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Wednesday 6 August 2008

Heating that harnesses the Earth's energy

By David Waller

Last Updated: 4:01pm BST 19/06/2007

Have your say Read comments

The alternative

The suppliers

Ground source heating

What you'll need and where to get it

Nature's free energy

Last summer, Richard Soper became one of the first homeowners in the country to install a type of eco-friendly heating system that experts believe has the potential to slash greenhouse gas emissions.


	Mr Soper: Our annual heating bills are now virtually nothing, whereas we were paying over £1,500 annually for running our oil boiler

It works by deploying the technology used in a refrigerator to absorb warmth from the ground to provide heating and hot water.

Although ground source heat pumps are commonplace across much of northern Europe, Mr Soper is one of fewer than 5,000 homeowners to have installed the technology in the UK.

"I only found out about it when rising oil costs led me to look into renewable technologies," he says. "I was amazed by the efficiency of heat pumps and their 'green credentials' compared with other renewables."

His traditional five-bedroom country home in Worcestershire benefits from a decent sized garden and a paddock, allowing him to lay a pipe vertically along a 1.5 metre deep trench.

The pipes are filled with a mixture of water and anti-freeze, which is pumped around the system absorbing heat from the ground.

In properties with less outside space, the pipes can be laid vertically in boreholes, although this increases the cost.

"The installation took just under a week and the main time was spent digging the trenches in the paddock to install the pipe work," Mr Soper says.

"Actually installing the heat pump was relatively quick and easy.

"I did need to have two of the downstairs radiators enlarged, which caused some very minor disruption within the house, but the majority of the work was outside and away from the property."


	Ground source heat pumps compare very favourably with other 'green' renewable energies

Although the technology, which was supplied by Worcester Bosch, can't be described as cheap - Mr Soper's system cost £11,500 - the savings are substantial.

"Our annual heating bills are now virtually nothing, whereas we were paying over £1,500 annually for running our oil boiler. As the heat pump runs on electricity, we have seen an increase in our electricity bill, but overall the saving is massive."

Government grants of up to £1,200 are also available to soften the initial financial blow.

Although ground source heat pumps are particularly suited to new builds and properties with large gardens, they can be fitted in small urban properties.

And few come much smaller than Luke Tozer's home in Bayswater, west London, which is just 8ft wide. "If I can fit the technology anyone can," he says.

The architect, who works for Pitman Tozer, built his four-bed eco home in the gap between two semi-detached houses. Unable to lay the pipes horizontally, he had two 50 metre boreholes sunk into his tiny garden.

But he offers a word of warning. "If you live somewhere like London, make sure you check in advance that nothing lies below your property. I've heard of people drilling their borehole down into the Tube system and getting a nasty shock."

Sketch of the system that Luke Tozer has built at his west London home

The system, which was supplied by Geothermal International and cost a total of £18,000 due to the expense of drilling the boreholes, warms his home through underfloor heating and satisfies all his hot water requirements. And it also offers an added bonus.

"You can put the system into reverse and it will cool your home in the summer," he says. "That has the advantage of replacing the ground heat lost in the winter, ensuring the system continues to work effectively."

And it's not just eco warriors such as Mr Tozer that are embracing the new technology, pensioner Sue Southwell had a heat pump installed in her large Georgian property near Perth in central Scotland in December. After installing it on the advice of her son, she has become something of an eco trailblazer in the area.

"Lots of friends have come round to look at it and are now thinking of having it installed in their own home," she says. "I think the system could become particularly popular in remote parts of Scotland, such as the Shetlands, where obtaining oil supplies can be problematic and costly."

As Mrs Southwell's grounds are quite spacious she had a series of channels laid horizontally across her garden, rather than boreholes.

"If you've got the room for channels, it's more economical, I believe."

And the disruption was minimal. "Channels were dug across my lawn, but after a few months you would not have known any work had been carried out."

Her heat pump is connected into her existing heating system and provides heat through radiators, although the steady but moderate warmth provided by this technology is particularly suited to underfloor heating.

She has already noticed a big fall in her energy bills, but is just delighted that she's doing her bit for the planet.

"I like the fact that my energy is coming from my garden rather than polluting the planet. I'm sure that if you install this in your property it will add a great deal to its value. After all it's got to be the future."


	Illustration showing how a ground source heating installation works

In fact, in some parts of Europe it's the present. In Sweden, 97 per cent of all new homes are built with heat pumps and already more than 20 per cent of homes have the system.

