A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 1987

In the case of domestic applications, thermosyphon water heater is ideally suitable. The initial cost, however, is the major hurdle. The reduction in cost can be achieved by combining storage with the absorber unit. In this study, two built-in storage type solar water heaters ,namely conventional rectangular box type and prismatic type , were designed, fabricated and experimentally tested. In the case of conventional type heater ,the collector is a flat plate type, the solar radiation is absorbed by an absorber plate which is the top surface of the storage tank and then transferred to water in the tank. In the case of prismatic type, the collector works on the phenomenon of total internal reflection. Its apex angle is selected in such a way that on proper orientation, the sun rays entering the prism are trapped within it . Some of the solar radiation trapped within the prism is absorbed directly by the water and the rest by the absorber plate. The heat absorbed by the absorber plate is later transferred to the fluid in contact with it. The experimental results show that, when considering as collectors, the prismatic type solar water heater has better instantaneous collector performances than the conventional type due to the fact that the prismatic type has 80% optical efficiency and a 13.1 W/m2C overall heat loss coefficient while conventional box type heater has a 73% FRn 0 and a 12.1 W/m2C of FRUl . The prismatic type water heater has also a better daily system performance compared with the conventional box type . The preliminary economic analysis shows that for all possible stationary orientations, both type of solar water heaters produce useful energy at about half the price of electricity. The conventional type heater produces about 2% more annual energy output and about 7% lower cost of useful energy than the prismatic type heater. On the other hand, the prismatic type water produces about 5% more energy output during summer and winter periods in the cases of the orientations for both maximum summer and maximum winter energy output .If both types of water heaters take the orientation for maximum summer energy output during April to September and take the maximum winter orientation during the rest of the year, the prismatic type water heater will produce about 5% more useful energy output and has about 1% lower cost of energy compared with the conventional box type solar water heater.