Keeping cool without electricity

Keeping cool when temperatures start to rise and humidity levels soar is a luxury for millions of shop- and office-workers in the developed world. But in developing countries it can be a matter of life and death.

The ability to keep vaccines and other medicines cool can play a crucial role in healthcare strategies, but communities often do not have the funds or even the access to electricity to run cool and chill cabinets.

But a small pioneering company in Austria may have found a solution. In 1996 Gerhard Kunze was given the challenge by the Austrian ministry of science of developing a solar-powered milk refrigeration system for Tanzania. The chiller had to be easy to build and had to work without electricity. The project was never completed but Kunze continued the research. In 2001 SolarFrost Research and Development was founded using money from a fund supporting environmentally friendly projects.

Conventional cooling technology works by compressing a refrigerant, such as freon gas, to raise its temperature, running it through coils to dissipate the heat so it condenses into a liquid, then forcing the liquid through an expansion valve so it evaporates and its temperature falls. This cold gas is then run through a set of coils so that it absorbs heat, cooling the inside of a refrigerator, a cold store or, in the case of air conditioning, a building.

SolarFrost uses water-ammonia-absorption technology, which was first developed more than 70 years ago. Powered by the sun, it turns heat into cold without requiring electricity or any moving machinery. Traditionally water-ammonia-absorption cooling technology needed very high heating input temperatures, around 150°C to chill down to temperatures below zero. These temperatures are difficult to reach with standard solar thermal collectors which use sunlight to heat water or air. SolarFrost has developed a new ammonia cooling cycle and a method of using more of the waste heat of the absorption process which has improved the efficiency of the cooling system, allowing it to operate with lower input temperatures of between 70 to 120°C.

The technology can be built in units which can be combined depending on cooling needs. For example, one option is for a machine with an output of 0.5 and 1 kilowatt (kW) for vaccines, medicines and beverages. But SolarFrost’s technology could be used to build machines with an output of up to 200kW for refrigerated warehouses. True to the original concept’s development goals, the machines can be used to provide cold storage for agricultural products, enabling farmers in developing countries to extend the shelf-life of foodstuffs.

While SolarFrost has developed these advanced techniques, it does not actually build the cooling units. Instead, it grants licences for using the technology in machines. It has sold one licence to an Austrian company, Econic systems, specialising in heating and cooling systems, to develop a 2-12kW machine for residential and light commercial applications.

Despite winning several awards including the International Co-operation Award for Sustainable Development, SolarFrost has faced difficulties in getting funding for its research activities. Kunze, who is now chief executive of SolarFrost, is keen to attract new investors in return for licences.

Kunze explains that existing cooling technology is like "dinosaur fossils". Research in thermal dynamics stopped in the 1930s when nuclear fission was discovered, he suggests. But, he claims, SolarFrost’s research has made a leap forward in cooling technology equivalent to the move from room-sized computers in the 1950s to today’s personal computers. "The unit you needed for a cold store used to be the size of a closet. Now it’s the size of a book," he says.

While using the sun’s energy in some of the world’s hottest countries to keep cool may sound nonsensical, the technology could be a life-saver in the developing world.

Keeping cool when temperatures start to rise and humidity levels soar is a luxury for millions of shop- and office-workers in the developed world. But in developing countries it can be a matter of life and death.

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