“ How do natural circulation solar energy systems work ? „
Natural circulation (pump less) systems are type of systems in which the thermal transfer fluid circulates all by itself. It is simply based on the principle of decrease and increase of the density of water that heats up in the collectors. Within these systems, the tank should be placed at least 30 cm higher than the top of the collectors. The cold (heavy) water that is received from the bottom of the tank is heated in the collectors and gets lighter and rises to the upper level of the tank. As a result of this process which keeps on running throughout the day, the water becomes heated. Natural circulation systems are installed for very small quantity water needs. Because the placement of tank should be at the top, they cannot be applied within the greater systems. Since the system does not require a pump and an automated control circuit, it is much cheaper when compared to pump systems.
“ How do forced circulation solar energy systems work ? „
They are the systems that the thermal transfer fluid is circulated by a pump system. There is no necessity of the tank to be placed at the top. Because of the lack of natural water circulation as a result of the resistance in the water lines increase within the greater systems, and the difficulty of installing and maintaining the tank at the top level, the requirement to use a pumping system has arisen. Pumping systems operate with the support of an automated control circuit. If the water in the collectors is hotter by 8 – 10 ºC than the water in the tank, then the sensors of the differential thermostat that is placed to the outlet of the collector and to the base of the tank, intake the hot water by running the pump; and when this temperature difference reduces to 4 – 5 ºC, the pump stops running. When compared to the natural circulation systems, these forced circulation systems are more difficult to operate because the pump and the automated control circuit fail from time to time.
“ What are open systems and closed systems ? „
Open systems are the systems in which the domestic use water is the same as the water which circulates in the collectors. When compared to closed systems, they have high efficiency and low costs. They are used in the regions where there are no problems of freezing or calcification for water supply. Closed systems are the systems which the domestic use water is different from heating water. The water which heats up in the collectors, transfer its heat to domestic use water by means of an exchanger. They are used as a solution against problems such as freezing and calcification. Their cost is relatively high and the efficiency is low because of the exchanger.