Solar panel anatomy
There are two specific types of solar panels: solar thermal and photovoltaic (PV). The latter changes sunlight into electricity, while the former transfers energy from the sun to a liquid substance flowing through the panel (usually glycol or pool water), which then absorbs the heat.
Glazed thermal panels comprise aluminum frames covered with tempered glass. A series of copper tubes run under the glass through which water or antifreeze runs. The glass insulates the copper as the sun warms them by preventing the heat from escaping to the colder, outside air. These are efficient for heating hot potable water for a home, as they can surprisingly collect a lot of heat, even in February on cold sunny days. This system can also significantly reduce the cost of water heating. To use a glazed thermal panel heating system for pool heating, a heat exchanger must be incorporated.
Unglazed thermal panels are designed and built to heat pools and are not covered in glass, allowing the sun to shine directly on the rubber or plastic matting. This is especially effective when heating outdoor swimming pools during the warm summer months, as none of the sun’s heat is reflected away by the glass. Unglazed thermal panels also tend to be more cost efficient, due to their simple design, ease of installation and small part components.
While there are slight variations in swimming pool solar heating systems, they generally use the same components, i.e. a solar collector made of varying materials, the piping to connect the collectors to an existing pump and filter and a manual/automatic controller with a three-way valve.
As pool water travels through the network of solar panels via the existing pump and filter, the panel’s collect the sun’s energy and transfer heat to the water, which is then pumped back into the pool via the return line. The process can be likened to turning on a garden hose for the first time on a warm sunny day; the water sitting inside the garden hose, which has been out in the sun, will run very hot.
Each solar thermal panel contains several hundred feet of tubing, which provides a large surface area to continuously warm the pool’s water as it runs through the panel. In warmer climates, some pool owners may opt to run the panels at night to help cool the pool water. They will operate similar to a large, roof-mounted radiator and release heat from the pool water into the atmosphere.
Generally, a solar heating system will pay for itself in the first one to two years, simply by eliminating the heating costs associated with fossil fuels or electricity. Most systems also come with long warranties to provide pool owners with several years of ‘free heat.’ Maintenance is also minimal as the automatic controller does all the work (though draining the system for winterization is required).