NATIONAL REPORT—If you are reading this article, it can be assumed that you either own or operate a heated swimming pool. If so, you probably would like to reduce your pool heating costs and save money. Beyond turning down the pool’s thermostat and keeping the pool covered, your options are limited. The purpose of this article is to explore those options.
Businesses such as hotels, motels, resorts and water parks have no choice but to keep their pools at a comfortable temperature. Fossil fuel prices fluctuate significantly and are expected to rise over the next decade. Commercial pools are perfect for hybrid solar pool heating systems, which can provide a clean, domestic and affordable way to reduce the monthly energy bill for heating these swimming pools.
Currently, there are more than 186,000 heated commercial swimming pools in the United States. Of these pools, approximately 39 percent, or 115,540 are indoors; meaning they must be heated 12 months per year. Most of these pools are heated with fossil fuels such as natural gas, propane, or electric heat pumps. This increases the U.S. dependence on imported fuels and adds to global warming and pollution. Assuming natural gas is used to heat these pools, the CO2 emissions produced from an annual pool heating load of 261,294,380,000,000 BTUs is equivalent to the CO2 emissions produced by 6.6 million cars on the road per year.
The heating of any swimming pool exclusively with natural gas, propane or electricity is a costly habit that is not sustainable. If a facility has become accustomed, by habit to a heated swimming pool with the convenience of “anytime heat” from a natural gas, propane, or electric heater, the owners/operators may want to consider the sustainable benefits of hybrid solar pool heating. Payback time on an investment in hybrid solar pool heating can be just five years.
The Hybrid Solar Pool Heater
In most cases, hybrid solar pool heating should be designed so as to be as economically efficient as possible. Since the swimming pool in question is already being heated by natural gas, propane or electricity, it already has the ability to maintain whatever temperature it is set to. The major question then becomes one of determining what level of solar contribution a facility owner/operator is willing to invest in.
It would be exceedingly rare and much more costly to engineer hybrid solar pool heating to provide every possible BTU of solar heat that a specific year-round climate is capable of providing. However, this is actually possible if money is no object.
Hybrid solar pool heating can be engineered to give you a “reasonable balance” between cost and BTU heat collection from solar. Hybrid solar pool heating can save a facility 40 percent to 60 percent of the energy costs needed to heat a year-round pool and up to 100 percent energy savings on pools heated only seasonally depending upon the climate.
Only hybrid solar pool heating using unglazed polypropylene solar thermal panels (collectors) can pay for itself in five years or less if it is engineered to provide a reasonable balance between energy savings and initial cost.
Remember, a commercial pool is still going to be set at whatever temperature regardless of how many BTUs of heat are provided by solar because you already have an existing pool heater. A reasonable economic balance is what you should strive for with hybrid solar pool heating.
Current Solar Technologies
When heating a swimming pool, not only is hybrid solar pool heating able to provide the same energy savings and environmental benefits to society as photovoltaic (PV) electric systems provide in terms of money saved and greenhouse gas (GHG) emission reductions, it can do so at nearly one-tenth the cost.
Rather than converting solar energy to electricity, and then converting a second time back to heat (as would be the case when using PV systems), hybrid solar pool heating systems heat water directly, thereby eliminating conversion losses. Hybrid solar pool heating systems simply pump the water directly through the solar thermal panels (collectors) where it is heated by the sun and then returned to the pool. Since this process does not require expensive PV panels, heat is transferred to the water at a fraction of the cost. Not only is the overall cost of the technology 90 percent less than a PV system with equivalent heating capacity but also the same amount of GHG emitting fuels is offset, thereby reducing the carbon footprint. Due to the smaller overhead cost and practically no operating costs, the total cost of hybrid solar pool heating will be recovered much quicker through the displacement of fuel and/or electricity purchases that were originally needed to heat the pool.
Hybrid solar pool heating has space and location requirements similar to those of PV
systems in order to achieve optimal efficiency: an area of open space that is unobstructed to the sun, either on the roof or on a ground rack, the size being determined by the surface area of the pool to be heated and the percentage of hybrid heat from solar that is chosen to be invested in, based upon cost considerations. Hybrid solar pool heating can be used with both indoor and outdoor heated swimming pools. A solar analysis by a trained professional will determine if a swimming pool is suitable for hybrid solar pool heating and determine the most cost effective solution.
Solar Thermal Technologies
For hybrid solar pool heating, there are two distinct designs of flat-plate solar thermal panels (collectors) that may be used. They are either glazed or unglazed.
