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Solar Power to heat a swimming pool

  • 23-03-2021 11:37pm
    #1
    Registered Users Posts: 4,984 ✭✭✭ Chris_5339762


    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???


Comments

  • Registered Users Posts: 726 ✭✭✭ athlone573


    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


  • Registered Users Posts: 2,737 ✭✭✭ graememk


    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.

    Cheaper to buy a wetsuit!


  • Moderators, Sports Moderators Posts: 16,088 Mod ✭✭✭✭ slave1


    Lap Pool is what they’re called.


  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,884 CMod ✭✭✭✭ unkel


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

    6kWh according to this:

    Linky


    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

    Linky


    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

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Registered Users Posts: 726 ✭✭✭ athlone573


    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?


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  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,884 CMod ✭✭✭✭ unkel


    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?

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Registered Users Posts: 726 ✭✭✭ athlone573


    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.


  • Registered Users Posts: 2,987 ✭✭✭ haphaphap


    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: 5,168 ✭✭✭ Ubbquittious


    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

    Ireland's premier property crash prediction site




  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,884 CMod ✭✭✭✭ unkel


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

    Walt, is that you?

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



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  • Moderators, Society & Culture Moderators Posts: 15,527 Mod ✭✭✭✭ Manic Moran


    If you just want to do some straight line swimming and maybe use it as a dipping pool for the four hot days a year (Unless you're my uncle, the sort of person who goes swimming in the Irish Sea on 01 January), consider an endless pool? Think of it as a treadmill for swimming, it pumps a current against you so that you stay in place. Much smaller volume, much less water to heat.

    Looking at a 'standard' basic size, it's 9,010 litres of water, it uses a 4kW heater. Someone else can do the rest of the maths to convert to solar.
    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

    Worked fine for me. Extended our swimming season by several months. Lets the sunlight through to heat the water, but keeps the heat trapped a bit better. Also didn't hurt it reduced maintenance by stopping leaves etc falling in. Only catch is it has to be removed for one day a week to let the pool breathe, or else all sorts of algae growth would start.


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