Yesterday I was looking at a commercial pool and hot tub for a potential commercial client that wanted a proposal from Simply Efficient and I was reminded of some of the best uses for flat plate solar thermal collectors, and one of my favorite designs.
The potential client has a hot tub that is heated year round and a pool that is heated to 82F May-August and 42F the rest of the year. In my experience, most pools are drained in the winter so this was a surprise. When I heard that they heated the pool at 42F, I thought ‘right-on’. That’s perfect for a flat plate solar system to run at its most efficient at a time of the year when most flat plate solar thermal systems are running at their worst.
Flat plate solar thermal collectors are at their most efficient when the outdoor temperature is close to the temperature of the fluid temperature that is going to the collectors. Since they ran the pool at 42F, just to keep it from freezing. I essentially would have the collectors running with 42F fluid to them on 20-40F days. That’s equivalent to running the collectors in the summer time. So we get much more output from them than we would when heating fluids up to higher temperatures in the winter.
This worked very well for a client that we installed seven 4’x10′ collectors to heat their snowmelt system. Generally I don’t see a solar thermal system as compatible with snowmelting systems since snowmelting systems run infrequently and when they do they need a massive amount of heat. Solar thermal systems operate much better with a constant load. This snowmleting system was on a condo and they ran it constantly in the winter, regardless of whether or not it was snowing. They did this to reduce liability from someone slipping on ice. With this in mind, I tied the solar system directly into the snowmelt system so that I could run 40F fluid back from the snowmelt cement slab and into the collectors. So this system was running at peak efficiency, even in the winter.
Feel free to comment or ask questions.