Solar cooling: Low-cost solar vaccine refrigerator

About 2 million people around the world die each year of diseases preventable by widely used vaccines. In Africa and parts of Asia, over half of all vaccines that require refrigeration spoil before they can be administered. Millions of lives and billions of dollars are lost due to a lack of refrigeration. The Appropriate Technology Collaborative (ATC) worked with engineering students and professors at Michigan State University to create the technology. The ATC Solar Vaccine Refrigerator is a robust, easy-to-maintain technology that can be made in the country or region where it is to be used, using simple materials found in most cities: steel, charcoal and ethanol or methanol. The finished product has no moving parts that need maintenance and it doesn't use electricity. The steel box is the solar collector/adsorber. The box is painted black so that it converts sunlight to heat. When the solar collector gets hot in sunlight the charcoal rejects ethanol vapour. The rejected ethanol vapour flows into the condenser, which is a series of pipes with cooling fins. The temperature of the ethanol vapour is reduced to the ambient air temperature and it condenses into a liquid. The liquid then flows into the evaporator inside an insulated box. This process produces liquid ethanol in the evaporator and cool charcoal in the adsorber. Cool charcoal can absorb ethanol vapour again. At night, some of the liquid ethanol is adsorbed back into the charcoal. The ethanol that remains behind in the evaporator becomes very cold and the temperature in the insulated box drops to the desired temperature of 0 to -10°C. Source: http://contest.techbriefs.com/medical-2010/448