[[Image:solar water heater icon.png|right|100px80px|]][[Image:solar water heater.jpg|thumb|right|250px200px|A Solar water heater is installed on several rooftops in South Africa. Photo: [http://www.chinapost.com.tw/international/2011/06/27/307611/Solar-water.htm AFP]]]__NOTOC__<small-title />
A solar water heater is any system that uses the thermal energy of the sun to heat water. They are usually aimed at heating water to a temperature hot enough for washing clothes, washing dishes, and personal hygiene, but not hot enough to cook with straight away. However, as long as it is clean, the hot water can also be used in cooking to save time and fuel.
Thermosyphons use the fact that hot water rises above cold water. In a passive thermosyphon system, the tank is always above the collector. As the water in the pipes heats up, it rises up into the top of the tank, causing cold water from the bottom of the tank to flow down into the collector. The flow continues until the water in the pipes and the tank is at the same temperature. One-way valves are fitted to stop water flowing back the other way when the temperature drops at night.
===Suitable conditions===[[Image:solar water heater2.jpg|thumb|right|250px200px|A solar water heater can be on any kind of roof. Photo: [http://sustainablog.org/2011/03/solar-water-heaters-south-africa/ Sustainablog.org]]]
There are 165 approved India solar water heater manufacturers/suppliers (as at 01 August 2011) and over 1000 companies capable of installing them, and these figures are growing each year, particularly in areas such as Bangalore, Pune, Delhi, Hyderabad, Mumbai and Chennai.<ref>[http://www.solar-water-performance.com/india-solar-water-heater.html Top Three India Solar Water Heater List]</ref>
* If you usually heat water with gas or electricity from fossil fuels, a solar water heater helps reduce the carbon dioxide produced by your household, helping in the fight against global warming.
===Construction, operations and maintenance===[[Image:solar water heater chart.jpg|thumb|right|250px200px|How a solar water heater works. Drawing: PACE.]]
====Tips on maintaining your tank====
# '''Climate''': nothing much you can do to alter the weather except move somewhere else but it will have a major performance impact on a commercial and homemade solar water heater due to temperature variations and clouds. [http://www.nasa.gov/ NASA] estimates that on average worldwide only 57% of the sunlight that strikes the upper atmosphere reaches the earth's surface due to cloud cover and pollution.
===Costs===
The cost will vary widely around Africa, depending on the size of the system and whether the materials used have to be imported. Import taxes and taxes on business sometimes add to the expense. Governments could help promote solar water heating by reducing taxes for businesses selling solar water heaters. In South Africa in 2005, a 70 litre solar water heating system cost R3000 (US$455). Larger systems with electric back-up cost up to R10000 (US$1520).
===Field experiences===
====India====
The Ministry of New and Renewable Energy is responsible for maintaining the standards of solar water heating in India and they provide approval for a number of efficiency test centres around the country such as the School Of Energy Studies , University of Pune.
Each one tested by the SABS receives a rating (Q-factor), which indicates the kilowatt-hours (kWh) of electricity it's expected to save on a typical day and the units ability to produce hot water.
===Manuals, videos, and links===
* MANUAL: [http://georg-ritter.info/wp/wp-content/uploads/2011/12/WATER_FOR_EVERYBODY.pdf WATER FOR EVERYBODY: A Selection of Appropriate Technologies to be used for Drinkable Water], EMAS. The solar water heater section is at the very end of the document under two headings: '''EMAS pattern solar heater with no tank''' and '''Two ways for changing a drum into a tank for hot water in a water heater'''. By Wolfgang Buchner, 5th edition, 2006.
* BLOG: [http://www.solar-water-performance.com/solar-water-blog.html Solar Water Blog.]
===References===
<references/>
===Acknowledgements===
* [http://www.paceproject.net/UserFiles/File/Energy/solar%20water%20heating.pdf Solar Water Heating, Action Sheet 64.] PACE. Paceproject.net.
* [http://www.solar-water-performance.com/homemade-solar-water-heater.html Improve Your Homemade Solar Water Heater Systems Performance.]