Solar pool heating

How does it work?

With a solar energy system, the pool's water is pumped through the filter and then through a solar energy collector instead of directly back to the pool. The collector then uses the sun’s energy to heat the water and returns it to the pool via the pump. If you add a solar swimming pool heater, you may need a pump larger than your present one, or a separate, smaller pump to pump the pool's water to and through the solar collectors. Adding any swimming pool heater, solar or otherwise, will preclude selecting the smallest pump. Nevertheless, you also may reduce pumping time to help cut costs. Unlike solar domestic water heating systems, which raise a small amount of water to a high water temperature of about 60°C(140°F), swimming pool heaters raise the pool water temperature of several thousand gallons of water to about 27°C(80°F) by circulating the water at a relatively fast rate through the collectors. This allows most of the solar energy falling on the collectors to transfer to the pool water. Commonly, solar pool heating systems consist of four components that work together to provide heat:

1. a solar collector - this is a device through which pool water circulates in order to be heated by the sun
2. a filter to remove debris from the water before it is pumped through the collector
3. a pump which enables the water to circulate through the filter and collector, and back into the pool
4. a flow control valve - an automatic or manual device used to direct the swimming pool water through the solar collector

An added plus for hot climates is that a solar collector can be used to cool the swimming pool during peak summer months by circulating cool water through the solar collector at night. The collectors lose heat by radiation to the night sky. Additionally, some systems have sensors or valves to divert water through the collector when its water temperature is sufficiently greater than the swimming pool water temperature; and when the swimming pool and collector have similar water temperatures, the water bypasses the collector and is returned directly to the pool.

Solar pool collectors

Collectors for swimming pool heating normally do not require glazing or insulation because they operate during warmer months when solar radiation and ambient temperatures are relatively high. This allows for a simpler design that is usually much cheaper than collectors for domestic warm water, which is a great advantage. Many solar pool collectors are made of heavy-duty rubber or plastic treated with a UV light inhibitor to extend the life of the panels. The best material for warmer climates, where the temperature is predominantly above freezing, is specially formulated unglazed plastic. The advantages of plastic collectors are that they're usually less expensive and weigh less than metal collectors. Metal collectors generally are made of copper tubing mounted on an aluminium plate. The advantage of glazed metal collectors is that they are more efficient at capturing the sun's heat on colder days. For swimming pools that require heat on a year-round basis, especially in colder climates, buy a plastic collector that has been treated with metal components and glazed with a glass covering. These are more costly, but make up for the expense by accommodating a wide range of temperature and climate changes. All panel systems should include freeze protection if they'll be used in colder conditions.

Installing solar pool collectors

Before buying swimming pool products like a solar pool heater, it is worth having a solar resource analysis to make sure you will have adequate sunlight to heat your pool. Most of the South European countries have plenty of sunlight, and regions with less can take advantage of new technology which uses either direct or scattered sunlight for swimming pool heating, but the amount of heat generated at a particular site depends on how much solar energy can reach it. Achieving the best angle for your collector is of the utmost importance as well. A south-facing orientation is best, but the collector can face up to 90 degrees east or west without sacrificing performance. The angle at which the collector is tilted is also essential and varies with your latitude and the time of year in which the solar pool heater is needed. For use only in summer, tilt the collector 10-15 degrees less than your latitude; for year-round or winter only use, the tilt should be 10-15 degrees more than the latitude. However, slight variations in this will not decrease performance.

Disadvantages of solar pool heating systems

First, swimming pool products like solar pool heaters do not always work with the decor of one’s house and garden, and some communities restrict their use because of unsightly appearance. Second, solar swimming pool heaters can also be cumbersome: a general rule is that you will need one square meter of solar panelling for every square meter of pool surface area. Another problem is that solar energy depends totally upon the weather, and for times when there is little or no sun a back-up electric or fossil fuel swimming pool heater may be required. Solar panels are completely exposed to the elements and consequently have a short life, being highly susceptible to damage by the sun and wind. Last but not least, solar pool heaters are difficult and expensive to install, and offer slower swimming pool heating than any other swimming pool heater.