ESTABLISHING THE LIFE CYCLE PRIMARY ENERGY BALANCE FOR POWERHOUSE KJØRBO

Transcription

1 Copenhagen, August Passivhus Norden Sustainable Cities and Buildings Brings practitioners and researchers together ESTABLISHING THE LIFE CYCLE PRIMARY ENERGY BALANCE FOR POWERHOUSE KJØRBO Henning Fjeldheim 1,*, Torhildur Kristjansdottir 2,3 and Kari Sørnes 3 1 Skanska Norge, Norway 2 The Norwegian University of Science and Technology, Norway 3 Sintef, Norway * Corresponding henning.fjeldheim@skanska.no SUMMARY Powerhouse Kjørbo is a refurbished commercial building in Sandvika, Norway which was completed in The goal of the project was to make an energy positive building by compensating the energy demand for the production of materials and components, the construction installation process, energy for operation and end-of-life treatment with onsite production of renewable energy. LCA-methodology was used to establish the primary energy balance and was used actively throughout the interdisciplinary and iterative design process to ensure decision making based on a lifecycle perspective. The results show a net positive primary energy balance over the lifecycle for Powerhouse Kjørbo. This shows a huge potential for developing the existing building stock to become, not only much more energy efficient, but also energy positive. Key words: Zero energy building, nzeb, ZEB, LCA, energy positive, embodied energy, greenhouse gas emissions INTRODUCTION The background for this work was the establishment of the Powerhouse alliance and their goal to create buildings in though Nordic climates that have a positive lifecycle primary energy balance. The Powerhouse alliance consists of the real estate company Entra, the construction company Skanska, Snøhetta architects, the environmental non-governmental organization ZERO, the aluminium company Hydro, the aluminium profile company Sapa and the consulting firm Asplan Viak. Powerhouse buildings have to comply with an ambitious set of criteria regarding the design and production of energy. In general the term Powerhouse is similar to a life cycle zero energy building as introduced in Hernandez and Kenny (2010), Voss and Musall (2011), Berggren et al. (2013) and Cellura et al. (2014). Even though the life cycle zero energy balance has been introduced, there are to the authors knowledge no previous studies of life cycle zero primary energy office buildings in the Nordic climate. Also, there is no scientific consensus on how to calculate a life cycle primary energy balance for a zero energy building. Powerhouse Kjørbo is a pilot building within the Research Centre on Zero Emission Buildings (ZEB). The balance indicator used for Zero Emission Buildings is measured in carbon dioxide equivalents, thus parallel calculations were performed also for this metric. The building analysed and descried in this paper is the refurbishment of two office building blocks connected by a common stairway. The building is located in Sandvika, Norway and was originally finished in This is the first Powerhouse to be built and was completed in This paper Page 1/9

2 presents the efforts made and calculation methods applied for establishing the lifecycle primary energy balance for the building. The objective of this paper is to present the experiences that were made from this pilot building with focus on documenting the efforts for reducing the environmental loads as well as the calculations method applied. Furthermore the objective is to establish the initial calculation scenarios for which future performance studies can be compared to. The Powerhouse Definition The main definition of a Powerhouse is a building that shall produce at least the same amount of energy from on-site renewables as the energy used for production and transport of materials, the construction installation process, maintenance and replacement, demolition and operation (excluding plug-loads), demolition and end-of-life treatment. In addition, the exported energy shall in average not be of less quality than the imported energy. This implies that produced and exported electricity can offset corresponding amount of imported energy for both electricity and thermal purposes, while produced and exported thermal energy cannot offset imported electricity. The building shall also as a minimum fulfil all the requirements of the Passive House standard. Design process To meet the requirements of the definition, the work on the energy balance was started at the very beginning of the design process. The key to success was the multidisciplinary design process involving all participants and the very clear common goal. Experts in LCA defined the criteria for the calculation method for the materials, transportation and construction. The design team completed an iterative process of establishing alternative solutions, creating inventories and assessing these according to the defined method. The results were used as input to further design of the building. Energy designers worked with the design team to bring the energy demand in operation to a minimum. Case description Powerhouse Kjørbo is two office buildings of 3 or 4 floors respectively connected by a shared stairway. The building was originally completed in The heated useful floor area is about m 2. Energy efficiency measures and materials with low embodied energy have been crucial for obtaining the energy goal. A very efficient ventilation concept has been developed. This has to a great extent reduced the over all energy demand for operation. Sandvika is located at approximately 60 degrees north latitude. The annual mean outdoor temperature at the location is about 5,9 C and the annual mean horizontal irradiation is about 110 W/m² (955 kwh/m²a). The design occupancy schedule is 12 hours a day, 5 days a week, 52 weeks a year. The energy concept is based on the principle of first reducing the lifecycle primary energy demand, including both operational and embodied energy. Secondly the remaining energy demand is balanced by locally produced renewable energy. Due to the fact that the energy need for ventilation normally comprises a large share of the energy budget in office buildings, there has particularly been a high focus on reducing the energy need for ventilation for Powerhouse Kjørbo. This includes both using low emitting materials to reduce the ventilation demand, demand control, displacement ventilation, low pressure design to minimize fan energy, and highly efficient heat recovery. During normal operation, the average ventilation air volume is about 3 m3/m2h wintertime, and about 6 m3/m2h summertime (on warm days). Furthermore the very energy efficient building envelope summarized in Table 1 combined with daylight utilization, a lighting control system suiting the different user needs, energy efficient fixtures and a ground source heat pump reduces the electricity demand for operation. Page 2/9

