|SEMICONDUCTOR NON-TRADITIONAL ENERGY SOURCES|
Photoelectric systems include connected solar panels, load matching devices, electronic converters of current, energy accumulators. In according with the system purpose electronics can convert direct voltage to direct voltage or direct voltage to alternative voltage. In the simplest systems the electronic converter may be absent
The data of the annual solar exposition in the place of solar system installation are the important the entry condition for design of solar system. The designer chooses optimal direction and inclination of solar panels the base of these data and calculates power feedback and the total annual energy production.
The output of solar battery changes unpredictably. Therefore it is necessary to have an energy accumulator for alignment of fluctuations or buffer system. Accumulator stores energy under intensive solar exposure and supplies it in the case of low exposure. There are various ways of accumulation of energy, the main are electrochemical and mechanical.The electrochemical accumulators as storage batteries have found the greatest distribution. The basic characteristic of the accumulator battery it capacity (ampere hour), electro motive force (e.m.f.) E.m.f. is determined by electrochemical potential of a separate element and number of elements, efficiency, self-discharge. The important characteristic of the battery is power capacity on 1 kg of weight. Acid-leaden batteries are widespread. For them e.m.f. makes 2 V for an element, the standard battery have six elements with e.m.f. 12 V.
On the other hand, the accumulators should not be discharged up to meanings less than 25 % from a complete storage, as, if the accumulator is in this condition for the long period, occurs sulfatation of plates, capacity of the battery falls, and term of its service is reduced. The advantage of this type batteries is their high efficiency, rather low cost, small self-discharge. Their lacks: rather small number of cycles of the complete charge- discharge, sensitivity to over voltage, low currents of the charge - discharge
In transport systems sometimes use Ni-Cd storage batteries. For them e.m.f. of an element is equal 1,2 V. Their advantages are high mechanical durability, admissibility of the deep discharge, large number of cycles the charge - discharge, admissibility of the large charge currents high-energy capacity. Their: low efficiency, large self-discharge, high cost.The load line of the accumulator battery not bad approaches to solar, however it not quite meets position of an optimum point and depends on a degree of the battery storage (see right figure). As it is visible from figure, after the battery achieves 100 % storage, the charge current falls at the expense of a working point deviation from optimum. So the system the solar battery - accumulator has effect of self-restriction.
The mechanical energy
accumulation use transformation of the electric power into potential mechanical
energy. For example, lifting water on height or carrying it out. Compression of
air by compressors so may be used for energy accumulation. The water lifting is
widely used in small solar systems. For powerful systems the very large volumes
of water are required which should be lifted on significant height. Compression
of air and pumping it in underground tanks under high pressure, process more difficult, however it
provides the large concentration of energy and is more perspective, than hydro
The hydrogen stores use the electric power for decomposition of water. This process requires low voltage, that will well be coincide with the characteristics of solar elements. The made hydrogen collects in metal cylinders, or in metallic-hydrate. The back transformation of hydrogen to electricity can be carried out in fuel elements by oxygen interaction with hydrogen, this electrochemical process is opposite to electrolysis. In the long term hydrogen can become alternative ecologically pure fuel in power sources of the future. Now basic obstacle of hydrogen power creation- low efficiency of hydrogen accumulation and production.
In the case of electric network accumulation, converted to electricity solar energy transformed to the network standard (220 V, 50 >Hz and is transferred in the electric system, whence consumers take it. Thus per solar days the consumption of fuel on power stations decreases the saved fuel is spent at the night or those days, when solar activity low. In this case electric system can be considered as some store with almost unlimited capacity.