Solar Water Heaters

Limitations

Technical Information

Case studies

Solar water heaters (SWHs) are employed in residential, commercial/industrial/public buildings for the provision of hot water. Another application is the heating of swimming pools. SWHs convert solar energy to heat energy, which is then used to heat water.


Solar water heaters installed in a Nairobi housing scheme

The solar energy converted by the absorber is removed by a heat transfer fluid, such as water (direct) or a water glycol solution (indirect) for transport directly to the load or storage for later use. Insulated tanks are used in small systems to store hot water. Storage capacity in residential building is limited to that required to meet the hot water demand for one or two days.

State of the art solar water heaters incorporate features such as selective surface absorbers, anti-reflective glazing, well-designed collector arrays, efficient storage systems achieving operation efficiencies of the order of 35 to 40%. Market brands include Solahart. Edward and Mega Sun, Chromagen, Beasley and Amcor.

Local assembly of imported collectors exists. Less costly solar water heaters can also be manufactured on a cottage industry basis as is done in Kenya, Ethiopia and Tanzania. Such locally engineered solar water heaters have lower conversion efficiencies and shorter lifetimes than factory produced models.

The most important markets for SWH in Africa are middle and high income households, institutions (i.e. hospitals), commercial establishments and tourist facilities.

Solar water heaters save large amounts of foreign exchange- in terms of fuel oil that would otherwise be needed to heat water, or electricity that might have had to be generated to heat water. A 300-liter system, typically suited for family of 4-6 persons will displace up to 1000 kWh of electricity every year.

SWHs can also prevent deforestation when used by schools, game parks, hospitals and households in places that otherwise would cut trees to heat water.


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