Passive Solar Water Heating

Using the sun to provide hot water is a good idea. It can reduce your energy costs while providing a greener environment for everyone. The easiest way to use the sun for hot water is to build a passive solar water heating system.

Any time contained water is exposed to sunshine, it heats up. You know this if you have ever turned on a hose that was sitting in the sunshine -- the water that comes out is hot. This is passive solar water heating -- and the same principle can be used to provide hot water for your house.

There are several passive solar water heating systems that can be designed, but the simplest is the batch water system. This is a box which holds one or more metal water tanks which have been painted black. The box itself has a black interior and is insulated to retain the heat.

The box is fitted with a glass or plastic double glazed cover which is angled to the greatest exposure to the sun. The heat inside the box heats the water inside the tanks which can be used by the household on demand.

When somebody turns on the hot water tap, water is drained from the storage tank in the solar water heater, which is replaced by cold water which will then be again heated up by the sun. The length of time the water will stay hot after sunset depends on the exterior temperature.

Another type of passive solar water heating system is the thermosyphon system. A water tank is positioned above a solar collector which heats a liquid such as anti-freeze. Gravity circulates the anti-freeze through the solar collector and the heated liquid is used to heat water in the tank through a heat exchanger.

Hot water is drawn from the top of the tank and replaced by cool water at the bottom of the tank.

Passive solar water heating systems can provide plenty of hot water during the daytime so if the members of the household can coordinate their use of hot water to minimize nighttime use, a passive solar water heating system can provide most if not all of the hot water.
 

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