Solar pool heating panels sold by professionals in Florida are not all the same. Panels fall into three basic categories:
- Welded Tube
- Separated Tube
Each type of solar panel has advantages and disadvantage. Each type will heat your pool, performing at varying levels depending on the conditions. Some of the differences are high-tech, and some are common sense. Adding to the confusion is that manufacturers of each type of panel have other features and manufacturing methods that change the design, performance, and longevity. Fortunately, some features of each type of panels are generally well defined, and I will attempt to do that here.
Welded Tube Solar Pool Heating Panels
Welded tube solar pool heating panels feature a series of tubes where the tube walls themselves are “welded” together. There is no space between tubes, which means that the entire top surface of the solar panel is exposed to solar radiation where there is water directly on the other side of the panel wall. Some call this a “fully wetted” panel, which exposes the largest possible internal surface area of water to the sun. Welded tubes allow no air to flow between the tubes, which means they heat water very well relative to others in windy conditions. They also do not give up heat to ambient air during cooler conditions, making them an excellent performer when you need solar pool heating most – when the air temperature is cool relative to the pool water. Welded tube solar panels require a relatively flat surface on which to mount them, which requires a racking system on some roof types. These panels require straps to keep panels firmly mounted to your roof. The major downside is the reliability of the panels, which tend to develop leaks.
Tube-On-Fin Solar Pool Heating Panels
Tube-on-fin solar pool heating panels are similar to welded tubes in that they do not allow air to flow through the panel body. This design allows the panel body to bend slightly horizontally and is easier to manufacture compared to welded tubes. Tube-on-fin solar panels perform better than separated tube panels and similarly to welded tube panels. Tube-on-fin panels perform especially well in windy and cool ambient air conditions relative to other panels. Like welded tube panels, tube-on-fin panels require straps to keep panels firmly mounted to your roof. This is the best balance of heating performance, longevity, reliability, and cost.
Separated Tube Solar Pool Heating Panels
Separated tube solar pool heating panels advantages include conforming to uneven roof surfaces and allowing wind to go through the panels, requiring less stringent strapping requirements. Some roof obstructions can be avoided by placing panels where tubes go around them. That’s where the advantages end usually. Because air goes right through the panel body, heat is more readily lost to the ambient air. This is like blowing on a cup of soup. Separated tube panels test well under conditions where the ambient temperature is high relative to the pool because the entire tube is exposed to warm ambient air. Unfortunately, this is exactly when you don’t need to heat your pool! In cooler air conditions, wind and ambient air sucks heat out of the tubes, making them less efficient. In addition, much of the sun’s radiation goes right through the panel body. Separated tube panels consistently test poorly in conditions where solar pool heating is needed most (SRCC Category B), and performance drops off dramatically under very difficult solar conditions. That’s not to say these panels don’t have their place. On some roof types, this is really the only or the best choice.
Each manufacturer’s panel will test differently, even if the design is virtually the same. There is a lot more that goes into solar pool heating panel design and manufacturing. Generally a full body design will win on performance when heating is needed most — it’s common sense. More surface area exposed to the sun and less wind between tubes means more water heating. Separated tubes allow air flow, performing well in hot and calm conditions and poorly in cold and windy conditions. Without hesitation we recommend the tube-on-fin design, because ultimately you want a warm pool without hassles, and this design performs the best while improving longevity and reliability. The separated tube is really relegated to certain roof types where welded tube installations are impractical, or obstructions exist.
The type of solar panel you select will come down to a combination of price and performance, but don’t limit your research to the panel type alone. A solar pool heater is a system, and there’s more to the system than the panels alone. Naturally, if you want the best you will pay a little more. The poorest performers will usually have the lowest cost. You get what you pay for!