Getting Warmer a Field Trial of Heat Pumps Report

8/8/2019 Getting Warmer a Field Trial of Heat Pumps Report

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The Energy Saving Trust

Getting warmer: a feld trial oheat pumps



Getting warmer: a feld trial o heat pumps

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The Energy Saving Trust would like to thank ourpartners, who have made this feld trial possible:

Government organisations

The Department o Energy and Climate ChangeThe North West Regional Development AgencyThe Scottish Government

Manuacturers

Baxi GroupDanoss UKMitsubishi ElectricNIBE Energy SystemsWorcester Bosch

Specialist heat pump contractors

Earth Energy Ltd

Energy suppliers

British GasEDF EnergyE.ON Engineering UKNIE EnergyRWE npowerScottish Power LtdScottish & Southern Energy PLC

Technical consultants

EA Technology LtdEnergy Monitoring CompanyGastec at CRE LtdThe Open University

Energy Saving Trust project team:

Simon Green, Project DirectorJaryn Bradord, Project Manager

“The Department o Energy and Climate Change (DECC) is very pleased to support the Energy Saving Trust’s feld trials into heat pumptechnology. Field trials such as these are avaluable way o establishing true perormance in situ, as opposed to in the laboratory, and provide useul insights as to how perormance may be improved. This is benefcial or industry,householders and the Government. DECC considers that heat pumps have an important role in achieving Government policies to reduce CO 2 emissions”

Air source heat pump




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Contents

Foreword 5

Executive summary 6

Key ndings 6

Further ndings 6

Conclusions 7

The background 8

The eld trial 8

Site selection 9

What is a heat pump? 10

The science: inside a heat pump 11

What is a heat source? 12

What is a heat sink? 14

Key fndings 15

The key ndings rom the eld trial 15

Further ndings rom the eld trial 17

Summary 17

Conclusions 18

Advice or customers 19

Consumer checklist 20

Advice or installers 21

What’s next 22

Training and standards roadmap 22

Getting warmer: areas or additional work 22




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Foreword

The green market is denitely growing, as more andmore consumers opt to install heat pumps and other“microgeneration” technology in their homes, helped bya number o government incentives. Until recently,despite encouragement to install these systems, therehas been little data on how well the technology

actually perorms in real lie. Instead, customers havehad to rely on manuacturers’ perormance claims,which are based on lab testing in ideal conditions.

The Energy Saving Trust is the UK’s leading impartialorganisation helping people save energy and reducecarbon emissions. One o the key ways we do this isby providing expert insight and knowledge aboutenergy saving. Our activity in this area includes policyresearch, technical testing, and consumer advice. Thiseld trial, developed in 2008, orms part o the EnergySaving Trust’s extensive market transormation activityin the household-scale low-carbon technology sector.It ollows last year’s report on our trial o domesticsmall-scale wind turbines, “Location, Location,Location.” Also in progress is our eld trial odomestic solar water heating; the results will bepublished in 2011.

The Energy Saving Trust is impartial, and not tied toany particular commercial organisation or driven bypolitical or corporate motivations. This enables us towork with a variety o industry stakeholders, who

know that our ndings will be without avour. We usethis inormation to inorm our advice services to thepublic, the industry, governments, local authorities andour other customers and stakeholders.

As a result o this eld trial, we will be doing urtherwork with trade bodies, heat pump manuacturers, theDepartment o Energy and Climate Change, and theMicrogeneration Certication Scheme (MCS) to identiyimprovements to heat pump installation guidelines andinstaller training.

The trial will continue or another year to enableurther investigation into the actors that infuenceheat pump perormance. This will enable both theEnergy Saving Trust and the wider industry to give

better advice to consumers on their heating needs, aswell as improving uture installations.

In keeping with the Energy Saving Trust’s workthroughout Europe and the UK, the results o this rstyear o the trial have been peer-reviewed by leading

EU heat pump experts, including the SP TechnicalResearch Institute o Sweden, Planair (Switzerland)and Germany’s Fraunhoer Institute, as well as UKstakeholders including the Energy TechnologiesInstitute (ETI).





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Executive summary

Given the lack o data on heat pump perormance incustomers’ homes, the Energy Saving Trust undertookthe rst large-scale heat pump eld trial in the UK todetermine how heat pumps perorm in real-lieconditions. The year-long eld trial monitoredtechnical perormance and customer behaviour

observed at 83 sites across the UK.

The ndings provide valuable inormation about theactors that aect the success o a domestic heatpump installation. Instead o revealing outcomes alongstatistical grounds, or acting as a “brand-vs-brand”competition, the eld trial ndings provide adiscussion o key points o interest to potentialconsumers, including:•• Measured coecient o perormance (COP) and

system eciency

•• Installation practices (both system design andperormance)•• Customer behaviour•• Heating patterns and average internal temperatures•• Economics

This report makes recommendations or consumers,installers, manuacturers and policy makers, andidenties areas that require additional investigationand research.

