You all probably know by now that the weather here has not been the best in recent memory. It has been, relatively speaking, very cold so far this year. Our swimming pool temps have been in the high 60's & low 70's. That's a bit cool for causal swimming and frolic-ing. We had a contractor quote a heating system for our pool water but his quote was off the map. $$$$$$$ Also the cost to run this system would be astronomical in Cancun. So my friend Karl (whom has done most of this work) and I came up with the idea to try and build a “solar heating” system that would be almost free to run. It only requires enough electricity to run a small pump to circulate the water. (1/2 HP 110v) We started building it this past Monday and today we got it operational. It works mechanically, and now we have to refine it, to make it work well enough to raise the temperature of the pool water from 72-74 to close to 80. The system is basically simple. You pump water from the pool with a pump up to some coils of tubing that are mounted on a black surface that is in the sun all day thereby absorbing the heat in the coils into the water and then back to the pool where the now hot water is added to the cooler pool water. I have a casita/pool house that is in the sun most of the entire day, so its roof was put into service as the place to mount the heating coils. I painted two 4x8 sheets of plywood flat black for maximum heat absorbsion. Then we mounted 3/4" dia. black plastic flexible tubing to it in a continuous coil. We only built up one of the proposed two panels to make sure the concept works mechanically. We still have to tilt the coils approx. 30 deg. to better face the sun. We borrowed the pump from our tenacca cistern system and ran PVC piping to the pool to provide a suction line from the pool to the pump. Then we constructed another PVC line from the pump up to the rooftop and joined it to the coils of plastic tubing at its lowest point. The water circulates through the tubing absorbing the heat along it's way through the serpentine coils of tubing. Then the water is taken from the high point of the system back down and into the pool. So far we have measured only about a 3F rise in temp, but we know that we have sized the pump correctly and that the system is workable. Now we plan to build the second set of coils and add it to the system, which should allow it to gain more heat transfer into the circulating water. We have a check valve to prevent water from backing into the pool to prevent the pump from losing prime. After the pump we put in a ball valve to alter the flow up to the roof. This way we can have some adjustment to control the temperature. If we can get this to work it will greatly extend the usability of the pool in cooler weather and be very cheap to run. Stay tuned for the outcome.
Nifty setup! This reminded me of a segment I saw on a tv show in Saskatchewan years ago called Farmgate. In that case a farmer wanted to heat his outdoor pool (summer only of course) with solar heat and used the same principles that you are doing in your pictures. What may help is that it appeared he made a pannel using 2" PVC pipe instead of 1" hose like you are using. Since I am a hydrogeologist I spend a considerable amount of time working around water pumps and one very significant truth is that making the diameter of a pipe larger slows down the water considerably. If you are looking for more bang for the buck you may want to consider a larger pipe which would slow down the waters path through your heating circuit letting more heat get into the water. The downside is that you may have to do a little engineering to use your existing pump, for example a valve on your discharge (to control the flow rate into the pool) and perhaps a small open tank on the roof so your pump won't be overwhelmed by the pressure head in closed system. If I recall correctly (and again this was years ago) the system the farmer set up with 2" pipe would heat the water enough he had to choke back the flow into the pool to keep it from getting too hot! But again very good setup and keep the water wings on if you have too many beverages!
Looks great. Looks like the same principal as the solar water heater units I have considered buying for the ranchito. Neat idea!!
Some details This is a shot of the small centrifugal pump and motor and the associated piping. This is the shut off valve and 45 deg. run to add water if the pump loses it's prime. The ball valve on the straight run is used to throttle the flow to add or subtract flow residency in the coils on the roof above. This is just a close up of the pump and motor we used. Thanks for the comments and suggestions. I really welcome them, this is a learning process and I invite you to jump in with any ideas. (We didn't go with a all pvc system because the cost of all the fittings was prohibitive and we would have also had to paint them all black)
Fantastic, I may have to steal your invention, I nearly went into shock on Saturday after diving into our pool.
I remember back when I was younger we had some sort of solar cover that you laid over the surface of the water heat and keep the heat in... dont know if such a thing can be found here, but doing a google search of "solar pool cover" shows you what I'm talking about.
A FEW TWEAKS The original concept had some encouraging results. When we had some direct sun for a few hours this is our in and out temps: At one point I had a 20.2 deg.F increase in temp. I've had some problems with getting the pump to consistently prime, and I found out it was cavitating due to air trapped in the impeller housing. Solved that problem but thought I might have to add a vacuum break up on the high point, but that kind of valve is not available in Cancun. So we decided to add a tank up on the roof and just pump into it. A switch in the tank would turn the pump on and off, and now we solved two problems. We had a vacuum break and the pump doesn’t run all the time. The tank drain is attached to the solar coils and the system is now gravity fed back down to the pool! Overview of the system: We added a ball valve to the discharge at the pool to control the amount of time the water remains in the solar coils. An added benefit to the tank addition is that because it is also painted black it will provide some amount of pre-heating to the water prior to it's going through the coils. So we are hoping to pick up another 10 degrees there. At this point I feel that we need to gain about 30+ degrees in order for it to make a difference in the pool water temperature. The pool contains about 12,200 gals. The new tank holds 100 gals. and the pipes and coils maybe another 10-15 gals. I really appreciate all the suggestions and comments.
Very interesting? How much do you lose overnight...ie, what do you end up with and then start with in the morning...is it building heart?
Overnight Isla Zina.......this type of system must be used in conjunction with a solar cover. The cover is floated on top of the water overnight to retain the days heat. Then it is removed in the morning or left in place to enhance the absorption of the suns heat. Otherwise you just can't keep up with the cooling overnight. In the summertime the system can be used to pump cool water held in the system overnight and thereby cooling the water when it gets too hot.