And it's not just Sweden that's wising up to the benefits of the technology.

"Ground source heat pumps are now one of the fastest growing applications of renewable energy in the world, with annual increases of 10 per cent in about 30 countries over the past 10 years," says Martyn Bridges, director of marketing technical support for Worcester Bosch.

Although the number of heat pumps installed in the UK is still minuscule, the recent growth of interest has delighted the Energy Saving Trust, an independent, non-profit making organisation set up to tackle climate change.

"The increase in awareness of ground source heat pump technology is a welcome advance for the UK and can be a viable option for householders who have the space for installing the technology," says Mat Colmer, of EST.

There are grants available under the Government's Low Carbon Building programme. The overall maximum for ground source heating is £1,200 or 30 per cent of the relevant eligible costs, whichever is the lower.

More information can be found at: www.lowcarbonbuildings.org.uk/about/hfaqs/

The alternative

As the name suggests, air source heat pumps extract heat from the air and can be installed either inside or outside a property. They have the distinct benefit that the heat source is easily accessible without the need for buried pipes, making them particularly suitable for a retro fit or where ground space is limited.

The efficiency of air source heat pumps is slightly lower than ground source due to the fluctuation in air temperatures, but they are designed to work at temperatures as low as -20°C.

Because they require no expensive ground collectors, air source heat pumps are considerably cheaper to install than ground source units. Sales of air-to-water heat pumps have already overtaken ground source in countries such as Germany and France.

Air source heat pumps are eligible for grants of up to £4,000 in Scotland, but no such grant scheme exists in England and Wales.

The suppliers

To find a ground source heat pump installer in your area, go to the Low Carbon Building Programme website at: www.lowcarbonbuildings.org.uk/info/installers/find/installerfind

To check on the products available go to: www.clear-skies.org/households/RecognisedProducts.aspx?intTechnologyID=43

Have your say

External links

Ground source heating - Energy Saving Trust

Worcester Bosch

Pitman Tozer Architects

Comments

Mr E Ward. What you mean "Do you know it is possible to run a boiler off water?" I do not, and I would like to I think.
Posted by P Martin on July 21, 2008 12:52 PM
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A very useful thread, I've been researching the
possibility of building an energy independent
house for a few years now, I worked on the
principle that the energy crisis and housing value
crash were an inevitability. Geo thermal heating
may not be all that it seems, but it is used
successfully in Scandinavia and Switzerland for
instance. If the heat pumps energy use is a
problem why not use solar panels to generate
the electricity?
Like all alternative solutions it's the combination
of wind, solar and possibly geo thermal that
works best.If cost return is your benchmark, then
watch energy prices soar over the next few years
and then think about it.
I agree with a great deal of what Paul Hadley has
posted, but I'd just add that I don't share his view
that coal etc will be the fuel of choice. Whatever
the rights and wrongs of the case, Russia's
actions have made sure that the world will now
look to alternative energy sources, energy
security added to climate change is the issue and
I for one don't feel like getting ransomed! Its all
a matter of public perception, or as John
Maynard Keynes so eloquently said 'animal
spirits". The future is energy independence for
each home.
Posted by Melvyn Butler on July 16, 2008 2:09 PM
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Hi there everybody,
I work in research and development for a gas boiler manufacturer. We are offering heat pumps for sale - it is consumer demand that's driving it. For every 'free' 2.5 to 3kWh you get out of it you have to put in 1 kWH in electricity. Look at your electricity bill what that costs. And this is only applicable if you are running with underfloorheating or the like. We figured out that a high efficiency boiler is cheaper to run than this. But what can you say - if the customer wants it, we will sell it to him.
Keep up the good work everybody, these items are high margin for our business. Thanks
Posted by m smith on February 25, 2008 12:48 PM
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I have no problem with idea of heat pumps, just some of the details ………. returning to my original 'query' in this thread, namely: the location of the 'ground heat source' – i.e., shallow buried heat exchangers – which are ground stored solar energy extraction devices.

Some alternatives - that DO extract geothermal heat (as apposed to ground stored solar energy):-

THE IDEAL would be: hot rocks, close to the surface, which are laden with water.

