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# Solar Power to heat a swimming pool

• 23-03-2021 10:37pm
Registered Users Posts: 5,687 ✭✭✭

Ok Blue Sky idea here, just wondering if anyone else has thought of this.

Suppose I were to want a 15-20m swimming pool in my garden, just wide enough for me to swim the breast stroke or something, say a meter and a bit deep.

Now, I have in my house at the moment 3x solar panels heating hot water. My dad put them in so I don't know what type, but they are not the pipe based ones and are radiative I think. These can heat a 300liter water tank up to 60C in really nice weather.

Obviously I wouldn't want a swimming pool that hot, but is there a sweet spot where you could have X number of solar panels that could keep a whole swimming pool at a reasonable temperature, or does the maths simply not work out?

Since solar is so good at heating hot water, my maths brain tells me that it should be possible (with perhaps a heat dump for the summer). Anyone ever thought about it???

• Registered Users Posts: 726 ✭✭✭

Ok Blue Sky idea here, just wondering if anyone else has thought of this.

Suppose I were to want a 15-20m swimming pool in my garden, just wide enough for me to swim the breast stroke or something, say a meter and a bit deep.

Now, I have in my house at the moment 3x solar panels heating hot water. My dad put them in so I don't know what type, but they are not the pipe based ones and are radiative I think. These can heat a 300liter water tank up to 60C in really nice weather.

Obviously I wouldn't want a swimming pool that hot, but is there a sweet spot where you could have X number of solar panels that could keep a whole swimming pool at a reasonable temperature, or does the maths simply not work out?

Since solar is so good at heating hot water, my maths brain tells me that it should be possible (with perhaps a heat dump for the summer). Anyone ever thought about it???

There's an awful lot of liters in that swimming pool

Say, 15 x 4 x 2 x 1000

Heated to say 15 degrees above ambient and that's just taking the edge off it

I doubt solar will do the job on its own

• Moderators, Home & Garden Moderators Posts: 4,905 Mod ✭✭✭✭

Oh! Math/physics, lets have a go,

Say 15m Long, by 3 m wide by 1.5 deep, = 67.5m2 of water or 67,000L or 67.5 tonnes of water.

And we want to heat that by 10 degrees,

Sticking that into a specific heat calculator

Will use... 783.994 kwh of "power" ( I knew it would be a lot, but,, :eek: )

A 20 tube solar system could generate on average maybe 3ish kwh per day of heat.. going on some stats from the web.

I don't know how much power you would need to maintain such a system once you get it up to temperature, just to be lost to the outside- I would be putting that pool inside.

• Moderators, Sports Moderators Posts: 18,107 Mod ✭✭✭✭

Lap Pool is what they’re called.

• Registered Users Posts: 63,550 ✭✭✭✭

graememk wrote: »
A 20 tube solar system could generate on average maybe 3ish kwh per day of heat..

6kWh according to this:

Which seems a very low estimate or maybe it's the average over a whole year. We have 40 tubes ourselves and my brother in law does indeed partially heat up his indoor swimming pool with a 90 tube system

I'd estimate our 40 tube system could heat up our 360l tank to 60C about twice on a good long day in summer.

According to this calculator

That's about 40kWh produced on a good day. For a system of only about 4m2 that is very good and many times what a solar PV system of the same size would produce as the efficiency of solar thermal is much higher

• Registered Users Posts: 726 ✭✭✭

So has anyone got a lap pool and can tell us what their electricity bill is? To know how much heat is leaking out into the ground?

• Registered Users Posts: 63,550 ✭✭✭✭

athlone573 wrote: »
So has anyone got a lap pool and can tell us what their electricity bill is? To know how much heat is leaking out into the ground?

So many variables in that. What temp do you heat it too, what size is the pool, what rate of electricity do you pay - some idiots pay up to 25c / kWh or even more on "pre-pay", some people get night rate for under 5c / kWh. How often do you heat it, just in the summer months or all year round? Do you heat it from electric only or from gas / oil boiler / solar PV or thermal?

• Registered Users Posts: 726 ✭✭✭

unkel wrote: »
So many variables in that. What temp do you heat it too, what size is the pool, what rate of electricity do you pay - some idiots pay up to 25c / kWh or even more on "pre-pay", some people get night rate for under 5c / kWh. How often do you heat it, just in the summer months or all year round? Do you heat it from electric only or from gas / oil boiler / solar PV or thermal?

Exactly

I'm thinking it might work if you live in New Mexico but here not so much.

• Posts: 0

The calorie was originally defined as the amount of heat required at a pressure of 1 standard atmosphere to raise the temperature of 1 gram of water 1° Celsius...That is the problem you are dealing with.

first thing I'd do if I were you is move to a sunny country or one with thermal springs but failing that I'd paint the surfaces of the pool black to maximise solar gain and wait for a day when the sun is splitting the rocks....oooh....just had another idea. heat rocks in a fire and throw them in to pool.
edit. you could release your own internally contained pre-heated supply of water to help too but that will only turn the water yellow.

• Registered Users Posts: 5,985 ✭✭✭

If you could come up with a well insulated cover for it you wouldn't need to put in as much heat. Some foam slabs that cover the whole thing nicely perhaps and not too heavy to remove. In De States they use some plastic blue sheet that floats on the water to keep in some heat but they do a pis-poor job tbh

Tis not such a problem to dump a few MWh into the thing if it retains the heat. The craic will go off it fairly fast if you have to spend a few €100 on electricity every time you want to go for a swim

• Registered Users Posts: 63,550 ✭✭✭✭

athlone573 wrote: »
I'm thinking it might work if you live in New Mexico but here not so much.

Walt, is that you?