CALCULATIONS AND MEASUREMENTS OF ENERGY GAIN FROM SEMI-SPHERICAL SOLAR COLLECTOR

In Latvia because of its geographical and climatic conditions are some features in use of the solar energy. There is a long path of the sun at summer, but frequently large nebulosity, which both enlarges necessity to receive the energy from all sides. Therefore conditional flat plate solar collectors are not efficient enough, but new constructions of solar collectors are required. One of such new constructions can be a semi-spherical solar collector, capable receive the solar energy from all sides. Such semi-spherical solar collector with radius 0.56 m what corresponds to base area 1 m(2) has been made, and measurements of water heating have been carried out at summer 2009. Theoretical calculations of the energy gain from such collector have been performed and verified by comparison of calculated daily energy sums with measured ones, and good coincidence has been obtained. Results obtained from these calculations shows, that the energy gain from the semi-spherical solar collector with base area 1 m(2) is similar to that of tracking to sun flat collector of 1 m(2) area. The tracking to sun solar collector is complicated, expensive and not durable, but the semi-spherical solar collector is simpler, durable against impact of wind and with good appearance. Measurements shows, that the energy gain from such semi-spherical solar collector, made from simple materials, is similar to that from 1 m2 of the industrially manufactured vacuum tubes solar collector. The energy gain from the semi-spherical solar collector can be increased by using in its construction contemporary special materials and technologies, such as special absorbing colours and selective coatings.