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263-269 I. Pelēce, U. Iljins, and I. Ziemelis
Theoretical calculation of energy received by semi-spherical solar collector
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Theoretical calculation of energy received by semi-spherical solar collector

I. Pelēce, U. Iljins, and I. Ziemelis

Latvia University of Agriculture, Liela str. 2, Jelgava LV3000; e-mail: ilze.pelece@llu.lv


Solar energy is widely used as an environmentally friendly energy source in many countries, Latvia among them. However, geographical and climatic conditions in Latvia, low maximal height of the sun and maximal irradiance, as well as comparatively great cloudiness, present particular challenges. Long days and the long path of the sun in summertime means traditional constructions of solar collectors are not efficient enough for use in Latvia.A new principle in the construction of the solar collector has been developed: a solarcollector with the absorber in the shape of a semi-sphere. It has advantages in comparison with the traditional fixed flat-plate model: it effectively receives both direct and diffuse solar radiation all day. In addition, it is durable against the destructive impact of the wind.This article reports theoretical calculations of received energy which have been carriedout, based on continual visible position of the sun in the sky. Results of these calculations have shown that on a clear sunny day, a semi-spherical collector with the base of 1 m2 receives 1.3 times more energy than a flat-plate collector positioned at optimal (approx. 40o) inclination, and 1.6 times more than the flat horizontal one. In cloudy conditions, the difference is greater because of greater diffused radiation.Such a semi-spherical solar collector has been constructed. Experimental investigation ofthe received heat energy from the semi-spherical solar collector will be carried out in field conditions this summer.

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