Water-source heat pumps...

[AE-NMidlands]

https://www.theguardian.com/environment ... ead-of-air

Scientists in Edinburgh have developed a home heating system that draws its energy from the world’s most abundant resource: water.

The equipment can use sea water, rivers, ponds and even mine water to heat radiators and water for baths and showers, using the same technology as in air source heat pumps.

It is being trialled by Edinburgh University in an affordable housing project close to the Firth of Forth near the Forth Bridge, at a gold-mining museum in south-west Scotland and in a commercial greenhouse in Fife.

Another system is due to be installed this summer at the Scottish Seabird Centre in North Berwick, also drawing its energy from the Firth of Forth. All of the systems use water from the sea or nearby rivers.

Well well well! Who would have thought it?
I suspect they have misreported what they have been told (or something got edited out) with "The warmth of the sea or river water is captured by glycol, the liquid used in anti-freeze, which is then compressed in the heat pump. That compression makes it hot enough to heat water for radiators or baths" but it's not bad overall!
p.s.
I have now found https://www.sea-warm.co.uk/product/ which says they use a plastic heat exchanger in a primary circuit which is where I guess the glycol is.

[Countrypaul]

I if the journalist thought it easier to say Air Source Heat Pump rather than Ground Source which would seem far more relevant?

[nowty]

Sounds like its just a ground source heatpump using water as the heat source.

No different than here at Nowty Towers except they use a plastic heat exchanger and I use copper.



My project is documented here,
https://camelot-forum.co.uk/phpBB3/view ... f=17&t=487

[AE-NMidlands]

Sounds like its just a ground source heatpump using water as the heat source.

No different than here at Nowty Towers except they use a plastic heat exchanger and I use copper.

Yes, I was thinking of yours as I read it... How many decades has it taken them to catch up with you? It's good news anyway.
Somewhere I think they said that it is much better than ground-source as that often ends up with the soil loops over-cooled and performance suffers. This one says

Extreme conditions resilience: Through the innovative design, SeaWarm can also heat your home/business through ice formation in the heat exchanger. The Latent Heat of Ice Fusion is 80 x larger than the heat capacity of water. This feature ensures that under the most inclement conditions a stable and reliable heat source is available.

which I suppose means "until warmer water comes past again!"

[Oliver90owner]

As usual, a hyped-up story to interest the uninformed public.

I was under the impression that all ground-loop heat pump systems used water plus an antifreeze.

Water has a far higher specific heat capacity than glycol. Actually the heat capacity of water is, in fact, higher than the latent heat of fusion - water could be heated from zero Celsius to 100 degrees, before boiling. But it’s all good reading for someone somewhere.

Nowty’s system is now quite old, but here we have a crowd re-inventing it in a slightly different form. I expect the only difference between a ground source system and this is the cost of burying the loop (or drilling the borehole!).

[nowty]

Yes water alone is more efficient than glycol solutions, both with heat transfer and less viscosity so less energy used to pump the liquid around the closed circuit, especially at cold temperatures.

But if there is a risk of freezing you have to use some glycol. The more you put in, the lower the freezing point is, but also the lower the efficiency is. I think I use a 20% solution which is good for -10 degrees. From what I read it was not recommended to go any higher. I also use food grade glycol as recommended by the environment agency for use on rivers in case of leakage.

My heatpump does trip out if the return (from the water source) goes below 0 degrees. But at that point the liquid leaving the heatpump has been cooled to about -5 degrees. If I don't keep my heat exchanger clear of silt, ice can form on the return (to the water source) pipe.

[AE-NMidlands]

As usual, a hyped-up story to interest the uninformed public.
I was under the impression that all ground-loop heat pump systems used water plus an antifreeze.

Water has a far higher specific heat capacity than glycol. Actually the heat capacity of water is, in fact, higher than the latent heat of fusion - water could be heated from zero Celsius to 100 degrees, before boiling. But it’s all good reading for someone somewhere.

Nowty’s system is now quite old, but here we have a crowd re-inventing it in a slightly different form. I expect the only difference between a ground source system and this is the cost of burying the loop (or drilling the borehole!).

apart from the fact that most ground-sources have to rely on the thermal conductivity of the ground - and they say that it can get over-cooled and cut efficiency. I am sure the thermal conductivity of the ground is a lot less than water (unless the loop is buried in river-gravel with a water flow through it!) Also they point out that it will take the latent heat of crystallisation out of the water around it if ice forms, but that must be clutching at straws for justification as I wouldn't think it could compete with flowing water as a heat source.

[Oliver90owner]

I don’t think I mentioned thermal conductivity? Surface area of the collector will have a bearing on the cost - slinky loops, for instance, meaning more collector pipe to be buried. The cost of burying the slinky is substantial compared to one tank of water for the energy collection.

Boreholes don’t need much space but the deep shaft is likely to cost an order of magnitude more than burying a slinky type of collector.

[AE-NMidlands]

I don’t think I mentioned thermal conductivity? Surface area of the collector will have a bearing on the cost - slinky loops, for instance, meaning more collector pipe to be buried. The cost of burying the slinky is substantial compared to one tank of water for the energy collection.

Boreholes don’t need much space but the deep shaft is likely to cost an order of magnitude more than burying a slinky type of collector.

You didn't, but I thought that

"As usual, a hyped-up story to interest the uninformed public.

I expect the only difference between a ground source system and this is the cost of burying the loop (or drilling the borehole!)

completely missed the point that this takes heat from surface water, and as such isn't handicapped by heat movement through subsoil. Not many people have hot earth near the surface, and the cost of drilling deeper is significant as you say. I note that you don't comment on the risk of GSHPs over-cooling the ground...

[Oliver90owner]

I don’t think I mentioned thermal conductivity? Surface area of the collector will have a bearing on the cost - slinky loops, for instance, meaning more collector pipe to be buried. The cost of burying the slinky is substantial compared to one tank of water for the energy collection.

Boreholes don’t need much space but the deep shaft is likely to cost an order of magnitude more than burying a slinky type of collector.

You didn't, but I thought that

"As usual, a hyped-up story to interest the uninformed public.

I expect the only difference between a ground source system and this is the cost of burying the loop (or drilling the borehole!)

completely missed the point that this takes heat from surface water, and as such isn't handicapped by heat movement through subsoil. Not many people have hot earth near the surface, and the cost of drilling deeper is significant as you say. I note that you don't comment on the risk of GSHPs over-cooling the ground...

You may not have noted that my comments were addressed to ground source heat energy compared to this supposed “new invention” rather than the intricacies of each. I addressed the quality of the report, which was heavily distorted.

Boreholes most certainly will not materially change the temperature of the surface soil.

Personally, I would prefer a borehole to a slinky system as the COP for the system will/should be constant for the life of the installation, needs little area for installation (far more homes, with minimal plot size could be served) and will not affect the immediate area. But that is my preference/opinion without considering the differing expense of each system which is considerable.

The first GSHP system I became aware of was of a network of collector pipes under a couple of acres (at least?) under a field near Ottawa, Canada. I don’t think the pipes were buried as a slinky loop for that installation. Slinky systems are used for smaller area installations. Adequately sized installations would avoid excessive soil cooling, but (of course) it is very much down to system cost reduction.

If you wish to quote my posts, please keep the comments appropriate to it, not deviate at a tangent to the content.

RAB