GSHP, loops in a lake.

[Russell griffiths]

So as normal the complexity of building this house is doing my nut in, piling no problem, foundations no problem, building the whole bloody house no problem,  BUT how the hell do I heat it and produce hot water. 

My situation may be different to many people as we live on the banks of a lake (see pic ) 

so everything screams GSHP, or does it

the quotes we are getting are stupid, not eye watering, just stupid

so anybody got any thoughts, both quotes we have got look like they are based on the rhi payment not what the equipment is going to cost. 

So has anybody done this, can anybody shed any light on the rhi scheme. 

Im due to call the welsh wizard @Nickfromwales but have got tied up sorting out roofing quotes, I wish I could just get on and build the bloody thing. 

Any thoughts appreciated before I put the oil boiler back in. 

[scottishjohn]

5 minutes ago, Russell griffiths said:

So as normal the complexity of building this house is doing my nut in, piling no problem, foundations no problem, building the whole bloody house no problem,  BUT how the hell do I heat it and produce hot water. 

My situation may be different to many people as we live on the banks of a lake (see pic ) 

so everything screams GSHP, or does it

the quotes we are getting are stupid, not eye watering, just stupid

so anybody got any thoughts, both quotes we have got look like they are based on the rhi payment not what the equipment is going to cost. 

So has anybody done this, can anybody shed any light on the rhi scheme. 

Im due to call the welsh wizard @Nickfromwales but have got tied up sorting out roofing quotes, I wish I could just get on and build the bloody thing. 

Any thoughts appreciated before I put the oil boiler back in. 

My guess is its will use so little energy that the RHI payment will not be worth having an MCS man fit your system .

I got a good payment cos i got calculation done when house was in poor insulated state--then upgraded it

I,m guessing if you built it this far you can fit most  of the GSHP  yourself with some help from the "collective". you could always import a welsh man.but be quick they want to go independant now  !!

I,ll row the boat  round the lake dropping the pipe in .LOL

 

[PeterW]

Black 25mm MDPE in 500m reels ..?? Just lay it out as a slinky and tie wrap the overlaps and then just tow it out with a boat ..??

 

kensa really are the only trick in town unless you buy from Alibaba..?? If you don’t need too much heat then could be the best way ..??

[Onoff]

Does the pipe need to be weighted down?

[Jeremy Harris]

Yes, the pipe would need to be weighted down as the MDPE and biodegradable antifreeze will be less dense than water by a fair bit.

[Onoff]

4 minutes ago, JSHarris said:

Yes, the pipe would need to be weighted down as the MDPE and biodegradable antifreeze will be less dense than water by a fair bit.

 

Just reading about one that uses "special stainless steel weights". My fabricator would happily quote for st/st "polos" I'm sure.

 

How about tying a st/st wire rope to the pipe? 8mm wire rope is about 0.25kg/m. 

 

Could float the loop out into the lake suspended under plastic water containers then cut the "strings" so it sinks.

[Jeremy Harris]

12 minutes ago, Onoff said:

Could float the loop out into the lake suspended under plastic water containers then cut the "strings" so it sinks.

 

Story time:

 

Years ago, a friend I used to go water skiing with, asked me to help make a mooring weight to act as an anchor for a shore winch driven ski wire.  This was at the local reservoir, so we opted to cast a concrete weight, using a tractor tyre, laid on a plastic sheet, filled with concrete and loads of scrap metal, with a big iron eye poking out the top.

 

Having cast this thing on the side of the reservoir, we needed a way to tow it out and sink it.  We made a raft from oil drums, lashed the weight to it and managed to drag and manhandle the thing into the water.  My mate sat on the raft while I towed it out, with the ski boat, to the spot where we were going to sink it. 

 

This is where the fun started.  The plan was to just cut the rope and let the weight drop.  My mate duly cut the rope, then found himself flying up through the air, as the very buoyant raft leapt up when freed of its load.  I was laughing so much that I could barely see to pick him up...

[scottishjohn]

1 hour ago, JSHarris said:

Yes, the pipe would need to be weighted down as the MDPE and biodegradable antifreeze will be less dense than water by a fair bit.

not sure if it would work ,but remember seeing brine gshp systems used in  holland ?

and now I remember seeing a water supply pipe floating on a lake --typical farmer just ran it straight across the lake to trough as it was less pipe +yes it floated just on surface

Edited May 8, 2019 by scottishjohn

[Russell griffiths]

Couple of things, my neighbours pipe work floated so he weighed it down with half an engineering brick every couple of m just cabletied on. 

 

Second funny and not connected bit, we have a small man made island in the lake that was built out of breeze blocks on top of 3 huge tractor tyre inner tube, the concrete blocks where all bonded together with expanded metal and once dry the tractor tubes inflated, it was then floated out to a shallow spot where the previous owner and 2 mates swam out with pen knives in their mouths like a royal marine commandos, on the count of 3 they all stabbed the tubes and down it went, still in position 30 years later. 

[Onoff]

Engineering bricks with holes in...thread the pipe through the bricks? How to hold in place...expanding foam seems best but hardly environmentally friendly.

Cable ties friendlier? Would want the UV proof ones I'd say if the lake is a bit shallow.

[Onoff]

Wish I had a lake.

[Russell griffiths]

42 minutes ago, Onoff said:

Wish I had a lake.

Buy a digger. 

