A solar water heater is a device that harnesses the heat energy given by the Sun and uses it to heat water. This water can be used for cooking, cleaning, bathing etc. and is commonly installed in residences and apartment complexes to heat water in a larger scale. The main advantage of solar water heaters is that since it uses the energy of the Sun, it saves electricity and is therefore an environmentally friendly way of heating water. Moreover, heating water using electricity is inefficient and consumes a large amount of power, especially when heating larger quantities of water and if done on several occasions throughout the day. Therefore, solar water heaters are an investment that pays off in the long term as although the initial cost is high, the operating costs are almost zero and has a lifetime of over 30 years. The main limiting factor of solar electricity generating units is the battery, which is absent on a solar water heater. This does mean, however, that water heating capabilities are only available at times the sun shines and delivers a usable amount of heat. A solar water heating system can be obtained by consulting organisations such as Solar Hot Water Sunshine Coast who offer both the hardware/equipment as well as installation services and consultations on the applicability and maintenance aspects.
How it works
The main principle behind a solar water heater is that it can conduct heat obtained from the Sun to a liquid. The solar energy is captured by a collector containing an absorber plate which absorbs the energy and converts it to heat which can be transferred to liquid in metal pipes via conduction. To increase the amount of liquid heated simultaneously, the liquid is sent into several cylinders or pipes which increase the surface area of exposure to sunlight.
Solar water heaters can be classified as direct or indirect circulation systems based on how the heat is transferred to water. In direct circulation systems, the above-mentioned heat transfer occurs with the liquid being water to be heated. In indirect circulation systems, the heat is first transferred to another transfer fluid which is resistant to freezing and can store the heat energy which is then circulated through stored water to heat it. The former is preferred in countries where the weather rarely reaches freezing temperatures whereas the latter is popular in climates where freezing temperatures are common. However, indirect systems are more expensive.
Water heaters can also be classified according to their method of operation as active and passive solar water heaters. Active solar water heaters use pumps and controllers to control the flow of heat transfer fluid and/or water whereas passive solar water heaters use gravity. Hence, active solar water heaters consume a small amount of power during operation but are more efficient. Passive water heaters require their storage tanks to be placed higher than the other components to ensure flow due to potential energy but are less complicated to install.