Key fndings

The ollowing key ndings are also described inurther detail in the report:

1. The perormance values we monitored in thesample heat pumps varied widely; the best-perorming systems show that well-designed andinstalled heat pumps can operate well in the UK.

2. The sample o ground source heat pumps hadslightly higher measured system eciencies than

the air source heat pumps. The ‘mid-range’ groundsource system eciencies were between 2.3 and2.5, with the highest gures above 3.0.

3. The system eciency gures or the sample oground source heat pumps were lower than thosemonitored in similar European eld trials.

4. The ‘mid-range’ o measured system eciencies orair source heat pumps was near 2.2 and thehighest gures in excess o 3.0.

5. Heat pump perormance is sensitive to installationand commissioning practices.

6. The householders in our eld trial sample reportedgood levels o satisaction with both space heatingand hot water provision. There was no signicantdierence between users’ satisaction with groundand air source systems.

7. Heat pump perormance can vary considerablyrom one installation to another and customerbehaviour is a variable that was shown to impactperormance.

8. Many householders said that they had dicultiesunderstanding the instructions or operating andusing their heat pump. This highlights a need orclearer and simpler customer advice.

9. A comparison between carbon emissions rom heatpump installations and electric or gas heating(based on the UK government’s current predictionsor grid decarbonisation) shows that a well-installed heat pump can lead to carbon savings,both at present and over the lietime o the pump.

10. The eld trial shows that heat pumps haveachieved reductions in heating bills or somecustomers – especially those whose installationsare o the gas grid and are thereore replacingheating uels such as electricity, LPG and oil.

Further fndings

In a number o instances there was limited success inexplaining the variation in measured perormance. Thisnding may suggest that there are infuences caused

by actors that were not, or could not be, measured.An investigation o each site will be undertaken tohelp explain the large variation in perormance, evenin apparently similar installations.




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Executive summary

Conclusions

1. Heat pumps are sensitive to design andcommissioning. The eld trial covered a variety oearly installations, many o which ailed tocorrectly apply the heat pump. This result

emphasises the need or improved training.2. Keep it simple. There were many system

congurations monitored in the eld trial. In mostcases, the simplest designed systems perormedwith higher eciencies.

3. The impact o domestic hot water production onsystem perormance is unclear. Heat pumps can bedesigned to provide domestic hot water atappropriate temperatures, but more investigation isneeded to determine the actors which impactsystem eciency.

4. Heating controls or heat pump installations have tobe comprehensively reviewed. There has been aailure to explain proper control requirements toboth installers and heat pump customers.

5. Responsibility or the installation should be with onecompany, and ideally be contractually guaranteedto ensure consistency in ater-sales service.

6. Further study needs to be undertaken on aninstallation-by-installation basis, to record whathas been done wrong (or well), what could be donebetter, and what exactly should be done in the uture.

Defnitions

Coefcient o perormance (COP)The amount o heat the heat pump producescompared to the total amount o electricity needed

to run it. The higher the COP, the less electricalenergy is required to deliver a given amount oheat: a high COP shows good perormance, and alow COP shows poor perormance.

System efciencyThe amount o heat the heat pump producescompared to the amount o electricity needed torun the entire heating system (including domestichot water; supplementary heating; and pumps).This report’s conclusions and recommendationsare based on the measured system eciency.

Ground source heat pump




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The background

The UK has adopted the most ambitious target inEurope or reducing carbon emissions. By the year2020 the UK is obliged to reduce greenhouse gasemissions by 34% (rom 1990 emission levels). 27% oBritish carbon dioxide emissions come rom the energywe use in our homes, so around a quarter o this 34%

saving must also come rom our home consumption.

“Green” micro-generation systems – including solarphotovoltaic panels, solar thermal water heating,small wind turbines, micro combined heat and power,biomass heating, and heat pumps – have the potentialto make a signicant contribution to the UK’s energyeciency, as well as reducing uel bills. Even byconservative calculations, the Energy Saving Trustestimates that up to 10 million micro-generation unitscan be installed by 2030, which will save up to 10megatonnes o CO2 per year – equivalent to the CO2 produced by around two million average homes today.

With this in mind, the government has introduced arange o initiatives to encourage consumers to investin microgeneration. The Low Carbon BuildingsProgramme (LCBP); Energy Saving Scotland’s homerenewables grant, and its Community and RenewableEnergy Scheme (ormerly Scottish Communities andHousehold Renewables Initiative (SCHRI)) grants; theCarbon Emissions Reduction Target (CERT); and, mostrecently, the proposed Renewable Heat Incentive (RHI)

consultation all exist (or existed) to encourageconsumers to install heat pumps and other orms omicrogeneration in their homes.

Heat pump technology is relatively new to the UK market,and there has been little evidence on how well itperorms in real lie. This lack o independently-assessedperormance inormation could potentially make peoplereluctant to invest, even with incentives in place; this,along with the need or inormation to back up consumeradvice, prompted the Energy Saving Trust to propose aeld trial to monitor the perormance o a sample oheat pumps in real homes. The aim was to gather theinormation needed to inorm existing and potentialcustomers, policymakers, and the industry.

