People living in Weya, Zimbabwe, do not have access to electricity and have little money to buy fossil fuels. A German organisation, Werkhof Darmstadt, held a workshop in 1993 to help the community produce a solar water heating system.
The system collects solar energy in panels on the roof. Each panel consists of a series of pipes and flat metal sheets, painted black to absorb the heat. Water in the pipes expands as the sun heats it, and rises by a siphon effect into a storage tank set above the panel (this is because hot water is less dense than cold). Insulated oil drums are sometimes used as storage tanks.
Hot water can be taken from the top of the tank when it is needed. Cooler water from the bottom of the tank is pushed through the pipes to the panels, where it too is heated by the sun.
The system can produce enough hot water for a family of six people that uses an average of 20 litres of hot water each day.