How to make your pool green - but not slimy
Steps to take for a more energy-efficient luxury
While completing an energy audit for a large custom home in Las Cruces last month, I did some interesting online research on energy efficiency and swimming pools. Typically, our analysis of a home’s energy use focuses on the structure and mechanical systems inside the home. If you have a swimming pool at your house, I learned that it is critical to understand and evaluate the pool system as carefully as your home envelope and its heating and air conditioning systems. Pools are great for family fun, keeping cool and staying fit, but their energy use can account for more than half of the energy consumption at a residential property and can be a large contributor to summer peak demand for electricity. Fortunately, there are many ways to keep pool energy costs down and still enjoy your backyard oasis.
Variable-speed pumps
Pool pumps almost always represent the largest single electrical end-use for a residential premise, typically using over three times the energy of a new refrigerator. Conversion from standard, single-speed pumps to a rightsized and properly programmed variable speed pump system can reduce electricity use by more than 80 percent. Depending on the size and type of pool, that can mean $300 to $600 in savings the first year the new pump system is installed. The energy savings that come from replacing a single-speed pump with either a multispeed or variable-speed pump are based on an engineering concept known as the Pump Affinity Law. It basically states that with pool pump systems, reducing the motor’s speed (rotations per minute or RPM) creates less resistance within the pool piping system. This makes the system more efficient and exponentially decreases the amount of power required. If a pump operates at half of its original speed, resistance in the system will decrease to a quarter of the original head pressure. As a result, the amount of power required to move the water with only a quarter of the resistance decreases to an eighth of the original amount. In order to maintain the same turnover rate provided by the pump at its original speed, the pump needs to operate twice as long.
Correct pump sizing, programming and timer setup
Some contractors and pool owners specify pool pumps that are oversized for the application, and may also program these units with run times that are longer than necessary to assure water clarity and sanitation. This typically occurs because it requires less effort on the part of the pool contractor while building in a “performance buffer” designed to ensure that customer expectations, in terms of water, quality are satisfied. In assessing opportunities for “right sizing” pumps and duty cycles in residential applications, the key factor to consider is whether the pump size and run time are capable of providing one turnover per day, while also delivering the necessary flow rates required for the various pool loads for the number of hours needed. According to industry standards, one turnover per day is considered sufficient for most residential pools. More turnovers may be required during periods of heavier use, such as during a pool party when you have more kiddos in the pool. Most variable-speed motor replacements have on-board timers that allow for more control and customization to maximize energy savings. This allows the pump motor system to change speeds based on the time of day, seasonal and or weather changes or level of use, as well as to maximize total energy savings. If an upgrade to a variable-speed pump system is not within your short-term budget, be sure to check and optimize the timer settings on your single speed pump. If your pump is running more than six hours per day, you may be wasting electricity and dollars.
Robotic pool cleaners
A robotic pool cleaner works like the “Roomba” type autonomous house floor sweeper systems but under water. Studies by Pacific Gas & Electric Co. in 2009 and 2010 indicate robotic pool cleaners can cut electricity use for cleaning in half – more than $300 in annual savings for a typical family pool – when compared to suction and pressure-side cleaners, which draw power either from the pool pump or from a separate booster pump. While these savings are interactive with the pool filtration pump savings, keep in mind that they can only be achieved if the robotic cleaner is used in conjunction with the upgrade to a multi-speed or downsized single-speed filtration pump. Simply replacing a suction or pressure-side cleaner with a robotic cleaner will not result in energy savings, since most single-speed pool pumps are sized to handle filtration and cleaning duties and will use nearly the same amount of energy regardless of what type of cleaner is deployed. A robotic cleaner can deliver significant savings, even with singlespeed filtration systems, as long as the booster pump is removed from the system.
Pool heaters and covers
When pools are heated for some portion of the year, there are energy savings available from converting to more efficient heating equipment. There are several different technologies that offer heating efficiency improvements, including high-efficiency natural gas heaters, heat pumps and solar thermal systems. In our sun-filled area, a simple solar thermal system can provide most of the heat energy needed. Comparatively low natural gas pricing also makes high-efficiency (90 percent EF or higher) gas furnace pool heaters a practical option. Also, when water heating is not needed, be sure to take the opportunity to reduce the resistance to the flow of water through pool heaters by means of an automatic bypass, which will lead to cost savings. Pool covers provide energy savings by preserving warm water temperatures, limiting evaporative losses and reducing the volume of debris that collects in the pool. According to the Department of Energy, each pound of 80 degree water that evaporates takes 1,048 British thermal unit of heat out of the pool. The evaporation rate varies depending on the pool’s temperature, ambient air temperature and humidity and the wind speed at the pool surface. The higher the pool temperature and wind speed and the lower the humidity, the greater the evaporation rate. Such is the case here in high, dry Las Cruces. Covering a pool when it is not in use is the single most effective means of reducing pool heating costs and can achieve 50 to 70 percent savings over uncovered installations. Hopefully some or all of these energy-saving strategies can help. Getting control of your pool system utility costs this fall is sure to add sparkle to next summer’s swimming fun. For more information on pool efficiency, contact one of our many quality local pool supply and installation service providers.
Miles Dyson is the owner of Inspection Connection LC - Professional Home Energy Rating and Home Inspection Services. For more information visit: https://www.InspectionConnectionTexas.com.
Las Cruces Bulletin Friday, September 13, 2013 Miles Dyson Living Green