As early as in the ancient Roman Empire and Greecepeople assembled dark barrel on the rooftops of their homes to have the supply of free hot water. They were the first installations of solar panels. As you can see there is a solution neither new nor complicated. Solar collectors are used to heat water, mainly for utility purposes (hot water) and operating dual system as the auxiliary power of the existing heating system. The diagram below shows a modern heating system supported by solar collectors.
When the sun radiation reaches the collector (absorber) it absorbs a large the solar energy heating fluid (glycol) located in tubes. When the liquid will heat up to a temperature a few degrees higher than the temperature in the lower parts of the water tank, then the water pump is switched on, and solar fluid flows through pipes heating the water tank at the same time cooling itself.. In the case where the solar radiation is insufficient to heat the water, the thermostat switches off the pump and the fluid in the collectors is not circulating and cooling water contained in the water tank. In a water tank in the upper parts of the main power source of heat (eg. Gas-stove, pellet or electric) islocated. It heats the water to a desired temperature in case when the solar collectors do not provide enough hot water. Thus, the user is assured of comfort water temperature while reducing the cost of heating water. When selecting the solar panels one should pay particular attention to size of the system. For installations with large absorberssurface in the summer time the overheating of the system can occur. Such a phenomenon is bad for the system and reduce the product life. on the other hand, gains during the winter months, due to the small amount of radiation that reaches the earth surface do not provide a large amount of hot water. For the same reason, it make no sense to use solar collectors to heat the house, because in the coldest months of radiation is also low. On the other hand, installing a smaller number of collectors will not allow the full potential of what we can achieve solar energy. The amount of energy reaching the earth's surface in Polandis shown in the figure below.
The amount of energy reaching the earth's surface in Poland during the year