Solar Pool Heater: A Weekend Project
We enjoy swimming a lot. Regardless of the water temperature, our boys swim. Unfortunately, considering Maryland’s weather, it’ll be mid- to late-June before the pool is warm enough for Mrs. BelAirLife and myself. So, in order to be able to swim earlier in the spring and later into the fall, I began looking at heaters. But I’m a scrooge. It’s helpful to be aware of this up front. Some call it thrifty, but I like the term “cheap.” So, after I got over the shock of learning that heat pumps and gas heaters cost $3,000- $5,000 (or even more) and can cost anywhere between $200 and $800 per month to operate, I promptly ruled them out. Then I began looking at wood heaters. I like wood heaters because I can collect all the free rubbish firewood I need to power one. However, they still cost $3,000 or more, require feeding wood every few hours (because to the size of the firebox), and regularly pump smoke across my backyard (the smokestack is only about 5 feet high). As a result, solar is pretty much the only option.
I began researching several solar heating systems and eventually determined that I needed to be able to create my own solar heater that was both superior and (most significantly) less expensive. So I started looking at blueprints on the internet and came across one that I liked and began to think of ways to improve it. I opted to double the plans and make it 4′ x 8′ because my pool is in ground and holds roughly 22,000 gallons. Because our homeowners organization restricts solar panels on roof tops (another reason I despise HOAs), this would have to be done on the ground.
I went to Northeast Plumbing Supply in Rosedale first to see if they had irrigation hose. Irrigation hose resembles a flexible PVC pipe more than a garden hose, and my hypothesis was that it would be less expensive, solid black, and provide greater heat transfer while withstanding the higher heat conditions of the asphalt shingles I planned to use as backing. Northeast had a large quantity of tubing in a variety of sizes. I paid roughly $22 per 50′ roll for 200′ of 5/8″ tubing (although I only used 150′). Northeast’s guys (who were super nice and helpful) also assisted me in selecting the fittings and adapters I’d need to connect one end of the tube to the beginning of the next and break the tube down to a standard garden hose. I’m sorry, but I don’t recall the names, sizes, or thread patterns of all the fittings; the picture illustrates it better than I can.
Then it was over to Home Depot for a sheet of 4×8 plywood, three 2x4s, and two wire clamp and screw contractor kits. At Home Depot, the bill came to around $40-50. Thankfully, I had a lot of black shingles left over from my roof.
So when I got home, I set up the plywood on sawhorses and then spread out all of my shingles on top of it, but I didn’t secure them. After that, I framed out the plywood over the shingles with 2x4s. I intended to install the panel laterally, so I drilled holes for the hose to pass through the 2x4s with a 1″ drill bit, one for entry on the top right and one for exit on the bottom left. The plan was to enlist the assistance of gravity. I then inserted the hose into the panel and began coiling it. To maintain a circle, I chose two 4×4 coils, so water would never travel directly vertical for too long. Every now and then, I’d use a cable clamp to secure the tube and screw it through the shingle and into the board. To save clamps, I spaced them apart and secured everything using wire ties in between. I continued in this manner until my spiral was complete, at which point I moved on to the next one, and finally out the exit hole.
I also didn’t want to make any long-term alterations to my pump setup, so I used garden hose fittings. On the outside, I just have a garden hose that runs water into the pool’s side. I have a portion of garden hose running from the heater long enough to reach a jet on the pool’s side for the intake. I cut the line at the end and stuffed a 1′ length of irrigation hose into it. The pool jet can then be slid over the irrigation hose. Then I cut two 14-inch lengths of garden hose to slide over the irrigation tubing as stoppers. The jet can then be screwed back into the pool. When I run the panels this way, there is very little pressure increase at my pump, therefore I am comfortable doing it this way. I do recommend priming the entire system from a spigot at the house (at the start of the season) before operating it off of the pool pump.
My pump is set on a timer, so the panel comes on with the pump every day. It was quite effective this year, allowing us to swim in late May and early June. We should be able to swim considerably later in the fall as a result of this. We’ll have to unplug it by August to protect the water from getting too hot, then reconnect it in September. I also recommend using a solar blanket/cover to assist keep the heat at night so you don’t loose what you’ve built during the day.
I’ve never taken a temperature reading before and after the panel, but there is a noticeable difference. I’ve considered covering the panel to prevent heat loss due to the wind. Plexiglass is pricey and loses its clarity fast when exposed to bright sunlight. They produce UV resistant plexiglass, but it’s expensive, and if you haven’t noticed, I’m cheap. Glass, even tempered glass, is not an option for me when it comes to a vinyl pool. My approach was to place the panel in such a way that it is protected from the wind but yet receives as much everyday sunlight as feasible. During the summer, the panel receives direct sunlight from from 10:00 a.m. to about 4:30 p.m.
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