Solar heaters use the warmth of the sun to heat pool water, which, on the face of it seems more energy efficient that electrical or gas-powered heaters.
But do solar heaters really save energy?
Before investing in a solar heater, it is a good idea to consider the full cost of operation of solar heaters to determine if they are really less expensive to operate than traditional heaters.
The key is to pay attention to the additional pump energy requirements.
For an existing single-speed pump of ½ to ¾ horse power or better, there really is no difference in the operational costs because the pump will be running anyway.
If this is the case, the pool owner will reclaim the initial investment on the system.
But the existing pump may not be powerful enough to do the additional work that the solar systems require.
In that case, it is going to be necessary to upgrade the pump in order to provide enough force to lift the water to the roof, where the panels usually are located.
Solar heaters work best with variablespeed pumps because the optimum flow rate can be found to maximize performance.
Manufacturers of solar systems recommend a flow rate of 3 to 5 gallons per minute per panel. For example, if there are 16 panels, then about 64 GPM is suggested.
Less water lowers the efficiency, while more wastes money on pumping costs.
To minimize heat loss, the pipes from the equipment to the solar systems should be as short as possible.
Sizing
Unlike other types of heaters, there is really no exact formula for properly sizing the area of the solar collector. Weather conditions, site selection and efficiency must all be considered. As a starting place, the area should be about 75 percent of the surface area of the pool. The following guidelines can be used to refine the measurement:
• Depth of the pool- For pools deeper than 8 feet, add 10 percent collector area per foot. Pools shallower than 8 feet need 5 percent less collector area per foot.
• Angle of the roof- For roofs angled steeper than 30 degrees, add 10 percent more collector area.
• Shaded pools – Add the same percentage of shaded pool surface area to the collector area.
• Windy locations – Add 25 percent more collector area if there are frequent winds exceeding 15 miles per hour.
• Foggy areas – Use glazed solar panels, adding 15 percent more area than would be required for unglazed.
• Variable-speed pumps – If a variable speed pump is used, add 30 percent more collector area.
• Distance of array to equipment – If the distance is long (over 100 feet) add 5 percent more collector area per 100 feet.
Appropriately sized arrays should also take into account other factors such as the orientation of the solar collectors.
While they can be mounted anywhere near the pool that provides the appropriate exposure and tilt toward the sun, most people put the collectors on the side of a roof.
For pools in the Northern Hemisphere, it is best to orient the collectors to the south. However, they can face up to 45 degrees east or west of true south. Collectors should be tilted at an angle based on both the location’s latitude as well as the length of the swimming season. Year-round heating collectors should be tilted at an angle equal to the latitude.
When conditions are totally optimized, the size of the array can be as small as 60 percent of the pools surface area.
