An alternative to conventional methods of water heating is solar water heating. The annual operating costs of water heaters range up to $200. By using a solar water heater the operating costs can be reduced by 50% to 80%. Solar water heating systems are broadly classified into active and passive water heating.
An active water heating system uses solar energy to heat a solar collector. The main components of such a system are the collector, circulation pump, controller, and tank. The collector heats cold water that is drawn from the storage tank. In colder locations, a heat exchanger may be used to transfer heat. There is a temperature sensor in the tank, which measures the temperature of the water and compares it to that of the collector. The sensor will then shut down the circulation pump. Usually, the solar system has its own water storage tank. This is usually used as a pre – heater system which complements a traditional electric or gas water heater.
In a passive water heater system, the storage solar collector and the water storage is combined into one unit. The storage tank may be directly collected with the solar collector or located above the collector. This system is not connected to a conventional water heating system in any way. The passive system doesn’t require any pumps to circulate the water; rather it uses the natural flow of heated water upwards. This system aptly uses the sunlight to heat the water throughout the day. A passive system can be combined with a conventional system. Warm water from the passive system is drawn into the conventional system's storage tank. Since the water is already warm, the conventional heating system does not need to be turned on.
Solar energy is a renewable source of natural energy and hence makes water-heating systems that operate on this system energy efficient. As solar water heaters are used in tandem with conventional water heaters, care needs to be taken when installing the system so that they complement each other. In the case of passive water systems, special frames may be required to support the heavier heating system. When installing an active system additional wiring for the pumps and controllers will need to be installed. Proper insulation plays a crucial role in a solar water heating system. Lack of proper insulation can cause heat losses of up to 10%. Such water heating systems have thick foam insulation around the water tank along with insulated pipes.