3 Table 1 Thermal properties of the building envelope after refurbishment Properties After renovation U-value external walls U-value roof U-value floor on ground U-value windows and doors 0,13 W/m²K 0,08 W/m²K 0,14 W/m²K 0,80 W/m² Normalized thermal bridge value, (per m² heated floor area) Air tightness, air changes per hour (at 50 Pa) 0,24 0,02 W/m²K To reduce the embodied energy of the materials and components all existing reinforcing steel and concrete constructions is utilized in the refurbished building. In addition, the existing glass facade panels are reused as interior office fronts in the refurbished buildings. The new façade cladding is made of charred wood, with long lifetime and marginal need for maintenance. The photovoltaic modules generating locally produced renewable energy have been selected based on an evaluation of the overall balance between embodied energy and efficiency. METHOD This chapter describes the method that was applied to establish the balance for primary energy and greenhouse gas (GHG) emissions for Powerhouse Kjørbo. Life cycle approach According to the definition of Powerhouse, all life cycles of the building should be accounted for when establishing the primary energy balance. Thus, the method for the calculations is based on the method presented in the standard for life cycle analysis of buildings, EN 15978:2011 (CEN, 2011). Our analysis included the environmental impact categories global warming potential based on the IPCC 100 year perspective (Solomon et al., 2007) and primary energy use, based on the cumulative energy demand method (Frischknecht et al., 2007). The standard terminology used in the ecoinvent report for the cumulative energy is as follows: "The cumulative energy demand (CED) states the entire demand valued as primary energy, which arises in connection with the production, use and disposal of an economic good (product or service) or which may be attributed respectively to it in a causal relation." (Althaus et al., 2010) Biogenic CO 2 for the timber used in the construction is not accounted for in the analysis. Absorption of CO 2 by carbonatisation of the concrete is also not considered. Furthermore the production of energy from the incineration of wood in C3 is not included. The functional unit of the analysis is one square meter (1 m 2 ) of the refurbished heated floor area of 5180 m 2 over an estimated service lifetime of 60 years. From the standard EN15978:2011, the following life cycle stages are included: the product phase Raw material supply (A1), Transport (A2), Manufacturing (A3) the construction phase (Transport to the construction site (A4), construction and installations (A5) process, the use phase, replacement of components (B4), operational energy use and production of energy (B6) and the entire end of life phase (C1-C4). Inventory analysis The following sections describe the inventory gathered for the different life cycle phases and scenarios used for the calculation. The structure of the inventory analysis for the construction materials is according to the Norwegian standard, Table of building elements: NS 3451:2009 (Standard Norway, 2009). The product phase The material inventory analysis included the following construction parts based on the inventory suggested by Wittstock et al. (2011): Foundation and load bearing structure, basement walls, exterior walls, structural vertical elements, surface coating, floor structure and slabs, coverings and tightness Page 3/9

