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who understands pumps and heat?


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nirvana

 I came across this interesting snippet on a forum, regarding getting heat from a well

'you get 0.001163 kwh out if you cool 1 litre of water by 1'C
you've got 212 cubic feet of water in a hole 30feet*3feet, which is 6003 litres
so you'll get a hair under 7kw out if you cool it down by 1'C
COP depends on the temperature of the water
if it's a wet area, it goes down 30feet, and it's always full the temperature should be pretty constant
best to pump 1000 litres out and see how fast it fills up again so you get an idea of how wet the area is and how much water movement there is
if you use the water for a heat pump, it's better to drop a load of coils of pipe into the well than to pump the water out and use it that way, if you pump it out you'll end up with silt/cr*p/whatever building up in your heat exchanger
the pipe is cheap enough for you to stick a load in so you get high efficiency
if you put something across the top of the well, you could hang the pipe down inside the well (with some suitable rope/whatever) so it hangs like a giant slinky spring :-)'
 
this is what I've got to play with....it's about a meter across and bloody deep.....I'd like a waterproof bluetooth monitor to measure the temp down there methinks...
 
 

IMG_20201126_200015.jpg

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Heat pumps are better described as thermal energy movers.   So, your pit that descends into hell itself has got some thermal energy in it, and you could move some of that into your house; your house gets hotter, the bottom of the pit gets colder (as the thermal energy has been moved from it).  But, your house needs constant top-ups of thermal energy, as it keeps losing energy into the air around it.  

So, the question isn't 'oh, x thousand litres of water blah blah blah', but rather 'can the earth and water around the pit keep on supplying new thermal energy as the old thermal energy is extracted'.  If it can't do this you'll just make the bottom of the hole colder and colder until it freezes up and makes it even more difficult for the energy to balance out.

Typically, this is relatively more difficult to do for a 'well like thing' and easier to do for a 'river like thing' or a 'boggy field like thing'; you might extract water and cool it down, but you'll end up putting the colder water back down the well where the energy won't balance.  For heat pumps it is more usual, if using water extraction, to have two boreholes and extract from one, return via the other.

But water extraction is quite rare -- far easier to dig a long trench and put down a slinky (there's also various legal stuff to worry about with water extraction -- although you don't actually have to tell anyone).

Edited by dgul
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I suppose the fundamental question is 'can your source of thermal energy continue to supply it over winter'.  This is easy to work out for a damp field or river, much less easy to work out for Quatermass's pit.

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nirvana

@dgulthanks for your input.......it's quite an interesting piece of engineering for the middle of nowhere, somebody went to the trouble of digging a large hole and lining it with concrete rings......

there was a 3 phase pump attached at one stage but I had to get rid of that; 400+volts is too much for me...

apparently they are some granite and clay 'earthy dislocations' around here.......and a big meteorite hit some field somewhere up the road a while ago o.O 

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A first question might be 'if you lowered the water level by 2m, how long would it take to return to the previous level'.  This would tell you how damp the earth is around there, and thus indicate the thermal conductivity of the rocks/clay at the bottom (ie, if it was less than an hour then there's lots of water sloshing around down there -- and that'll increase thermal conductivity).

Then the question is 'how much energy do you want to extract?'  I'd suggest that the answer should be 'a bit, but not lots' -- an excellent compromise for countryside properties is to use a heat pump for the majority of coldish days, and use a logburner for the very cold days/nights.  This actually limits the energy extracted quite considerably.

I'd suggest using a slinky, as water extraction is a bit of a minefield if building regs get involved (which they will do when it comes to selling).  

I'd get a second hand ground source heat pump from ebay and connect to a slinky.  It wouldn't cost too much and it would almost certainly give some benefits.  Getting anyone professional involved would likely cost more than it cost to dig the pit (not that they deserve it -- heat pumps are still a sign of 'people with too much money' for installers).

[You can get some sort of government payment for heat pumps, but it wouldn't cover the cost of installation by the professionals necessary to get the forms signed off etc]

Edited by dgul
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swiss_democracy_for_all

You might find that although in winter it's colder down at the bottom of that, along with all the remains of the female hitchhikers it's also a lot wetter and what little heat there is in the surrounding rock/soil will conduct better into the well. Depends where you are in France and at what altitude - I forget.

 

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nirvana

Forget building regs etc I do as I please :P And forget about selling, I'm a lifer now prolly....

I'm at 300 meters in an undisclosed location ;) I'd like to send a probe down there.......failing that I've got a long ladder but it's quite heavy and actually it's got wide feet so it wouldn't fit through the inspection hole....I'd need to take the whole lid off....

Actually I'm probably wasting my time when I've got 101 diy jobs to finish off and lots of wood to burn but it gives me something to dream about........and I can dream a lot some nights, rather scarily xD

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nirvana
52 minutes ago, dgul said:

I'd get a second hand ground source heat pump from ebay and connect to a slinky

cheers I will keep an eye out for any bargains

rather ironically I ripped the whole central heating system out cos it was rather old and I wanted to get rid of the big fuel tank and not have the liability of it breaking down in the middle of a -10 winter.....

BUT stuff hidden in the ground is different AND new technology is always fun!

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Bobthebuilder
43 minutes ago, 5min OCD speculator said:

cheers I will keep an eye out for any bargains

rather ironically I ripped the whole central heating system out cos it was rather old and I wanted to get rid of the big fuel tank and not have the liability of it breaking down in the middle of a -10 winter.....

BUT stuff hidden in the ground is different AND new technology is always fun!

Get yourself a log burner with a back boiler. You won't need anything else.

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reformed nice guy

Im actually considering something similar.

I was planning doing a bore hole with a ground source heat pump. Was considering just using a circulating pump/shower pump attached to that slinky coil pumping water/antifreeze mix. Then just add an expansion tank to the central heating system with a coil passing through it.

The reason for doing so is that I have hydro power so it would be more productive than running it through oil filled electric heaters when im not using it for something else.

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To measure the temperature of the well water, lower an aquarium thermometer on a thin rope. Just enough to have its (weighted) external probe submerged.

When you haul it back after an hour, the min temp reading will be what the water is.

 

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nirvana
8 hours ago, Bobthebuilder said:

Get yourself a log burner with a back boiler. You won't need anything else.

yes with hindsight but I've already installed the free standing log burner and it took 3 of us to get it up the outside stairs (upside down house) and another mate helped rebuild the wall when I took the old fireplace out and the walls are half a meter thick and the floor is suspended concrete with breeze.....

The more I think about it, the more I reckon I probably need to get some cheap solar panels and build a 'powerwall' with second hand 18650 cells and go as much 'cheap leccy' as possible.....Leccy is a lot cheaper on the Continent too

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nirvana
7 hours ago, reformed nice guy said:

The reason for doing so is that I have hydro power

As in you already have a stream? Wish I had a stream, just drop a mini turbine thingy in and endless power

Please send a link to what sort of circulating pump can be used, I'll look out for a cheap one of those too......or buy one off aliexpress?

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reformed nice guy
6 hours ago, 5min OCD speculator said:

As in you already have a stream? Wish I had a stream, just drop a mini turbine thingy in and endless power

Please send a link to what sort of circulating pump can be used, I'll look out for a cheap one of those too......or buy one off aliexpress?

I was thinking about a DIY bodge using a broken shower pump - it was a double sided pump and one side cracked. I replaced the pump and was planning on using the side that works.

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nirvana

right I've had the measuring string out.....

4 meters to the water, then another 4 meters to the bottom, 1 meter diameter

so volume of water = pi x radius squared x height = about 12.5 cubic meters of water down there....so that's 12,500 liters

The well is only about 7 meters away from the house.....then I have another large hole that acts as a soakaway about 7 meters further down the garden so I could use that as a dumping ground for any water pumped out

I'd like to know the temperature at the bottom, is it likely to be any higher than the temp at the top of the water?

If I get a system working I only want to run 2 or 3 radiators at the back of the house......but pipes are a PITA, leccy wires are so much easier, hmmmmm

Edit: according to that original post the geezer reckons if you cool 6000 litres by 1 degree you get 7kw of energy!!! Is that really true????

