ground source heating

[The Natural Philosopher]

Thats incorrect.

air varies at this time of year from may +5 to -5 here anyway = over a day.

Subsoil is pretty constant at a meter down at about 2-4 degrees.

It's was a little warmer in winter, due to summer solar heat and geothermal energy, and its never as warm in summer.

ASir source can gice up at very low temps..-25C and you want see a lot of eat out, when youy need it.

They are beter in urban situations., because you can pump waste heat from all tehe cars :-)

geothermal...there was a nice Swedish scheme that use the (insulated) ground under the house and a pond in summer to run the aircon. Heated up a huge block of subsoil, and pumped it all back in winter. Cool idea.

would be piss all use if you did. need contact with wet soggy ground.

[The Natural Philosopher]

Mire a 3 ton digger and do in in a couple of amusing days.

[The Natural Philosopher]

It is..but even so in winter, the deeper the warmer. Average UK temps and that reflects the subsoil, are about 9C.

Go deep enough and thats what you find.

Hence the need for a s deep a pipe run as is practicable with a digger.

Generally a couple of meters max.

[Tim Lamb]

I would expect to get between 2 and 3 feet. The water table is at about

18" during the Winter. I have an old single leg subsoiler which can be fitted with a short length of 2" steel pipe to form the hole for the collector pipe. The usual trick is to run the subsoiler through the ground first to check for obstructions and then couple up the pipe for the pull.

Try mole plough:-) Lots of horsepower needed to pull one.

AFAIK mole drains only work in certain soils and then only for a limited period.

Drain to where? Do you have a ditch or pond? What is the soil? Why not hire in a mini digger, there must be lots laid up.

regards

[JimK]

or a borehole? JimK

[Roger Chapman]

snip

I have an old mini digger so I suppose I could dig it out but making good would still be hard work and the volume of water doesn't really deserve much in the way of a drain.

[Roger Chapman]

snip

The source of the water is only really a seep which is why I didn't manage to find where it has come from when I dug for it a year or two back. I was hoping than ploughing a 'molehole' would provide sufficient to drain a puddle than always forms in front of a particular gateway at the beginning of winter.

Land drains in these parts consist of 2 walls about 6" apart and 6" high built of loose pieces of local stone covered by a selection of larger stones. The Romans built drains that way but considerably better constructed. Most around here are either collapsed or silted up, or even ploughed out when traditional grassland was ploughed up during WW2.

[dennis]

That's what I said, if the neighbours do the same the ground temp drops because there isn't an infinite heat source in the ground.

[Calvin Sambrook]

Similar. The heat you're tapping into is mostly coming from underneath rather than from the sun. The problems being suggested for the town sized schemes have more to do with the rate of transfer of heat from the deeper earth rather than the quantity available. For your purposes it's pretty much infinite provided you go down far enough, which might only be a few metres anyway depending on conditions.

Now things might get interesting way into the future when our civilisation approaches the boundary of what the theoretical physicist Karu calls "type 1 civilisations". At that point we would be able to extract *all* of the energy from the earth. We're quite some way off that though so I wouldn't fret just yet.

[dennis]

I doubt if I could go deep enough to find any geologically active bits around here and the heat coming up from the core is not significant AFAIK.

[The Natural Philosopher]

good, but expensive.

[The Natural Philosopher]

well just fill it with hardcore, topsoil over, and let the water run underneath it all.

That's how this garden works.

[Roger Chapman]

snip

The soil is far from ideal. Mostly hard clay with stone inclusions but with some soft spots in unexpected places. The shortest route to open water (a once culverted stream) is probably less than 100 yards but that might be slightly uphill and in any case somewhere close to the stream is the mains water supply to an isolated house which was allegedly moled in long before I moved here in 1978. I don't know how deep that is but I suspect it is fairly close to the surface.

[The Natural Philosopher]

You don't have to find geologically active bits dennis.

Go down any coal mine - below a mile its about 30C plus

This is a well written article IMHO

[andrew]

It was Lord Kelvin

AJH

[andrew]

How many Watts/m2?

I've a well in the garden but I suspect I'd freeze it if I took more than a few hundred Watts out of it.

So how deep a borehole to get 5kW out?

AJH

[The Natural Philosopher]

wrong question.

but you can get 5kW out of about 200m of subsoil, so try 200m. Not deepo enough to have serous geothermal heating tho.

ideal house. Insulation barrier and 'cold room' cellar underneath. freeze the shit out of it and pump the heat from uninsulated walls in contact with the subsoil.

If you have a cellar, tank it, fill with water and put a coil in that.

[dennis]

Does not compute.. go down a cave, its nowhere near 30C. Mines have stuff in them that warms them up, people, machines, etc.

Even if it did I have no chance of boring down 1700 m.

"Ground Source Energy is latent heat within the top 100m or so of the earths surface which is generated and replenished from the sun. "

A bore hole will only work as long as the neighbours don't get the same idea as there isn't enough spacing between the homes for the sun to replace the heat.

[Tim Lamb]

In message , The Natural Philosopher writes

I know:-)

This is flood plain land. Historically, the Lea valley was used for water cress production. Ditches were dug at the edge of the flood plain, presumably to intercept clean spring water from the valley sides. The strip I have in mind is sandwiched between the ditch and the river. Meanders will have deposited permeable gravels through the subsoils and any hole deeper than 18" in winter contains water.

I assume there will be convection/mingling of underground water allowing heat extraction from shallow pipes. Trenching would be problematic and the EA have an input to *works* within 8m of the bank.

As an aside of the deep well system... the danger of linking two or more underground water bodies was mentioned in my original discussion. I suppose they are concerned that a new well might put contaminated water in contact with drinking water supplies.

regards

[safety]

Dear Stewart I recommend that your son (and you?) knuckle down to some serious reading and study. I know FA about this apart from O level physics from about 1962! I spent about 3 months studying and reading it up in order to be in a position to judge the snake oil salesmen I came across selling heat pumps. I looked at the whole range. I made the serious mistake of listening to a firm called Ice Energy who entered into a contract to survey my site and whose final work did not comply with the contract to survey and whose service fell below what a reasonable lay man would call "fit for purpose". It cost me =A3500 and my suggestion that they pay some of it back (some because not all of their work was unfit for the purpose) has fallen on deaf ears. I eventually designed my own system which has proven to be efficient in practice.

I opted for a straight line style of collector as this from simple physics is the most efficient COLLECTOR per metre run. If you have a pond then that is probably the best possible source of collection but for my money I would put it in the ground just a few inches under the soil at the bottom of the pond. You will get the neat transfer with no complications of needing to take it out when / if you have to drain the pond or clean out the base and less chance of damage.

If I did my design again I would have knocked the house down (it was a refurb) and put in a foot of insulation a la ~Passivhaus. The need for a heat pump is largely eliminated but I would get one regardless but just the smallest one possible to heat up DHW

I would also have a couple of buffers one for DHW one for Heating into each buffer I would have as many sensible sources as I could for input eg solar water (with a thermostatic switch to go from DHW to CH when DHW is up to temp Wind generation DC Heating element say 1.5 kw + AC input from the grid Gravity primary circulation from a wood burning/ multifuel? heater with a back boiler (will need to be near the buffer for gravity circulation) I would not bother with PV but would set aside a location for later installation when the price comes down

a link where you can see quite a lot of the work I have done in the past

Chris