDISCO is recombining solar and cooling technologies in a new way that could change development decisions in remote areas unlikely to receive electricity, or affordable fossil energy, anytime soon. MEDISCO says it is “aiming at the best compromise towards innovative technologies use, primary energy savings and economic issues.”