Solar-Heated. Swimming Pools

We’ve saved our discussion of solar-heated swimming pools for last — not because it’s least {or most) important, but because it’s different. On one hand, swimming pools are still consid­ered luxury items, even in the minds of most affluent Americans. Domestic hot water, on the other hand, is something we take for granted in most homes in the United States. To put it another way, we see hot showers as one of life’s necessities, but heated swimming pools as ex­pensive frills.

As we get more and more strapped by our dwindling supply of traditional energy sources, the public will disapprove more and more of burning precious fuels to heat pool water. Already legislatures in California, New York and Illinois lean quite specifically on pools that have gas – powered heaters. And laws against nonessential consumption of fossil fuels will only get tougher as time goes on.

If you already have a heated pool, or want one in the worst way, heating your water by the sun is an easy — and acceptable — way out. You see, you have two things working for you before you even start. In the first place, the pool itself is a natural solar collector. Second, it’s a ready-made solar storage tank.

When you come right down to it, what most people are trying to do with any pool heater is just raise the temperature of the water to about 80 degrees Fahrenheit, and then keep it there. The idea, usually, is to extend the swimming season for several weeks during the spring and fall — and to be comfortable. In light of what we’ve al­ready learned about solar potential, it doesn’t seem that hard to collect enough free BTU’s to heat a pool that much. And it isn’t.

On a bright sunny day in summer, a typical pool will gain 2 to 3 degrees of temperature on its own — without help from any artificial heating system, solar or otherwise. If the surrounding air temperature stays reasonably high at night, so there’s not a lot of heat loss, the pool will con­tinue to collect and store BTU’s of solar energy during the day. This process will continue until the water is about 10 degrees warmer than the ambient air. At this point, it can’t go any higher, because it reaches a state of equilibrium: it loses as much heat at night as it gains during the day. in other words, unless it has some kind of heating assistance — or some sort of insulating cover — the water in a swimming pool can almost never get warmer than 10 degrees above the surround­ing air temperature.

Updated: August 21, 2015 — 3:32 am