Pool Heating with Solar
The most obvious cost-effective application of solar energy is heating a swimming pool . The Canadian Solar Industries Association counts over 250,000 swimming pools in Canada of which about 40% are heated. Homeowners tend to spend more money heating their pools than heating their homes. Using a solar thermal system instead of fossil-fuel or electric heating can get back your initial capital in around 2.6 years or less, with a ROI of about 38%. A pool heated by natural gas costs more than $2,000 in the summer, even for sunny southern California!
An increase in water temperature with a longer swimming season are both possible when a solar thermal heater and a solar blanket are used. You enjoy enormous savings on heating bills while eliminating greenhouse gas emissions by the ton. (Personal greenhouse emission considerations are for the environmental and financial effects while governments consider carbon taxes and allowable emission levels.)
The Pool Heating System
To get the best from your solar pool heating system, you must mount south-facing solar collectors and angle them according to your geographic latitude. A ground mount rather than a roof mount may cause a drop in heating efficiency which requires more collectors or acceptance of lower performance. The size of the collector area depends on the swimming pool's surface area, the preferred water temperature and the amount of shade in the surroundings. Normally, the collector surface area is set at 60%-70% of the pool's surface area. A partially-shaded site or flat mount collector should have a bigger surface area. So a swimming pool of 10' x 20' (3 m x 6.1 m) needs at least:
Minimum solar collector area = 10x20 feet x 0.6 = 120 sq.ft. (11m2)
Most filter pumps function well using solar panels. If freezing is an issue, consider drain spigots on the system or well-sloped plumbing lines for total water drainage before storing for the winter. You can control the swimming pool's temperature by using a timer to switch the circulation pump on or off according to sunrise and sunset times. This method is simple and cheap but gives little control over the pool's water temperature.
Solar pool heating with automatic control comes with an automatic diverter valve that can channel the water to the solar collectors depending on the difference between atmospheric temperature and preferred pool temperature. As the pool temperature reaches the preferred temperature, water will be redirected by the diverter valve from the solar collectors into the filtration system. Both auxiliary fossil-fuel and electric pool heater designs can be considered for the system.
These configurations allow the solar collectors to heat the water first, before going to the backup heating unit. Electricity or fossil fuel is used only when there is a difference between the preferred pool temperature and the solar thermal output temperature. All these drawbacks can be overcome with a pool thermal blanket .