Solar swimming pool heater

We have an in-ground pool with solar. Normally, we lose 3 to 4° overnight when the temperature drops about 15° overnight. Solar brings it back plus some so that we get a steady increase. Your drop will probably be more since the sides of the pool are exposed.

You will need to raise the pool temperature higher than the desired morning temperature based on the amount of heat loss over the night. That is not a fixed number, but depends on how cold it gets. Probably not a good option.

An alternative is a natural gas heater which you could time to start before the swim.

You could also build a huge hot water storage tank, but the cost will eat you out of house and home, plus you must also treat the extra water, which will tax your filter and chemical treatments (it's like a bigger pool).

A third option is a pool blanket to help reduce heat loss. I don't know how the solar bubble covers work. The ones I have seen are a light translucent blue bubble wrap. I assume they act as a blanket that lets IR pass through them, but acts as an insulator with the trapped air bubbles. However, it sounds like you use that now. You might insulate the pool sides, but that may be a poor return on investment.

I would contact some pool installers in your area, but I think your best bet is to use a gas-fired pool heater and use it to boost the temperature based on a timer.

If it is close to the house, you could place acouple hundred feet of hose on your house and garage roof or paved driveway your choice- and circulate water throught this hose using your pool pump cover portable pump. (mine is a little giant brand)

Pump water from pool with submerged pump through the hose and it will pick up heat from roof/driveway and return warmed water to the pool. Run it for four or six hours of peak temperature during the day Say noon- six standard time.

Should pick up a couple of degrees, without burning fuel except at the generating plant for the electric to drive the pump.

Put insulated cover on at night to keep heat in , and take pump out of pool at night to avoid system thermosyphoning (running backwards) at night and cooling the water by radiation into the night sky.

milo

At the top of the solar collector, place a 1-way valve, once the circulating pressure is released and the water wants to fall back to ground level, or pool level, the valve allows air into the system, when you start your pump for the solar, the valve closes (assisted with a light spring)

In this situation, the pump will be loaded until you have a flow of water thru the solar piping, and down the other side, then its just circulation restrictions.

Now, when you turn off the pump, and the system drains, no worry about the heat circulating in the pipes and cooling your pool water.

Hey Milo. Just want to add to your comment. When using a large volume of hose or polycarb black pipe, just be carefull where it is put. Remember that the more water into the pipe the more the weight. Some roofs/structures might just not handle the extra weight.

Conrads, I've been in countries where even the weight of the empty hose would be a challenge for the typical roof!

You make a good point. but a hundred feet or so of hose on my garage roof hasn't been an issue.

Good thinking.

milo

A couple; of 1/2 inch copper pipes painted black in a 4x8 box with a piece of glass from and old sliding door a delta T controller set for a 10 degree difference from pool to collector will raise temp in pool to a state that you could boil lobsters if not careful.

Make sure to install p @ t valve at upper most part of collector and temp sensor in the middle

You may also want to install a max temp cut out and drain back valve to empty out collector in winter and high heat situation's make sure to use temp and psi valve to as I have seen big holes in roof from over heating and that was in north Carolina

I once visited a friend who lived in Walnut Creek, California. He had an above ground pool. For heating he had two spirals of black flexible piping on his roof facing the morning sun. I would guess that the two spirals were about 15 feet in diameter and they were close wound. The pipe was about 1-1.5 inches in diameter.

He had a small electric pump that would pump water from the bottom of his pool, around the first spiral, then around the second spiral. The water would then flow back to the pool. I placed my hand on the outflow at the pool and the water was extremely hot. If you were filling a bath tub you would want to mix in some cold water. The pump would have to be powerful enough to get the water to the highest point on the spirals. Once you got the water up on the roof in the spirals I wouldn't think that there would be much resistance to the water flow so the demand on the pump wouldn't be all that great.

It was very effective and the cost was only a small electric pump capable of pumping water up to the roof, and quite a length of flexible black tubing. Maintenance could not have been very demanding as it was independent of the pool filter plumbing I believe.

Many years ago a friend experimented with threading the black hose suggested above through a number of glass bottles with their ends removed, so as to produce a 'greenhouse effect' on the hose. It worked a treat, and it was as cheap as chips.

One of the simplest I've seen was a length of black PVC pipe around the pool. Water from pool was pumped through the pipe after being filtered.

It only made a 3-4 degree difference, but was cheap and gave them a few extra weeks use in spring and fall.

If you use a large AC unit for your home (more than 3 Tons, 4800 Btu), have an AC guy add a water heat exchanger (nickel plated) to dump the AC heat into your pool. I have this at home and it works much better than my neighbor solar system on its roof. It was also less expensive (about $1000). I added a relay to turn on the pool pump when the AC runs as this is how the water circulates in the exchanger. Since they are on the same level, I don't overload the pump. Finally, the AC is much more efficient because the water absorb the heat much better than the AC air coil, especially on hot days. On cooler days, I often run the AC simply to remove the house humidity that damages the wood floor and it keeps the pool warm.

Other people install a dedicated heat pump to heat the pool but I find it a wast of energy when we also have an AC unit.