4 elements, roof framework, partitioning walls, internal doors, suspended sealing, windows and joinery work, exterior doors, floors, painting and wallpaper coverings, heating and ventilations systems, electricity wiring (high and low voltage), communication and network, elevator and photovoltaic systems with inverters. The amounts of materials have been gathered by using material takeoffs from the Revit BIM (Building information model) for the construction materials and MagiCad for the ventilation system. During the construction phase quantities have been updated if changes were made to the design. The primary energy and GHG emissions are based on data gathered and analysed directly from producers, type III environmental product declarations (EPDs), ecoinvent database v2.2 (Swiss Center for Life Cycle Inventories, 2010) and scientific articles. The analysis by (Fthenakis, 2012 ) provided inputs into the embodied energy in the PV modules. The construction installation process For the design phase an estimate was made for the energy demand in the construction installation process based on registered data from previous construction projects and adjusted based on known differences. During the construction phase the estimates were updated with actual registered transport distances as well as electricity and fuel consumption. Replacement scenarios The replacement scenarios were based on service lifetimes available from the product category rules (PCR) from the relevant building material type when available, like presented in EPD-Norway (2007) for insulations materials. When PCR where not available, guidelines for service lifetime of building components, SINTEF Building and Infrastructure's guidelines Byggforskserien was used.the calculations equations presented in EN15978 (CEN, 2011) were applied for the number of replacements necessary. In general the replaced components are based on the same inventory as the initial inventory, assuming no change in technical performance or production. The service lifetime for the PV modules was based on Fthenakis (2011). Scenario for technical developments for PV modules It was assumed that the embodied energy and emissions from the production of the PV modules will be reduced with 50% in 30 years. This is of course uncertain, however analysis presented by Frischknecht et al. (2015), Bergesen et al. (2014) and Mann et al. (2014) support that there is a continuous improvement in the in the production of PV modules. The improvements are mainly connected to increased material efficiency, improved production processes and the transition to increased use of renewable energy in the production process. It is also assumed that the efficiency of the PV modules installed after 30 years will have an increased efficiency by about 40 % from 20 % to 28%. This is based on the average historic development of Single Junction GaAs - Single crystal cells and Thin film crystal cells recorded by Wilson (2014) (NREL 2014). This is also in accordance to the optimistic scenario presented in (Frischknecht, 2015). Operational energy demand The simulations of operational energy demand are done using the dynamic energy simulation tool SIMIEN (Programbyggerne 2012) and are in accordance with the Norwegian Standard NS 3031:2007+A1:2011 (Standard Norway 2007). However, energy demand for lighting and equipment is in accordance with expected real use, but for a normalized operation period. Development of grid based electricity mix The primary energy factor for grid based European electricity mix has been assumed to decrease linearly from 3,43 in 2010 to 2,38 (kwh primary energy/ kwh energy consumed) in 2050 according to Kindem Thyholt et. al. (2015). This results in an average primary energy factor of 2,55 for the service life of Powerhouse Kjørbo. This scenario is in accordance with the guidelines from the ZEB centre and is based on the technological development scenario to meet the 2-degree target. Correspondingly the CO 2 -factor for the electricity mix has been assumed to decrease linearly from 0,53 kg CO 2 eq./kwh in 2010 to 0 g CO 2 eq./kwh in 2054 with an average of 0,17 kg CO 2 eq./kwh for the service life of Powerhouse Kjørbo. According to guidelines for the Norwegian EPD foundation, EPD-Norge, prior to the 12 th of June 2014 EPDs for products in Norway should be based on the nordic grid electricity mix including imports for the last three documented years (The Norwegian EPD Foundation 2012). EPDs providing static information have been used in the calculations. Thus a nordic grid electricity mix has been applied for the calculation of embodied energy to maintain coherent system boundaries for the calculations. Page 4/9

