Life Cycle Primary Energy Use Research Articles

Primary Energy and Carbon Impacts of Structural Frames with Equivalent Design Criteria: Influence of Different Materials and Levels of Prefabrication

This study aims to analyze the life-cycle primary energy and climate impacts of structural frames, paying particular attention to the design and prefabrication of different structural materials. The study considers an existing single-story office building with a composite concrete–steel structure and compares it with two functionally equivalent structures, i.e., a conventional reinforced concrete structure and a conventional steel structure. The existing building is located in San Felice sul Panaro, Italy. This study integrates dynamic structural analysis and life-cycle assessment (LCA). The study finds that the use of different materials can reduce the life-cycle primary energy use and CO2-eq emissions by up to 12%. Furthermore, the benefits derived from the recovery and recycling of materials can reduce the primary energy use and CO2-eq emissions by up to 47% and 36%, respectively. The prefabrication of structural elements can also reduce the primary energy use and CO2-eq emissions in the construction stage. A sensitivity analysis considers changes in the electricity supply system and shows that the primary energy and CO2-eq emissions due to prefabrication decrease when assuming marginal electricity based on renewable energies. This analysis supports the development of sustainable structural design to meet the standards concerning the whole-life-cycle carbon emissions of buildings.

Implications of different modelling choices in primary energy and carbon emission analysis of buildings

In recent years, several comparative life cycle analyses have shown that increasing the use of wood in buildings can reduce the life cycle primary energy use and carbon emission of buildings. This study reviews the life cycle inventory methodology of primary energy use and carbon emissions, based on ecoinvent database, considering different modelling choices for (i) materials heating values; (ii) biogenic carbon; (iii) calcination and carbonation processes; (iv) electricity production scenarios; (v) impact distribution of multi-functional processes; (vi) post-use benefits. The analysis relates to the standards while the implication of different modelling choice is shown by comparing the primary energy use and carbon emission in the production and end-of-life stages of a multi-storey residential building with concrete, cross laminated timber and modular timber structures, respectively. The results highlight the displacement between different modelling choices in terms of primary energy use and carbon emissions. Such modelling options especially influence the LCA results in the product stage and beyond the end of life stage, and especially wood- and/or cement-based materials.

Lifecycle Impacts of Structural Frame Materials for Multi-storey Building Systems

In this study the lifecycle primary energy and greenhouse gas (GHG) implications of multi-storeybuilding versions with different structural frame materials as well as construction systems are analysedconsidering flows from the production, operation and end-of-life phases and the full natural resourceschains. The analysed building versions include conventional and modern construction systems withlight-frame timber, reinforced concrete-frame, massive timber frame, beam-and-column timber frameor modular timber frame structural systems and are designed to the energy efficiency level of thepassive house criteria. The results show that the lifecycle primary energy use and GHG emissions forthe reinforced concrete building system are higher than those for the timber-based building systems,due primarily to the lower production primary energy use and GHG emissions as well as greater amountof biomass residues when using wood-based materials. The operation primary energy use and GHGemission for the buildings are lower when heated with cogenerated district heating compared to whenheated with electric-based heat pump, showing the significance of heat supply choice. The findingsemphasize the importance of structural frame material choice and system-wide lifecycle perspective inreducing primary energy use and GHG emissions in the built environment.

Effect of different frame materials on the primary energy use of a multi storey residential building in a life cycle perspective

Primary energy implications over the life cycle of a multi storey residential building with different building systems are explored here. The main structural materials of the buildings include precast concrete, cross laminated timber (CLT) and prefabricated timber modules (modular). The analysis covers energy and material flows from different life cycle phases of the building versions, designed to meet the energy performance of the Swedish building code (BBR) and passive house criteria. The CLT and modular buildings were found to result in lower production primary energy use and higher biomass residues compared to the concrete alternative. The heating value of the recoverable biomass residues from the production phase of the CLT building is significantly larger than the primary energy required for its production. Primary energy use for production and construction constitutes 20–30% and 36–47% of the total primary energy use for production, construction, space heating, ventilation and demolition for the BBR and passive buildings, respectively. Space heating with combined heat and power (CHP) and ventilation electricity for the BBR and passive building versions form 70–79% and 52–63%, respectively, of the total primary energy use for production, construction, space heating, ventilation and demolition for a lifespan of 80 years. The CLT and modular buildings give 20–37% and 9–17% lower total life cycle primary energy use, respectively, than the concrete alternative when space heating is from CHP.