The eld trial collected data on the perormance oheat pumps in a wide-ranging sample o homes acrossthe country, and surveyed the occupants on theirexperience o living with and using the heat pumps.

This publication (along with a orthcoming set o best

practice guidance or the industry) is the outcome. Itcontains the Energy Saving Trust’s specic insights onheat pump installation and perormance, customerbehaviour and attitudes; and inormed advice orconsumers, installers, manuacturers, and the UKgovernments.

The feld trial

The Energy Saving Trust has a well-establishedreputation or developing and delivering projects to

monitor the in situ perormance o energy-eciencyand low-carbon technologies. The objective o eachproject is to determine the actual perormance andcarbon savings when used by domestic customers.These monitoring projects help the Energy Saving Trustto understand how customers use new, innovativetechnologies, and to identiy the potential utureuptake o these technologies.

The purpose o the eld trial was to gain insight intothe actors that aect the perormance o domesticheat pumps, including:•• Building eciency•• User behaviour•• Types o heat source and sink•• System sizing•• Heating patterns and average internal temperatures•• Installation practices




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The background

Site selection

We monitored a representative sample o air andground source heat pump installations in a variety oproperty types, ocussing primarily on retrotinstallations. The sample included owner-occupiers

and social housing tenants.

Potential trial sites were identied via a number osources, including the project’s unders and the widerheat pump industry. In 2008 the Energy Saving Trustcontacted people who had installed a heat pump usingthe Low Carbon Building Programme (LCBP) andScottish Communities and Householder RenewableIncentive (SCHRI) grants, inviting them to join the trial.Further sites were identied through housingassociations and energy suppliers.

It should be noted that this eld trial started beorethe Microgeneration Certication Scheme (MCS) wasintroduced. None o these heat pumps had beeninstalled under the scheme; however, they wereinstalled and accredited through MCS’s predecessor,the Clear Skies programme. The eld trial thereoremonitored installations o products that were currentas o 2008. The technology, standards, manuacturer/installer knowledge and practices continue to evolveand improve.

The rst monitoring equipment was installed early inNovember 2008. The study monitored 83 heat pumps– including 29 air source (ASHP) and 54 groundsource (GSHP) heat pumps – rom 14 manuacturers,in a varied range o housing conditions. Manuactureswho are listed as partners in the eld trial were not the sole suppliers o the heat pumps in the eld trial.

The sample was chosen to be broadly representativeo the market at the time o commissioning theproject, and included:•• Air source and ground source heat pumps•• Heat pumps installed in private and social housing

properties

•• Heat pumps installed in new-build and retrotinstallations•• Heat pumps providing heating only•• Heat pumps providing heating and hot water•• Heat pumps installed with dierent heat deliverysystems: under-foor heating and/or radiators•• Grant-unded installations through LCBP and SCHRI•• Systems combined with solar water heating

A total o 83 heat pumps were monitored in the Energy SavingTrust heat pump eld trial, distributed across the UK




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The heat pumps in this study serve the same purposeas a domestic boiler but, rather than burning a uel toproduce heat, they move heat rom a low-temperatureheat source (ambient air, or example) and “pump” itto a higher temperature where it can be used toprovide central heating or produce domestic hot water.

This is the same process as in a ridge or anair-conditioning unit. In the case o a ridge, the heatenergy is pumped rom the interior o the ridge to theelements at the back. Removing this heat energymakes the interior o the ridge cold and the elementsat the back warm. As the elements become warmerthan room temperature, the heat energy (which wasoriginally inside the ridge) is lost into the air o theroom. A heat pump heating system does exactly thesame thing, though on a bigger scale, and removes its

heat rom a source outside the room – such as theoutside air, or the ground.

In the cases o both ridge and heat pump, someadditional energy must be supplied to the system topump the heat rom the low temperature to the higher

temperature. There are systems that use other typeso energy to achieve this – or example, gas-heatedabsorption ridges and heat pumps – but this studyconcerns only electrically-driven heat pumps.

Defnitions

Heat sourceThe place rom which heat is taken.

Heat sinkThe place where the heat is delivered to.

Coefcient o perormance (COP)The amount o heat the heat pump producescompared to the total amount o electricity

needed to run it. The higher the COP, the lesselectrical energy is required to deliver a givenamount o heat: a high COP shows goodperormance, and a low COP shows poorperormance. For example, a COP o 3.0 meansthat or every unit o input electricity there is anoutput o three units o useul heat.

System efciencyThe amount o heat the heat pump producescompared to the amount o electricity needed torun the entire heating system (including domestic

hot water; supplementary heating; and pumps). Asystem eciency value o 3.0 means that orevery unit o input electricity to the heating systemthere is an output o three units o useul heat.

What is a heat pump?