5 On-site energy production The onsite production of renewable energy from photovoltaic modules was calculated using the program PVsyst and the NASA-SSE (Power 2013) database as the source for irradiation data. Deconstruction In lack of good data, the deconstruction phase is assumed to be equal to the construction installation process. Less heating will be needed as the duration will be shorter, but deconstruction of concrete structure will require more fuel for machinery. These differences are assumed to balance each other. End-of-life treatment The scenarios for the end-of-life treatment of the various materials are based on the average distribution of recycling, incineration and landfill of concrete, aluminium, glass, gypsum, insulation, plastic, steel, wood, textile, bitumen and generic waste between 2006 and 2011 (Statistisk Sentralbyrå 2013). The transport of waste from site to treatment facility and disposal were based on Erlandsen (2009) and supplemented with generic distances from Wittstock et. al. (2011) where necessary due to lack of data. Limitations and simplifications As the Powerhouse Kjørbo is a refurbishment project, there were possibilities to reuse a selection of the building materials on site. As an example: The loadbearing structure from the previous building has been adjusted and reused in the new building. According to section 7.3 in EN15978:2011, environmental loads from components shall be allocated based on the remaining service life. Analyses concluded that based on the calculation rules of the standard, the impacts of demolishing the old structure and rebuilding it with todays materials would result in a 50% reduced environmental impact. This was decided to be counter intuitive and it was chosen to disregard the environmental loads of the existing structure which is not in line with the standard. This decision was made to encourage reuse of materials and because the reused components were older than 30 years. Transport of materials and components to the site was registered and accounted for. The tonnage for each transport of materials and components is not known and the total tonnage of the building has therefore been evenly distributed over the total number of transports distances. Due to the static information of the EPDs, there is an inconsistency between the primary energy factors and CO 2 factors used for the operational energy demand and the production of materials and components. RESULTS The overall balance for primary energy and GHG emissions are presented in Table 2. The negative sum for primary energy indicates an overall surplus of produced local renewable energy. The positive sum for GHG emissions shows that the ZEB balance related to GHG emissions is not fulfilled. Figure 1 and Figure 2 show the distribution of the embodied energy and GHG emissions in materials and components according to NS 3451:2009 and the major categories of materials respectively. Page 5/9

6 Table 2 The overall balance for primary energy and GHG emissions Life cycle stages Primary energy (kwh primary energy/m 2 year) GHG emissions (kg CO 2 eq/m 2 year) A1-A3 Raw materials supply, Transport and Manufacturing 20,11 3,77 A4 Transport to site 0,11 0,02 A5 Construction and installation on site 2,67 0,23 B4 Replacements 10,34 1,82 B6 Operational Energy Use - Energy demand 58,10 3,89 B6 Operational Energy Use - Energy production -121,80-7,03 C1 Deconstruction 2,67 0,23 C2 Transport 0,27 0,06 C3 Waste treatment processes for reuse, recovery or/ and recycling 0,11 0,02 C4 Disposal 0,47 0,43 Sum -26,96 3,44 Figure 1 Embodied primary energy in materials and components distributed on the major categories of materials Page 6/9

7 Figure 2 Embodied GHG emissions in materials and components distributed on the major categories of materials DISCUSSION The finalized energy balance shows a positive margin for the production of local renewable energy from photovoltaic modules relative to the lifecycle energy demand. It must be pointed out that the primary energy balance presented is based on the energy demand calculated in the design phase and not the resulting energy budget with updated numbers after monitoring and verification of the actual energy demand in operation. However raw data measurements from the first year of operation show that the actual energy consumption is slightly lower than the calculated results from the design process was an especially sunny summer in Oslo giving great solar energy output but should at the same time increase the demand for cooling. The results also interestingly show that materials, transport, construction, deconstruction and end-oflife treatment make up 39 % of the total lifecycle primary energy demand and 63% of the lifecycle GHG emissions of which the production of materials and components make up about 85% in both cases. This shows the increasing importance of addressing these aspects when designing buildings with low energy demand. Efficient resource use, transport logistics, construction and end-of-life treatment should be considered in an integrated way. It is important to keep in mind the exclusion of the existing load carrying system of concrete and the inclusion of the photovoltaic modules in the results when comparing with other calculations as both have significant impact on the overall results. An inclusion of the embodied energy for a load carrying system would or example increase the primary energy demand over the lifecycle by approximately 5%. There are always significant uncertainty issues related to lifecycle counting of primary energy and GHG emissions. Scenarios are set based on probable outcomes, emission factors related to material, energy and transport inputs are based on databases giving average production values and scenarios for waste treatment is made on the basis of todays practice. The method of lifecycle accounting is always developing and the practice for how to account for energy and carbons related to materials such as wood is something that has been a large discussion since the work related to Powerhouse Kjørbo started. In the calculations presented the energy related to energy feedstock and carbon uptake is not taken into account. Low energy efficient and low carbon housing is often associated to new buildings where fewer constraints are given. Having in mind that Powerhouse Kjørbo is a refurbishment project shows the Page 7/9

