Solar water heating, otherwise known as SWH, is that the water becomes hot with solar energy acquired from sunlight for commercial, industrial or residential activities. Solar heating system consists of a water storage tank, heat transfer fluid HTF and solar heat collectors.
How SWH works:
Solar water heaters are available in two versions: active pumped or passive compact. The solar collector, mounted on a wall against the sun or a roof, heats the liquid which is then circulated through an active SWH or driven by convection in a passive system. Collectors are composed of an insulated box with a glass lid with a black painted solar cell absorber that is flat and attached to the copper tubes, or several metal tubes surrounded by a close vacuum evacuated eyewear. The heat is stored in a padded water storage tank with inlet and outlet connected to and out of the collector. Passive or active domestic water heaters consist of a secondary energy source electricity or gas that is activated on non free days to ensure a steady hot water supply when the tank is watering at a certain temperature, usually fifty five celsius.
Active water heater:
Active solar water heaters use a pump to distribute water or heat transfer fluid in the middle of the collector and the cistern. Available in two types Direct non passive devices deliver water to the collector and then to the tank while indirect non passive devices circulate HTF through solar heat collector and a heat exchanger. The produced heat is transported to the tank water.
Passive solar heater:
Integrated aggregate storage units ICS or batch heaters consist of thin rectangular glass tanks fixed on walls to the sun or roof. Water tanks serve as storage and collectors. Water supply is dependent on gravity flow. Batch heaters are efficient, simple and very suitable in warm climate.
Convection heating systems, also known as CHS or thermosifon, are either flat or evacuated pipe collectors with integrated padded water tanks. CHS units utilize convection to bring water in the collector to the cistern. More useful than ICS as solar thermal collector heats a smaller amount of water that is constantly fed to the water storage tank. CHS devices are installed in regions with not as much sunshine than ICS.
Direct water solvents draw water from the residential water supply to circulate between the collector and storage tank. When the water is heated, the convection penetrates it and flows towards the storage tank. These solar water devices are not suitable for cold weather, because water in the solar thermal collector can heat up and damage the panel. Indirectly non active water heaters use non toxic, non freezing heat transfer fluid in the collector. As soon as this liquid is heated, the convection leads to flow to the storage tank where an inactive heat exchanger carries the heat to the tank water.
The maintenance of inactive water heaters is cheap and simple, non passive appliances are much more useful when heating and retaining hot water. Non passive water heating systems are more expensive and more complicated to fix.
Collectors collect and contain solar heat. Three types of solar collectors are used in domestic water heating systems: