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Notes on building a geothermal heating system.
taken during a plumbing apprenticeship
I became interested in geothermal home-heating during my plumbing
apprenticeship years. This document records what I learned and was
written in 2010. It's not fully operationalized, but pretty close: A
plumber with a bit of experience in well-drilling could take this and
run with it.
Here you go!
Study resources for geothermal heating include:
- advgeo.com
-
ghpc.org
-
igshpa.okstate.edu The international ground source heat pump
association. Very useful guides and knowledge here. Interestingly,
Chinese membership of the IGSHPA is going gangbusters, they really
want to do the right thing there, and not pay unnecessarily for heat;
more so than in the US where we don't mind wasting a lot of energy,
and maybe our drillers and plumbers cost so much and our energy so
little, that we are less motivated.
- copper.org: Copper tube based geothermal: Consider 65'
(shallow!) wells with copper pipe on the down pipe and plastic
on the up pipe: Copper for huge heat transfer rate per foot of
well depth. Relatively thermally insulating plastic piping for
better thermal separation between downflow and upflow which
diffuses the captured BTUs with delivered BTUs. We ideally
want to move the most-conditioned, ground-heated,
best-temperature water from its best point, i.e., at the
deepest point in the well, back up into the system with as
little loss of captured heat, and as little downmixing with the
outbound BTUs as possible. So capture the heat in copper on
the way down, then insulate the result in plastic on the way
back up. This isn't a standard approach, but if there is heat
cross-flow between up and down pipes in a 300' vertical hole,
then at a certain point, to a certain degree, the heat that
goes down the hole is recaptured coming back up the hole and
there's no point in going deeper because the ground won't
contribute more heat to the system. Know that limit before
digging very deeply, is what I suggest.
- Vertically drill a 200' x 6" well.
- Drop into it 1" or 3/4" black plastic pipe HDPE (e.g., from Oil Creek
Plastics in Titusville PA)
- With a return bend glued on the two ends and
- Unspooled and allowed to soften in the sun for a day before the
drilling, so it'll slide down the hole easy instead of trying to hold
its rolled-up shape while being jammed down a tiny hole.
- Duct tape the end as small protection during the push-down-the-hole.
- Wire on a 3/4" steel pipe as a tie-it-to-the-poker-and-poke tool.
- Dig cover to wellhead,
- Dig trench from wellhead to pond,
- Dig pond for well sputum to flow into,
- Supply water (filtered pumped pondwater) to the drill, so that it
travels down the drill-driven pipe.
- Thicken the pondwater to help seal and keep the hole walls from collapsing and to help the solids come up more easily. For example, Barasol biodegradable polymer
- Up comes the claywater, flows to pond.
- Afterwards, trash pump the settled clay or claywater to a removal tank on a truck.
- Quik-Grout, a Halliburton product, (11 bags for 3 wells, maybe)
mixed with water is pumped down the hole to connect the pipes
thermally to the surrounding dirt.
- Connect wellheads with a 4' trench, connect piping in series or
parallel with reverse return.
- Bring supply and return into the building to the heat pump,
- Insulate the piping that is <4' underground.
- Joints heat-fused at 500 degrees on an Aquatherm style iron.
- Benseal (Halliburton grouting bentonite product (Barold
Industrial Drilling Products, baroldidp.com)) for grouting
building entry.
- Air test at 80psi is a big no-no because you don't air-test
plastic pipe. So pressure test with water.
- Penetrate foundation,
- Run to pump-and-reversing-valve station,
- Charge with Environal until no bubbles,
- Install heat pump to air exchanger,
- Install thermostat control pad.
- Wire them up, wire up the power,
- Connect potable water through system to pre-heat hot water as possible
- Connect air in/out to existing forced-air ductwork.