Solar Water Heaters
Solar water heaters are a cost-effective way to generate hot water for your home. They can be used in any climate, and the fuel they use, sunshine, is free.
Solar water heating systems include storage tanks (Geysers) and solar collectors. There are two types of solar water heating systems:
Pumped, which have circulating pumps and controllers, giving reliable service and allowing the homeowner to easily control the functionality and getting the best savings from the system.
Thermosiphon or passive, which don’t require circulation pumps. In thermosiphon systems, water flows through the system when water heated by the collector rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank.
Two types of solar collectors are used for residential applications:
A flat-plate collector consists of an absorber, a transparent cover, a frame and insulation. Usually a low iron safety glass is used as a transparent cover as it lets trough a great amount of the radiation from the sun. Simultaneously, only very little of the heat emitted by the absorber escapes the cover (greenhouse effect). In addition, the transparent cover prevents wind from cooling the absorber.
Evacuated-tube solar collectors
Evacuated tube collectors contain a copper heat pipe, which is fitted into an absorber plate, inside a vacuum sealed glass tube. The heat pipe is hollow and the space inside is also evacuated. Inside the heat pipe is a small quantity of freeze resistant liquid. When sunlight falls onto the surface of the absorber, the liquid in the heat tube quickly turns to hot vapour and rises to the condenser top of the pipe. The condenser is plugged in to a manifold and water from the geyser flows through the manifold and absorbs the heat.
Heat pumps and solar water heaters can be retrofitted to work with an existing conventional storage water heater (geyser).