Internal components o an air source heat pump

Internal components o a ground source heat pump integrated

storage system




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The science: inside a heat pump

A heat pump works by reducing the pressure o aliquid, known in this report as a working fuid, sothat it evaporates at a very low temperature. Thisevaporation process needs heat, which is usually

sourced rom the ground or the air.

When the vapour is compressed rom a low pressureto a higher pressure, its boiling point is raised, so thatit wants to condense into a liquid again. In order to dothis it needs to release the heat it has absorbed. Theheat sink is the place the heat is transerred to; inthis report, normally the central heating system anddomestic hot water store.

At point (1), the working fuid is cooler than the heatsource, so heat fows naturally rom the heat sourceinto the evaporator. This causes the working fuid toevaporate.

At point (2), the vapour (rom the fuid) enters the

compressor. The compressor, driven by an electricmotor, compresses the vapour, raising its pressureand increasing the temperature.

At point (3), the high-pressure vapour enters thecondenser where it condenses at a higher temperaturethan the heat sink; thus, heat fows naturally rom thecondenser to the heat sink.

At point (4), the high pressure liquid enters theexpansion valve, which reduces the pressure to itsoriginal point, and the cycle is complete.

The workings o a heat pump

Condenser

CompressorElectricity

Heat Sink

Heat Source

Cold vapour

Hot vapourWarm liquid

Cool liquid

Expansionvalve

Evaporator1 2

34




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What is a heat source?

The heat source is where heat is taken rom. In aridge, it is inside the ridge; in a heat pump system itis the outside environment. Most heat pumps take heatrom either the air or the ground, but water (rom

ponds, rivers and boreholes) can also be used.

Ground source heat pumps (GSHPs)

The two most common types o GSHP systems areknown as horizontal (or trenched) ground loops andvertical borehole loops.

The gure below shows a ground loop made o plastictubing laid in a shallow trench. An electrically-drivenpump circulates a mixture o water and glycol throughthe coil, extracting heat rom the ground. The size o the

ground loops, whether horizontal or vertical, needs to bematched to both the peak heat demand and annualenergy requirement o the property. The longer the loop,the more energy the pump is capable o producing.

Vertical boreholes work on the same principle, but theplastic tube is arranged in a U-shape going downwardsinto the ground. Boreholes can be anywhere rom 15 to100 meters deep, depending on the heat demand romthe house.

Ground source heat pumps, once installed, areunobtrusive. As the ground maintains a more constanttemperature than the air, GSHPs are not prone, likeASHPs, to fuctuations in eciency in colder weather.However, installing the ground loop can be expensive,and sizing it depends on geological actors – a real

issue in the UK, where local geology varies widelyacross locations.

Borehole, or vertical ground loop

Horizontal loop

A typical ground source heat pump system layout




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Air source heat pumps (ASHPs)

Most ASHPs are sited just outside the property. Anelectrically-driven an draws air across the evaporator,cooling the air stream and supplying heat to the heatpump. Below about 7°C, ice may orm on the evaporator

as the air is cooled, restricting the air-fow andimpairing perormance. For this reason ASHPs alwaysinclude a derost cycle. A common derosting method isto extract heat rom the heat sink (the house or hotwater tank) and re-supply it to the evaporator to meltthe ice – in eect, operating the heat pump in reverse,so that the evaporator becomes the condenser and thecondenser the evaporator. While this is happening, notonly is heat being taken rom the house, but no heat isbeing sent to the house, which may temporarily lowerthe heat pump’s COP.

Exhaust air heat pumpsAnother potential heat source is air rom the house,extracted by an exhaust air heat pump (see below).Exhaust air systems have the advantage that their heatsource has a airly constant temperature o around20°C, but they need to be careully designed to balancewith the ventilation requirements o the house. They areusually only suitable or well-insulated houses.

Exhaust air heat pump


A typical air to water heat pump system layout




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What is a heat sink?

A heat sink is the place the heat is delivered to. In ourridge model, this is the kitchen. In a domestic heatingsystem it is the house, where it can supply bothcentral heating and hot water.

Although the eld trial shows that the perormance oa heat pump can be aected by the dierence intemperature between heat source and heat sink, thereis no clear correlation o this in the ndings.

Central heating

Methods o providing central heating with a heat pumpvary according to the property and its existing heatingsystem. Most existing properties in the UK, as well assome new-build homes, have central heating systems

with radiators.

Heat pumps can also be installed with under-foorheating; this is more common in new properties, butolder houses can be retrotted with it as well. Becauseunder-foor heating works with water at 30° to 40°C –as opposed to between 50° and 60°C in radiators – it isconsidered a more energy-ecient option.

Standard radiators are the cheapest option, and mostretrotted heat pump systems use them. Radiatorsrequire higher-temperature water, which would tend to

make the heat pump work harder and thus achieve alower COP and system eciency. Heat pumps installedwith radiators could still be an energy-ecient optionor central heating, especially compared to traditionalelectric or coal-red heating. “Oversized” radiatorscan also be used successully i designed andinstalled appropriately.

