Industry sees greater interest in renewable energy systems

April 1, 2013

By Connie Sue Centrella

Microsoft PowerPoint - Slides for PSM Heater 2012[1]
Commercial air-source heat pumps are designed to meet the needs of large pools at hotels, swim clubs, schools, and multi-family facilities.

The demand for more energy-efficient pools and spas has pushed industry professionals to examine alternative heating technologies. Over the past several years, heater manufacturers have taken new strides to improve efficiency. This is in part due to a shift in government guidelines, whereby building codes are now demanding a rise in ratings to improve the overall energy efficiency of all pool equipment.

In midst of this ‘greening of the pool industry’ there has been increased interest in using geothermal and solar technologies. Heat is naturally abundant from the sun as well as within the earth. Innovative heating technologies have found a way to capture and redirect this heat to warm swimming pool water. These renewable energy technologies are capable of providing a cleaner, greener environment, assuring a more sustainable future.

Historically, heat pumps were considered mainly for warmer climates; however, in the last decade, one of the fastest growing regions to use this heating technology has been in the cooler, northern climates. This is because the heat pump industry has developed highly efficient heating systems, which can operate at lower temperatures. Clean energy occurs within the heat pump technology.

Three heat pump options

Air-source heat pumps do not actually burn energy to create heat; they only use energy to transfer heat from the outside air to the pool water.

A hybrid method is a water-source heat pump. These geothermal heat pumps extract heat energy from the ground through wells, earth loops, surface water, and even from cooling towers.

Heat exchanger technology transfers the heat from the ground source to the pool water. Numerous applications throughout North America have proven this technology to be the future of pool heating. While the upfront expense may seem out of reach for standard pool heating, data shows the payback is within range and acceptable to most pool owners, especially those who are dedicated to greener living.

In many cases, for example, the pool heating system can be partnered with the home’s heating, ventilation, and air conditioning (HVAC) system to increase overall efficiency. During the summer months, the geothermal application transfers the heat from ground loops, cools the home, and captures the exhausted heat to warm the pool water.

An example can be found at the historic Fontainebleau Hotel in Miami Beach, where engineers retrofitted the hotel’s cooling system to incorporate the pool’s heat pump unit with the air-conditioning cooling towers. Some may perceive that geothermal is only from water within the ground; however, this installation example and others prove the versatility of geothermal heat pump systems.

While warmer regions play an important role in the viability of geothermal heating, Andrew Chiasson of P.E. Geo-Heat Center[2], presented a case study in 2004 stressing that cooler climates require additional ground loops because the air extracts heat from the earth; however, in warmer climates, the economic feasibility of payback is approximately five years.

The four types of source water commonly available to this new technology are open loop, closed/group loops, surface water, and HVAC loops.

Open-loop system

Microsoft PowerPoint - Slides for PSM Heater 2012[3]
As illustrated, pool water passes by the thermostat and through the heater prior to returning to the pool. When the thermostat senses the pool needs heat, the system cycles on and the well pump begins to deliver water to the heater. The well and pool water never mix.

The majority of water source heat pumps utilize the open-loop system. This requires two wells, one to supply warm water to the heater and the other to return the water to the extraction depth in the ground.

This technology is highly specialized and only professionals familiar with this type of engineering should install these systems. It is also strongly recommended that local codes be checked to ensure the return water does not interfere with any underground springs.

Closed-loop system

Closed_Loop_AquaCal Heat Pumps[4]
Closed-loop systems collect heat from the ground by absorbing it into tubing, which is filled with a mixture of water and ethylene glycol.

The closed-loop system uses heat from the ground; however, different from an open-loop system, the heat is absorbed into tubing, which is filled with a mixture of water and ethylene glycol. The heat energy is then brought to the heat pump to be used as the heat supply source.

Surface water

Drilling geothermal well[5]
Water-source heat pumps extract heat energy from the ground via drilled wells.

The third source of heat energy may be obtained from surface water, e.g. from a lake or pond near the pool. This surface water must be examined and approved for the water-to-refrigerant heat exchanger. Caution must be taken to ensure the heat exchanger is not damaged by organic materials that could clog the system.

A variation of this system uses closed-loop piping placed under the surface water to capture the heat beneath. Saltwater and coastal wells can be used if a secondary heat-exchange system is installed to prevent corrosion.

HVAC loops

Numerous applications that partner HVAC cooling tower systems with water-source heat pumps are now accepted as a viable source of renewable energy. The cooling towers are designed to ‘reject’ the heat extracted from the building with the air-conditioning system. These loops are typically connected to a gas boiler to supply heat to the building in the winter months. These types of heat sources are high-water pressure systems and require specialized plumbing accommodations.

Heat energy can be obtained from surface water, e.g. from a lake or pond near the pool. This system uses closed-loop piping placed under the surface water to capture the heat beneath.

Consideration should also be taken in low-temperature conditions as the equipment can freeze the heat exchanger and cause damage. This is why special equipment engineering must be part of the overall project development.

New, larger heat pump applications

Heat pumps were traditionally developed for residential and small commercial applications. In 2012, however, a larger commercial air source heat pump was designed and is now available in the marketplace. These larger units meet the needs of large pools at hotels, swim clubs, schools, and multi-family facilities. The heating capacity of these units, which are engineered for longer operating cycles, range from 35 to 145 kW.

Solar heating

Solar energy is an economical and environmentally friendly initiative to achieve sustainability. The efficiency of a solar system depends on how the sun reaches the panels. The solar panels are tilted to the latitude of the pool’s geographic region. Further, panels should have a southern exposure to allow them to absorb the most amount of energy from the sun and to achieve maximum solar efficiency.

During the day, water flowing through the solar panels collects heat and is redirected back to the pool. In the evening, however, the use of a pool cover is advised to prevent heat loss via evaporation. Studies show by simply covering the pool with a blanket at night can reduce heat loss by as much as 50 per cent.

An excellent technology combines solar energy with an air/water-source heat pump. This provides an alternative to gas, thus eliminating carbon emissions into the atmosphere.

Changes in heating technology will be ongoing as more consumers look for ways to reduce their energy costs. Other industries are offering variations of these heating methods to homeowners; it is only prudent the pool industry also take the initiative to study and become well versed in newer technologies.

As with all past articles, the author encourages comments from readers. Please send comments and/or suggestions with regards to what you have done to improve your knowledge on new heating methods as well as any experience you have had with respect to newer heating technologies, including geothermal and solar applications to



Centrella_Headshot_edited-1Connie Sue Centrella is a professor and department chair for the online Aquatic Engineering Degree Program at Keiser University eCampus. She was honoured with the Evelyn C. Keiser Teaching Excellence Award ‘Instructor of Distinction’ and holds certification as a chief sustainability officer for the Team Horner Group. Centrella is an industry veteran with more than 40 years of experience in the aquatics field. She is also a former pool builder with extensive knowledge in pool construction, equipment installation, and manufacturing.

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