Simulation and analysis of a geothermal energy network : A technical and societal perspective on modern energy infrastructure

Responsible for roughly 40 % of global greenhouse gas emissions, energy usefor heating and cooling in the built environment constitutes a significant portionof annual total carbon emissions. The effort to decarbonise the heating andcooling sector necessitates efficient production, distribution and end use ofenergy. In this context, district heating and cooling is considered one of thecost-efficient, reliable and low-emission systems. The benefits are furtherextended by modern district networks, which facilitate bi-directional energyflows, allow heating and cooling from the same network, promote decentralisedenergy production and most importantly, allows integration of multiple energysources, including low-grade thermal sources and energy sharing betweenbuildings.As local thermal resources, such as the shallow geothermal systems, areintegrated and energy flows between connected buildings are started, role ofmultiple stakeholders comes into play in these modern district energy systems.Unlike the conventional district networks where energy flows from energyproducers to consumers, the role of “prosumers” here becomes of paramountimportance. This combined effort for decarbonization of the overall heatingand cooling system is still under a development phase and demands for acomprehensive technical, social, economic and regulatory breakthrough for itswider adoption and application.This thesis aims to contribute to this body of developing knowledge by firstpresenting a practical design of a low-temperature geothermal district heatingand cooling network that features sectoral coupling of electricity and heatsources with seasonal thermal storage by using geothermal borefields. Thethesis comprehensively describes the role of system components including thedecentralized heat pumps, and system structure in achieving energy sharingbetween connected buildings and also quantifies possible energy exchange.Furthermore, the decarbonization potential of such systems is presentedthrough a comparative study against conventional and alternative energysystems. Secondly, the social perspective related to the adoption of thisimproved district heating is discussed with a focus on the influence of businessmodels, ownership structures, and legal frameworks on prosumer participation.Using a digital twin modelling approach, the thesis presents substantialbenefits of low-temperature geothermal energy networks with energy sharingbetween connected properties. The results show an enhancement in thecoefficient of performance (COP) of the decentralised heat pumps, therebyreducing electrical energy consumption by approximately 14 %. Whenconnecting the buildings by energy sharing, thermal load sharing betweenborefields (energy source) of different properties was observed. Further analysisshowed enhancement of the operational performance of borefields owing tothe energy exchange. Additionally, the comparative analysis of operationalemissions from the presented district network against alternative energy sourcesproved substantial environmental benefits of these networks.The thesis also discusses the evolving ownership structure and businessmodels of modern district thermal networks. The thesis discusses that becauseof its “hassle-free” nature for the end user, “heat-as-a-service” models areperceived to grasp wider public acceptance in future. Furthermore, owing to thelonger technical lifespan of district networks, prosumers may be interested to“own” the network to capitalise on the continuous revenue stream that itgenerates. Additionally, low energy price, and “green value” which the modernenergy infrastructure offers were considered as the main drivers for prosumers'participation. Alternatively, the unclear legal definition of “waste heat” inresidential buildings was considered as a potential barrier for energy sharingsolutions. The thesis suggests that explicit regulatory frameworks to define“heat prosumers” and consideration of waste heat as a financial instrument maypotentially enhance prosumer involvement in modern energy infrastructure.