This eld trial monitored both under-foor and radiatorsystems. Although there are no enhanced (anned)radiators in the trial, the extension to the project

planned or 2010 to 2011 may include them.

A number o manuacturers oer air-to-air systems, inwhich air acts as both heat source (outdoor air) andheat sink (indoor air). The air can be released into the

sink at only a ew degrees above required roomtemperature, which can increase the energy eciency othese systems. They are usually split, with an externalunit (compressor) and an internal unit or warm airdistribution. The drawback is that an internal unit maybe necessary in every room, which can be expensive.

These installations are not yet common in the UK.

Domestic hot water

Most heat pump installations will be designed toproduce domestic hot water at temperatures between50 and 55°C. Good practice assumes that heat pumpsshould be sized to meet the total space and waterheating needs o the home.

The general advice in the UK is that hot water storedin a cylinder should be kept above, or periodically rise

to, 60°C, to avoid the danger o Legionella bacteria.This temperature is sometimes achieved with the helpo an electric immersion heater, but some heat pumpsare capable o delivering the 60 degree temperaturesrequired without the use o immersion heating.

Some o the working fuids in common use producelower COPs when operating at such high temperatures.For this reason some manuacturers oer heat pumpsonly or central heating, with electric immersionheating o a hot water cylinder.

Further investigation o domestic hot water productioneciencies will be undertaken in the second year o theeld trial.




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This eld trial is the rst in the UK to monitor howheat pumps perorm in real conditions in actualhomes. The 83 sites we monitored yielded a widespectrum o perormance results, even in installationsthat seemed similar. Some installations perormed aswell as heat pumps studied in European eld trials,

but many ailed to meet these levels.

The major dierence between the UK and Europeaneld trial ndings is that the UK has particularly oldand inecient housing stock. The British climate alsotends to be cold and damp, rather than very cold anddry like Scandinavia. But as well as these predictableactors, heat pump perormance is aected by theexisting heating systems in UK homes, the attitudesand behaviour o heat pump users, and the quality oinstallations. The heat pump market is more mature inthe rest o Europe, and installers have more experience.The act that heat pumps have been shown to workeectively in Europe suggests that the technology hasthe potential to provide good carbon savings in the UK.

Although every home is unique, it has been shown that awell-perorming heat pump can produce a COP andsystem eciency ratio o at least 3.0. This means that orevery input unit o electricity there is a useul output othree equivalent heat energy units. These best-perorminginstallations should give consumers condence that heatpumps can provide good levels o internal heating, lower

carbon emissions, and reduce uel bills when installedproperly. Approximately 13% o all sites in the trialachieved system eciencies in excess o 3.0.

The worst-perorming sites we monitored illustrate theneed or customers to be vigilant when purchasing a heatpump, to be sure that they are buying the best systemor their property and their liestyle. Manuacturers andinstallers should also take care to ensure that heatpumps are specied and installed properly.

The heat pump industry also needs to ensure that utureinstallations are carried out in accordance with anagreed set o norms and standards. Installers need tobe aware that they play an important role in educatingcustomers on the best way to control their system.

The ollowing section discusses the key ndings inmore detail.

The key fndings rom the feld trial

Key fndings

Distribution o measured system eciencies (ASHP)Shaded bars denote estimated eciencies

Distribution o measured system eciencies (GSHP)

System efficiency (air sourced)

N u m b e r o f o c c u r r e n c

e s

0

2

4

6

8

10

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

System efficiency (ground sourced)

N u m b e r o f o c c u r r e n c e s

0

2

4

6

8

10

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4




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Key fndings

Measured coefcient o perormance (COP) andsystem efciency

1. The perormance values we monitored in thesample heat pumps varied widely, as shown in thetable below. The best-perorming systems show

that well-designed and installed heat pumps canoperate well in the UK, and that the technology hasreal potential to help the UK meet its carbonreduction targets.

2. The sample o ground source heat pumps hadslightly higher measured system eciencies thanthe air source heat pumps. The ‘mid-range’ groundsource system eciencies were between 2.3 and2.5, with the highest gures reaching over 3.0.

3. The system eciency gures or the sample oground source heat pumps were lower than thosemonitored in similar European eld trials.

4. The ‘mid-range’ o measured system eciencies orair source heat pumps was near 2.2 and thehighest gures were above 3.0. The sample o airsource heat pumps perormed comparably withother European studies

Installation practices

5. Heat pump perormance is sensitive to installationand commissioning practices. A thorough review oinstallation guidelines and training should beundertaken.

User perceptions and behaviour

6. Heat pump perormance can vary considerablyrom one installation to another and customerbehaviour is a variable that was shown to impactperormance.

7. The householders in our eld trial sample reported,overall, good levels o satisaction with both spaceheating and hot water provision. There was nosignicant dierence between users’ satisactionwith ground and air source systems.

