Would a 10mm pipe inside a 28mm pipe in a narrow borehole work for GSHP

[justsomeguy]

Ok i know i ask mental questions... but thats what this part of the forum is for.. .and it stops me annoying the wife.

So the question is as i have limited space in the garden (100sqm), and no (easy) access for plant, it makes GSHP kind of hard... but
I was thinking if i can dig a 1 meter trench and then bore say 2-3 meters down (london clay) with a home made drill (a 1.2 meter 30mm arbor on a long extension then place a 8/10/15mm copper pipe inside a 28mm pipe so the flow is down one and out the other (using t pieces and reducers) make a hard nose cone and drop (hit) it in, connect up the rest as per normal should give me 300m3 enough to run a little 5kw GSHP...

Or as my wife should say, nope you are being mental again do the washing up.

Dave,

[baker]

Hi Dave
seems a lot of hard work, and it may not work and the heat pump may not last
why not fit a air source heat pump  its the fashion now  and just as good cop 3.9
make sure to get a heat pump for low humid temperature as the Europe one will ice up in winter
we have fitted for your costumers and had good results, its the way forword if you do not have natural gas

 

[dhaslam]

It is a lot of drilling,  a lot of fittings and a lot of places to leak.   If you could  manage to get a small  mechanical digger  into the garden   and dig a couple of fairly deep holes and refill with  the  continuous coils  of the usual  pipe.  Then direct roof water into the holes so that there is  good heat transfer.    Temperatures  may not be as good as the usual very long trench but it still should be a good bit better than an air source system in  very cold weather.  

An  alternative would be to use an air to water  heat pump with some underground heat assistance.   It would involve a much shorter  underground pipe than a GS system  but would  bring the input air above freezing in most conditions.    I had planned on doing a simple system like that but have decided to make something bigger  that can store heat from the summer.    

[renewablejohn]

If you are clay you can make an underground pond. We used to do this to keep a fresh supply of water without losing any land. Start by digging a pond in the clay. Insert feed and overflow pipes then fill pond with clay drainage pipes to within 2 foot of the surface and then cover with topsoil.

I am sure you could adopt this method for a ground source heat pump

[justsomeguy]

Thanks guys, back to the drawing board... (the one with crayons and a funny white suit with extra long arms)

I do like the idea of an underground pond for storing rain water for the garden.... under the lawn..... but no plant access unless it goes thought the front door and front room..... wife makes me take off shoes... if i'm even THINKING about coming inside. (or over a 12 foot wall)

[mick]

I've seen somewhere, Austria I think, where they fed air to an ASHP through some buried plastic drainage pipes to slightly preheat the air. If I recollect correctly there was a bundle of pipes (6?) in a trench. Have to be quite deep, or maybe under the house (not retrofit!).

Just a thought.

Mick