Borehole option with heatpump

iplogger1

I am going to carefully consider the option of the borehole option
as opposed to the ground horizontal loop collector for our central
heating system.

From what I can gather our drainage properties on the site we
are building on aren't great. We have a condition of planning
to put in raised percolation beds. Someone mentioned that this
might provide a useful location from where to site the start
of the collector ground loops. However, then when I've mentioned
the fact that we plan to line the perimeter area of the site
with deciduous trees (another condition of planning) it has
called into question the suitability of using the ground area
(in excess of 1 acre) for the placement of a horizontal collector.

It seems that if I want to do things right with horizontal collector
I might be best served by getting a private contractor
in to do a second percolation test to measure drainage. We might also
need to import sand to put under collector pipes and might
require more intensive excavation work to dig out drainage
channels to aid drainage in the vicinity of the collector area.
The more I think about it and looking at the increased funding
for borehole option I'd feel much more comfortable with going
down that route.

Has anyone installed the borehole or received quotes side
by side borehole versus horizontal collector ? What is the
difference in cost typically ? I believe that the heat pump
energy input might not need to be as high with borehole so
adding up the extra groundwork and tests I'd need to be
comfortable to go with the horizontal system I'd be almost
as well going with the brute force approach of borehole.

Any price comparisons anyone. I'm just twiddling my thumbs
on it until the quote comes in from the supplier.

~ipl

Idleater

iplogger1 wrote:

I am going to carefully consider the option of the borehole option
as opposed to the ground horizontal loop collector for our central
heating system.
...

Any price comparisons anyone. I'm just twiddling my thumbs
on it until the quote comes in from the supplier.

~ipl

Hi,

I am afraid I am not going to be much help to you on the actual costs etc, but I have spoken to some Renewable Energy guys from Sweden at work here recently and they were saying that in Sweden the Bore Hole is what everyone that can do, is doing. I can imagine that it makes a big difference up north that far because the ground gets much colder and therefore reduces the efficiency of the horizontal collector.

It would definitely make sense to find out about costs etc.

I have no space to put in a horizontal collector in my house but I am vaguely thinking about a bore hole if the Air/Water collector does not work out.

The guys were (anecdotally) saying that in Gothenburg all houses were installing the air/water and air/air converters and anywhere that would take a bore hole they would do that.

They were saying that because the coil in the bore hole is deeper the overall efficiency is greater because there is very little variance in temperature. You will lose out though in the warm weather where the ground near the surface heats up which increases the efficiency of the horizontal collector. But in warm weather you are not going to be using as much hot water so perhaps it is even in the long run.

I would also be interested in hearing if anyone has gone for a bore hole collector. I can imagine that it is quite an initial outlay because of the specialist machinery required.

L.

starman100

Hmm, we were talking in work today about using boreholes for heating
and someone mentioned that when you go deep, then you have to keep
pumping out the water in the borehole to extract the most heat i.e. once
you go below the water table, groundwater may have cooling effect.

This is only hearsay but might be an issue with this option.

sunnysoutheast

hi, we're also looking at boreholes vs. ground collector - it is a more expensive option but may result in a higher CoP and some of the increased cost is covered by a slightly higher SEI grant. One other advantage is that you can drill it and forget it - bury it under a patio for example.

I wasn't aware of the issue regarding water mentioned - I thought the major advantage of a borehole was that you got the heat xfer from any water flowing underground vs. the limited supply of heat near to the surface with a ground collector.

one thing to watch is that you have two costs:
* drilling the hole(s) in the first place
* purchasing the collector for the borehole, which is usually more expensive than a slinky ground collector

SSE