Cooling UFH slab, using Rainwater harvest tank.

[Jenki]

Although planning a building on the East coast in the highlands, I do have a concern for over heating.

Heating to be thermal store - ASHP - PV and ( possible Solar thermal)- all DIY, possibly a small  wind turbine connected to DC immersion - it is windy all the time.......

Anyway I got to thinking about cooling, and read some people use the ASHP and buffer tank to cool the UFH. 

I plan to have  6000L rainwater tank ( it also rains a bit), this tank will be underground and relatively cold, so I thought a couple of three port valves and a dedicated loop of pipe running through the tank would provide all the cooling needed and a possible heat dump for the solar. 

 

Any thoughts , problems you see.

 

[Nickfromwales]

Hi.

At 6000L and at ground temp or close to, there will not be a great deal of useful cooling ( heat energy ) capacity to come from that before the uplift from the return diminishes the delta T to a point where it becomes completely ineffective. The need for cooling occurs in the summer period, so ground temps will already be seasonally elevated ( albeit only marginal differences occur from summer to winter for true geothermic heat considerations ) further reducing the possibilities of utilising RWH tanks for cooling.

I would forget solar thermal unless you have an abundance of roof / other 'solar space' after fitting a reasonably sized PV array, as ST is a one-trick pony and all summer long the extremely high temps stored in the hot water cylinder ( not buffer ) will add to the core concern of overheating. PV will provide most of the energy to run the ASHP in reverse, direct to UFH, so why integrate more complexity where it is not going to be of much or any use   

Edited October 8, 2021 by Nickfromwales

[Jenki]

38 minutes ago, Nickfromwales said:

PV will provide most of the energy to run the ASHP in reverse, direct to UFH, so why integrate more complexity where it is not going to be of much or any use   

 

Thanks Nick

I was intending of using a thermal store - for both DHW and UFH, no buffer?  Main reason is I can do it myself as its not pressurised, ASHP monobloc so again fit myself. 

So is reverse ASHP an option. with a dedicated loop, i.e bypass the thermal store  with valves ?

Can all ASHP run in reverse?

 

[Nickfromwales]

Fit a Telford Tristore if you want no G3   

 

[PeterW]

Warming up a large body of water to room temperature with an organic and unfiltered feed of food and microbes is a recipe for growth of some particular nasties. I’d leave well alone 

[Nickfromwales]

2 hours ago, PeterW said:

Warming up a large body of water to room temperature with an organic and unfiltered feed of food and microbes is a recipe for growth of some particular nasties. I’d leave well alone 

Yup. RWH water is class 5 which is about as bad as a septic tank.