Heating with Heat PumpsLessons from EST Field Trials &

Electricity Network Studies

27th September 2010Dave A Roberts

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1. Why Heat Pumps?2. What is a Heat Pump? 3. Heat Pump Characteristics4. EST Field Trials – some practical issues5. MCS Guidance6. Network Impacts7. Future studies8. Conclusions

Heating with Heat Pumps

1. Why Heat Pumps

• Decarbonising domestic heating – One of major challenges in meeting CO2 targets

• Heat Pumps a promising option– Assuming low carbon electricity supply

• DECC estimates of 60 – 90% houses by 2050– Planning to introduce incentives (RHI)

• But currently only limited one-off “Premium Payments”

• Rapid growth required

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Growth Scenarios

2. What is a Heat Pump

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Heat Pump performance

• Measured as Coefficient of Performance

• Dimensionless– kWthermal / kWelectrical - instantaneous– kWhthermal / kWhelectrical - more usual & more useful

• Often called System Efficiency – includes pumps & fans etc.

Types of Heat Pump

• Ground-source• Air-source• Water source

• Air to air • air-conditioning

hydronicRadiators

Under-floorheating

• Ventilation• Mainly exhaust air

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Under-floorheating coils

Heat pump

Ground loop

Ground Source

Ice Energy

Ice Energy

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Air-source

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Air Source or Ground Source

+ Lower capital cost+ Simpler to install- Appearance - Some external noise- Performance sensitive to ..outside temperature

- Higher capital cost- Disruption during installation++ Visually unobtrusive+ Quiet++ Performance less (not) sensitive…..to outside temperature

Air Source Ground Source

3. Heat Pump Characteristics

• Very different from a boiler• Performance very sensitive to source and sink

temperatures• the Air or Ground temperature (source)• the Heat Emitter temperatures (sink)

• Installers & Users need to understand this

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COP curve*

Illustrative example: GSHP brine at 0oC

* COP of installed system

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Energy Use Curve

Illustrative example: GSHP brine at 0oC

Electricity units to deliver 100 units of heat

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Air Source

Illustrative example

Electricity units to deliver 100 units of heat

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Air Source - capacity

Illustrative example

4. EST Field Trials

• Phase 1 ~ 80 houses– Mix of ASHP & GSHP – Results generally disappointing but explainable

• Phase 2 ~ 50 houses– Improvements to:

• Systems (including replacing heat pump)• Instrumentation

– Monitoring now finished• Results to be discussed with manufacturers next month• Public report ~ April 2013

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Some learning points from Phase 1• Heat emitter temperatures

– Generally too high for good performance• A few low ones (usually under-floor heating)

– Scope for improvement• “Over-sized” radiators• Fanned radiators

• Parasitic loads (pumps, fans) – Significant impact on overall performance– Scope for reduction

• High efficiency pumps• Avoid unnecessary use

• Overly complex controls– Users need to understand them

5. MCS Guidance

• Microgeneration Certification Scheme• Outcome of EST field trial

– Updates to installer guidance MIS 3005

• Three key areas– Sizing– Ground loop design new supplementary documents– Heat emitter guide on MCS web site

• DECC road-show to publicise changes & train installers– Social Housing road-show soon (Glasgow 1st November 2012*)

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* http://www.decc.gov.uk/en/content/cms/news/heat_pump_road/heat_pump_road.aspx

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Sizing

• Issue was “Scandinavian” design– Under-sized heat pump + electric flow boiler “top-up”– Field trial experience

• Poor seasonal performance• High bills

• MIS 3005 addresses this– Size for 100% load at design day condition– Requires a full heat loss calc. on property

• Even with this approach..– Some days (colder than design day) where heat pump won’t cope

• Reduce some room temperatures / warmer clothing /

6. Network Impacts

• Both sizing and penetration levels are of concern– Large additional loads c.f. other (non electric heating) domestic

loads

• Network specific (urban, rural, local constraints)– But often Networks already stretched

• Coldest day analysis– Heat demand determines the Heat Pump electricity load

• Brief example– 7kW (design day) heat demand house– Assume no diversity on coldest day

• i.e. all heat pumps will be running flat out – especially at peak times– Look at both 24/7 and “bimodal” operation

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Heat Pumps 10% penetration, 24/7

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Heat Pumps10% penetration, 24/7, 1 hour interrupt

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Heat Pumps10% penetration, 24/7, MD unchanged

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Heat Pumps100% penetration, 24/7, big increase in MD

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Heat Pumps100% penetration, bimodal, big problem!