8. Many householders said that they had dicultiesunderstanding the instructions or operating andusing their heat pump. This highlights a need orclearer and simpler customer advice.

9. A comparison between carbon emissions rom heatpump installations and electric or gas heating

(based on the UK government’s current predictionsor grid decarbonisation) shows that a well-installed heat pump can lead to carbon savings,both at present and over the lietime o the pump.

Economics:

10. The eld trial shows that heat pumps haveachieved reductions in heating bills or somecustomers – especially those whose installationsare o the gas grid and are thereore replacingheating uels such as electricity, LPG and oil.

1 Please note that it was not possible to directly measure system eciency at seven o the ASHP installations. The system eciency at these sites

has been estimated as denoted by the shaded base in the char t o distribution o measured system eciencies (ASHP).

Heat pump COP System efciency

Airsource

Groundsource

Airsource

Groundsource

Range 1.2 - 3.3 1.3 - 3.6 1.2 - 3.21 1.3 - 3.3




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Key fndings

Further fndings rom the feld trial

As well as the key ndings above, the eld trial hasrevealed some secondary ndings which will also helpus to understand what actors determine heat pumpperormance.

•• The wide-ranging perormance values can beattributed to a number o observed actors, namelythe system design and installation and thecustomers’ use o controls.•• Eciencies or domestic hot water production werelower than expected in a number o cases, mainly insystems producing domestic hot water in the summer.•• Control systems were generally too complicated or thehouseholders to understand. Some householders oundit dicult to control the ambient room temperature.•• Many systems appeared to be installed incorrectly.

•• Oten there was no single contractor responsibleor the installation, which might involve a groundworks contractor, a plumber, a heat pump installerand an electrician. This meant that there was otenno single point o responsibility or any liability orthe eventual perormance o the whole installation.•• Running costs are one o the main negative actorsaecting user satisaction. Dissatisaction may berelated to the substantial increases in uel costswhich occurred just beore and during the project;however such eedback is subjective. There were

many more dissatised social housing residents(42%) than private householders (13%).

Summary

These ndings and observations lead to some simpleconclusions:

1. Heat pumps are sensitive to design andcommissioning. The eld trial covered a variety o

early installations, many o which ailed to applythe heat pump correctly. This result emphasises theneed or improved training.

2. Keep it simple. There were many systemcongurations monitored in the eld trial. In mostcases, the simplest designed systems perormedwith higher eciencies.

3. The impact o domestic hot water production onsystem perormance is unclear. Heat pumps can bedesigned to provide domestic hot water atappropriate temperatures, but more investigation is

required to determine the actors which impactsystem eciency.

4. Heating controls or heat pump installations have to becomprehensively reviewed. There has been a ailure toexplain proper control requirements to both installersand heat pump customers.

5. Responsibility or the installation should be with onecompany, and ideally be contractually guaranteed toensure consistency in ater-sales service.

6. Further study needs to be undertaken on aninstallation-by-installation basis, to record what

has been done wrong (or correctly), what could bedone better, and what exactly should be done inthe uture.




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Installers must work with customers to ensure that they understandhow to use the controls

Results o the eld trial show that well-designed andwell-installed heat pump systems can perorm well inthe UK. Among the 83 sites we monitored, there weregood, average, and poor perorming sites. Thisvariation in perormance has been infuenced by anumber o actors, including system design (sizing o

the pump, and type and size o heat source and heatsink), system installation, and customer behaviour.

Attempts to explain the variation in perormance usingstatistical methods have given only partial answersand unclear trends. More insight has been gainedwhen individual sites were considered as case studies.When a site has been looked at in isolation, reasonsor the good, average, or poor perormance canusually be ound.

In order to get the best perormance rom a heatpump, it is essential that installation and systemdesign meet the heat demand o the building. TheEnergy Saving Trust is actively working with relevantstakeholders, including the trade associations, heatpump manuacturers, the Department o Energy andClimate Change, the Scottish Government, and theMicrogeneration Certication Scheme (MCS), to identiyimprovements to heat pump installation guidelines andinstaller training.

This eld trial has highlighted the need or improved

consumer advice regarding the appropriate use osystem controls, and choice o the appropriateelectricity tari. Customers should take an active parto the installation process so they gain a goodunderstanding o how to operate the system. This isparticularly important or social housing residents astenants, who may not have been involved in choosingthe technology or commissioning the installation.

Findings rom the eld trial show that heat pumpshave a real potential to reduce carbon emissions,compared with other traditional domestic heatingsystems (such as electric storage heating). Thepotential or carbon savings on a site-by-site basiswill increase over time as the grid is decarbonised.

The eld trial has identied a number o useuladditional benets to be gained by a second year omonitoring to investigate perormance in more detailat a number o sites. Thereore, it has been agreed toextend the eld trial through June 2011 to undertakeadditional site measurements, analysis o data, and

study o customer behaviour.

