Life Cycle Primary Energy Use and Carbon Emission of Residential Buildings

Transcription

1 Life Cycle Primary Energy Use and Carbon Emission of Residential Buildings Ambrose Dodoo Sustainable Built Environment Linnaeus University 26 January 2012 VÄXJÖ

2 Global primary energy supply Mtoe 1 Mtoe = EJ

3 Why buildings matter Buildings account for up to 40% of the global total primary energy use

4 Why buildings matter Buildings account for up to 40% of the global total primary energy use A third of the global total CO 2 emissions is linked to building energy use

5 Why buildings matter Buildings account for up to 40% of the global total primary energy use A third of the global total CO 2 emissions is linked to building energy use Improved material and energy efficiency in buildings is crucial for transition to sustainable energy future Offer large potential to reduce CO 2 emissions to mitigate climate change

6 Studied building 4-storey building with 16 apartments and 1190 m 2 living area Wood-frame building Concrete-frame building Built in Växjö, Sweden, during the 1994 building code regime Hypothetical building with identical size and function

7 Characteristics of buildings Description Wood-frame building Concrete-frame building Roof: Thickness mineral wool (cm) U-value (W/m 2 K) External walls: Thickness mineral wool (cm) U-value (W/m 2 K) Windows: Type Double glazed Double glazed U-value (W/m 2 K) External doors: Type Double glazed Double glazed U-value (W/m 2 K) Foundation Floor: Expanded polystyrene (cm) 7 7 U-value (W/m 2 K) Airtightness: l /(m 2 s) at 50 Pa Ventilation Mechanical, exhaust air Mechanical, exhaust air Water taps Conventional Conventional

8 Material mass of buildings Material mass (kg). Macadam Concrete Plasterboard Lumber Mortar Plywood Insulation Particleboard Iron/steel Glass Putty/fillers Blocks Appliances Paper Plastic (PVC) Ceramic tiles Paint Porcelain Copper Zinc Wood frame Concrete frame

9 Modeled activities and flows Production / Retrofitting phases -Extraction, processing and transport of materials -Energy recovery from biomass residues - On-site construction work Operation phase - Space heating - Electricity for ventilation - Tap water heating - Electricity for household and facility management End-of-life phase - Demolition - Energy recovery from wood -Recycling of concrete and steel to replace virgin raw material Energy supply system -Coal-based electricity for material production -Bioenergy replace coal - Full energy chain accounting, including conversion / fuel cycle losses Energy supply system -Resistance heating, or heat pump, or district heating -District heating produced with a biomassfired CHP plant -Electricity produced with a biomass-fired condensing plant - Full energy chain accounting, including conversion / fuel cycle losses Energy supply system -Bioenergy replace coal -Full energy chain accounting, including conversion / fuel cycle losses

11 Material flows from natural resources to building Ore Forest Extraction Energy supply Processing Construction Biomass residues Building Material flow Fuel-/energy flow

12 Flow of biomass residues in building s production Harvested roundwood Wood-based building materials Forest residue Processing residue Construction residue

14 System perspective on energy supply and demand

16 End-of-life building materials Demolition Wood residues Concrete waste Iron / steel scrap

17 Production primary energy balance of buildings 800 Concrete frame Wood frame 600 Primary energy use (kwh/m 2 ) Material production On-site construction Biomass residue recovery Total

18 Annual profile of final space heat demand of buildings in different climatic locations Building heat demand (kw) Wood f rame (Kiruna) Wood f rame [Östersund] Wood f rame {Växjö} Concrete f rame (Kiruna) Concrete f rame [Östersund] Concrete f rame {Växjö} Location Relative location Average temperature Växjö South 6.5 o C Östersund Middle 2.5 o C Kiruna North -1.2 o C Day

19 Annual profile of final space heat demand of buildings built to different standards and located in Växjö 40 Wood f rame (Passive) Concrete f rame (Passive) Wood frame [BBR 2009] Concrete frame [BBR 2009] Wood f rame {Ref erence} Concrete f rame {Ref erence} Building heat demand (kw) Day

20 Annual primary energy use for space heating of buildings with different heating systems in Växjö 250 Concrete frame Wood frame Primary energy use (kwh/m 2 ) Electric resistance heating Heat pump District heating, 85% CHP Supply system: Biomass-based steam turbine