Looks like with this, if you get into the ear of the aircon manufacturers, you could have this idea incorporated into the exchangers, and make yourself a small tidy income ;o)

I'd like to suggest a constant flow ground loop (you could run this on PV solar if you like) which would raise the water temp to about 25 deg C. If you want higher than this it could be used as a per heating system with additional "boost" to requirement.

Of course, you'd need a fair partch of ground to bury the loop (about 1 acre) and about a kilometer of 1 1/2" pex pipe. Not sure of the final calculations but the longer the loop the better...

Gentlemen. 25C is barely enough to use a pool unless it is a very hot day. Once again, one must consider the power absorbed by a hose exposed to the sun. It is not because that stagnant water in a hose gets warm that it has a lot of heating power. Once the water starts flow it stays cold. Even with 30 meters you will not get more than one or two KW which will not have much effect on the water temperature. A typical pool heater begins at 10KW, and 20KW units are frequent in the northern latitudes. This means that at least 10-20 square meters of solar captors need to be used.

Here is how you can evaluate the power needed:

You need 4 Mega Joules to heat up a cubic meter of water (1000 litres or about 250 gals.) by 1 degree C. That is 4KW during 1000 Seconds (about 15 minutes). A typical pool has 50 to 100 cubic meters of water. The small pool temperature will increase by approximately 1 degree every 6 to 7 hours with the typical 10KW heater. We didn't take into account the losses by evaporation of the heat gain from the sun. This degree will cost you 10*7*$0.1/KWh = $7. As the temperature of the pool gets higher than the average ambient air and solar gain, you will spend many dollars per day just to keep it warm.

A heat pump will help as it cuts the cost of electricity by about four. You have to invest a few thousand of dollars to get it installed. How many years for payback? Increased maintenance?

Solar panels will work if you have about 10-20 Square meters. What is the cost? Increased maintenance?

You can isolate the outside and the bottom of the pool and use a good thermal blanket for a few hundred of dollars if you do it yourself. Then you will get the best results in my opinion.

Hello Mag,

you pose an interesting question.

As I understand it the, Bubble type Solar-'cover/heater' is more of a cover than a very efficient heater.

I realise you are probable talking about Solar-Panels as we think of them now. The kind that generate power, but, this is an 'old fashioned' type of Solar Panel I built. And, it worked well. And as long as there was some kind of water cover to prevent water freezing on the glass and cutting efficiency, the one I built produced warmed the water enough, even in winter, to stop the pool freezing.

I found once the in-ground pool reached its optimum heat, which could take a week or two, the pumped water through the Solar panel reaches, as long as there is some sort of pool cover the heat should not decrease by more than about 4°.

It may sound a little silly and extreme, and though I did not do it, you could perhaps use either batteries or mains power to shine Ultra-Violet lights on the pumped water Solar Panel during the night to heat the pumped water.

I built a Solar pool heater over twenty years ago. I cannot recall any exact technical details of heat transfer etc but, the pool was about Tennis Court sized. The Solar Panel was based on easily available components-off the shelf.

The pool you have is about half the size I worked on but, using water radiators painted black on a black background with each panel covered with double-glazed glass, you can connect the output to the pool pump and circulate the pool water continuously. I insulated the area behind the whole length of panels with at least sin inches of fibreglass and aluminium or equivalent. And, if you need an extra panel it is easy to install and connect to the row of panels you already have. Angle the whole length of panels backwards at roughly 30 degrees to catch the most rays. This can of course be situated some way away from the pool and connected by the insulated pumping pipe, as it is not a pretty thing to have on the pool-side.

One roughly the same as the 'length on the shortest side of the pool' itself, excluding the 'Doubles-line'. The Solar cell was made from 6 ft x 6 ft panels, of water radiators painted with blackboard black. Five panels side by side which was 30 ft x 6 ft six tall. Of course you need to orientate to the South.

jfmfit

I have an above ground pool, 15' diameter, 5' deep. The solar heater I use consists of 100' of 3/4 copper pipe, painted black, coiled in a 4" deep 4'x8' box (also painted black) covered with a sheet of glass on the roof of my garage. The pool pump is on a timer, so it starts a couple of hours after the sun is up, pumps the water through the heater and runs until a couple of hours before sun down. Assuming good weather, it will heat the pool from cool (tap water temp) to 25 - 28 Centigrade in about a week, and thereafter keep it in that range. I don't know haw hot it is first thing in the morning, but when I get home after work its like having a bath. By the way, I live up north in Edmonton Alberta Canada.

The biggest issue is the increased use in chemicals at that temperature, but since I switched to a saltwater pool with chlorine generator, that s pretty much a non issue to.

BTW, I found out that the salt concentration in the pool is not enough to kill plants outright, though they don't like it much, after a hose became disconnected in the morning and dumped half the pool on the girlfriend's flower bed!

Is it possible to run a solar powered pump, so there is no need to use the utility power, saving you further costs (yeh, I know in the long run)

Thanks to all who have replied.

I'll cogitate a bit. Wish my pool was nearer buildings or pavement.

Mag