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Primary energy efficiency and CO2 mitigation in residential buildings
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In order to control climate change it is important to limit the atmosphericconcentration of carbon dioxide (CO2). Increased energy efficiency, as well as ashift from fossil fuels to renewable resources can reduce net CO2 emission. Theenergy required for constructing and operating buildings is significant in manycountries, and it is thus important to design energy efficient buildings and energysupply systems.Improvements in existing buildings are needed in order to achieve short-termemission reductions. The Swedish building stock expanded greatly during the1960s and 1970s. The energy efficiency of these houses was often quite low, andmany of them were built with resistance heating. In this thesis increased energyefficiency in such buildings is studied, as well as conversions from resistanceheating to other heating systems, and various technologies and fuels for theproduction of electricity and heat. The effects of these measures are analysed withrespect to primary energy use, CO2 emission and societal cost. The studies wereperformed using process-based systems analysis in a life-cycle perspective. Thesystem boundaries include energy chains from the natural resources to the usefulelectricity and heat in the houses. The results show that the choice of heatingsystem in the house has a greater effect on the primary energy use than measureson both the house envelope and the energy supply chains. District heating basedon cogeneration of heat and electricity and bedrock heat pumps were found to beenergy-efficient systems. The net emission of CO2 is dependent on the fuel and theCO2 emissions from these systems are comparable to those from a wood pelletboiler, if biomass-based supply chains are used. Conversion from resistanceheating to any of the other heating systems studied is also profitable from a societaleconomic perspective.The decision to implement energy-efficiency measures or install a new heatingsystem in a detached house is taken by the house owner. In order for successfulimplementation the alternatives must either be sufficiently attractive or incentivesor policy instruments that affects this large, inhomogeneous group must beimplemented. In this thesis, the house owners’ economic situation when changingthe heating system and implementing energy-efficiency measures on the buildingenvelope is analysed. The economic analysis includes current Swedish policyinstruments, such as an investment subsidy for heating system conversion, anincome tax deduction for replacing windows, levying a consumer electricity tax

and increasing real estate tax. House owners’ perceptions of different heatingsystems are analysed through the results of comprehensive questionnaires. Societaleconomy, private economy and individuals’ perceptions are compared. Theconversion subsidy provides some incentive to house owners to act according tothe national energy policy, as does the electricity tax, which has a significantinfluence on consumer costs. The use of economic instruments seems efficient inpromoting systems in line with environmental goals since environmental factorsare ranked much lower by the home owners. However, the effect on the annualcost of most of the policy instruments studied is smaller than the price variationsbetween different energy suppliers. Energy suppliers thus have considerableopportunity to influence house owners.To achieve long-term changes in the building sector new houses should beconstructed with as low primary energy use and emission as possible, seen overtheir entire life cycle. The primary energy use is analysed for both the productionand operational phase of several types of residential buildings. When the demandfor operational primary energy decreases, due to a high energy standard orenergy-efficient supply, the relative importance of the energy required forproduction will increase. The amount of primary energy required for theproduction of a new low-energy building is significant compared with the primaryenergy required for space heating. One way of reducing both primary energy useand CO2 emission in the production phase is to use constructions with woodframes instead of concrete.The energy supply system is nevertheless still important also for low energybuildings. A new house built to passive standard, heated with fossil-fuel-basedresistance heating gives rise to higher primary energy use and CO2 emission than aconventional detached house from the 1970s that is heated with an energy-efficientbiomass-based heating system. The results thus indicate that wood-framed houseswith a high energy standard, together with efficient energy supply systems, couldbe an option for sustainable residential construction.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2008. , p. 89
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 58
National Category
Other Environmental Engineering
Identifiers
URN: urn:nbn:se:miun:diva-7865ISBN: 978-91-86073-04-6 (print)OAI: oai:DiVA.org:miun-7865DiVA, id: diva2:132717
Public defence
(English)
Available from: 2009-02-02 Created: 2008-12-29 Last updated: 2009-02-13Bibliographically approved
List of papers
1. Energy conservation and conversion of electrical heating systems in detached houses
Open this publication in new window or tab >>Energy conservation and conversion of electrical heating systems in detached houses
2007 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 39, no 6, p. 717-726Article in journal (Refereed) Published
Abstract [en]

In this study, a Swedish house built in 1974, heated with resistance heaters was analysed. Different options for changing the heating system and electricity production were compared for this type of detached house, assuming coal-based electricity production as a reference. Changes in the fuel used, the electricity production technology, the end-use heating technology and the heat demand were analysed. The aim was to show how these different parts of the energy system interact and to evaluate the cost-effectiveness of reducing CO2 emission and primary energy use by different combinations of changes. The results showed that the CO2 emission and primary energy use could be reduced by 95 and 70%, respectively, without increased heating costs in a national economic perspective. The choice of end-use heating system had a greater influence than the energy conservation measures on the parameters studied. The energy conservation measures were less cost-effective in combination with the more energy-efficient heating systems, although the fact that they reduced the heat demand, and thus also the investment cost of the new heating system, was taken into account.

