Sevindik, Selman; (2023) Modelling Scenarios for Low Carbon Heating Technologies in the Domestic Sector Towards a Circular Economy. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The UK Government’s Net Zero strategy requires strong commitments to avoid catastrophic impacts of climate change. The built environment puts major pressure on the natural environment, especially with space heating-related emissions; therefore, transitioning to a circular economy is vital. In this direction, the heat pump market in the UK has been growing gradually whereas the number is still low (43,000 units in 2021). The UK Government aims to reach 600,000 heat pump installations per year by 2028, and according to the Climate Change Committee (CCC), this number should reach 1 million by 2030. In order to accelerate the transition, the Boiler Upgrade Scheme (BUS) has been introduced to provide a £5,000 grant in the UK, and the Scottish Government granted Home Energy Scotland (HES) loan and cashback scheme providing a £7,500 grant and a £2,500 interest-free loan for heat pumps. Islands are facing environmental, economic and social pressure due to the lack of connection to the mainland and dependency on fossil fuel imports. Exploring the benefits of renewable energy and low carbon heating technologies is crucial to overcome these issues. Orkney has a huge potential for renewable energy by producing electricity more than its needs. Therefore, this study chooses Orkney as a case study to explore potential heat pump uptake scenarios in line with government targets towards Circular Economy (CE). The study aims to create a comprehensive holistic approach to evaluate the environmental, energy and economic impacts of heat pump deployment scenarios. The consequences of replacing conventional heating technologies with heat pumps have been assessed through (i) comparative life cycle assessment (LCA) of heat pumps with gas boilers in UK houses, (ii) energy systems modelling (ESM) to optimise the performance of a heat pump coupled with thermal energy storage (TES) tank to reduce use phase related impacts in Orkney, (iii) building stock modelling (BSM) of Orkney’s domestic sector to understand the housing condition, (iv) economic modelling to analyse life cycle cost of an air source heat pump and potential savings when existing conventional heating systems are replaced with heat pumps in Orkney, and (v) heat pump diffusion model to quantify hourly electric load curves of variable heat pump operation optimised by the energy model. The integrated methodology creates a more holistic and life cycle-wide approach to both demand, supply and end-user side of the system; therefore, the results are illustrated in both individual house archetypes level to provide guidance to the end-users and at the Orkney level to calculate cumulative savings for the policymakers. The results show that the use phase is the major contributor to the environmental impacts; therefore, increasing the renewable share in the UK’s electricity mix could help to reduce negative impacts in most of the categories. However, the high deployment of wind farms also creates toxicity and metal depletion problems. The heat pump uptake scenarios in Orkney shows that 82% reductions in energy supply could be achieved when ambitious energy efficiency improvement measures are taken in the CE scenario. The use phase-related emissions could be reduced by 98% when the heat pump becomes the only heating technology in Orkney. However, the life cycle-wide approach suggests that strong commitments are required in the manufacturing stage of these technologies through implementing circular principles such as including the use of secondary materials, eco-design and reusability of all components. Moreover, a market introduction program should be provided before shifting from one technology to another so greener production lines could be achieved. Total heating costs paid by consumers in Orkney could be reduced by 84% in the CE scenario when heat pump uptake is coupled with energy efficiency improvement measures; however, it requires a £130 million investment to insulate the unrefurbished housing stock of Orkney. Therefore, subsidies and incentives are also required for efficiency improvements such as reductions in VAT on equipment and labour costs, grants similar to BUS/HES and interest-free loans for the remaining costs. Future scenarios indicate that decision-making has significant importance on overall results; therefore, CE standards for heat pump manufacturing and deployment are crucial to reduce the negative impacts of fuel poverty and reach the Net Zero target.

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