Comparative Life-Cycle Analysis of Building Materials for the Thermal Upgrade of an Existing Building

The existing building stock is estimated to need major renovations in the near future. At the same time, the EU energy-efficiency strategy entails upgrading the energy performance of renovated buildings to meet the nearly-zero energy standard. To upgrade existing buildings, two main groups of measures can be adopted: thermally-improved building envelope and energy-efficient technical devices. The first measure usually involves additional building materials for thermal insulation and new building cladding, as well as new windows and doors. A number of commercially-available materials can be used to renovate thermal building envelopes. This study compares the life-cycle primary energy use and CO2 emission when renovating an existing building using different materials, commonly used in renovated buildings. A Swedish building constructed in 1972 is used as a case-study building. The building’s envelope is assumed to be renovated to meet the Swedish passive house standard. The entire life cycle of the building envelope renovation is taken into account. The results show that the selection of building materials can significantly reduce the production primary energy and associated CO2 emissions by up to 62% and 77%, respectively. The results suggest that a careful material choice can significantly contribute to reduce primary energy use and CO2 emissions associated with energy renovation of buildings, especially when renewable-based materials are used.

Effect of Energy Efficiency Requirements for Residential Buildings in Sweden on Lifecycle Primary Energy Use

In this study we analyze the lifecycle primary energy use of a wood-frame apartment building designed to meet the current Swedish building code or passive house criteria, and heated with district heat or bedrock heat pump. We employ a lifecycle perspective methodology and determine the production, operation and end-of-life primary energy use of the buildings. We find that the passive house requirement strongly reduces the final energy use for heating compared to the current Swedish building code. However, the primary energy use is largely determined by the energy supply system, which is generally outside the mandate of the building standards. Overall, buildings with district heating have lower life-cycle primary energy use than alternatives heated with heat pump. The primary energy for production is small relative to that for operation, but it is more significant as the energy-efficiency standard of building improves and when efficient energy supply is used. Our results show the importance of a system-wide lifecycle perspective in reducing primary energy use in the built environment. A life cycle primary energy perspective is needed to minimize overall primary energy use, and future building energy-efficiency standards may reflect the full energy use during a building's life cycle. This could include primary energy implications for production, operation and end-of-life of buildings.

Life cycle primary energy use and carbon footprint of wood-frame conventional and passive houses with biomass-based energy supply

In this study the primary energy use and carbon footprint over the life cycle of a wood-frame apartment building designed either conventionally or to the passive house standard are analyzed. Scenarios where the building is heated with electric resistance heaters, bedrock heat pump or cogeneration-based district heat, all with biomass-based energy supply, are compared. The analysis covers all life cycle phases of the buildings, including extraction of raw materials, processing of raw materials into building materials, fabrication and assembly of materials into a ready building, operation and use of the buildings, and the demolition of the buildings and the post-use management of the building materials. The primary energy analysis encompasses the entire energy chains from the extraction of natural resources to the delivered energy services. The carbon footprint accounting includes fossil fuel emissions, cement process reaction emissions, potential avoided fossil fuel emissions due to biomass residues substitution and end-of-life benefit of post-use materials. The results show that the operation of the building accounts for the largest share of life cycle primary energy use. The passive house design reduces the primary energy use and CO2 emission for heating, and the significance of this reduction depends on the type of heating and energy supply systems. The choice of end-use heating system strongly influences the life cycle impacts. A biomass-based system with cogeneration of district heat and electricity gives low primary energy use and low carbon footprint, even with a conventional design. The amount of biomass residues from the wood products chain is large and can be used to substitute fossil fuels. This significantly reduces the net carbon footprint for both the conventional and passive house designs. This study shows the importance of adopting a life cycle perspective involving production, construction, operation, end-of-life, and energy supply when evaluating the primary energy use and climatic impacts of both passive and conventional buildings.

Lifecycle primary energy analysis of conventional and passive houses

In this study we analyse the primary energy implications of thermal envelope designs and construction systems, for a 4-storey apartment building, including the full lifecycle phases and the entire energy chains. We maintain the architectural design of the reference building, and alter the thermal properties of the envelope components and include heat recovery of ventilation air to achieve buildings with thermal properties similar to three existing passive houses in Sweden. We also vary the building frame material from the reference wood case to reinforced concrete, and vary the heat supply system between district heating and electric resistance heating. We follow the lifecycle of the buildings and analyse and compare their lifecycle primary energy use, considering the production, operation and end-of-life energy uses. The results show that the lifecycle primary energy use of a passive house building is substantially lower when it is heated with district heating instead of electricity. A passive house with...