Keywords
heating system, energy eficiency, CO2 emission, energy system, fuel, conversion technology
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-3667 (URN)10.1016/j.enbuild.2006.06.014 (DOI)000246315600011 ()2-s2.0-34047116331 (Scopus ID)3778 (Local ID)3778 (Archive number)3778 (OAI)
Note

VR-Economics

Available from: 2008-09-30 Created: 2009-11-02 Last updated: 2017-12-12Bibliographically approved
2. Energy efficiency measures and conversion of fossil fuel boiler systems in a detached house
Open this publication in new window or tab >>Energy efficiency measures and conversion of fossil fuel boiler systems in a detached house
2010 (English)In: Energy Efficiency, ISSN 1570-646X, E-ISSN 1570-6478, Vol. 3, no 3, p. 223-236Article in journal (Refereed) Published
Abstract [en]

There is a large potential to reduce primary energy use and CO2 emissions from the Swedish building stock. Here detached houses heated by oil, natural gas or electric boilers were assessed. CO2 emissions, primary energy use and heating costs were evaluated before and after implementing house envelope measures, conversions to more efficient heating systems and changes to biomass fuel use. The study included full energy chains, from natural resources to usable heat in the houses. The aim was to evaluate the societal economic cost effectiveness of reducing CO2 emission and primary energy use by different combinations of changes. The results demonstrated that for a house using an electric boiler, a conversion to a heat pump combined with house envelope measures could be cost efficient from a societal economic perspective. If the electricity was based on biomass, the primary energy use was at the same time reduced by 70% and the CO2 emission by 97%. Large emission reductions were also seen for conversions from oil and gas boilers to a biomass-based system. However, for these conversions the heating cost increased, leading to a mitigation cost of around €50/tonne C avoided. The price of oil and natural gas greatly influenced the competitiveness of the alternatives. House envelope measures were more cost-effective for houses with electric boilers as the cost of energy for this system is high. The results are specific to a Swedish context, but also give an indication of the potential in other regions, such as northern European and large parts of North America, which have both a cold climate and a widespread use of domestic boilers.

Keywords
CO2, mitigation cost, energy conservation, biomass, boiler, residential, electricity
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-7863 (URN)10.1007/s12053-009-9062-x (DOI)000293067400004 ()2-s2.0-77955052439 (Scopus ID)
Available from: 2008-12-29 Created: 2008-12-29 Last updated: 2017-12-14Bibliographically approved
3. District heating and energy efficiency in detached houses of differing size and construction
Open this publication in new window or tab >>District heating and energy efficiency in detached houses of differing size and construction
2009 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 86, no 2, p. 126-134Article in journal (Refereed) Published
Abstract [en]

House envelope measures and conversion of heating systems can reduce primary energy use and CO2 emission in the existing Swedish building stock. We analysed how the size and construction of electrically heated detached houses affect the potential for such measures and the potential for cogenerated district heating. Our starting point was two typical houses built in the 1970s. We altered the floor plans to obtain 6 houses, with heated floor space ranging between 100 and 306 m2. One of the houses was also analysed for three energy standards with differing heat loss rates. CO2 emission, primary energy use and heating cost were estimated after implementing house envelope measures, conversions to other heating systems and changes in the generation of district heat and electricity. The study accounted for primary energy, including energy chains from natural resources to useful heat in the houses. We showed that conversion to district heating based on biomass, together with house envelope measures, reduced the primary energy use by 88% and the CO2 emission by 96%, while reducing the annual societal cost by 7%. The choice of end-use heating system was decisive for the primary energy use, with district heating being the most efficient. Neither house size nor energy standard did significantly change the ranking of the heating systems, either from a primary energy or an economic viewpoint, but did affect the extent of the annual cost reduction after implementing the measures.

