Sizing the Solar Pool Heating System
The size of a solar swimming pool heating system depends on several factors:
1. Pool size
2. Length of swimming season
3. Average regional temperatures
4. Desired pool temperature
5. Site’s solar resource
6. Collector orientation and tilt
7. Collector efficiency
8. Use of a pool cover.
Pool size – Generally the surface area of your solar collector should equal 50%–100% of the surface area of your pool. In cooler and cloudier areas, you may need to increase the ratio between the collector area and the pool surface area. Adding collector square footage also lengthens the swimming season. The use of a pool cover will decrease the required collector area by as much as 50% .
For example, a 15-by-30-foot outdoor swimming pool in Florida typically requires a collector that equals 100% of the pool’s square footage to accommodate year-round use. This equals 450 square feet of collectors. In northern California, most people use outdoor pools 6–8 months per year, so they typically size their systems at 60%–70% of the pool’s surface area.
You’ll also want a properly sized pool pump for a solar system. If you’re replacing a conventional pool heating system with a solar system, you may need a pump larger than your current one or a separate, smaller pump to move the pool’s water to and through the collectors.
Solar system contractors use worksheets and computer programs to help determine system requirements and collector sizing.
CR is defined as the ratio of square feet of collector area needed divided by the pool surface area.
CR = Collector Ratio = Collector Area/Pool Surface Area
A CR of 1.0 signifies that the collector area is equal to the pool surface area. A CR of 0.5 indicates the collector area is half the size of the pool surface area. The amount of solar heat provided for the pool depends on the size of collector. A higher CR value denotes more heat gained, warmer water and a longer swimming season.
A number of solar companies have developed calculators to determine the size of the collectors: