Comparing Solar Pool Heating Products

Solar Pool Heating Products

Solar Ontario does not manufacture solar collectors. We have had experience with many different brands of solar collector from many different manufacturers and suppliers (more than 19 different collectors). The one thing that has been common from all of the manufacturers and suppliers, is that they have all claimed to have the best product!! (no real surprise there!)

There is quite a range of pool heating products available. To simplify the comparative process we have sorted them into the following groups:

Unglazed plastic, Unglazed rubber,  Glazed,  Evacuated/vacuum tube.

Unglazed Plastic

Unglazed plastic collectors can be the most efficient solar collectors available in the world. Some of these collectors approach 90% gross area efficiency! The features that make them efficient are: many tubes with no gaps in between them, thin plastic, built to lie against the roof surface - not stand above it, one-pass water flow - not flowing back and forth through a group of collectors.

Unglazed Rubber

Unglazed rubber collectors have been available for almost as long as the unglazed plastic collectors. They are typically significantly less efficient than unglazed plastic collectors (by 20% to 40%) for a number of reasons; fewer tubes, gaps or spaces between the tubes, thicker rubber in the tubes. The gaps between the tubes have two negative effects upon the efficiency of the collectors. 1) the gaps miss the sun. Both rubber and plastic are not good conductors of heat, so sunshine energy that falls into a gap between tubes is not efficiently conducted to the pool water in the tubes - heat is lost to the air or re-radiated. 2) the gaps between the tubes allows the wind to remove heat from the exposed surface areas of the tubes. In fact, an unglazed plastic panel actually has been shown to have the poorest efficiency because it has no web between its tubes at all - which allows the wind to blow right through it and cool it off like a fan on a car radiator!

Glazed

 Glazed collectors should only be used on indoor pools & hot water systems. There are several reasons for this. 1.) Glazed collectors actually start out less efficient than unglazed collectors because the glazing reflects or absorbs a minimum of 10% of the available solar energy - you actually need a larger glazed solar collector area than unglazed for an outdoor pool. 2.) Glazed collectors must use metal absorbers (plastic absorbers would melt). Pool water should never be passed through a metal absorber (unless it's made of titanium). Pool water will rapidly damage copper, aluminum or steel absorbers. 3.) Pools typically are operated between 26 and 30 degrees C. (79 -86 degrees F.). Glazed collectors are designed to operate at much higher temperatures and cost much more per square foot than unglazed collectors.

Evacuated/Vacuum Tubes

Evacuated or vacuum tubes suffer from all the same issues of inappropriateness that glazed collectors do for outdoor pools, plus a couple of others. 1.) Evacuated/vacuum tubes are fragile when compared to any other type of solar collector. The tubes must never be installed close to a pool area due to the potential for glass breakage. Unlike flat plate glass, tube glass is not tempered and will break into long, sharp, dangerous shards which could harm the pool or people in or around the pool. 2.) Evacuated /vacuum tubes will create extremely high temperatures while not actively heating a pool. Starting a tube collector up after it has sat in the sun can generate dangerously high temperature and pressures! We discuss vacuum tubes in depth in this section.

A Detailed Review of Vacuum Tube Solar Pool Heating Systems

  A note about solar blankets:

The surface of a swimming pool is a large solar collector - but it also loses a great deal of heat through evapouration (especially at night). Solar blankets (of all colours) block some of the sun's energy from getting into the pool, but can dramatically reduce a pool's heat loss if used properly. Some "ring-like" solar products make incredible claims (read "lie") about how their products are actually solar collectors - they are not. They are actually not very good solar blankets either because they expose significant areas of pool water to the air, allowing evapouration to take place. A single solid blanket is MUCH more effective than multiple pieces with gaps and "leaks" all over the place. Customers we have spoken to who have used the "ring-like" products have not been happy with the performance or durability of the products. See our recommendations about using solar blankets in the solar pool heating FAQ's.

Next: A Real World Comparison of Solar Pool Heating Collectors