So if I cooled 12000 litres by 2 degrees I could get 28kw? That's bloody loads! That'll keep me going for a week!! :)

edit again: I think I found some pipe, 224 meters of it, anyone near Aberystwyth? xD

https://www.ebay.co.uk/itm/Ground-Source-Heat-Pump-Pipe/283863554369

Muchos gracias amigos!

@dgulany new thoughts?

Edited by 5min OCD speculator
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53 minutes ago, 5min OCD speculator said:

so volume of water = pi x radius squared x height = about 12.5 cubic meters of water down there....so that's 12,500 liters

 

Volume of water is largely irrelevant unless it is a lake or river.

54 minutes ago, 5min OCD speculator said:

I'd like to know the temperature at the bottom, is it likely to be any higher than the temp at the top of the water?

Probably not.

55 minutes ago, 5min OCD speculator said:

Edit: according to that original post the geezer reckons if you cool 6000 litres by 1 degree you get 7kw of energy!!! Is that really true????

So if I cooled 12000 litres by 2 degrees I could get 28kw? That's bloody loads! That'll keep me going for a week!! :)

kW is a unit of power, not energy.  I can't be bothered to do the sums, but it is probably kWh (oh, just checked it and it is about right for kWh).

So, cooling your 12,000 litres by 2 degrees would be about 28kWh -- 28kWh heating for a week is the equivalent of heating your house using a one bar electric fire for 4 hours a day (ie, crap).

The only question that matter is something along the lines of 'how much energy would it take to lower the temperature of the water by 5 degrees (say) and then maintain that temperature over a longish period of time, with energy from the surrounding rocks/soil/clay/sand/etc trying to warm it back up again'.

This can be difficult to calculate as it depends on the rocks/soil/clay/sand/etc around the pit.

It might be reasonable to think that during the winter you'd need to continually extract about 5kW of thermal energy from the water down there in order to keep a 'house' at a reasonable temperature.  Of course, this number depends on size of 'house', insulation, etc.  It could well be lots more for a big old house.  A very well insulated modern house with energy recovery ventilation could probably manage with far less.  (note '5kW' in this context is the capability of the heat pump to move heat.  It'll use maybe 1.5kW of electricity to do this.  Heat pumps are pretty much always described by the heat movement, not the electrical input).

1 hour ago, 5min OCD speculator said:

The well is only about 7 meters away from the house.....then I have another large hole that acts as a soakaway about 7 meters further down the garden so I could use that as a dumping ground for any water pumped out

Hmm.  You're probably not allowed to do that (ie, you're unlikely to get permission), but if you didn't tell anyone no-one would find out (until you sold).

But, to do the calc, to move 5kW worth of heat per hour (ie 5kWh) with a 5 degree temperature difference (thermal energy extracted) would need about 1000 litres of flow in that time period.  Ie, your soakaway would need to be able to take 1000 litres/hour (without overflowing, obviously), and your well would need to be able to supply that much water (without going dry).  Continuously.

All this isn't to say it couldn't be done.  There's quite possibly at least 5kW of available heat transfer into the well from the surrounding stuff, and even if there isn't, you'll be cooling down a far greater mass than just the water, so it could be that you'd not lower the temperature of the rocks close to the well by that much over a season, and it could then recover during the summer.

But I'd suggest chucking a pile of water pipe down there would get you what you want, and would keep things nice and simple.

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Andersen

I have a bit of experience with heat pumps & systems.

Scandinavia - a new build there is *very* well insulated (hence very little heat needed to raise the temp), ground source heat pump via long slinky under the lawn. There is a limit how much heat they can take over the winter - soil temp needs to rise again during the summer to balance otherwise next winter you have no heat.

