How Does a Solar Swimming Pool Work? How Does a Solar Swimming Pool Work?
If you want to swim in warm water, and don't want to pay a fortune in pool heating costs, a solar swimming pool could be just what you need. As the name implies, a solar swimming pool is heated by heat generated by the sun's rays during the daytime on days where skies are clear and there is not a lot of cloud cover.
Understanding Basic Solar Water Heating Theory
In order to understand how the sun can heat a swimming pool, you first need to understand the process of convection. Water (we are referring to its liquid state and not ice or steam) does not contract or expand as its temperature goes up or down. However, water's density or mass does change, and it becomes lighter as its temperature increases. If you boil water, warmer water will move upwards as it becomes lighter. If you introduce cold water into the bottom of the pot (say with a small pipe or tube), you have what is known as a convection system. Even when you introduce cold water into the bottom of a pot or heated container, the water temperature at the top changes very little.
If you were to place another tube near the top of the heated pot of water, the colder water would gradually push the warmer water further and further upward until it flowed out into the upper tube. So, if you were able to constantly provide cold water to the intake pipe of the pot, while maintaining constant heat, warm water would continue to flow out of the upper pipe or tube. Thus, you have a natural circulation or pump system with no moving parts. This is basically how solar pool heating works.
How the Sun Actually Heats the Pool
In a solar heated pool, the pool is heated via a large water collector and a series of pipes. A pipe leading from the bottom of the pool (where the water is usually coldest) is connected to a collection tank that is heated by the sun. The pipe running from the pool is usually connected at the lowest point of the collection tank. Another pipe that is located near the top of the collection tank runs back into an inlet pipe and back into the pool.
As water in the tank begins to heat up, warm water rises to the top and is slowly pushed out the pipe that leads back into the pool. Cold water from the bottom of the pool flows into the solar collector tank and replaces the water that has flowed out. The cycle continues and as the water slowly circulates from the pool to the tank and back again, the pool's temperature slowly rises.
Although this is an oversimplified description of solar pool heating, it does work. However, there are ways to make it better. For obvious reasons, you should always have a filter for warmer water that flows back into the pool. Also, adding a bleed valve at the highest point in the system will help to release air that may become trapped in the system and reduce flow pressure. Finally, adding a non-return valve to the cold water inlet of the collector tank will prevent cold water from flowing back into the pool. Also, covering the pool at night will help reduce the amount that night air cools warmer water on the surface.