Solar energy

Solar panels and solar collectors.

Solar radiation is one of the most perspective energy sources of the future. During fine sunny weather 1mground surface receives 1 000 W of sun light energy. Solar energy enters the Earth surface in unbalanced way: there are 320-350 sunny days in one region, but for another region a sunny day is uncommon thing. Therefore, before installing the solar panels for electricity extraction, it is strongly recommended to calculate the efficiency of using this method in specific climatic conditions. 

 Energy conversion is performed in 2 ways:

  • photoelectric (the direct conversion of sunlight energy to electric energy) 
  • phototermal (the conversion of light energy to thermal power)
    According to the data of EPIA (European Photovoltaic Industry Association), in 2011 about 28 GW of new solar plants were lined up, their total capacity comprises 67,4 GW. 

Today, the traditional kW.h is more expensive than the solar one. However, it is planned that already in 2012 there will be price equality for “traditional” and solar kW.h at least in several regions of the world. The part of solar electricity output before 2020 will comprise 4-7% in Russia and 12% in Europe. Solar photovoltaic system’s main working principle is direct conversion of sunlight into the flow of direct current. Energy can be used whether direct or can be stored in the accumulator battery. Converters are apllied if  220 W of alternating current is needed.  

The advantages of solar photovoltaic system:

  • environmental friendliness 
  • the simplicity of maintenance operations
  • independence of working process
  • noiselessness of working process
  • significant service life

Solar batteries keep on working during:

  • temperature span from -50 up to + 75 C
  • atmosphere pressure 84-106.7 kPa
  • relative degree of humidity up to 100%
  • rain intensity up to 5mm/m
  • snow and wind  pressure – up to 2 000 Pa

Types of solar photovoltaic transducers:

Independent photovoltaic transducers (converters) are made for independent object’s power supply. It is mainly for the objects away from main powerlines, (hard-to-reach places, places with problems in stringing the powerlines, or places, where these powerlines are not of economic benefit). The photovoltaic converters capacity varies from 0.01 up to 100kW.h. 
Photovoltaic power plants, lined up to powerlines send the produced energy to powerlines, after that energy is distributed to consumers. Such systems, installed in the city, can supply the building’s need in electricity and compensate the electric energy shortage during the peak energy consumption at noonday time. Their capacity reaches up to several MW.

The back-up solar converters are lined up to centralized power supply lines and in the case of power cutoff. 

Solar collector – a device, which uses solar radiation energy for heating and hot water supply. There are several types of solar collectors: plain solar collectors, augmentor solar collector, industrial solar collectors, vacuum solar collectors and dual purpose solar collectors. 
The usage of vacuum solar collector with high efficiency output level in subzero conditions is appropriate. 



Special surface, linked to copper pipes with circulating heat carrier, absorbs the radiation. Heat carrier, circulates through whole collector’s surface, heats and goes to reservoir, where it gives all it’s heat through heat exchanger into reservoir - storage plant (heat accumulator). 
Collectors and pipelines have reliable insulation against loss of heat. This construction is placed in vacuum glass pipes. The glass has high level chemical durability, thermal endurance and impact toughness. There is vacuum in circumferential space between inner and external pipes to raise the efficiency of heat loss reduction. These pipes work in cloudy weather and in low-temperature conditions, they convert direct and scattered sunbeams into warm. As a result, the convector saves 95% of heat energy.


 

Nevertheless, the minimal power of solar system should be not below 100 W/m.  The solar collector’s efficiency coefficient depends on solar radiation and environment temperature (from 20 up to 65%). During cloudy weather –up to 650 W/m, during sunny weather – up to 10 W/m

The usage of this system can help in heating expenses reduction for 30 %, for hot water supply at 70%. In weather conditions of midland part of Russia solar water heating units can be effectively applied during 6-7 months a year (from March to September) – in private houses, small hotels, and also can be used as back up source of hot water in hospitals, kindergartens, car wash, gasoline retail stations. During summer period, the solar unit from 2-3 m2  of solar collectors will supply the daily heating of 100 L of water to the temperature not below 45 C with probability 70-80 %. 

  Annual sunshine period in Belgorod region comprises 2 300 hours a year. Usage of solar energy in region is appropriate in combination with other energy extraction methods. 

Solar collector allows keeping positive temperature in building during winter period, supplying the needs in hot water during summer period and above all that - to save the electric energy.

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