Solar refrigeration

Abstract

Absorption refrigeration systems utilise low-grade heat and convert it to a refrigeration effect. When solar radiation is at its peak the need for refrigeration (especially domestic) is greatest. The situation thus seems quite in favour of use of solar energy in lieu of the low grade heat. The project involved experimentation on a standard refrigeration absorption system with a view towards the possibility and feasibility of converting it to work on solar energy. An old Electorlux model running on kerosene was used as the test unit. Performance curves were obtained with both kerosene and gas as fuel respectively, and ranges of energy in puts and temperature of the source were determined for best performance. The requirements for conversion to solar were then assessed and various different types of solar radiation focusing collectors were analysed so as to determine which type would stand the greatest chance of working when coupled with the test unit. The type chosen, a paraboloidal concentrator with a secondary reflecting mirror at its focus, was first tested by means of a small model paraboloidal concentrator. Some new theory in relation to the secondary reflector was drawn up by the author himself and this was tested experimentally. A larger system of paraboloidal concentrator and secondary reflector was then designed on the lines of the model system. When constructed, however, the system did not function quite as desired owing to imperfections in the construction of the main reflector. The idea of utilising a secondary reflector had therefore to be discarded, and the possibility of using, in its stead, a heat-exchanger, was studied. A heat exchanger working on the principle of Thermo-Syphoning was designed and constructed and conclusions were finally drawn.