Experiences with ground source heat pumps?

Mike: Please keep posting your findings here. We live in a similar, probably slightly colder and with a longer winter, climate to the UK. While we have no immediate intention of installing a heat pump, we have a property with potential to install one in a new build within the next few years. So we are very interested. Thanks.

I am also very interested, especially in view of the fuel situation that is rapidly developing. From what I've read the best source is running water, however it does not matter how cold the source is it still has plenty of heat. I know someone is bound to say what about absolute zero! :-)

Whilst looking for something else, I came across this site

Dave

Someone mentioned this site a while ago (links directly to their heat pump page)

suggest alt.solar.thermal, and somewhat less likely, maybe sci.energy etc. Youve done the maths, the issue with heat pumps is that

1. as outdoor temp drops, efficiency drops too, so they effectively drop out at some minmum outdoor temp.
2. Below freezing (at the cold coils) they have to pump heat through ice, and ice insulates. So again, efficiency dies at low temps.

You could provide a significant amount of heat with simple passive solar space heating, and with very attractive figures. And you could possibly use a solar thingy to boost your heat pump efficiency some of the time.

The solar jobs that pay best are homemade flat plates (haeting air not water). Add some reflectors and the performance goes right up.

Regards, NT

I thought the point with ground source heat pumps (as opposed to the air variety) was that the pipes were buried deep enough to be in that part of the ground which never freezes and which is at a relatively constant temperature year-round. Granted if you take heat out and there's no gain from above there's a slight efficiency drop...

What about the borehole type? Presumably since they go deeper they are both more efficient and able to be installed in a smaller area.

Hwyl!

M.

Boreholes are naturally more efficient, but expensive to get drillers in.

In winter a heat pump may not be able to produce enough hot water at high enough temperatures.

The alternatives are:

• large solar panels storing water in alarge thermals store using very low temp underfloor heating.
• Windpower, again using a thermal store and UFH.

You may find that either of the above may come in cheaper than the heat pump.

I have a couple of friends in Sweden with these.

They are effective, but not as the entire source of energy - at least in their climate. THe attraction is partly because of the high cost of electricity.

Taking the heat from the ground does cause the plants to be delayed by

They have to switch the system off for at least a month in the summer, to allow recovery of the ground,

.andy

To email, substitute .nospam with .gl

Did they use a borehole or surface laid?

I believe near the surface, which would account for the effect on the vegetation. I can find out if you're interested.

.andy

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Near the surface is pants. Much pants. Using a borehole would mean you don't turn the system off and higher water temps are available.

Uh? Why would higher temperatures be available from bore holes, it's not as if you're getting heat from the earths core.

The bedrooms in our house are cut back into rock, and in summer they're like a fridge on the hottest of super hot days.

I'd have thought pipes a metre below the surface would be able to extract a far higher amount of the heat from the sun as you'd be taking it from the hottest part of the ground, i.e. the part closest to, and directly heated by, the sun.

CO2 heat pumps are coming available that do a good job of generating hot water for DHW.

cheers, Pete.

In the depths of winter 1 metre down can be near freezing whereas 10 metres down is always around 8 deg C.

But drilling a borehole if you are sitting on hard rock can get seriously expensive on drill heads. In these cases surface is the only option.

Quite. This particular area near Stockholm is most definitely rock, both at the surface or not too far down at all.

.andy

To email, substitute .nospam with .gl

Ah I see. Many thanks G&M

Expensive at the mo'. A full solar south facing roof (easier on a new build), would be very effective. Simply as you have a very large area of solar collector a lot of heat can be gained for the cost of running a pump. Also the cost of converting, or building new, a full integrated solar roof is not as much as you might think. Depending on the work done, etc, about the same, or less than installing a heat pump. A heat pump still needs a heating system, DHW, etc, etc, just like all the others. A wind genny, if you can have one, is very effective. Just have a large thermal store to store all the heat in water, for when . Then use low temperature UFH.

The best of heat pumps at the mo', in running costs, is the equiv to a natural gas condensing boiler. A condensing boiler can be had for £500-700. LPG may even work out cheaper too. As LPG condensing boilers are only slightly more expensive than NG boilers, doing the figures, it may also be more appealing than a heat pump. A condensing boiler is very low capital cost compared to a heat pump. The extra 4-5K spent on a heat pump buys a lot of LPG. If you are off the gas mains, and they may be run in the future, then an LPG boiler that can be converted back to ng is the answer.