8 great potential in the existing building stock. There is a huge need for upgrading the standard of buildings already built, both in Norway and internationally. If the renovation processes happens in the right way, the gain is double we are reusing the resources already extracted and are at the same time making an energy efficient building for the future. CONCLUSIONS The primary energy balance presented for the project Powerhouse Kjørbo is net positive. The results show that the energy demand for the production of materials and components, the construction installation process and transport impacts the overall energy demand significantly. This proves the importance of expanding the focus from operational energy demand to considering the whole lifecycle when designing sustainable buildings. ACKNOWLEDGEMENT The Powerhouse Kjørbo project received funding from Enova, a Norwegian public enterprise with the aim to facilitate the transition to a more sustainable consumption and production of energy. The authors gratefully acknowledge the support from the Research Council of Norway and several partners through the Research Centre on Zero Emission Buildings (ZEB) [4] as well as the close cooperation with the Powerhouse alliance partners and the design team to make this project a reality. REFERENCES ALTHAUS, H.-J., BAUER, C., GABOR DOKA, ROBERTO DONES, ROLF FRISCHKNECHT, STEFANIE HELLWEG, SÉBASTIEN HUMBERT, NIELS JUNGBLUTH, THOMAS KÖLLNER, YVES LOERINCIK, MANUELE MARGNI & NEMECEK, T Implementation of Life Cycle Impact Assessment Methods. In: HISCHIER, R. & WEIDEMA, B. (eds.) Data v2.2 (2010). St.Gallen: ecoinvent centre. BERGESEN, J. D., HEATH, G. A., GIBON, T. & SUH, S Thin-Film Photovoltaic Power Generation Offers Decreasing Greenhouse Gas Emissions and Increasing Environmental Cobenefits in the Long Term. Environmental science & technology, 48, BERGGREN, B., HALL, M. & WALL, M LCE analysis of buildings Taking the step towards Net Zero Energy Buildings. Energy and Buildings, 62, CELLURA, M., GUARINO, F., LONGO, S. & MISTRETTA, M Energy life-cycle approach in Net zero energy buildings balance: Operation and embodied energy of an Italian case study. Energy and Buildings, 72, CEN EN 15978: Sustainability of construction works. Assessment of environmental performance of buildings. Calculation method. DOKKA, T. H., SARTORI, I., TYHOLT, M., LIEN, K. & BYSKOV LINDBERG, K A Norwegian zero emission building definition. Passivhus Norden. Gothenburg, Sweden. EPD-NORWAY Product-category rules (PCR) For preparing an environmental declaration (EPD) for Product Group Insulation materials In: NORWEGIAN EPD FOUNDATION (ed.). ERLANDSEN, L. M., System Analysis of Commercial Waste Recovery Options. FRISCHKNECHT, R., ITTEN, R., WYSS, F., BLANC, I., HEATH, G., RAUGEI, M., SINHA, P. & WADE, A Life cycle assessment of future photovoltaic electricity production from residential-scale systems operated in Europe, Subtask 2.0 "LCA", IEA-PVPS Task 12. FRISCHKNECHT, R., JUNGBLUTH, N., ALTHAUS, H.-J., BAUER, C., DOKA, G., DONES, R., HISCHIER, R., HELLWEG, S., HUMBERT, S., KÖLLNER, T., LOERINCIK, Y., MARGNI, M. & NEMECEK, T Implementation of Life Cycle Impact Assessment Methods Data v2.0 (2007) ecoinvent report No. 3. Dübendorf: Swiss Centre for Life Cycle Inventories. FTHENAKIS, V Methodology Guidelines on Life Cycle Assessment of Photovoltaic Electricity: IEA PVPS Task 12.: International Energy Agency. GRAABAK, I. & FEILBERG, N CO 2 emission in different scenarios of electricity generation in Europe. SINTEF Energy Research. HERNANDEZ, P. & KENNY, P From net energy to zero energy buildings: Defining life cycle zero energy buildings (LC-ZEB). Energy and Buildings, 42, THE NORWEGIAN EPD FOUNDATION Vekting av CO2 ved bruk av elektrisitet i produksjonsfasen (A3) uttrykt i EPD. MANN, S. A., DE WILD-SCHOLTEN, M. J., FTHENAKIS, V. M., VAN SARK, W. G. J. H. M. & SINKE, W. C The energy payback time of advanced crystalline silicon PV modules in 2020: a prospective study. Progress in Photovoltaics: Research and Applications, 22, Page 8/9

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