In the meantime, the Energy Saving Trust will continueto provide impartial advice to customers who areinterested in purchasing a heat pump. Customers areencouraged to visit the Energy Saving Trust’s website(www.est.org.uk) or phone our advice line (0800 512 012)to speak to a local advisor.

Conclusions




19

The inormation gained rom this eld trial makes itpossible or the Energy Saving Trust to give muchmore accurate and targeted advice to people who areconsidering whether to install a heat pump.

Results rom the rst year o research suggest that

heat pumps can both perorm well and save on CO2 emissions in many property types. We particularlyrecommend considering a heat pump i your home isone o the approximately ve million properties thatare o-gas, or or a new-build property.

Phase one o the eld trial shows that there ispotential or more widespread use, but the secondyear o study is needed to give a clearer picture othat potential in actual conditions across the UKhousing stock.

The main considerations in choosing an air source or aground source heat pump are installation costs; theamount o space available (ground source heat pumpsrequire land or a ground loop or a borehole) and orair source heat pumps, proximity to neighbouringproperties. The Energy Saving Trust stronglyrecommends that you use an installer certiedthrough the Microgeneration Certied Scheme (MCS),which is currently the most robust installer standardin the UK.

A heat pump with a mid-range eciency can beexpected to use only a third o the energy o anaverage existing gas boiler (78% ecient) or oil boiler(82% ecient) to produce the same amount o heat. Aheat pump draws on a small amount o electricity topower it, which is more carbon-intensive than gas andoil. Taking these actors into account, and based onGovernment projections or grid electricity carbonactors, a heat pump installed in 2010 produces 9%less carbon dioxide than an average gas boiler and28% less than an average oil boiler do per unit oheat. The potential or carbon savings will increase inuture under the UK Government’s plan to decarbonisethe electricity grid.

Although every home is unique, a well-perorming heatpump should typically produce a system eciencyratio above 3.0 – comparable to heat pumpinstallations monitored in European eld trials.

Assuming a mid-range system eciency, at current

electricity prices a ground source heat pump willprovide a payback on the marginal installation costscompared with direct electric heating in 18 years. Thispayback period increases to 29 and 47 years whencompared with new oil and gas boilers, respectively.At current electricity prices an air source heat pumpwill provide a payback on the marginal installationcosts compared with direct electric heating in 10years. This payback period increases to 16 and 31years when compared with new oil and gas boilers,respectively. The dierence in payback is due todierences in capital costs o dierent heatingtechnologies and uel prices. I energy prices increase,as is being predicted; the Renewable Heat Incentive(RHI) is enacted; and as heat pumps become cheaperdue to wider adoption and economies o scale,payback periods could become shorter.

The government has recently proposed the RHI toprovide a subsidy payment to heat pump users. TheRHI is still under ormal consultation, but on theproposed gures a ground source heat pump could beexpected to pay back installation costs in around eight

years, and air source heat pump in around ve years.

Heat pumps also have the potential to providesignicant carbon savings at present and over thelietime o an installation. For example, i all vemillion o-gas properties were installed with a heatpump in 2010, it could save 10 million tonnes o CO2 and £2 billion on uel bills per year.

Advice or customers




20

The Energy Saving Trust advises householders to berigorous in their research beore purchasing a heatpump. This checklist also suggests questions thatcustomers should ask installers beore purchasing aheat pump.

When you should consider a heat pump•• In a well-insulated existing property o the gasnetwork. Heat pumps have the potential to reducerunning costs compared with oil, direct electric,LPG, or coal, and can provide substantial carbonsavings over the lietime o the installation.•• In new-build properties

How to get the best perormance rom a heat pump

•• Make sure that your home is as well insulated aspossible (with. cavity and lot insulation) beoreinstalling a heat pump.•• Install the heat pump with low temperature under-foor heating or properly sized radiators..•• Insist upon understandable, user-riendly controls.

What to expect rom a heat pump

•• Since heat pumps provide a lower temperatureheating than boilers, radiators will eel warmrather than hot.•• A house with radiators may heat up more slowly.

•• The heat pump will run or longer hours than aconventional boiler, but i properly controlled it willswitch on and o with the heating requirements othe house.•• A properly sized and installed heat pump should beable to provide all o a household’s domestic hotwater, but many systems are installed with asupplemental electric immersion heater.

What to expect rom a heat pump installer

Potential customers need to ask the right questions whenchoosing a heat pump, as with any other heatingtechnology. Proper installation is essential to achieve thebest perormance rom a heat pump.

1. Ask the installer to explain how he or she hasdetermined the appropriate type and size o heatpump or your property. The installer should explainhow the heat demand o your property wascalculated.

2. Make sure the installer explains how the heatpump will work with your existing heating system(including radiators and hot water supply).

3. Ask or guidance to operate the heat pump systemcontrols.

4. Ask how oten you should run the heat pump.

Finally, the Energy Saving Trust recommends thathouseholders speak to one o our advisors beoreinstalling a heat pump. Additionally, customers shouldspeak to MCS accredited installers and manuacturersto determine whether a heat pump is a viable option.

