Geothermal - soil type question

dryan

Hows things?

Currently building and have decided to go with the Geothermal heating with the horizontal ground pipes. When the foundations were dug out i noticed that in places appeared some small reams of really fine sand (Fox sand) here and there (2 places). The depth of the foundations ranged from 1 meter to 2 meters in places due to a slight slope on the site.
The clay itself is unusally very fine and dry as well and i didnt see a single stone or rock dug up. At no stage has stoney sand or gravel appeared either.

My question is can i get the ground/soil tested in any way to see how suitable it is for the geothermal heating?
I have plenty of room out the back as well so i can go with some extra pipe as well if required.

The rep for Heatlink was on site one of the days and said that the soil is ideal for the system..... Not that i dont trust him or anything but id like to do a bit more research.

Any advice/help appreciated

jones085

When you are looking at wether soil is suitable for a horizontal collector. You are looking at three main factors.
1. The potential for digging and mechanical damage to the collector.
This is weather or not it is possible at all to dig or weather once dug there is likley to be any mechanical damage or not from large sharp rocks etc.
2. Free draining soil.
One of the biggest factors in a efficient collector is the abilty for the collector to replenish the energy taken from the soil surrounding the pipe. The way this is acheived is water movment in the soil (Mainly).
3. Moisture content.
It is ultimatly moisture that is the mechanism for heat tranfer from the ground to the pipe.

So. When looking at a sight at one end of the scale you have clay or marl. Tends to have a high moisture content but no movment and on the other end fox sand or shale witch has a high movment but no moisture. It does not mean that it's not possible to make a collector work in these scenario's but it can be cost prohibitive.
Remember if a collector is working properly COP's of 4 or even 5:1 are acheivable. Get is wrong and it can be as low as 2:1 That's more than twice as expensive to run. If in doubt get a second opinion.

Regards

Simon

dryan

Thanks for the feedback Simon.
Is there a way of getting the soil tested to see how suitable it is as a heat collextor, etc.

Are there any companys out there that do these kind of tests?

Im on the midlands so any help appreciated.

D...

jones085

HI

There are not really any indipendant consultants in soil testing. The only poeple with experience tend to be the technical poeple in the geothermal companies themselves. Your best bet is to get at least three quotes from experienced companies this should hopefully give you balanced view.

You certainly should not talk to anyone who is not prepared to volanteer a site visit before selling a system.

Do not freak to much though in most cases it's ok.

Kind regards
Simon.

boarduser01

Due to a dip in the land on our site we need to build-up by infilling with soil to level the ground about a metre higher. Since we also are laying horizonal ground source pipes, can we lay the pipes on the ground as it is and just cover with top-soil? or will this not work? Sorry if it is a stupid question.

jones085

There is no problem with doing just that.
Although remember that the collector could be quite big maybe 20m x 35 so unless the dip you are talking about is that large you may need to cut into the soil at either side, if that make sense.
Also this also assume that the ground you are potting it on is also the right type. Assuming there is a foot or so of top soil I would say it is ok.