Solar Water Heating

One of the easiest installs to perform to get an immediate cost savings is solar water heating. It also happens to be one of the simplest things to change out when migrating to a green home.

Most people think of solar power in terms of large, dark blue panels supplying electricity to a home or business. While this is a very popular application there are other ways to harness the energy of the sun. Solar heating is one, and its roots actually go back much further back than the use of photovoltaic arrays. The use of direct sunlight for heating water dates back thousands of years to ancient Greece where crude mirrors and lenses were used to harness the sun’s energy for heating water.

Some municipalities in the 1920s used solar power for heating the water that was supplied to people’s homes – today, those applications have taken on the shine of high technology. One common form is the use of collector panels, often mounted on a rooftop. Unlike photovoltaic modules, these arrays don’t use layered silicon wafers to generate electricity – rather they resemble large, thin, double-paned windows that contain water often mixed with types of salt. The sunlight heats the water by means of the greenhouse effect and the water moves through a series of channels, tubes and pipes into homes and businesses.

The greenhouse effect occurs when light enters a transparent medium; a fact made common through discussions of global warming but not all the energy is allowed to escape out again. It happens with glass to a greater degree because the material allows certain wavelengths of the light spectrum, infrared, for example to enter more efficiently than letting the energy back out again. This means that there is a net gain in energy on the inside.

Hot water has obvious direct uses such as showering or washing dishes etc and the only thing that needs doing with the water it to make it available. Typically this is done by storing the heated water in much the same way as with ordinary water heaters.

In an ordinary hot water system the water heater storage unit also heats the water; a solar-powered water heating system however obviates the need for this as the water that enters the tank is usually between 95F-150F (35C-66C). The storage tank acts like a big thermos bottle as it is double-lined and/or made of well-insulated material so less heat is dissipated out through the walls of the tank.

The temperature range of such systems is more than adequate for bathing or washing clothes etc; the only difficulty is ensuring that there is enough sunlight to generate sufficient heat, and minimizing heat loss through the panels and pipes. This can however, cost more than fifty thousand dollars and local climate conditions may limit the usefulness of the system. However, the local cost of electricity or gas is such that a home or business solar water heating system may well pay for itself within 10 years.