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Mitigation measures

• Network investment• More efficient heat pumps

– Typically lower flow temperatures

• Under-sizing– Counter to MCS guidance but can be a good solution with top-up

heat from:

• Storage electric

• Gas

• Other storable fuels

• direct electric

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Under-sizing• Helps with design day• Only a small top-up

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SGF:WS3* (Phase 2):Network Model Schematic Overview

*Smart Grid Forum: Workstream 3

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The spread of (network related) investment from the model is significant

Spread of GB network related investment (non-discounted cumulative totex showing the two most extreme scenarios) to accommodate projections in Low Carbon Technologies connecting to the electricity distribution network

Output: The potential impact of future GB energy scenarios on power networks is material

Output: The challenge ahead is technically demanding and of a scale not seen in 50 yearsInvestment will require step changes

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Gross GB network related investment for the next four RIIO periods

Load related expenditure (LRE) – investment driven by changes in demand, i.e. that in response to new loads or generation being connected to parts of the network (connections expenditure) and investment associated with general reinforcement. Non-load related expenditure (NLRE) – other network investment that is disassociated with load. LNRE and LRE have simply been assumed to be 8/5th of the DPCR5 values for the extended RIIO periods

Output: Observations

An iterative process with evidence from innovation trials will improve the evidence base – version control advisable

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• A total of 45 separate variables in the model

• As more information comes to light, the model output will be improved

• For example:• LV network parameters• LCT profiles, e.g. electric

vehicle charging profiles• Solution costs & benefits

Refine input parameters

RunModel

Report output

7. Future Studies

• Low temperature heat emitters • 24/7 vs bimodal operation• Challenge MCS guidance on sizing

– Hybrid solutions

• Electricity Supply / End Use balancing– Problem or solution?

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8. Conclusions

• Heat Pumps important to the low carbon future• Designs need improving

– More the application than the Heat Pumps

• Owners & specifiers need to understand characteristics• Network capacity concerns

– Tools now available to investigate issues

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Appendix

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WS3-Ph2: A consortium-led approach on behalf of the GB Smart Grid Forum (Work Stream 3)

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Project Partners..

Working with..

2. Disruptive technologies have scope to create significant challenge to LV networks

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Heat Pumps

Photovoltaic

Electric VehiclesSource: SGF, WS1, DECC, Dec 2011

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B

C

A B

C

Not all networks are equal: The headroom of the networks differ throughout GB

Factors include:

Build specification

Customer type and customer density

Local geography

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The mix of customers along a feeder has a significant impact on its overall demand profile

LV feeder demand profile

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PV installations have clustered in different parts of GB

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Percentage of network

Percentage of low-carbon technology installations

1% 9%

4% 17%

25% 48%

30% 22%

40% 5%

Number of domestic PV installations per 10,000 households by Local Authority, end of December 2011

Source: www.azure.eco.co.uk

Source: DECC

Domestic Heat Pump

Point load demand profiles have a significant impact

• Winter Peak, Winter & Summer Average• Weekday• Temperature Sensitivity• Appliance Type & Efficiency• Validation

Standard Tariff Domestic Domestic E7 Storage Heaters

Temperature Sensitivity

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Fixing the problem: Selecting solutions with an increasing solution set

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ConventionalSolutions

ConventionalSolutions

‘Business-As-Usual’Investment

‘Smart’ Investment

SmartSolutions

Solution Enablers