Abstract

The Zero Village Bergen consists of a total floor area of ca. 92 000 m2, with more than 700 dwellings divided between terraced houses (68% of total floor area) and apartment blocks (25%) and some area dedicated to non-residential purposes such as offices, shops, and a kindergarten (7%). The project is currently in the planning phase and the strategy for achieving the ZEB-O goal1 is based on three steps: first, minimize energy demand through energy efficiency of the buildings; second, maximize PV generation on the buildings' footprint; and third, consider additional measures onsite and nearby (e.g. local heating system with biomass based cogeneration). At the current stage the project has reached the evaluation of step two, and the results are presented in this report, together with some useful insights for step three.

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Abstract

The scope of this study is a comprehensive analysis of the greenhouse gas emissions from the partial substitution of triple-glazing units with argon gas (U-value of 0.79 W/m2 K) with double-glazing units with either monolithic aerogel (U-value of 0.65 W/m2 K) or granular aerogel (U-value of 0.31 W/m2d K).

A residential building located near Oslo and fully upgraded with passive house solutions is used as a case study for this analysis. A cradle-to-site analysis is performed on the facade components. Two replacement schedules and three window-to-wall ratios are used to evaluate the differences in total emissions. Sensitivity analyses based on increasing the fraction of the aerogel glazing, varying the greenhouse gas emissions of the aerogel production, and changing the service life of the aerogel glazing are also performed.

Results show that both the options with windows with aerogel are effective in reducing the greenhouse gas emissions, regardless of the total window-to-wall ratio and the replacement schedule used. By increasing the share of the aerogel glazing, the savings in emissions increase from 5% to 9%. The sensitivity analysis shows that the greenhouse gas emissions from the production of aerogel should be at least 8 times higher than those currently reported to totally counterbalance the achieved energy savings.

Abstract

Greenhouse gas (GHG) emissions from the combustion of fossil energy need to be reduced to combat global climate change. For zero energy and Zero Emission Buildings (ZEB), photovoltaic solar energy systems are often installed. When the goal is to build a life cycle Zero Emission Building, all emissions come under scrutiny. Emissions from photovoltaic (PV) energy systems in Zero Emission Buildings have been shown to have a relative large share of material emissions. In this paper, we compare GHG emissions per kW h of electricity and greenhouse gas emission payback times (GPBT) for three residential PV systems in Zero Emission Pilot Buildings in Norway. All the buildings have roof mounted PV systems with different design solutions. The objective is to analyse the emission loads and GPBT of these three systems to facilitate for more informed choices of energy systems for Zero Emission Buildings. The results show that the total embodied emissions allocated per square meter of module area are around 150–350 kg CO2 eq/m2 for the three different systems. Emissions from the mounting systems vary from 10 to 25 kg CO2 eq/m2 depending on the material types and quantities used. When modules replace other roofing materials, such as roof tiles, mounting emissions were reduced by approximately 60%. GHG emissions per kW h electricity produced were in the range of 30–120 g CO2 eq/kW h for the different systems. The system with the lowest emissions was the largest system, which had a simple mounting structure and modules with reused cells. It was found that the GPBT was strongly dependent on the scenario used for electricity grid emissions. By applying a dynamic emission payback scenario with an optimistic reduction of emissions from the European electricity grid, the GPBT was 3–8 years for the different systems. When comparing the emissions with current Norwegian hydropower emissions, of around 20 g CO2 eq/kW h, it was found that all of the PV system’s emissions were higher. When compared to a mainly fossil fuel based grid, all the PV system’s emissions are low. This study highlights the importance of reliable emission documentation for PV modules and their mounting structures on the market.