Temporal Carbon Intensity of Current and Future Energy Carriers at NTNU Gløshaugen
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In recent years, an increasing attention has been given to the temporal variations in indirect greenhouse gas emissions connected to energy use in buildings. The traditional approach in Life Cycle Assessments has been to use annual average emission intensities. In this study, carbon emission intensities [g CO2-eq/kWh] have been developed for energy carriers relevant for a university campus in Norway. This includes an hourly carbon emission intensity for purchased electricity based on historical production and physical flow between regions. The carbon emission intensities of heat from a district heating grid and a local heating grid based on heat pumps are assessed based on monthly production data and relevant plans for future development. The emission intensities are further combined with the simulated energy use of the university campus future building stock to estimate the energy-related greenhouse gas emissions from the building stock in the period 2018 to 2050. The use of high temporal resolution on emission intensities was found to give lower emissions from the building stock than with average annual emission intensities. The absolute value of the emission intensity of district heat, together with how it varies throughout the year, is highly dependent on allocation choices in modelling the heat supply system. It is shown how different assumptions give different results for the carbon emission intensities and overall emissions towards 2050. This will again have implications for strategies regarding the deployment of new renewable energy solutions at the university campus in the years to come.