21 Annual operation primary energy use of buildings with different heating systems located in Växjö 500 Household electricity Tap water heating Ventilation electricity Space heating 400 Primary energy use (kwh/m 2 ) Concrete frame Wood frame Concrete frame Wood frame Supply system: Biomass-based steam turbine Concrete frame Wood frame Electric resistance heating Heat pump District heating

22 End-of-life primary energy balance of buildings 100 Concrete frame Wood frame Primary energy use (kwh/m 2 ) Demolition Concrete recycling Steel recycling Wood recovery for biofuel Total

23 Life cycle primary energy use of district heated buildings in Växjö for a 50-year lifespan Demolition Household electricity Tap water heating Ventilation electricity Space heating On-site construction Material p production y y Concrete recycling Steel recycling Wood recovery for bioenergy Supply system: Biomass-based steam turbine Primary energy (kwh/m 2 ) Concrete frame Wood frame Difference Total used Benefits from production and end-of-life Balance

24 Carbon flows due to cement reactions for buildings Calcination Carbonation Concrete-frame Emission due to calcination (tc)) Uptake due to carbonation (tc)) Wood-frame 0 Concrete frame Wood frame Year 0 Year

25 Net carbon emissions of buildings at year of construction 150 Concrete frame Wood frame Net carbon emission (t C) Material production Net cement reactions Biomass fossil fuel replacement Forest carbon stock change Building carbon stock change Total

26 Net carbon emissions of buildings over life cycle of buildings 100 Concrete frame Wood frame Net carbon emission (t C) Material production Net cement reactions Biomass fossil fuel replacement Forest carbon stock change Building carbon stock change Recycled concrete and steel benefits Total

27 Impacts of building energy-efficiency standards Annual final energy use for operation iifinal energy use (kwh/m 2 year) Space heating Ventilation electricity Tap water heating Household electricity Final energy use BBR1994 BBR2009 Passivhus BBR1994 BBR2009 Passivhus Electric heated building District heated building Supply system: Biomass-based steam turbine

28 Impacts of building energy-efficiency standards Annual final and primary energy use for operation 500 Primary energy use iifinal energy use (kwh/m 2 year) Space heating Ventilation electricity Tap water heating Household electricity Final energy use BBR1994 BBR2009 Passivhus BBR1994 BBR2009 Passivhus iiprimary energy use (kwh/m 2 year) BBR1994 BBR2009 Passivhus BBR1994 BBR2009 Passivhus Electric heated building District heated building Electric heated building District heated building Supply system: Biomass-based steam turbine

29 Impacts of building energy-efficiency standards Space heating and production primary energy 100% Space heating and ventilation Production Relative distribution of primary energy 80% 60% 40% 20% 0% BBR1994 BBR2009 Passivhus BBR1994 BBR2009 Passivhus Electric heated building District heated building

30 Impacts of building energy-efficiency standards Life cycle primary energy implications (Assumed building lifespan of 50 years) Primary energy use (kwh/m 2 ) Building demolition Household electricity Tap water heating Ventilation electricity Space heating On-site construction Material production Demolition residues/ End-of-life benefit Production residues BBR 1994 BBR 2009 Passivhus BBR 1994 BBR 2009 Passivhus Electric heated building District heated building Supply system: Biomass-based steam turbine

31 Impacts of energy efficiency retrofit measures Annual final operation energy, before and after retrofit measures are applied Parameter Retrofit measure Annual final operation energy use (kwh/m 2 year) Space heating Tap water heating Ventilation electricity Household /facility electricity Total Cumulative change Initial Taps Efficient hot water taps Roof U-value from 0.13 to Windows U-value from 1.9 to Doors U-value from 1.19 to External walls U-value from 0.20 to Ventilation Heat recovery, η = 85% U-values in W/m 2 K

32 Impacts of energy efficiency retrofit measures Annual primary energy use for (space and tap water) heating and ventilation Primary energy use (kwh/m 2 ) Initial Improved taps Improved taps + Roof Improved taps + Roof+ Windows Improved taps + Roof+ Windows + Doors Improved taps + Roof+ Windows + Doors + External walls Improved taps + Roof+ Windows + Doors + External walls + Heat recovery 50 0 Electric resistance heating Heat pump District heating, 50% CHP District heating, 90% CHP Supply system: Biomass-based steam turbine