Consumer checklist




21

As well as monitoring equipment and surveyinghouseholders, this eld trial has reviewed relevantinstallation standards in the UK and Europe. Theguidance set out in those standards, combined witheedback rom customers in this eld trial, suggeststhat installers should ollow these “top tips” when

engaging with customers to install heat pumps.

The Energy Saving Trust will produce urthercomprehensive technical guidance or both ASHP andGSHP installations in Autumn 2010.

How installers should approach their nextinstallation design

1. Keep it simple. The eld trial ndings categoricallyshow that the simplest system designs achieve thebest eciencies.

2. Keep controls simple. Controls need to beappropriate or the installation, but it is vital that thecustomer can understand how to use them properly.

3. System sizing is key. Ensure that the system issized correctly to meet the property’s centralheating demand.

4. Be transparent with customers. Discuss systemrunning costs and the likely perormancecustomers should expect as honestly and ranklyas possible, so they understand what to expect.

5. Be realistic. Advise your customers about the need

or any supplementary heating.

6. Be aware o the margin o error. I a heat pump isinstalled even slightly wrong, the outcome or thehouseholder may be very wrong.

7. Manage your subcontractors rigorously to ensurethat their work is appropriate or your heat pump.Installers need to take overall responsibility andsupervise each stage o the installation.

Advice or installers

Sizing and positioning a heat pump are critical to running eciency




22

Training and standards roadmap

In the UK there are a number o standards andguidelines or heat pumps and installers.

The MCS product standard, MCS 007, sets out

guidelines or product certication. The MCS installerstandard, MIS 3005, sets out guidelines or the supply,design, installation, and commissioning o heat pumpsystems. MCS certication is a prerequisite or accessto grants and incentives through the Low CarbonBuildings Programme (LCBP), and has been suggestedas a prerequisite or the proposed Renewable HeatIncentive (RHI).

As well as these standards there are a number oguidelines that promote good practice in heat pumpinstallation, including Technical Report 30 (TR 30): Guide to Good Practice – Heat Pumps, and the Energy SavingTrust publication Domestic Ground Source Heat Pumps:Design and installation o closed-loop systems (CE82).

We recommend that the trade and government agree aroadmap outlining changes to product and installationstandards, within six months. To this end, we willparticipate in a working group o leading industryplayers to make recommendations as to how the UKcan achieve the needed improvements.

In autumn 2010 we will publish an updated version oCE82, which provides guidance or installers o GHSPinstallations, and will also develop a similar set oguidelines or ASHP. We view these documents as vitalto support the success o heat pumps in the UK.

We are actively working with the MCS and the heatpump industry to improve the availability o training orheat pump installers, including skills-based trainingcourses. Heat pump standards in North America andEurope contain much guidance that can help the UKmarket. For example, Denmark and Sweden have EUquality assurance certication schemes or sizing,installation and installers. The Energy Saving Trustwill work with the UK government and industry tore-assess appropriate training or installers.

This ongoing work is crucial to the success o heatpumps in the UK, and the achievement o the carbonsavings they can provide.

Getting warmer: areas or additional

workThe Energy Saving Trust’s heat pump eld trial givesthe industry some very useul inormation about howheat pumps are perorming in the UK when installedin actual customers’ homes.

It also shows that additional research is necessary toexplain the reasons or the wide-ranging perormanceobserved across the sample. For this reason, a secondyear o the study has been planned, during which wewill continue to monitor the participating sites, and

thoroughly investigate various actors.

This will allow the eld trial to bring into ocusexactly what makes a high perorming heat pumpretrot installation, and to ensure that this becomesstandard practice. The work proposed or the secondyear will allow the Energy Saving Trust to investigateand modiy installations, to identiy exactly whatmakes an installation perorm well and, conversely,what practices should be avoided. These measures arein line with similar eld trials in Europe which have

run or a number o years.

Extension o the heat pump eld trial will help us toprovide the best possible advice to customers.Building on the results rom the rst year o the study,this urther research will enable us to give potentialcustomers a more precise understanding o how heatpumps perorm in real homes, allowing them to makethe most inormed decision regarding the purchase oa heat pump. Ultimately it should mean that morepeople decide to opt or the option o microgeneration.

What’s next



Energy Saving Trust, 21 Dartmouth Street, London SW1H 9BPTel 020 7222 0101 Fax 0845 120 7789energysavingtrust.org.uk

Prepared by the Energy Saving TrustSeptember 2010

The Energy Saving Trust is the UK’s leading impartialorganisation helping people save energy and reduce

carbon emissions. We do this by providing expertinsight and knowledge about energy saving, supportingpeople to take action, helping local authorities andcommunities to save energy and providing qualityassurance or goods, services and installers.

Getting Warmer a Field Trial of Heat Pumps Report

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Transcript of Getting Warmer a Field Trial of Heat Pumps Report