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New GSHP idea / concept

 
Ground Source Heat Pump (GSHPs)
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 RonV.
(@ronv)
New Member Member
Joined: 1 week ago
Posts: 1
Topic starter 14/10/2026 6:20 pm   [#3193]

Hello from (Eastern) Canada,

I'm no HVAC professional, but have been very interested in GSHP systems since the early 2000's.

A concept my mind has been playing with (mainly to reduce installation expenses, and maybe increase efficiency is to use underground liquid tanks instead of ground or water loops.

My specific idea is (for a 3 Ton pump) to have two ±20,000 liter underground tanks, at a good distance from each other. Instead of using one source for all temperatures, have one designated hot liquid tank, and one cold / ice tank.

To further mitigate the risk of everything freezing up, I'm thinking to connect a set of evacuated solar tubes to heat the hot liquid, and connect the hot and cold tank with mixing valves so temp can be kept at ideal temperature.

The benefit of this would be that you can freeze the cold tank at the end of winter, and use this energy for cooling in early spring, while hot tanks should be warm enough by then to provide a bit of heat if needed. In the fall the reversed process will be used. I figure you may be able to completely turn the heat pump off for a month or so in the spring and fall ...   

As said I am no pro, but this idea is stuck in my mind for over a year now ... Am I onto something, or are some of my ideas not realistic? I'm looking forward to your professional opinions, for which big thanks in advance!



   
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Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
Famed Member Moderator
Joined: 5 years ago
Posts: 2164
15/10/2026 10:43 am  

Hi, @ronv, and welcome to the forum. Good to have a new International member as well.

I'm certainly no professional but at a first glance I think you may have an issue with scale. In effect, by using an underwater tank, you are designing a water source heat pump rather than a ground source one, and in the UK the recommendation for a water source for a typical domestic installation is a body of water that's at least 1.5 - 2 metres deep and 0.5 to 1 acre in size to ensure the heat pump doesn't start freezing up the pond/lake. Doing the maths, that means a realistic minimum of 3 million litres so even if the minimum recommendation is wildly cautious a 20,000 litre tank is still orders of magnitude too small.

I'd also be interested to know what kind of costs would be involved to excavate a hole large enough to accommodate a 20,000 litre tank compared with the costs to sink a vertical coil for a typical ground source heat pump. In the UK, garden space is at a real premium and access is often restricted so I suspect the costs here would be far higher than in many sites in Canada, so perhaps what would be financially unlikely here might be perfectly feasible for you.

As I said, I'm purely an interested layman and so I could well be wrong. However, it's hard for me to look past the disparity in liquid volumes.


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
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