We don’t have any of these in the UK. However, we do have ‘hot dry rocks’ – these are closest to the surface in Cornwall

AS an aside:-
A UK gov dept project investigated the opportunities for commercial electrical generation from the ‘hot dry rock’. Their initial work was drilling 2 km down, there, the temperatures were 80 degC . The project had intended to drill to 8 km depth, to get sufficiently high temperatures for driving a steam turbine that would drive an electrical generator. After experiments with injecting water at high pressure – a costing was performed, which indicated, that commercially produced electricity (2.5 MW plant) would cost between 18p/KWHr and 30p/KWhr. The project was stopped.

Drilling down 2km for a domestic heating – is ambitious, and extraordinarily expensive – but wouldn’t require a heat pump! He he !

However, vertical drilling down, 30 to 100 metres ( there are a substantial number of contractors for this operation ) has interesting possibilities for a heat pump installation – including (1) the heat source temperature will be higher than ‘slinky coils’ and shallow buried heat exchangers( at most least ) in the latter part of winter ( i.e., when the store temperature of the heat around the shallow types has fallen sub zero ) , and (2) with a postage stamp sized garden ( like mine ) drilling down is an option, whereas horizontal, shallow buried / slinky heat exchangers - are not , there isn’t the ground area available. ( see the part of the article : Luke Tozer's home in Bayswater, west London )

Nut shelled: If the ground ‘source’ temperature is higher (geothermal), then the compressor will be smaller, then the electricity consumption will be less.

And manufactures note! No tiny heat exchangers guys – every temperature degree drop across the heat exchangers, means more electricity needed!

Coefficient of Performance( C.o.P.) = 7.0 isn’t a dream, its do able ………. Buyer Beware!

( C.o.P.) = 3 or 4 ?????? - insist on more !

Posted by paul hadley on February 19, 2008 7:34 PM
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James, I sincerely believe, that in 10 years time, the majority of electricity generated in the UK will still be from coal and gas ( the coal from south america - Chile ? and an increasing proportion of the gas from the middle and far east). The uk nuclear will reduce as the older powerstations close. Electricity from nuclear power will be increasingly imported from France, as the recently announced next generation of uk nuclear plant will not be ready, and not enough.

Electricity from 'Renewables' has limits, yes, there is enough renewables 'around' the uk to supply all of our electrical needs - BUT, and i am sorry to say, that is a huge 'BUT', the electrical supply network, can only stand approximately 20 - 25% of the total electrical supply to be from 'variable' , ie, renewable sources.

So, reducing power consumption on electricity, like exchanging tungsten light bulbs for the 'low energy' bulbs - is a good move. Increasing power consumption , by running a compressor with a multi KW electric motor to drive a heat pump, as compared to say 150W of electricity to drive a gas/ oil fired central heating system - is regretably - dubious.( ok, where does the gas / oil come from for the central heating then ! ! ! )

Heat pumps , having coils / pipes buried 1 metre under the ground, arent true geothermal sourced heating - it is stored solar.
In most of the uk ( excluding 'hot spots' ), to obtain geothermal heat, it would involve drilling several kilometres downwards to access very high temperatures. However, in order to obtain temperatures high enough to heat a house / boil a kettle - the distance downwards would be substantially less - and no large compressor would be required, and no multi KW electric motor would be eating through your wallet, nor would a large gas / oil bill for heating. However, geothermal is outside my area of expertise, so please 'google' or similar the subject.
Posted by paul hadley on February 9, 2008 8:30 PM
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It's interesting those arguing that because electricity currently comes mainly from coal and gas that a ground source heat pump is thus not so 'green'. Do they sincerely believe that this will continue to be the case? With wind, solar, other renewables, hydro-electric and nuclear likely to fall in price as carbon taxes raise the cost of carbon fuels, in ten years the situation may - nay, will - be very different. Already it is possible, as a consumer, to buy 'carbon-free' electricitity - buy this to supply your heat-pump and 'green' domestic heating is truly yours!
Posted by James Eaton on February 6, 2008 4:52 PM
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As a geologist I know that geothermal heat is a great energy source BUT, placing the earth heat exchanger in shallow holes will not get much heat. Also heat is conveyed from the depths in part by water and if the pipes are burried into clay then this water will not get to the pipes in any beneficial way. We must also consider the thermodynamic aspects. Any system is less than 100% efficient and the more links in the heating chain so the less the overall efficiency, ie. direct heating for a house with oil or coal is much more efficient than using electricity to drive a heat pump to heat the house. The most efficient answer must be to insulate well and use a direct heating method. I use oil and wood and don't spend a fortune. Any method will produce pollution, the volume of which will depend on the overall efficiency of the system used.
Posted by John Marshall on December 11, 2007 11:22 AM
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We are considering installing a ground source energy system with either slinky or compact collector pipes. Our garden is an old farmyard with lots of debris and with heavy clay at about 1m deep. Will the presence of debris and clay impact on the efficiency of the pipe work and any ideas on what would be the best backfill material for the trench. Any thoughts will be much appreciated.
Posted by Lynn Asquith on November 18, 2007 6:00 PM
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further to my earlier post , a few notes, to expand on the possibilities with domestic heat pump installations:-

