Abstrakt

Nowadays, fossil fuels are the main sources of energy from which electricity is obtained. But these sources will not last forever, so in due course renewable energies will have to replace them in this role. One of these new sources is solar energy. To generate electricity from sunlight, solar (photovoltaic - PV) cells and modules are used. The increasing interest in PV cells and modules worldwide is due mainly to the fact that they convert solar radiation directly into electricity without generating any pollution, noise or other environmentally harmful side-effects. At the same time, production costs of PV system components, especially the PV cells, are falling steadily. The governments of many countries are actively encouraging the development of renewable energy sources and a whole range of governmental programmes are dedicated to photovoltaics. This has considerably enhanced the profitability of investments in this field. Over the past 30 years, the photovoltaics industry has grown at an annual rate of 34%. Photovoltaic is therefore the most rapidly developing technology, besides wind turbines, for the conversion of energy from renewable sources. In this paper the long-term analysis of the sun-tracking photovoltaic system performance is presented. The system, located on the roof of a four-storey building, was designed and built at the Gdansk University of Technology. The amount of absorbed solar radiation energy and energy generated by the photovoltaic system strongly depends on the incident angle of the solar radiation, therefore an automatic two-axis mechanism, by means of a computer-controlled electric drive, was designed. The required values of the angle of slope and the surface azimuth angle of the tracking modules’ surfaces have to be calculated continuously. Global irradiation and electrical energy produced in the form of monthly and yearly sums was measured and analysed for the horizontal and optimally inclined modules. The ambient temperature and wind velocity were continuously monitored as well. For the aim of comparison, the results of the abovementioned calculations were presented for the nominal power system of 1 kWp. The obtained results were compared with those which have been obtained by other researchers.

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