The buzz about energy conservation has come to life with the green movement, and industries and organizations are doing more than just talking about it. The rising fuel and energy costs over the past several years--combined with a growing awareness of the need for renewable energy sources--have stirred many to take action. This includes the aquatic industry. Today, it is vital for all operators and managers of public aquatic facilities--including municipal pools, water theme parks and fitness and wellness centers--to recognize that one of the greatest operating expenses is the cost of maintaining heat within both indoor- and outdoor-pool facilities.
Newer technologies now enable operators to determine if retrofitting existing heating equipment to a more efficient method will achieve a purposeful “payback” period. Approximately 95 percent of energy (heat) losses come from evaporation, radiation and convection, while the remaining 5 percent of loss comes from conduction. Conduction is energy lost through the pool shell into the cooler ground behind the vessel. It is important that as much of the heat recovery in an indoor system be captured through proper ventilation and air distribution. Heat-recovery units have been developed to work in conjunction with the pool-heating equipment to maximize heating efficiency.
When evaluating a facility for cost savings, it is important to consider a comment made by Matthew Wald in a 2007 New York Times article: “Efficiency, not just alternatives, should be promoted as an energy saver.” Thus, facility operators and managers must look at the efficiency of the heating equipment when implementing a green renovation.
Here we look at three heating technologies--gas, solar and heat pump--and how to evaluate efficiencies and effectiveness for a facility.
Over the past decade, the gas pool-heating manufacturers have raised their efficiency levels to 95 percent. Twenty years ago, 65-percent efficiency seemed adequate conservation; however, as the gas energy costs began to rise, it was prudent to develop a more cost-effective means of using gas to heat pools. Operators renovating existing gas heaters with the higher efficiency ratings need to consider the cost of increased ventilation in the mechanical room, as well as the increase in gas heating piping from the original gas-line source. The positive is fast heat, and the quickest method of heating the pool is with fossil-fuel systems. Fossil-fuel calculations are based on a simple formula--the ratio of usable output to energy input. As an example, an 80-percent-efficient heater will produce $80 worth of useful heat for every $100 worth of fuel. The chart below shows the value of installing a more efficient gas heater.
Solar energy is at the forefront of developing higher standards for renewable-energy systems within the pool industry. This is not new technology. The Georgia Tech Aquatic Facility, which housed the swimming activities at the Atlanta 1996 Olympics, implemented photovoltaic Solar Electricity Generation. Incorporated within the facility was a solar thermal system to heat the pool. Solar energy is free; however, efficiency depends on how the sun reaches the facility. It is imperative that the sizing of the solar-collector panels be based on the following criteria:
1. Pool surface area
2. Length of swimming season
3. Average regional temperatures
4. Desired pool temperature
5. Site’s solar resource
6. Collector panel orientation and tilt
7. Collector efficiency
8. Optional pool-cover installation.
Solar panels may be installed on the facility roof or on the ground. The panels must be tilted based on the latitude of the pool geographic region. As an example, Florida’s latitude is 38 degrees north; therefore, the panels must be tilted at a 38-degree angle facing south. This will achieve the strongest sun rays and provide maximum solar efficiency. In addition, the operator also should be concerned with the location of the pool equipment pump, and whether the pump will be adequate to force the pool water through the solar collectors. Some designers prefer to have a booster pump installed to secure the proper amount of gpm through the panels. Depending on the length of sun time, it may require a supplemental gas heater for quick heat-up when weather turns cool or cloudy. Solar heating efficiency is based on a formula that allows for a 2- to 5-degree rise each time the water passes through the systems. Efficiency of solar-pool energy relies on cloud cover, air temperature, seasonality, strength of the UV rays, wind and temperature differential between the pool and air, as well as the angle of the sun and any shading of the panels.
Heat Pumps--Air And Water Source
An air-source heat pump does not burn energy to create heat. It only burns energy to transfer heat from outside air to pool water. The design is based on efficiency, which is denoted by the Coefficient of Performance (C.O.P.). The formula is the ratio of usable output to energy input. A C.O.P. of 5.0 means that for every $1 of energy input, the pool will gain $5 in heat. The C.O.P. varies based on air temperature, humidity and pool-water temperature. Because of the nomenclature between various heat-pump manufacturers, there are now testing standards developed by the Air-Conditioning, Heating and Refrigeration Institute to assure that all heat pumps will meet specific standards.
In an effort to utilize renewable energy to its fullest, geothermal or geosource heat pumps are now being manufactured for pool heating. In a water-source heat pump, the energy is generated by heat in the earth, and the absorbed heat is collected from underground. Geothermal heat pumps can also extract heat from ground wells, earth loops, surface water or cooling towers. It may sound simple, but retrofitting to a water-source heat pump requires specific engineering technologies to recover the heat from the water source.
Looking for additional methods of maximizing heating efficiencies, operators are combining two heating sources--installing a solar-heating system along with a heat pump or fossil fuel heater. A savings of just 5 degrees in heat energy will reduce the overall heating costs.
As renewable energy and greener eco-friendly heating appliances are in high demand, the aquatic-facility operator should consider the utilization of heat exchangers, boilers and radiant heat as alternative energy sources during the design stage of new pool construction.
The future of pool heating will depend on efficiencies of the heating equipment. Each type of heating has made strides to become more efficient in an effort to save aquatic facilities energy costs. It is valuable to look at the existing facility and review all costs before making a quick decision to change the method and mode of pool heating. To be a hero at the facility, the operator must do the homework--calculate the energy savings and the life cycle of the heating apparatus, assess the annual maintenance costs, and compare the return on the investment. When doing so, it is important to consider the target user-groups so the facility can maintain the specific water temperature needed for those activities. For example, teaching children to swim requires a 2- or 3-degree rise in water temperature over recreational swimming of 82.5 F. Keeping user groups coming back to the facility is a key to its success. All elements of operation and care must be considered to satisfy customers, including the proper heat of the pool.
Connie Sue Centrella is a professor and Program Director for the online Aquatic Engineering Program at Keiser University eCampus. She was twice-honored with the Evelyn C. Keiser Teaching Excellence Award “Instructor of Distinction.” Centrella is an industry veteran with over 40 years experience in the pool and spa industry. She is a former pool builder with extensive knowledge in pool construction and equipment installation as well as manufacturing.