Why energy-efficient heating is good for the pool business

by Sally Bouorm | January 1, 2010 9:24 am

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By Connie Gibson Centrella

With environmental and cost concerns still top of mind in the pool and spa industry, technological changes intended to promote the energy efficiency of pool heaters are being required by many jurisdictions throughout North America. Whether prompted by legislation or just good sense, the pool and spa industry is taking steps to improve efficiency on everything from pumps and filters to pool heating and air circulation. After all, promoting energy efficiency is good business.

The energy efficiency boom

Energy efficiency is defined as using less energy to provide the same result. Energy conservation in new construction or renovation requires an understanding of hydraulics; lower velocities, larger pipe diameter, larger filters and backwash valves are all critical when developing an energy conservation plan.

When it comes to heaters, new building codes propose natural gas models cannot be equipped with constantly burning pilots. They must also deliver a thermal efficiency of no less than 80 per cent and have an accessible on-off switch mounted on the outside of the heater, allowing shut off without adjusting the thermostat. The same codes also propose heat pumps must produce a co-efficient of performance (COP) of no less than 4.0. (Industry professionals should review energy codes in their area for any recent changes.)

People are not likely to change behaviour when it comes to temperature comfort. Recreational swimming traditionally mandates water temperatures ranging from 27 to 29 C (82 to 84 F). Facilities will continue to face the challenge of maintaining a preferred temperature without prostrating their budgets. Energy-efficient heaters provide an opportunity to make commercial facilities more profitable, while keeping customers happy.

Understanding energy loss

In both indoor and outdoor pool environments, maintaining the temperature depends on elimination of heat losses; there are constant heat gains and heat losses causing the temperature to rise or fall. Understanding the effects of energy losses is important in the determination of which type of heating is the most desirable.

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Energy loss primarily occurs from four different means: evaporation, convection, radiation and conduction. Ninety-five per cent of energy loss comes from the surface of the pool, while conduction heat loss of five per cent moves through structural components. Historically, energy loss has been controlled through sheltering the surface of the pool from wind, thereby eliminating surface temperature loss.

The pool environment itself also affects energy loss. In indoor pools, humidity control and ventilation produce a comfortable surrounding for bathers. Outdoor facilities are affected by wind and rain, ultraviolet (UV) rays, ambient temperatures and humidity. Relative humidity is important in heating efficiency. When the air temperature is high and relative humidity is low, evaporation (energy losses) increases; conversely, when the air temperature is high and relative humidity is high, evaporation is low. Most indoor facilities encourage a relative humidity of 40 to 60 per cent.

Choosing a system

Heating systems commonly used for pools include the following, each with its own advantages and drawbacks.

Fossil fuel heaters

Fossil fuel (gas and propane) heater manufacturers have made great strides toward improving product efficiency. Gas heater efficiency is based on the ratio of usable output to energy input. In other words, an 80 per cent efficient heater produces $80 worth of useable heat for every $100 of fuel. This increase in efficiency depends on the age of the existing heating unit. Within the past 20 years, the efficiency of gas heating appliances has increased from 60 to 80 per cent, a respectable improvement. Since gas heat offers the fastest heat, which can also be provided on demand, the increased efficiency is all the more noteworthy.

Solar-powered heaters

Solar energy is free once the system is in place and has passed through the payoff period—that is, the amount of time it will take to recoup the initial investment in the system. The design of solar heating depends primarily on how the sun reaches the pool area. The sizing of solar collector panels is vital to system efficiency. In addition, average regional temperatures, collector panel orientation and tilt and collector efficiency must be sized to fit the needs of the property. Solar heating efficiency is based on a solar performance rating, which is measured by the BTU per square foot, per day—the higher the rating, the greater the efficiency.

Most pool applications employ an open-loop system, which uses a single pump for both the pool and collector loops. When no heat is required, the pump bypasses the solar panels. A solar heating installation usually requires a backup heater to meet the desired temperature when cloud cover or cooler air temperatures prevail.

Air-source heat pumps

Air-source heat pumps are gaining acceptance even in cooler climates. A heat pump is actually a proactive collector of solar heat from ambient air. It does not burn energy to create heat; it only burns energy (electricity) to transfer heat from the outside air to the pool water. It is also considered an effective clean energy appliance.

Heat pump efficiency depends on the COP. Put simply, a COP of 5.0 means that for every dollar of energy input, $5 of heat will be gained. The COP varies depending on air temperature, relative humidity and pool water temperature. Therefore, the COP will not be high in cooler climates as it is in warmer ones.

The Montreal Protocol requires all heat pumps to be remanufactured to use R410A refrigerant as of January 1, 2010. The R-22 refrigerant is being phased out because of the chlorodifluoromethane (HCFC) affect on ozone depletion. The new R410A is a near-azeotropic, homogeneous mix that does not damage the ozone layer.

Geothermal heaters

Geothermal, geo-source, geo-exchange and water-source heat pumps are now available to generate energy from the earth’s heat. A study by the U.S. Environmental Protection Agency (EPA) concluded geothermal is the most environmentally friendly heating and cooling energy currently available.

Geothermal heat pumps extract heat from ground wells, earth loops and surface water, as well as heating, ventilating and air conditioning (HVAC) cooling towers. Open-loop and closed-loop systems are now being engineered to meet new energy efficiency initiatives.

A final note

While energy efficiency technologies are being implemented by most heating manufacturers, industry professionals should remember the buyer is ultimately looking for payback, which, depending on the system, can take anywhere from two to five years. In an economic climate where value shopping is more the norm, it is up to pool and spa professionals to prove to the customer the ultimate value of a system that may seem more cost-intensive up front.

As the next era of energy efficiency in pool heating dawns, the industry must be conscious of the initial cost versus the energy saving provided. Proving the value of these systems to the customer is the key to future sales. In short, just make good business sense.

As in the past, readers may submit their own experiences and opinions as to how we can best promote heating efficiencies. Send suggestions to ccentrella@keiseruniversity.edu[3]. Comments will be shared with the other participants in the threaded discussion forum.

 

Connie Gibson Centrella is professor and program director for the online Aquatic Engineering Program at Keiser University eCampus. She is an industry veteran with more than 40 years experience and is a former pool builder with extensive knowledge in pool construction, equipment installation and manufacturing.

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