water source heat pumps

[Adam Aglionby]

The next big thing apparently

[Brian Gaff]

Hmm, on top of that I understand there are plans to generate electricity at the weirs on the Thames as well. I never quite got how you could get warmth out of a cold river myself.

If that is true, why can't i just bury a load of pipes in my garden? Brian

[Malcolm G]

isn't that a ground source heat pump?

[Martin Bonner]

Same way you get warmth out of a cool fridge. You use a heat pump.

You can. It's exactly how a ground source heat pump works.

With any sort of heat pump you need to put some energy in (usually electricity, but there are fridges which work by burning gas, and there is no reason that a heat pump for a heating system couldn't be built the same). The point of the heat pump is that you get more energy out than you put in. The amount you have to put in to get a given output depends on how much warmer your output is than your input, but typical values are you get three or four times as much heat out as you put in.

The trick is to find something to pump the heat out of. Air (air-con running in reverse) is not very good, because reducing the temperature of a cubic metre of air by 1 degree doesn't release much heat. Ground can be better because it releases more heat per degree temperature drop. It also helps that ground temperatures are more stable, so on cold days (when you most want heat), the ground temperature is higher than the air temperature - so you get higher performance. The trouble is that ground doesn't move around, so you need a _lot_ of piping (otherwise you freeze the ground around your pipe, and can't get much heat out).

Water is best because it does moves around, but also contains a lot of heat. Of course, you do need to have a river accessible.

[Chris J Dixon]

The general guideline used to be that, so long as you have mains gas available, its cost relative to electricity, meant that it still won over heat pumps.

Have technical advances and changes of power tariff reached the point where this is no longer the case?

Chris

[Martin Bonner]

I don't know. A) Not everybody has access to mains gas. B) Some people are more concerned about the long-term cost to the environment of burning fossil fuels than the short term cost of fuel.

Those in group B (like me) will usually get a better environmental return on their investment by adding more insulation rather than installing a heat pump.

Actually, it may well be that those in Group A would be better off adding more insulation too.

[Tim Watts]

By making it a little bit colder...

Ground source Heat Pump - either a deep bore, or a long coil of pipe laid out over a large area 2-3 feet down.

[The Natural Philosopher]

You can, if you dont mind freezing the lawn to heat your house ;-)

[The Natural Philosopher]

No. especially with 'renewable' electricity,.

I did the sums and it turned out that at around 60p a liter for oil heatpumps started to get cost effective, bit the 25k I calculated I needed to spend to install one would buy 10 years of oil, and I wouldn't be in the house that long....

[The Natural Philosopher]

Indeed. The thing that made most sense when I did all the calcs was

- shitloads of insulation

- heat recovery ventilation

- heat pump

- nuclear power. ] But that was before I started to seriously investigate global warming, and subsequently decided that actually burning fossil fuelss was not an environmental issue at all.

[Roger Mills]

If you're extracting the heat from a flowing river, can you also have a water turbine to drive the heat pump?

[Roger Mills]

I wonder by how much it cools the rivers. What are the chances of converting them to glaciers?

Actually, the sewage from most of my village flows under my garden. I wonder if I could use that to heat my house?

[alan_m]

If you go green and allow fracking under your property you will get the pipework and the other infrastructure for a heat pump for free.

[harryagain]

You might as well use the turbine to make electricity. Which can be used for whatever you want.

[Chris Hogg]

'The Frozen Thames' 1677, by Abraham Hondius