EforA project RD2011 RADIant Cooling for Arid Locations (RADICAL) funded by EforA/EST

In the developed world we take for granted the ability to refrigerate food, homes and vaccines. In many parts of the developing world, mains electricity is not available at all or subjected to constant power outages. Hundreds of millions of people have no means to store drugs and vaccines at correct temperatures, preserve harvested crops or slow spoilage of prepared food. Even where there is local power, prolonged outages and poor supply quality result in expensive refrigeration unit failures. Often charity initiatives provide photovoltaic-powered refrigerators for vaccine storage in rural health clinics; but the technology (including batteries and inverters) is of relatively high cost. Batteries must be replaced after a number of years (5-15 years). Renewable energy systems also need inverters to convert the DC output to AC and these inverters can often be more expensive that the appliances themselves. Absorption refrigeration system (fueled by propane or kerosene) have other problems mostly associated with the inadequate fuel supply. Thus countless communities, which will remain off grid and without reliable electricity for the foreseeable future, have a pressing need for cooling facilities of some kind. Many developing regions have hot-arid climates where there are very high day/night temperature swings and the night skies tend to be clear. During a clear night, thermal radiation of any surfaces pointing towards the sky is lost into space, cooling these surfaces. Traditionally, night sky radiant cooling has been used to make ice in special shallow ponds; but the process is labour intensive, incurs water losses, and is hygienically risky. There has been research into radiant cooling by circulating antifreeze solutions through sky radiator devices – but the emphasis has been on solving developed world cooling problems using powered systems. Useful and affordable self-powered radiant cooling devices could be developed, based on phase change thermosiphon heat transfer. The only moving component would be the working fluid, and the fluids used would be cheap and commonly available hydrocarbon gases. The only maintenance would be external cleaning of heat exchange surfaces. The RADICAL project was a feasibility study to carry out work to identify the potential for the technology and to define and build a first stage prototype for further development. The partners involved were RD&T who have experience in developing and commercialising refrigeration systems. They were assisted by African partner organisations Practical Action and ACTS (African Centre for Technology Studies) who have experience of working in Africa and will work in Kenya, Rwanda and Tanzania during the project.