Keywords
supply system, residential, house envelope
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-6887 (URN)10.1016/j.apenergy.2008.03.012 (DOI)000260269000002 ()2-s2.0-52149097143 (Scopus ID)6071 (Local ID)6071 (Archive number)6071 (OAI)
Note

VR-Economics

Available from: 2008-11-13 Created: 2008-11-03 Last updated: 2017-10-09Bibliographically approved
4. A systems perspective on heat pumps and district heating for energy efficiency in the residential sector
Open this publication in new window or tab >>A systems perspective on heat pumps and district heating for energy efficiency in the residential sector
2005 (English)In: Proceedings of Heat Transfer in Components and Systems for Sustainable Energy Technologies, 2005, p. 429-434Conference paper, Published paper (Refereed)
Keywords
heat pump, district heating CO2 mitigation, resistance heaters, energy efficiency
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-2822 (URN)2987 (Local ID)2987 (Archive number)2987 (OAI)
Available from: 2008-11-18 Created: 2008-11-18Bibliographically approved
5. Perspectives on implementing energy efficiency in existing Swedish detached houses
Open this publication in new window or tab >>Perspectives on implementing energy efficiency in existing Swedish detached houses
2008 (English)In: Energy Policy, ISSN 0301-4215, E-ISSN 1873-6777, Vol. 36, no 1, p. 84-96Article in journal (Refereed) Published
Abstract [en]

In this study, we first analyse energy-efficiency measures in existing electrically heated houses in Sweden from a societal economic perspective. Measures to a house envelopes and to energy supply chains are evaluated through a system analysis approach and we include the external costs of climate change and the effect of different Swedish climatic zones. We find that in a typical house from the 1970s, conversion from electric heating is highly motivated since the mitigation cost of conversion is lower than the estimated external costs of emitted CO2. Both conversions and house envelope measures are more motivated in the northern part of the country, where there is a higher heat demand. A successful implementation of changes requires them to be attractive for consumers to adopt. We therefore secondly analyse the economic conditions for Swedish house owners to implement societal economic cost-efficient measures. We include the economic influence of an investment subsidy for heating system conversion, an income tax deduction for changing windows, customer electricity tax, real estate tax and of the cost of purchased energy from different energy suppliers. Apart from the economics, several other factors affect a house owner's decision to change heating systems. We therefore thirdly analyse house owners' perceptions of different heating supply alternatives based on the results of two comprehensive questionnaires. These different perspectives are combined in a discussion whether the studied policy instruments encourage house owners to implement changes in accordance with the energy-efficiency goals of decision makers. We find that the investment subsidy could be useful to break the lock-in effect of resistance heaters, which house owners seemed to experience. The electricity tax makes heating systems in line with national goals more competitive and efficiency measures to the house envelope more profitable. The reduction of the electricity tax in the northern part of the country has the opposite effect. Also, the increase in real estate tax when implementing energy-efficiency measures gives a contradictory message. The price differences between energy suppliers has a larger impact on the house owners' economic conditions than both subsidies and tax rate changes, and possibly also affect the house owner's attitudes towards various systems.

Keywords
heating system, residential, policy
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-4371 (URN)10.1016/j.enpol.2007.08.021 (DOI)000252301100009 ()2-s2.0-36549063678 (Scopus ID)5265 (Local ID)5265 (Archive number)5265 (OAI)
Note
VR-EconomicsAvailable from: 2008-12-09 Created: 2008-11-19 Last updated: 2017-12-12Bibliographically approved
6. Life cycle primary energy analysis of residential buildings
Open this publication in new window or tab >>Life cycle primary energy analysis of residential buildings
2010 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 42, no 2, p. 210-220Article in journal (Refereed) Published
Abstract [en]

The space heating demand of residential buildings can be decreased by improved insulation, reduced air leakage and by heat recovery from ventilation air. However, these measures result in an increased use of materials. As the energy for building operation decreases, the relative importance of the energy used in the production phase increases and influences optimization aimed at minimizing the Life cycle energy use. The Life cycle primary energy use of buildings also depends on the energy supply systems. In this work we analyse primary energy use and CO2 emission for the production and operation of conventional and low-energy residential buildings. Different types of energy supply systems are included in the analysis. We show that for a conventional and a low-energy building the primary energy use for production can be up to 45% and 60%, respectively, of the total, depending on the energy supply system, and with larger variations for conventional buildings. The primary energy used and the CO2 emission resulting from production are lower for wood-framed constructions than for concrete-framed constructions. The primary energy use and the CO2 emission depend strongly on the energy supply, for both conventional and low-energy buildings. For example, a single-family house from the 1970s heated with biomass-based district heating with cogeneration has 70% lower operational primary energy use than if heated with fuel-based electricity. The specific primary energy use with district heating was 40% lower than that of an electrically heated passive row house.

Keywords
Residential, passive, low-energy, district heating, cogeneration, supply, electricity
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-7864 (URN)10.1016/j.enbuild.2009.08.017 (DOI)000273837400008 ()2-s2.0-71649086165 (Scopus ID)
Available from: 2008-12-29 Created: 2008-12-29 Last updated: 2017-12-14Bibliographically approved

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