"Lawrence Jenkins" wrote in message
...
|
| "Joe Egginton" wrote in message
| ...
| I was watching a building program yesterday, and the builder said it was
| 12c constantly 2 metres underground. They was building a house in
| Maidstone, Kent.
|
| I know builders are known for telling porkies, but is it true that just
2
| metres underground the temperature is constant?
| --
| Joe Egginton
| Wolverhampton
| 175m asl
|
| Hmmm I wonder how that squares with heatpumps? May that's the temp they
| bring the mains up to.
|
|
Your builder was right. Sub-soil temperatures in the UK are standard at
about 50F (10C). This applies from 2 feet down to a couple of hundred feet,
but may vary depending on the depth of the water table. This is why
underground caves are always at pretty much the same temperature throughout
the year irrespective of surface weather conditions.

To use geothermal heat pumps, you would have to drill down a couple of miles
before finding any appreciable rise in temperature, and then the deeper you
go, the hotter it gets. Generally, for every kilometre depth, the
temperature rises by about 30C, so at 3km, the rock temperature will be 90C
above the surface temperature, enough to produce boiling water.

The above figures are not necessarily true in areas of volcanic activity,
and especially suspect in places like Iceland!

jim, Northampton