Solar for swimming pool

[PoolBoy]

Hi looking to power my swimming pool, that’s heat and circulation pump from solar only.
My heater is 1.8 kw air source heat pump and my circulation pump is 700watts. They run April until end of September. They start 10am - 6pm then shutdown for the night.
Looking for advice on spec on panels and inverter. I have 1.5 acres and will be ground mounting with uninterrupted south aspect. I may add battery at a later date. Will be off grid so no house electricals involved.
Any help will be very grateful.
Many thanks
Howard

 

[binky]

are the pumps and air source single or 3 phase?

 

[johnb2713]

Hi looking to power my swimming pool, that’s heat and circulation pump from solar only.
My heater is 1.8 kw air source heat pump and my circulation pump is 700watts. They run April until end of September. They start 10am - 6pm then shutdown for the night.
Looking for advice on spec on panels and inverter. I have 1.5 acres and will be ground mounting with uninterrupted south aspect. I may add battery at a later date. Will be off grid so no house electricals involved.
Any help will be very grateful.
Many thanks
Howard

1.8kW sounds very small for heating a pool ?

 

[PoolBoy]

All single phase

 

[PoolBoy]

1.8kW sounds very small for heating a pool ?

1.8kw with gop of 4.5 so was working very well last year

 

[johnb2713]

1.8kw with gop of 4.5 so was working very well last year

I'd assumed it would have cop of 4 to 5 but even so, 9 kW into a swimming pool just seems very low, 10 kW is used for a shower!
But, if it works for you, knockout, thats great.

 

[PoolBoy]

9 kw X 8 hrs x 7 days a week soon builds up and a top notch solar cover preventing heat loss I had it at 30 c all summer. Wondering if you can help on the solar question.

 

[binky]

so 9 kw, I would suggest an array of around double that to allow for poorer weather - solar rarely runs at max outputs. However, summer days are longer than 8 hours, albeit like sunburn, between 11am and 3pm is peak. Being single phase you wil need multiple inverters as most single phase stop at around 7kw. You have plenty of space for the array, so can use cheaper panels. Anything you could use surplus energy for like charging an EV? It might be worth getting an Octopuss smart tariff to sell some energy back to the grid, albeit payments are small, like around 5p per kW, but you coud sell back to the grid in winter. Rough estimates suggest you are spending around £4k per year, 4 kw on a roof is around £5k, which is far harder than a ground array, so payback could be 3-4 years. Good project! Ok you said off grid, but it's easier to keep a grid connection, unless the house is miles away

 

[Murdoch]

If you have space in your garden , one of these systems may make sense

https://heliomotion.com/

 

[binky]

If you have space in your garden , one of these systems may make sense

https://heliomotion.com/

Anything that moves will eventually seize up! Love the idea, but simple is best in my book

 

[binky]

Out of interest, have you considered solar thermal? Direct heating of water is more efficient than electrical heating. You do have some maintenance work with thermal stuff, but, if you are feeling keen, it's possible to make your own panels.

 

[PoolBoy]

Thanks for your replies very helpful

 

[johnb2713]

Out of interest, have you considered solar thermal? Direct heating of water is more efficient than electrical heating. You do have some maintenance work with thermal stuff, but, if you are feeling keen, it's possible to make your own panels.

Even more efficient than a heatpump with cop of around 4.5?

 

[Murdoch]

Anything that moves will eventually seize up! Love the idea, but simple is best in my book

Its simple and clever - and the output is higher pro rata than my fixed panels.

 

[johnb2713]

Its simple and clever - and the output is higher pro rata than my fixed panels.

But is it higher than panels feeding a heatpump with a cop of 4.5?

 

[Murdoch]

But is it higher than panels feeding a heatpump with a cop of 4.5?

No idea. Customer choose it.

 

[binky]

Even more efficient than a heatpump with cop of around 4.5?

But that's not the whole picture. The panels supplying the leccy are only 23% efficient. Solar thermal doesn't get talked about much these days, so I'm not sure what the figures are, but the few installations I've seen consist of only 3/4 panels on a house.

 

[johnb2713]

But that's not the whole picture. The panels supplying the leccy are only 23% efficient. Solar thermal doesn't get talked about much these days, so I'm not sure what the figures are, but the few installations I've seen consist of only 3/4 panels on a house.

Thats my point, if the Solar Thermal was 100% efficient comparing it to 23% efficiency of Solar PV, now put that into a heatpump with a COP of 4.5 the 23% becomes 103.5% which makes it more efficient than the Solar Thermal. Most pool heating heatpumps are rated higher than a COP of 4.5 too. The heatpump is also more useful when the solar thermal isnt getting the conditions it needs to make a comfortable temperature in the pool.

 

[binky]

I see what you are saying, but somehow those numbers don't feel right . Direct heating water, and a quick scan suggets 70-80% efficiency of thermal panels, seems a straight forward simple solution. All you would need is some panels and a pump. I also think solar thermal is still eligible for RHI payments - that scheme never caught on like the FiT payments for PV and I think it may still be open. I have a customer who uses a heat pump for his swimming pool, far cheaper to run than the all electric heating he had, but he had no space for thermal panels. So I would suggest it all comes down to cost of a large heat pump v cost of thermal panels. One question, how often do you get the full CoP of 4.5?

 

[johnb2713]

So I would suggest it all comes down to cost of a large heat pump v cost of thermal panels. One question, how often do you get the full CoP of 4.5?

COP of 4.5 is easily achieved for pool heating because the output temperature required isnt very high compared to central heating etc. The OP already has a heatpump so Solar PV seems to be the way he wants to go.