Will the well be used as a water supply or just as a heat source? For just heat - loop the slinky (as many coils as possible) under the water, run a feed & return to the house, no affect on water level, no contamination in the heating system pipes, downside is how will the water in the well warm up again? If as a water supply check the "rate of recovery" (time to refill after you take water out) - place I'm at has a 5m wide well - owner left a hosepipe running overnight weeks ago and the level has still not recovered! The level in boreholes can go down rapidly if you are a heavy user. Dry years also lower the level and can take years for the nearby water table to rise again. A large well here is 5m below a historical high level !

I'm currently getting an obsolete roof mounted solar underfloor heating working, very simple (diy level) using 2 central heating pumps. On sunny days warm water from roof panels circulates to a large storage tank, in the evening heat from the storage tank circulates to the underfloor manifold (valves control which rooms/floors get the warm water). Heating is slow and gentle but noticeable. Downside is performance in winter is poor - but that's when you need it most, 2 days without sun means the underfloor heating is cold.

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nirvana

@Anderseninteresting stuff cheers

the previous owner, who built the place and was here for circa 70 years used the well for house water BUT it had a 3 phase supply and pump which I had to dismantle when I swapped to single phase......

My idea of using a submersible pump was to extract some water overnight when leccy is cheap here, to bring in new, hopefully warmer water

This slinky pipe, can it be ordinary garden hose? Or needs to be thicker? Suppose it depends on your 'heat pump'? I fancy trying to knock up a 'DIY heat pump'* and seeing if I can drive a couple of radiators off it......shame I gave all my old radiators to the scrapman lol......

*wanders off to google if that's possible....

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nirvana

I can get 200 meters of 16mm or 20mm plastic 'plumbing pipe' for cheap......hmmmm 

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I once had some hobbyist engineering mags from the mid 50s. One article was about a building in London that used water from the Thames as a heat source. 

An electrician mate of mine reckoned that the numbers quoted for the kw/hrs generated and the wattage of the motors used meant that it was only using 25% of whatever leccy would be needed to generate the same amount of heat.

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nirvana

it was howling a hooley last night :S and plenty of rain, valley flooded on my daily bike ride....

the well is up about a meter or 25% or about 3000 litres......

I found a DIY contraption, just need to decode all the bits O.o

 

IMG_20160731_211154.jpg

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Andersen

Looks fun - ready made steampunk xD

I'd guess it's a diy heat exchanger based around a fridge motor - hopefully plumbed so you can extract heat (not my field so I could be 100% wrong). The pipework looks diy but the inlet/outlets look nice commercial?

You have 4 open pipes, expect 2 pairs. Blow into 1 to find the paired outlet. Repeat to prove the other pair are linked.

One pair should be feed/return loop to your heat store (well etc), the other pair to be cold in / warmed out (the loop for the radiators). Both loops will need to be driven by a pump, the system here uses standard central heating pumps to circulate water around the loops - both work fine on low power setting.

Hopefully the heat you get will justify running 2x pumps + the steampunk motor. Thinking ahead - I'd like to fit some controls to the system here so it only runs if there's heat available - maybe do something similar at yours?

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Dave Bloke
1 hour ago, Andersen said:

Looks fun - ready made steampunk xD

I'd guess it's a diy heat exchanger based around a fridge motor

it is. He'll end up with a well full of ice if he runs it.

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nirvana
5 hours ago, 5min OCD speculator said:

I found a DIY contraption

to clarify, I found it on the web, not in real life unfortunately :S

I think the compressor is from an air con unit......

I'll be rumaging around the tip next time I go there....and no doubt the gestapo officer will be telling me not to touch stuff cos I might get the deadly virus xD

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Kurt Barlow
On 26/11/2020 at 22:47, Bobthebuilder said:

Get yourself a log burner with a back boiler. You won't need anything else.

I noticed on Facebook markets you pick up for free all the wood you'll ever need.

Not going down that route again but its evidently a free supply of fuel minus time and bit of petrol. 

7 hours ago, 5min OCD speculator said:

it was howling a hooley last night :S and plenty of rain, valley flooded on my daily bike ride....

the well is up about a meter or 25% or about 3000 litres......

I found a DIY contraption, just need to decode all the bits O.o

 

IMG_20160731_211154.jpg

Whats the temperature of the water? 

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