Glazed solar thermal collectors with copper absorber plates for domestic hot water (DHW) are considered medium temperature solar collectors designed to heat relatively small volumes of water, generally for washing and bathing, to 120 to 160 degrees F but can be used for hybrid solar pool heating. Their cost per square foot installed runs $80 to $100 for a commercial installation.
When used for hybrid solar pool heating, the performance of glazed flat-plate DHW solar thermal collectors will drop 11 percent to 15 percent because all of the thermal energy does not reach the absorber plate due to losses through the glass as compared to unglazed polypropylene solar thermal collectors. This means that 11 percent to 15 percent more square footage of glazed DHW solar thermal collectors are required to match the thermal collection in BTUs of unglazed polypropylene solar thermal collectors when operating under similar conditions. In addition, the glazed DHW solar thermal collectors cost four to five times more per square foot installed than unglazed polypropylene solar thermal collectors. Since the absorber surfaces are mainly copper, they are not compatible with pool water and therefore a heat exchanger must be utilized, further reducing the system’s efficiency.
It is only at certain times of the year and in certain climates when the air is cold, where glazed DHW solar thermal collectors will provide more BTU thermal collection per square foot for hybrid solar pool heating than unglazed polypropylene solar thermal collectors.
Another design of glazed solar thermal collector, rarely mentioned when it comes to solar pool heating, are high temperature evacuated tube collectors, designed to heat relatively small volumes of water to 160 to 212 degrees F. These are primarily for use in industrial and process heat applications and cost hundreds of dollars per square foot installed.
The Solution
Unglazed polypropylene solar thermal collectors are economically designed to raise the temperature of large volumes of water in a swimming pool, 10 to 15 degrees F above the ambient air temperature. They are specifically designed for low temperature applications such as swimming pool heating. Their cost per square foot installed runs around $20 for a commercial installation.
Polypropylene solar thermal collectors will last 15 to 20 years or more. This means that they will actually last two to three times the life expectancy of your existing natural gas, propane or electric swimming pool heater. Because they are designed for swimming pool use, the collector directly heats the pool water and no heat exchanger is required.
For hybrid solar pool heating, a facility need not pay four to five times more in initial cost for glazed DHW solar thermal collectors simply to have them provide some minimal additional BTUs of heat over an entire year.
By creating a hybrid solar pool heating system through the addition of unglazed, low temperature polypropylene solar thermal collectors designed specifically to heat swimming pools, in conjunction with an existing natural gas, propane or electrically powered pool heater, a commercial pool facility will get the best of both worlds.
In summary, a hybrid solar pool heater provides the most cost effective “primary” swimming pool heater—solar pool heating for “free heat from the sun.” It also provides the most convenient “back-up” swimming pool heater—your existing natural gas, propane or electric pool heater for “anytime heat” for times when solar will not be enough. A hybrid solar pool heater is also the most sustainable “primary” swimming pool heater—solar pool heating for “CO2 emissions-free heat.”
In choosing hybrid solar thermal, make sure the entire solar collection system is NSF-50 certified. The National Sanitation Foundation Standard 50, which is required by most U.S. states, covers products that are used in public or commercial swimming pools, spas and other recreational water facilities like water parks.
NSF certification includes: material safety, corrosion resistance, design and construction, product marking, dimensional testing, hydrostatic pressure testing at 1.5 times the working pressure, design burst pressure testing at 2.0 times the working pressure, head loss or pressure loss testing, 20,000 cycle high/low pressure testing, high temperature burst pressure safety testing, marking, and labeling requirements.
To further insure that hybrid solar pool heating collectors are manufactured to the highest standards, the manufacturer should be audited and certified as an ISO 9001:2008 Quality Management System (QMS) and the product should be manufactured in the United States.
Conclusion
Hybrid solar pool heating using unglazed polypropylene solar thermal collectors is the most cost effective use of solar technology. Because hybrid solar pool heating using unglazed polypropylene solar thermal collectors is so cost effective, Congress chose to exclude all solar pool heating from the federal energy tax credit.
Jody Gorran is chairman of Aquatherm Industries Inc., Lakewood, N.J. Aquatherm Industries is the largest U.S. manufacturer of polypropylene solar thermal panels for hybrid solar pool heating of commercial and residential swimming pools. Gorran has owned the company for 22 years and its roots trace back to 1976. Aquatherm Industries is the first and only U.S. manufacturer of solar thermal panels for recreational water usage certified by NSF as well as certified ISO 9001:2008.
