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A look into the effectiveness of below-ground solar heating systems

By Max DesMarais

Below-ground solar collectors can pull the heat energy absorbed by hardscape (e.g. stone, bricks, pavers, wood) surfaces and use it to heat pool water.

Everyone knows pool heating can be costly for homeowners—especially if the pool is not being covered. As a result, many are making the move towards sustainable technologies such as solar energy. For most, when thinking of solar energy an image of large solar panels may come to mind. Very few think of invisible solar heating because it is a relatively new technology. This article will discuss how homeowners can potentially harness the sun’s energy without using typical roof-mounted solar panels.

Capitalizing on the heat absorbed by hardscaping

When walking along a driveway, backyard pool patio, or even a backyard deck, it becomes very clear how much energy is emitted by the sun. Paver, brick, stone, and even wooden patio temperatures often exceed 65.5 C (150 F)—enough to burn the skin within seconds—simply as a result of sun exposure. This can occur even on relatively cool days. On hot days, paver temperatures are known to exceed 82 C (180 F), which can burn skin immediately on contact. With these temperatures, beautifully designed spaces cannot only become uncomfortable, but even dangerous. In cooler climates, water temperatures can remain low, leaving bathers cold in the pool, but with burning feet upon exiting the water.

Today, there are methods available to capitalize on the heat absorbed by these hardscape (e.g. stone, bricks, pavers, wood) surfaces and other sun-exposed areas which are capable of holding significant thermal energy from the sun. This heat energy can be extracted, which will not only cool the surface down, but also allows it to be used elsewhere. Essentially, these surfaces are used as thermal batteries in which below-ground solar collectors can pull the energy out to use it elsewhere.


How does it work?

A below-ground solar heater (i.e. hydronic system) circulates fluid (glycol and water mix) through panels located under the paver surface and, as it heats up, it passes through a heat exchanger, which transfers it to the pool or hot tub water. This will in turn cooldown the surface of the patio to a more comfortable, safe temperature. Modular hydronic systems are capable of efficient heat transfer and, therefore, can effectively capture the thermal energy stored in pavers, stones, bricks, or deck surfaces.

In most cases, homeowners like to keep their pool at a standard water temperature. A hydronic system is capable of automatically circulating fluid to heat the pool to the desired water temperature and, when necessary, it will stop when that temperature is reached.

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