(1) Although the average temperature of soil/subsoil is 10 degC, this is only true, whilst no heat is begin extracted. Furthermore, 10 degC is an ANNUAL average, not a winter average. At 1 metre depth a winter average is more likely to be 4 degC - before any heat is extracted.

(2) With heat extraction ( clay soils ), expect temperatures of -3 degC in winter of the liquid flowing through the ground coils, at a depth of 1metre. Hardly much better than just laying the coils on the ground - to give a temperature of -7 degC !

(3) This suggests ground coils to be a poor source of heat compared to an air source, compared on temperature basis alone ( Remember : Anything that causes the difference in temperature of heat source and heat sink to increase – means more electricity is required )

(4) With a 10 degC heat source ( 6 degC at extraction ), and a 45 degC heat sink temperature – ( 60 degC at Compressor outlet ), a CoP = 7 is achievable with the Reversed Rankine Cycle. This isn’t a theoretical value – it’s a practicable value. Manufacturers are offering CoP = 4.3 . Why the discrepancy ? Its your electricity bill !

(5) Find a heat source in the depths of winter that will give 10 degC ????? A river / stream is about the closest – everything else is significantly less. For 99.5% of us, it is either air or ground as the heat source. And , as the source temperature falls, so does the CoP , and so the electricity bill increases.
An observation : At what position do you leave the central heating boiler water temperature dial through most of the winter months ? midway, a bit above, a bit below - quite low ? or very high ? DO you turn it up in the very depths of winter ? and then later turn it down again ?

If you are doing the latter – then a heat pump installation could be for you – for those 15 weeks out of 20 per year, when you want the heating on - but it isn’t bitter outside

Posted by paul hadley on September 7, 2007 3:26 PM
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Firstly, i need to declare , i am an ex-employee of Richard Soper, but I am not here to grind any axe, nor the contary.

In my final year thesis on a heat pump installation, i demonstrated the bad news , firstly a definition of heat pumps, to help with the later comparsion:-

Now, refering to the Coefficient of Performance for Heat pump installation - the CoP is a measure of the 'performance' of the installation, its value being equal to the heat output(kW) divided by the Work Input (kW) . The heat output being that discharged into the residence to be heated, and the Work Input being the electrical power to drive the installation.

Typical values for the CoP are 2.2 to 2.5 for ground source heat installations. Higher values , but less usually than 3 ( exceptional is 4 ) can be obtained by reducing the difference between the heat source temperature and the temperature at which the heat is discharged ( examples being : underfloor heating - which reduces the discharge temperature , and air source heating, - which conditionally can be of a higher temperature for much of the heating season, than a ground source )

Looking at the case where CoP = 2.5 then

2.5 =Heat Output divided by Electrical Input , so Heat Output = 2.5 x Electrical Input, so on the face of it , we get 2.5 kWh of 'free' energy for each kWh of electrical input

But now the bad news : Mains electricity is both an expensive source of energy, and, it is becoming more regarded as the 'dirty man' of the energy generating industries.

Specifically, economics aside, a differculty with heat pump installations as to their 'green' credentials has always been the answer to the question : From where is the electricity coming from to drive the installation ?

Offsetting aside, mains electricity is predominately derived from coal, natural gas and nuclear facilities.

Considering only coal, generating plant efficiency is approximately 30%. So, the heat released by the coal is 3.33.x the electricity obtained.

So on one hand we have 2.5 x the electrical energy heating the residence, BUT, back at the power station 3.33 x the electricity generated , is energy from Coal.

So we are burning more energy at the power station , than begin obtained for 'free' from the ground source.

For comparsion purposes : If a domestic heating system, fired on coal has an efficiency of 75% , then the heat drived from the coal is 1.33 x heat output into the residence.