33 Impacts of energy efficiency retrofit measures Primary energy use in complete life cycle of buildings Primary energy use (kwh/m 2 ) (Assumed lifespan of 50 years) Building demolition Household and facility electricity Tap water heating Ventilation electricity Space heating On-site construction Material production Demolition residues/ End-of-life benefit Production residues Initial Retrofit Initial Retrofit Initial Retrofit Initial Retrofit Electric resistance heating Heat pump District heating, 50% CHP Supply system: Biomass-based steam turbine District heating, 90% CHP

34 Impacts of ventilation heat recovery (VHR) systems Change in annual primary energy use for space heating and ventilation Change in primary energy use (kwh/m 2 ) Ventilation electricity, BST Space heating, BST Ventilation electricity, BIGCC Space heating, BIGCC Conventional Passive Conventional Passive Conventional Passive Conventional Passive Electric resistance heating Heat pump District heating, 50% CHP District heating, 90% CHP Supply system: Biomass-based steam turbine (BST) or Supply system: Biomass-based integrated gasification with combined cycle (BIGCC)

35 Impacts of ventilation heat recovery (VHR) systems Net annual primary energy savings 80 BST BIGCC Net primary energy savings (kwh/m 2 ) Conventional Passive Conventional Passive Conventional Passive Conventional Passive Electric resistance heating Heat pump District heating, 50% CHP Districtheating, 90% CHP Supply system: Biomass-based steam turbine (BST) or Supply system: Biomass-based integrated gasification with combined cycle (BIGCC)

36 Impacts of ventilation heat recovery (VHR) systems More optimally designed CHP production systems Net primary energy savings (kwh/m 2 ) VHR electricity is 4 kwh/m2 VHR electricity is 7 kwh/m2 Conventional Passive Conventional Passive Conventional Passive Conventional Passive 80% CHP-BST 83% CHP-BST 76% CHP-BIGCC 78% CHP-BIGCC Supply system: Biomass-based steam turbine (BST) or Supply system: Biomass-based integrated gasification with combined cycle (BIGCC)

37 Conclusions Energy savings due to thermal mass is small for a Nordic building Varies with the climatic location, and Energy efficiency level of building

38 Conclusions Energy savings due to thermal mass is small and varies with the climate and energy efficiency levels of buildings Concrete building has slightly lower space heating demand than wood alternative Higher thermal mass of concrete-based material

39 Conclusions Energy savings due to thermal mass is small and varies with the climate and energy efficiency levels of buildings Concrete building has slightly lower space heating demand than wood alternative Still, wood building has lower primary energy balance than concrete alternative Less energy needed for material production More energy available from biomass residues

40 Conclusions Energy savings due to thermal mass is small and varies with the climate and energy efficiency levels of buildings Concrete building has slightly lower space heating demand than wood alternative Still, wood building has lower primary energy balance than concrete alternative Wood building has lower carbon balance than concrete alternative, even if post-use carbonation is accounted Less fossil fuel emission for material production Less cement process emission More fossil fuel substitution by biomass residues Effect of carbonation of post-use concrete material is small, overall

41 Conclusions Energy savings due to thermal mass is small and varies with the climate and energy efficiency levels of buildings Concrete building has slightly lower space heating demand than wood alternative Still, wood building has lower primary energy balance than concrete alternative Wood building has lower carbon balance than concrete alternative, even if post-use carbonation is accounted System-wide and life cycle perspectives are required to evaluate implications of energy standards and measures Full energy chains, from natural resources to final energy service Energy demand and supply sides, and their interaction

42 Conclusions Energy savings due to thermal mass is small and varies with the climate and energy efficiency levels of buildings Concrete building has slightly lower space heating demand than wood alternative Still, wood building has lower primary energy balance than concrete alternative Wood building has lower carbon balance than concrete alternative, even if post-use carbonation is accounted System-wide and life cycle perspectives are required to evaluate implications of energy standards and measures Wood-frame passive house with cogeneration-based district heating gives low life cycle primary energy use

43 Thank you for your attention

44 Conclusions (II) The importance of the other life cycle phases increase as buildings are built to improved levels of energy efficiency Material choice matters and becomes more important as buildings are built to improved levels of energy efficiency Electric heated passive house does not achieve lower primary energy use than district heated conventional house