Solar thermal heating

by Sally Bouorm | October 1, 2010 9:03 am

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By Colleen Simmons

Have you ever noticed that organic fruits and vegetables cost more or that free-range chickens and their eggs are more expensive? What about the fact airlines charge extra for zero-carbon-footprint flights? We all would like to save the planet and feel good about doing something environmentally friendly, but it often comes at too high an expense, or too much of a compromise. It is not often someone can find a way to do what is right for the planet and still save some money; however, with solar swimming pool heaters, pool builders have the opportunity to encourage their customers to become more eco-conscious, while saving them money and increasing the company’s overall revenues.

There is seemingly constant coverage in mainstream media about solar and green initiatives, but for the average homeowner, these ideas require a huge lifestyle and financial commitment. Most people cannot make the leap to incorporate most types of alternative energy sources (e.g. a wind generator or hydroelectric turbine). However, introducing customers to the idea of solar pool heating can be the perfect start to an energy-conscious lifestyle. It offers a good entry to the world of alternative energy, both cost and commitment wise.

We think of a beautiful pool as a luxury, but we want to make sure this luxury is not wasteful in terms of energy requirements. Introducing environmentally responsible pool heating methods will encourage people to install new pools, as they will not flinch at the monthly heating bills. In addition, existing pool owners will swim more, which in turn increases the supply of and demand for chemicals, accessories and service.

The importance of alternative energy lifestyles

The world’s massive consumption of energy and natural resources has made the push toward ‘green’ living more a necessity than an option. Burning fossil fuels is dramatically increasing the levels of carbon dioxide (CO₂) in the atmosphere, resulting in melted glaciers, droughts and damaged eco-systems. Some economists are even estimating we could be living in a world without oil by as early as 2050. All of these doomsday scenarios point to one conclusion: alternative energy lifestyles need to be encouraged, sooner rather than later.

For example, 11.3 L (3 gal) of burned and refined oil provides 400,000 British thermal units (Btus) once; however, the same amount of oil used to make a 1.2- x 3.6-m (4- x 12-ft) solar panel can create more than 10 million Btus a year, using only the sun as fuel. For consumers, this is a reasonable incentive to adopt solar heating in place of more costly heating methods, such as natural gas or electricity. For the pool industry, this translates to an influx of business.

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.

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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.

Similar 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.

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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).

Sizing guidelines

When sizing a solar heating system, the general guidelines are to have a panel array that is approximately 50 per cent the size of the pool’s surface area. For example, the surface area of a typical 4.8 x 9.7-m (16 x 32-ft) pool is 47.5 m² (512 sf). To properly heat this pool, 24 m² (256 sf) of solar panels is recommended. (Most systems include an easy-to-use-sizing chart on the solar panel box, which makes it easier to calculate.)

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Solar panels can be mounted on the ground or a racking structure; however, the roof of the house is usually the best place for installation, as the panels will absorb heat from the roof and attic in addition to the sun. A south-facing position is optimal, as it will be exposed to the sun longer allowing more heat to be absorbed by the water. If a south-facing installation is not possible, the next best position is west-facing. As the sun is at its highest elevation point throughout the summer, the roof’s pitch is not crucial, just as long as it is safe and comfortable to work on.

Much like a thermostat, automatic solar controllers can be programmed to maintain a certain pool water temperature to eliminate the need to manually turn the system on/off manually. They use two sensors (one on the roof and one in the pool) to compare the actual water temperature to the desired temperature, as determined by the user. When the collector temperature differs by a few degrees, the three-way valve automatically opens to circulate water through the panel system. When there is no heat to be gained, the water simply bypasses the panels and travels through the pump back to the pool as usual.

Environment not the only benefactor

Ultimately, the benefits of these eco-friendly heating systems are clear for consumers who use solar thermal panels and the industry professionals who sell and install them. Retailers interested in offering these alternatives also benefit from an easy-to-install product and, in some cases, a manufacturer-supported launch.
By providing customers with a way to heat their swimming pools using free heat from the sun, they benefit from being able to swim guilt free (no heating bills and no pollution). In turn, the pool will be used more frequently prompting customers to visit their local pool store more often.

HOW TO KEEP THE HEAT

It is important pool owners take into consideration the three natural processes that cause their swimming pool water to lose heat (especially at night): convection, radiation and most prominently, evaporation, which accounts for more than three quarters of a pool’s total heat loss. By stressing the importance of using a swimming pool cover to trap heat underneath its surface, a pool owner can minimize heat loss immensely. In early spring and late summer, much of the heat gained during the day can be lost at night if a swimming pool is left uncovered. A simple ‘bubble’ cover effectively eliminates heat loss through evaporation, while silver pool covers can also reflect heat back into the pool. These are generally sold for a few dollars per square foot and are a good investment for pool owners compared to using a backup heating method. Liquid time-released pool covers are another viable option. These comprise a non-toxic liquid substance, which adds tension and density to surface water molecules, helping reduce evaporation by 40 per cent or more.

 

Colleen Simmons is president and team manager for Enersol Solar Products in Campbellville, Ont. Enersol is a family owned and operated business that has been involved in the solar heating industry for more than 30 years. She can be reached at colleen@enersol.com[5].

Source URL: https://www.poolspamarketing.com/trade/solar-thermal-heating/

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