Adding these comparsions together we get:-

Domestic Heat Pump installation : Energy to heat house = 2.5 x Electrical Input ( the heat pump installation ) , but this consists of

= 2.5 x ( 30% x Energy from Coal )

= 75% x energy from Coal

Domestic Coal fired Installation : Energy to heat house = 75% x Energy from Coal

To put into blunt terms , The quantity of pollution from BOTH heating systems is IDENTICAL ................now which is 'greener' ???????? Answer : ..........................

So, this suggests, burn the coal directly at the residence ( and cause the same amount of pollution, and NOT inccur the additional installation costs of a heat pump ) - not a 'green' solution either !

Posted by paul hadley on September 7, 2007 9:52 AM
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I suspect E Ward is referring to hot water tanks with are effectively a tank in a tank, correct me if I am wrong. I.e. like melting chocolate in a bowl floating on boiling water in a saucepan. Means you need a larger tank say 200 litres required to heat a 300 litres of water so may not be suitable for upstairs installations due to weight. Obviously you still have to heat the water somehow. This is really just the reverse concept of the traditional coil heating pipe that exists inside (rather than outside) hot water tanks. Newer tanks tend to be bulkier (even square in shape) due to their use of highly efficient insulation materials which are ESSENTIAL!.
Having looked carefully at all the options I am looking at installing an air source heat pump as they seem consistently cheaper than ground source pumps which are marginally more efficient in their use of energy but require the high capital outlay (not to mention the land requirement and general disruption or laying the ground pipes). Air source is potentially noisier than ground source but the latest units are much quieter than your fridge. I do feel frustrated that (in England) grants are only available for ground source but not air source pumps though. Solar can get grants but you really do need a decent south facing expanse of roof.

Posted by Jamie Macdonald on August 29, 2007 12:38 PM
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How can we find information on running a boiler on water?
Posted by Len Harvey on August 10, 2007 2:24 PM
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Ms Southwell is right that this technology is currently most economically interesting for properties without mains gas or easy oil supply - but if carbon taxes shift the balance towards renewable sources such as green electricity, that balance might change. It might also become more attractive if Combined Heat and Power (CHP) systems become widespread, as electricity production will increase in line with heat demands - meaning that electricity could become cheaper in colder periods.

What I'd really like to see is the outdoor tubes and underfloor heating being laid in new-build properties, even if it's then hooked up to a fossil-fuel boiler. The extra cost during building is surely minimal, but then the homeowner always has the option of cheaply and easily adding a heat-pump if they choose to do so.
Posted by Jonathan Melhuish on August 10, 2007 11:44 AM
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E Ward June 23, 2007 9:35 PM

Do tell us more on how "it is possible to run a boiler off water".

Posted by Al Hamilton on June 26, 2007 8:43 PM
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The ground source energy system does work,but look at the cost.I have seen 1 system in action and it still costs the owner £10 a week to run.It would cost at least 12 years to repay it's outlay apart from the 5% he could have invested his £11,000,by which time he would be thinking of replacing the unit which would cost a lot more by then. I am a roofing contractor and intend installing a solar water system on my roof to suppliment the hot water.Grants are available,but to qualify for the grant I must employ a "specialist" firm to supply and fit the system.To fit an evacuated tube system will cost at least £5000 with controls etc.A grant of £1200 would be given. If I do the job myself,which I am quite capable of,It would cost about £3000 or much less if I was to use a large radiator painted black behind a glass panel.The problem is I would not be given the grant if I done it myself.I can understand the fact that fraud could take place if dishonest folk put their mind to it,but all it needs is the local building control to inspect the installation on completion before the grant is paid.This is already done on other types of grants.I know because I have been involved in them as a contractor. Just as an aside concerning energy saving.Do you know it is possible to run a boiler off water? So why don't we? Because this Government will not allow it.Just think of the consequences. So we will bumble on merrily pretending to do things that are just a facard for people in high places not having a clue to improve anything or wanting to improve anything. All the high cost to so called improvements and energy saving gimmicks justs makes me smile.There are a lot of companies taking a lot of money off gullible people who actualy believe that global warming and climate change realy exists.I have saved thousands£££££ by doing simple things with basic materials.I live out in the sticks and we have learned to be independant of all the so called experts. Education is not wisdom. Regards.
Posted by E Ward on June 23, 2007 9:35 PM
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