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The photovoltaic system: From the solar surface to the heart surfase The structure of a photovoltaic system can be very varied; in its most general form, a block system is shown here. Even if, in general, the most practical realizations use only some components. The systems are usually composed of components assembled on a fixed carrying structure, generally at angle equal to the latitude of the site, so that the ratio of the energy to the pannel and the global cost of the system is optimum. Solar cell characteristics A photovoltaic cell is substantially a big diode behaving like a current generator when exposed to solar radiation. The maximum suppling power in specific conditions of lighting and temperature is measured in watt of peak (Wp). A junction temperature of the 25° C and a 1000 W radiation, are considered international conventional values [m²]. A photovoltaic cell efficiences, results from the ratio of its maximum power to the radiation on its surface (a cell): h = P max /1000 x A ceII PV cell operating block. Components of a complete PV system. Examples of elements on the market. PV block connected to the net. Photovoltaic station composed of pannels arranged in parallel lines. The photovoltaic block The photovoltaic block is composed of photovoltaic elements connected in series and in parallel so that the operating conditions you desire are possible the string is formed by: More components or panels electrically connected to get the nominal generation voltage. Finally the electric connection more laces constitute the block. In the planning phase of a photovoltaic block must be effects some choices.The block operation depends on them. A fundamental choice is, surely, the series-parallel configuration of the components of the photovoltaic block; such a choice, in fact, determines the electric characteristics of the block. As soon as the size of the photovoltaic block is over some kilowatts of peak, the sizes and the whole weight of the components are such to require the subdivision of the block in to panels. The panels in can be arranged parallel lines with the desired inclination. In this case the least distance among the lines of panels can not be accidental but must avoid that the shade of the anterior line covers those of the back line. It is therefore, necessary to calculate the least distance among the lines in accordance with the panel sheight, the place latitude and the inclination angle of the panels, morder that shading doesn`t take place at 12 o`clock of the winter solstice. Accumulators In the isolated photovoltaic system the energy is generally, stored by means of electrochemical accumulators. The presence of accumulation batteries allows to pace points of load, without the generators, as well as to guarantee the continuity of energy, supples also in the case of low radiation generator or temporary breakdown of the generators. Besides the accumulation battery, often effects, the excellent joining between the photovoltaic generator and the rest of the system. The technological development in this sector, tied up to the auto industry, has permitted to get acid lead accumulators with low auto discarge, long life (over 6 years) and reduced maintenance. Electrochemical accumulators Isolated village (segue nel file da scaricare)
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