• Roberts, Jennifer
• Morales, Alejandro Mar

Abstract

The University of Strathclyde, as part of their commitment to reducing their environmental footprint, installed a District Energy Scheme in 2018. The natural gas-powered Combined Heat and Power (CHP) system provides energy to 75% of the University campus and was designed to enable expansion to neighbouring buildings in Glasgow city centre. Here we present a lifecycle carbon assessment to quantify the upfront and operational emissions associated with the District Energy Scheme, understand how this might change with system expansion, and, ultimately, determine whether the scheme is compatible with the University’s longer-term climate goals. Further, such analysis can identify options to reduce the carbon footprint of district energy schemes. <br/><br/>We calculated the embedded carbon of the installed system, and the emissions associated with running the system, based on 2019/20 performance and demand. Emissions associated with installation were outside the scope of our work. We found that the District Energy Scheme has a total embedded carbon of 942 tCO2e, the majority of which (62%) sources from the pipe network for heat transport. Over the project design life of 30 years the footprint becomes 63 tCO2e/year. To reduce the embedded carbon of future (high temperature) district heating schemes pipeline lengths should be minimised, and, where possible, sourced from recycled or reused pipes, or pipes made from low carbon steel.<br/><br/>We analysed operational data for the current and potential future system and compared our results with the carbon intensity of heat from individual gas boilers and power from the electricity grid. We found that operational emissions are at least two orders of magnitude greater than the embedded carbon; the total carbon intensity of emissions associated with natural gas fuel consumption in 2019 totalled 15,095 tCO2e. For heat, compared to individual gas boilers, and taking into account the CO2 emissions from the boilers themselves, we calculate an annual net saving of 1,497 tCO2e. Thus, the carbon embedded in the pipe infrastructure is paid back within 8 months of installation of the District Energy Scheme. For power, compared to the current national grid, the CHP represents a carbon saving of 13%. However, the grid is decarbonising and, based on the current trajectory, the carbon intensity of the District Energy Scheme will be 65% more than the grid in 2050 (the end of the project design life). In total, the District Energy Scheme saves 25% compared to the University’s previous heating system and has saved an estimated 15,894 tCO2e in the 2 years since installation. Should the network be expanded, implementing a second CHP engine (to keep the more carbon intensive gas boilers as a supplementary heat source) would keep the carbon intensity of the CHP low.<br/><br/>For the University to continue to deliver on long term climate goals we recommend that (a) measures to reduce heat and power consumption across the University campus are accelerated, and (b) the District Energy Scheme is converted away from fossil fuel energy sources before 2030.<br/>

Topics

• impedance spectroscopy
• Carbon
• steel