Heating Engineers - Heat Pumps

[TeeDee]

Can any heating engineers here give me the low down on what I think is called ' Heat Pumps ' as a possible heat source for the UK environment.

Are they gaining ground here? are they efficient / or false economy? Who are the UK market leaders.

My basic understanding is that they take outside ambient air and heat it into the house via the difference , is that correct.

 

[sandbender]

That'll be an air source heat pump...

http://www.nibe.co.uk/Home-Owner/NIBE-Heat-Pumps/air-source-heat-pumps/

I have just finished work on a project that made use of a Nibe ground source heat pump, their site is full of useful information, lots of downloadable manuals etc.

It can be very expensive to buy and instal but the claim is that it'll pay for itself in the long run.



Edited to add:

I am not a heating engineer, I'm the one who makes the heating system and all the other electrical services work together.

 

[mrcharly]

An air-source heat pump is also known as a reverse cycle air conditioner. Not very economical to run. Not really much different to a refrigerator, really.

Ground source heatpumps are becoming more common, but you need a fair bit of ground for them to work, and a long trench must be dug.

 

[TeeDee]

An air-source heat pump is also known as a reverse cycle air conditioner. Not very economical to run. Not really much different to a refrigerator, really.

A bit of a white elephant then?

Ground source heatpumps are becoming more common, but you need a fair bit of ground for them to work, and a long trench must be dug.

Are these efficient then?

 

[mrcharly]

They are reportedly very efficient in the conversion of electricity to heat - but you have to bear in mind that electricity is (per unit) a very expensive form of energy. This is just a result of our energy market.

I'm not sure what happens in the event of a very sustained period of cold weather. As the ground cools, the efficiency drops (you are trying to 'pump' the heat up a higher 'hill'). I suspect serious gardeners would not want a ground source heat pump in their garden.

 

[ged]

I'm not a heating engineer either, but I am an engineer (with a first class honours degree).

Just to get things straight, a heat pump doesn't really generate heat. At least it's not supposed to - any heat it does generate is usually considered waste.

A heat pump pumps heat like a water pump pumps water.

A water pump takes water from where it is (say, a well) to where you want it to be (say, your storage tank).
As a result of the process of pumping water you have less water where you pump it from and more water where you pump it to.
So the well gets drier and the storage tank gets wetter.
Note that there can be a lower level of water in the well than there is in the tank, that's why we have water pumps.

A heat pump takes heat from where it is (say, a nearby stream) to where you want it to be (say, your living room).
As a result of the process of pumping heat you have less heat where you pump it from and more heat where you pump it to.
So the stream gets cooler and the living room gets warmer.
Note that the stream can be cooler than the living room, that's why we have heat pumps.

Unfotunately we haven't been making heat pumps for as long as we've been making water pumps so we're not very good at it yet.
If the installation isn't well designed it can cost as much to run a heat pump as it would to buy from an energy supplier the amount of heat that it can pump.

http://en.wikipedia.org/wiki/Heat_pump#Efficiency

The best you can probably hope for from a small air source heat pump installation if everything is with you is to pump two units of heat using one unit of electricity.
More likely it will be one for one, which still sounds like a good deal until you figure out how much a heat pump installation costs compared with a more traditional heating system.

There have been some real horror stories in the UK. There are whole Websites dedicated to this stuff some of which are actually responsible and not pitching sales.
I think you'd be better off looking in those places rather than BCUK.

 

[Toddy]

Sorry Ged; cross posted

So for places like Iceland they'd be brilliant, but unless we're sitting above a thermal vent, not much use in temperate UK ?

Interesting idea though

cheers,
Toddy

 

[ged]

... So for places like Iceland they'd be brilliant, but unless we're sitting above a thermal vent, not much use in temperate UK ?

The heat source is a vital consideration.

Flowing water is good as it's probably going to be at least at 0C. It's cheap but not everybody has flowing water handily situated.

Ground source is good, as if you dig deep enough the ground is going to be pushing 10C. But it's very expensive to dig deep holes.

Air source is good if you don't really need much heat anyway. It's cheap. But when you most need it, the air can be really cold so the pump is likely to be be horribly inefficient.

Best thing is to live near a power station and ask them for some of the heat that they throw away.

 

[sandbender]

My sister owns a very large, generally damp and cold Scottish farm house, the oldest part dates from the 1600's the newest from about 1910. We used to joke in the winter that we should open the front door to let the heat in.

She has recently built a large south facing extension, mostly of glass and knocked out two windows to form large doors into same, the transformation is remarkable, the house is drier and warmer than ever before and she didn't have to buy oil last winter as the heating was hardly ever on.

If you have a good south facing aspect, consider building a big glass extension/greenhouse, the sun is by far the cheapest way of keeping your house warm.



Edited to add:

You will also have the added advantage of cheap tomatoes and peppers.

 

[bushwacker bob]

Ground source recovery pumps are great if you don't wish to heat your building to more than 10 degrees. Above that temperature you will need to heat water, often this is Electricity based and costs lots. Last I heard Saint Gobain (jewsons) had lots of impending law suits as peoples heating bills soared with the addition of an eco friendly ground heat recovery system.

 

[santaman2000]

Heat pumps started getting popular here about 25 years ago or so. They started losing that popularity when people realized that they are meant to be a supplemental heating rather than the primary source.

 

[georann]

Did some research a while ago when my parents were looking at getting one for a new build they're doing. The conclusion is they can be good in the UK and save you a bit of money with some reasonable efficiency, but not if you have gas in your area. Gas central heating worked out cheaper every time.