Air-to-air heat pumps inFinnish single family houses

HP4nZEB Seminar 15.6.2015Ari LaitinenVTT

214.6.2015 2

Contents of the presentation

Background informationWhat is an air-to-air heat pumpAir-to-air heat pumps in our regulationsPrevious studies

Ongoing studyBuilding characteristicsCharacteristics of the air-to-air heat pumpsSimulation plan with some preliminary results

Summary

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What is an air-to-air heat pump ?

Indoor unit forheating and

cooling

Outdoor unitIncluding

compressor andevaporator

With the air-to-airheat pump we

can heat or coolthe room spaces

directly

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Background

The presentation is based on the running project which startedin march 2015 and will end in spring 2016

Interest rises from the renewal of our national building codes

Ministry of environment & companies want to know the energysaving potential of air-to-air heat pumps considering differentboundary conditions (capasity of the heat pump, heat demand ofthe building, geographical location)

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Air-to-air heat pumps in present regulations

New building (E-luku)Heating energy produced by air-to-air heat pump max. 1000 kWh

Old buildings (Energy label)Year - 1985 1985 - 10/2003 - 2008 - 2010 - 2012 -

Heat energy 6000 kWh/a<40 kWh/(m2 a)

5000 kWh/a<35 kWh/(m2 a) 2000 kWh/a 1500 kWh/a 1000 kWh/a 1000 kWh/a

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Previous study

Elvari is a program promoting energy savings in electrically heated single-family housesMain actors are Motiva Oy, Finnish energy industries (ET) & companiesElvari: Field measurements of the energy savings with air-to-air heat pumpsElvari started 2008 and will continue until 2016Results are based on 166 analysed electrically heated detached housesHighest saving over 8000 kWh/a, normal saving 1000 – 5000 kWh/a

Average electricityconsumption beforeair-to-air heat pump,kWh/aAverage electricitysaving after installationof air-to-air heat pump,kWh/a

Elec

tric

ity,k

Wh/

a

7

Ongoing project

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Objective

The objective of the study is to find out the energy savingpotential of air-to-air heat pumps in typical finnish detachedhouses

The boundaries of the study are:Space heating energy demand of the buildingArchitectural layout of the buildingHeat production charasteristics of the air-to-air heat pumpsCOP characteristics of the air-to-air heat pumpsNoise emission of the indoor unit of the heat pumpOperation of the air-to-air heat pumpWeather (Helsinki and Sodankylä)

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Buildings

The buildings are the same as used in Cost optimal projectFinnish declaration of the cost optimality of building codes toEuropean Comission

1-storey, old buildingOriginalRenovated

2-storey,new buildingAccording to present regulationsPassive levelOld constructions

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Detached house – old building

Floor area 136 m2

Volume 352 m3

U-values of the structures• floor 0,38 W/(m2 K)• External wall 0,50 W/(m2 K)• ceiling 0,27 W/(m2 K)• Windows 2,5 W/(m2 K)• doors 1,1 W/(m2 K)

Air tightness of the envelope q50 = 6 m3/(h m2)Mechanical exhaust ventilationSpace heat demand 200 kWh/m2, a

Renovation case:• Uwall = 0,17 W/(m2 K); Uceiling = 0,09 W/(m2 K)

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Layout

1st floorf1

f2

f3af3b

f3c

f3df3e

f4

Garage

Bedroom

Closet

Closet

Pathroom

Sauna

Living roomKitchenHall

Toilet

Bedroom

Bedroom

Air-to-airheat pump

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Detached house – new building

Floor area 180 m2

volume 468 m3

U-values• External walls 0,17 W/(m2 K)• ceiling 0,09 W/(m2 K)• floor 0,16 W/(m2 K)• Windows and floors 1,0 W/(m2 K)

Air tightness of the envelope q50 = 2 m3/(h m2)Mechanical supply and exhaust ventilation with heat recovery ( =45%)Space heating demand 50 kWh/m2, a

Passive house case:• Uwalls = 0,08 W/(m2 K); Uceiling = 0,05 W/(m2 K); Ufloor = 0,10 W/(m2 K)• Uwindows = 0,8 W/(m2 K) ; Udoors = 0,8 W/(m2 K)• Heat recovery from exhaust air = 80 %

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Layout

0.75 mf1

f2

f3

f4

0.75 mf1

f2

f3

f4

1st floor 2nd floor

Living roomand kitchen

Pathroom

Bedroom

Stairs Stairs

Hall

Bedroom

Bedroom

Bedroom

Air-to-airheat pump

Characteristics ofthe air-to-air heat pumps

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Characteristics of air-air heat pumps

• Data of air-air heat pumps is based on publicly available data

• Product measurements by VTT Expert Services available athttp://www.scanoffice.fi/fi/tuotteet/tuoteryhmat/ilmalampopumput/raportit-ja-sertifikaatit/vttn-testiraportit

• Product measurements by Energimyndigheten available athttps://www.energimyndigheten.se/Hushall/Testerresultat/Testresultat/Luftluftvarmepumpar-2013-2009/

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Example of the laboratory tests made byVTT Expert Services Ltd

Outdoor airtemperature, ºC

Electricpower

Sliding hourly average values including defrosting

Pow

er,W

Heatingpower

Time, h

Out

door

tem

pera

ture

,ºC

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Example of the laboratory testsMoving hourly average values including defrosting

CO

P

Outdoor temperature, ºC

Outdoor temperature, ºC

Pow

er,W

Heatingpower

Electricpower

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Combined data / Energimyndigheten & VTT

Differencies in the tests:• VTT drives the heat pump against linearly varying heat demand (0 kW at 12 ºC … 6 kW at -26 ºC)• VTT use fixed air flow in the indoor unit (middle position)• Energiemyndigheten drives the heat pump at maximum indoor unit airflow• Energiemyndigheten use fixed part load tests• Both tests include the defrosting of the outdoor unit

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Heat demand of the buildings vsheat output of the air-to-air heat pump

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Sound pressure level requirementin building code / C1

Will the requirements limit theoperation of the heat pump ?

Simulation of air-to-airheat pumps

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Simulation tool: IDA ICE

IDA Indoor Climate and Energy (IDA ICE) is whole-year detailed and dynamic multi-zone simulationapplication for study of thermal indoor climate as well as the energy consumption of the entire buildingand it’s systems.

The model considers heat transfer between zones (=rooms) trough openings (=doors):An opening between two zones (or in an external wall) gives rise to a (sometimes bi-directional)air flow due to density differences between zones, that will reduce the differences intemperature, humidity and carbon dioxide content between the air masses. The radiationthrough the opening is also considered.

Source: http://www.equa.se/en/ida-ice

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Option 1:Heating power as curve fitting in IDA

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Option 2: Apply IDA’s own air-to-air model

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Simulation strategy

Back-up heating (electric) will keep the room air temperatures at 21 ºCSet value for air-to-air heat pump is higher than 21 ºC

Set values: 21,5 ºC, 22 ºC, 23 ºC, 24 ºC

Set value forair-to-air heatpump = 22 ºC

Set value forback-up heating= 21 ºC

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Example of the preliminary results of thesimulation

Heating power of the air-to-air heat pumpin old and new building

COP of the air-to-air heat pumpin old and new building

Summary

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SummaryReport of the study will be ready next spring

The results will give the answer to questions like:

How much the of the space heating demand is covered by the heatpumpWhat is the SCOP of the air-to-air heat pump in finnish climate andbuilding typesWhat is the renewable energy utilization rateHow much can I save with the heat pump

Energy savings of the air-to-air heat pumps depend always onthe operation

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