Moving outside the water, there are slightly more aggressive ways to harness the sun’s heat energy and deliver it to the pool. These come in various shapes and sizes and can be no more complicated than a garden hose. In fact, some pool professionals and owners have experienced a do-it-yourself version of the solar collector when they leave a garden hose out in the sun for a few hours before filling the pool. Assuming the hose has been full of water as it sits in the sun, the water will be warm when it comes out. If the hose is long enough, the water’s warmth can make a difference when added to the pool.
Essentially, this is the concept behind solar collectors, whether they are large and flat or more compact and dome-shaped.
Dome-shaped collectors have some advantages over large flat mats. For example, by coiling tubes inside a semi-spherical receptacle, the collector itself is better protected from dirt, grass clippings, small animals, and other backyard hazards. Also, because they are relatively small, dome-shaped collectors designed for above-ground pools have far less impact on the lawn or landscaping design, compared to a large mat that may lie on the ground near the pool. The dome shape allows this type of solar heater to generate more heat per square metre/foot than a mat-style heater or collectors installed on a roof or large frame for support.
Whether dome-shaped or not, a solar collector for an above-ground pool should ideally be placed in close proximity to the pool. Otherwise, costly energy is required to pump the water from the pool to the collector(s) and back again. The dome shape is quite attractive for the small pool (and small budget) market because proximity is desirable.
Solar dome technology
Over the years, solar-dome technology has been successfully used internationally and installations with multiple large domes can heat industrial buildings. Some residential versions use a dome placed in a warm attic with plumbing used to connect the dome to the pool (or the home’s water heater). A pump (the pool’s pump or one dedicated to the heater) circulates water between the solar collector and the vessel of water being heated.
The simplest version of the solar dome sits right next to the pool, using no more energy than the pool’s filtration pump to generate heat.
More elaborate solar heating systems are available for bigger pools and for customers with larger budgets. In extremely hot climates, it may be desirable to run the system at night, actually cooling the pool by circulating the water though the collectors when it is dark and cool outside. These systems are more expensive and require sensors and digital controls to fully automate the heating and cooling cycles; however, they use the same basic concepts as more affordable systems—energy from the sun is free and can be captured to increase pool water temperatures.
It is important to understand—and to make sure pool owners understand—passively generated heat cannot provide on demand heating like a gas pool heater. (See Table 1, page XX.) Solar heating technologies increase the water temperature, but, for a price, gas-fired heaters will generate more heat faster.