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Pool heating with homemade solar thermal

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(@batalto)
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3655 kWhs
Joined: 3 years ago
Posts: 1091
Topic starter  

Not sure if this is officially on topic, so correct me!

Last year we made a couple of pool heaters from irrigation piping, some wood and a flood pump. The total length is around 300m of pipework which sits on a cabin and it works like a charm. We are currently heating a small pool (3m x 1.5m) and we've got it up to 27°. Current return temp is 35°. Last year we got the pool up to 36 and it was basically a hot tub.

Consider it just works by getting warm in the sun, it's excellent. Zero maintenance, no parts to change - warm pool for free (or a small amount of you need to pay to run the pump).

For anyone interested there are loads of YouTube videos on solar Pex coils. Some people even use them in a residential setting to lower heating costs via pre heating.

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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(@derek-m)
Illustrious Member Moderator
14399 kWhs
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Joined: 3 years ago
Posts: 4273
 

Hi Batalto,

This is actually a subject on which I have been doing some research for quite some time, not for pool heating since we don't have a pool, but more importantly to store thermal energy for later use. I actually built a small test rig using a 4 pint milk container and a piece of 15mm copper tube, with which I managed to heat 2 litres of water up to 40C using just solar energy.

It is part of a design I have been developing, that would store energy in a quantity of water during daytime, and then use this stored energy to preheat the air being drawn into an ASHP when the temperature falls to +5C or below at night. In this way it should be possible to maintain the efficiency of an ASHP for longer and hence improve its overall efficiency.

Anyone who would be interested in more details then please get in touch.


   
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setithing
(@setithing)
Active Member Member
0 kWhs
Joined: 3 years ago
Posts: 4
 

Hi Derek,

I'm really interested in your idea of using thermal store to boost a ASHP. I have been looking into trying to make a system work with GSHP and a ice storage tank to do the same thing. Inspired by an austrian system. (would this be better in a new thread?)

https://elkement.wordpress.com/2016/01/07/how-does-it-work-the-heat-pump-system-that-is/

To keep this more on topic, Batalto what material do you use for your collector? I have been weighing up using PVC vs PP I want to use PP due to better thermal conductivity but worried about UV damage. Also using ribbed conduit like is used for electrical work to increase suface area.

I hope this make some sence I'm a little to excited about Heat pump and just want to build things.

Setithing


   
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(@batalto)
Famed Member Member
3655 kWhs
Joined: 3 years ago
Posts: 1091
Topic starter  

@setithing it's just some generic irrigation pipe from eBay in a home made box. If I was doing a proper one (not for a 3000l pool) I'd build it properly using foil lined PIR boards, copper pipe and double glazing on the front - that would keep the heat get very hot. You could then just have them in series. However I think the main issue you'll have is that there is limited use in the winter (when you need it). Ideally you'd just use solar thermal or PV.

Have you consider mechanic heat recovery? Might be a good route. I've no idea how effective it might be using it in the winter and the issues around freezing.

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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(@swalker)
Trusted Member Member
15 kWhs
Joined: 3 years ago
Posts: 14
 

When doing research into GSHPs I came across this whitepaper - https://www.solarpatio.org/

At the end it discusses how the theory could also be applied to a swimming pool. There's some really fascinating innovations happening at the moment! We've just bought a house with a pool, and there's a lot of other work to be done first but will definitely be keeping an eye on this when we come to re-do the patio I think.


   
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(@diverted-energy)
Estimable Member Member
439 kWhs
Joined: 2 years ago
Posts: 64
 

I heat my daughters pool with a homemade panel.

Obtain:

Sheet of Kingspan

4x2 timber

Aluminum heat spreaders, used in underfloor heating

15mm reclaimed or new copper pipe

 

The double glazed window unit, you can usually find them where windows are being changed, so for free.

Make 4x2 frame the size of the glass unit. Cut Kingspan to fit inside you can put board order insulation but instead I used battons to stop it falling out.

Insert Kingspan into frame, Once Kingspan in place put stripe of roof battens inside rim to support glass just above frame. Cut and bend copper 15mm to match channels in the heat spreaders. Parallel connections better than series for efficiency. Bring out pipes to be met by PEX and connect to pump/filter or Obtain a pump.

Seal all joints and gaps with expanding foam and silicone to make air tight. Spray heat spreaders with matt black paint, ideally stove paint.

Place glass onto supports, use sticky back flashing onto edge of glass and over the frame to keep glass in and make water tight.

Use copper not PEX inside as heat transfer much better.

Secure somewhere sunny and enjoy!!

Also ideal for hot hubs and scalable to suit.

This post was modified 2 years ago by Diverted.Energy

   
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