Building energy-efficiency standards in a life cycle primary energy perspective

In this study we analyze the life cycle primary energy use of a wood-frame apartment building designed to meet the current Swedish building code, the Swedish building code of 1994 or the passive house standard, and heated with district heat or electric resistance heating. The analysis includes the primary energy use during the production, operation and end-of-life phases. We find that an electric heated building built to the current building code has greater life cycle primary energy use relative to a district heated building, although the standard for electric heating is more stringent. Also, the primary energy use for an electric heated building constructed to meet the passive house standard is substantially higher than for a district heated building built to the Swedish building code of 1994. The primary energy for material production constitutes 5% of the primary energy for production and space heating and ventilation of an electric heated building built to meet the 1994 code. The share of production energy increases as the energy-efficiency standard of the building improves and when efficient energy supply is used, and reaches 30% for a district heated passive house. This study shows the significance of a life cycle primary energy perspective and the choice of heating system in reducing energy use in the built environment.

Life cycle assessment of carbon fiber-reinforced polymer composites

The use of carbon fiber-reinforced polymer matrix composites is gaining momentum with the pressure to lightweight vehicles; however energy intensity and cost remain major barriers to the wide-scale adoption of this material for automotive applications. This study determines the relative life cycle benefits of two precursor types (conventional textile-type acrylic fibers and renewable-based lignin), part manufacturing technologies (conventional SMC and P4), and a fiber recycling technology. A representative automotive part, i.e., a 30.8-kg steel floor pan having a 17% weight reduction potential with stringent crash performance requirements, has been considered for the life cycle energy and emissions analysis. Four scenarios—combinations of the precursor types and manufacturing technologies—are compared to the stamped steel baseline part. The analysis finds the lignin-based part made through P4 technology to offer the greatest life cycle energy and CO2 emissions benefits. Carbon fiber production is estimated to be about 14 times more energy-intensive than conventional steel production; however, life cycle primary energy use is estimated to be quite similar to the conventional part, i.e., 18,500 MJ/part, especially when considering the uncertainty in LCI data that exist from using numerous sources in the literature. The sensitivity analysis concludes that with a 20% reduction in energy use in the conversion of lignin to carbon fiber and no energy use incurred in lignin production since lignin is a by-product of ethanol and paper production, a 30% reduction in life cycle energy use could be obtained. A similar level of life cycle energy savings could also be obtained with a higher part weight reduction potential of 43%.

Life cycle primary energy use and carbon emission of an eight-storey wood-framed apartment building

In this study the life cycle primary energy use and carbon dioxide (CO 2) emission of an eight-storey wood-framed apartment building are analyzed. All life cycle phases are included, including acquisition and processing of materials, on-site construction, building operation, demolition and materials disposal. The calculated primary energy use includes the entire energy system chains, and carbon flows are tracked including fossil fuel emissions, process emissions, carbon stocks in building materials, and avoided fossil emissions due to biofuel substitution. The results show that building operation uses the largest share of life cycle energy use, becoming increasingly dominant as the life span of the building increases. The type of heating system strongly influences the primary energy use and CO 2 emission; a biomass-based system with cogeneration of district heat and electricity achieves low primary energy use and very low CO 2 emissions. Using biomass residues from the wood products chain to substitute for fossil fuels significantly reduces net CO 2 emission. Excluding household tap water and electricity, a negative life cycle net CO 2 emission can be achieved due to the wood-based construction materials and biomass-based energy supply system. This study shows the importance of using a life cycle perspective when evaluating primary energy and climatic impacts of buildings.

Life cycle primary energy analysis of residential buildings

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 CO 2 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 CO 2 emission resulting from production are lower for wood-framed constructions than for concrete-framed constructions. The primary energy use and the CO 2 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.

Baseline model of a centralized pv electrolytic hydrogen system

This study performs an economic and environmental analysis of a centralized pv electrolytic hydrogen system scaled to supply H 2 to one million light duty vehicles and light commercial trucks. Annual H 2 production is 217-million kg. The size of the pv electrolysis plant to produce this quantity of H 2 is a 5.12-GW dc-in electrolysis plant and a 6.0-GW p pv power plant. The land area of the pv electrolysis plant is 260 km 2. The total capital costs of the pv electrolysis H 2 system is $12.4 billion. The levelized H 2 pump price estimate is $6.48/kg. The life cycle primary energy use is 36 MJ/kg of H 2 consumption, and life cycle CO 2 equivalent emissions are 2.6 kg/kg of H 2 consumption. The replacement of conventional gasoline powered vehicles with H 2 powered vehicles reduces primary energy use and CO 2 emissions by 90%.