[Tosh]

We bought our place with a scheme to install water source heat pump but like you the costs were ridiculous and hampered as well by the fact that the pool was 80m or so from the house. When speaking to the companies they were very keen to highlight how important the design was i.e. depth at which the pipes lay in the water, flow rate of the water, volume of water etc. CIBSE have a code of practice apparently but I think you have to pay for it!

 

We've dismissed the whole job mainly on 1. cost and 2. the volume of water didn't appear to be large enough but I don't think you'll have that problem. We're probably going with an oil boiler instead now ?

[Onoff]

3 minutes ago, Russell griffiths said:

Buy a digger. 

 

Half acre on a slope I could just berm down by the road and move the house back!

[Russell griffiths]

Easy peasey

[Jeremy Harris]

One effect of the water source heat pump collectors in the lake next to yours, @Russell griffiths, is that the areas of the lake over the top of the collectors freeze in really cold weather.  We stayed there around New Year about 7 or 8 years ago, when it was really cold, and the heat pump in the log cabin was working hard to keep the place warm (made a hell of a lot of noise, too).  The next morning it was clear that the section of lake over the top of the collector mat was frozen solid, whereas the area away from it was still unfrozen.

 

This photo shows the frozen area, behind the silver birch trees, whereas the water right in front of the cabin was still unfrozen:

 

[Onoff]

7 hours ago, Russell griffiths said:

Easy peasey

 

Are you digging the lake there or clearing for the house?

 

Edit: Half recalling the lakes are already there, old quarry pits weren't they? River fed? Think that can be better for GSHP than a static body of water.

 

Didn't you have issues finding an existing slab on made up ground?

 

How deep and is it your lake or shared?

 

Edited May 9, 2019 by Onoff

[Onoff]

10 hours ago, PeterW said:

Black 25mm MDPE in 500m reels ..?? Just lay it out as a slinky and tie wrap the overlaps and then just tow it out with a boat ..??

 

kensa really are the only trick in town unless you buy from Alibaba..?? If you don’t need too much heat then could be the best way ..??

 

Would a 500m reel be long enough?

 

Hoping someone here will shortly do the math and come up with a flat slinky mat design or is a single pipe loop design better as it covers a bigger area?

[Russell griffiths]

@Onoff, the lake is ours, not shared

the lake in the pic is a smaller one that we cleaned out a couple of years ago. 

 

My neighbours lake has 800m of pipe, he has 4 pipes that are 200m long, 100m out and 100m return to the house, all 4 pipes return to a big manifold in a box in the lawn, then there are two larger pipes that enter the house. 

His pipe is 32mm. 

 

Onoff has has a good memory, when we dug out for the house we found 2 existing footings in the ground that we think may have been from a conveyor belt or something. 

[Ferdinand]

So are you back to an ASHP?

 

Or, when the house is efficient, is oil back to being a reasonable option?

 

Ferdinand

 

[SteamyTea]

Why go to the bother of sinking pipes into the lake.

Why not just pump water out of the lake and feed that into the heat pump via a heat exchanger.  I think that is how it is meant to be done.

[Jeremy Harris]

15 minutes ago, SteamyTea said:

Why go to the bother of sinking pipes into the lake.

Why not just pump water out of the lake and feed that into the heat pump via a heat exchanger.  I think that is how it is meant to be done.

 

The problem then is that you need filters and a pump that costs a lot more to run, as it's not a circulating pump any more, but is running open loop.  I looked at using a standing column borehole collector system and that had the same problem, high pump power consumption, although the filtering problem wouldn't have been as demanding as with a lake.

 

If the collector loop is closed, then the pump power is a lot lower, as it's just circulating clean heat transfer brine around, with no net lift.  The filtering requirement is also a lot less demanding, as the brine should stay clean.

 

The need for filtering is driven by the fine passages in the primary heat exchanger in the heat pump, which has to be physically small in order to keep the volume in the refrigerant circuit as small practical.  If the primary heat exchanger size was able to be increased, maybe by a factor of ten or so, then the filtering requirement would reduce a fair bit, but that would have significant knock-on effects for the design of the heat pump.

[Jenni]

My partners parents have a system as described by SteamyTea.

It's quite a small pond with dribble of a stream running through it. They pump the water out (approx 100m to house with about 3m rise), through heat exchanger and back. I think it made more economic sense than the coils system, plus removed risk of accidental pollution of the water, where the fines are astronomical. 

 

They did have to jump through hoops with the Environment Agency though, to get an extraction licence, as even though water was being put straight back it came under their remit. iirc the same was true of pipes laid in the water, you are extracting heat so need a licence. That will definitely need checking if you decide to go the water source heat pump route. 

[ProDave]

I considered water source as we have the burn running through the gardens but it also looked like SEPA would have made us jump through lots of hoops to get permission.

 

If you want to use pure lake water, coud you pass it through a second heat exchanger near the heat pump with then just a very short  brine loop?

 

Isn't there a danger of freezing in the heat exchanger, if the water coming out of the ake is just 1 or 2 degrees and then gets cooed by the heat pump?

[SteamyTea]

21 minutes ago, JSHarris said:

The problem then is that you need filters and a pump that costs a lot more to run, as it's not a circulating pump any more, but is running open loop.

Yes, but I am sure all this has been sorted out already.

There are a few boats that have heat pumps fitted, they have the same problems.  The marine industry may be the place to look.