SOLAR WATER HEATERS
Solar water heaters can be classified in a numbers of ways:
- By the type of collector used
- By the means of heating fluid circulation
- By the relative storage tank/collector configuration
- By the method through which the water is heated.
These are elaborated on below:
Types of Collectors - Collectors are generally Flat panel or vacuum tube
- Flat panel - these collectors are cheaper and more robust than vacuum tube collectors, but are not as efficient in low ambient temperatures and need a freeze resistant heat transfer fluid in areas where it may freeze at night.
- Vacuum tubes - these collectors are more efficient in low ambient temperatures, but have a shorter life than flat panel collectors.
Heating Fluid circulation - circulation can either be by thermosiphon or by pump
- Thermosiphon - the heating effect in the collector causes the heating fluid to circulate,
- Pumped - the heating fluid is pumped, either by a DC pump driven by a PV panel, or by a pump running of the mains system and driven by a temperature controller.
Relative Storage tank configuration - the tank can either be connected directly to the collector in which case it is called a compact system, or separated from the collector in which case it is called a split system. Compact systems are always thermosiphon systems, while split systems are pumped unless the storage tank lies above the collector.
Method of Water Heating - The water can either be directly (i.e. It flows through the collector) or indirectly (a heat transfer medium flows through the collector and heats the water via a heat exchanger in the storage tank).
