Optimizing Urban Energy Flows: Theoretical Insights into Energy Sharing Between Buildings

Abstract

Space heating and cooling of buildings make up a substantial part of the total energy use globally. Apart from reducing the energy demand, improvements could be made to the energy supply of buildings. Such an improvement could be achieved by utilizing waste energy sources and connecting buildings with different energy demands. This master’s thesis evaluates the performance of a thermal source network (TSN), seen as the fifth generation of district heating and cooling or as a subclass to the fourth generation. A TSN has the ability to time shift energy through balancing units such as geothermal storage, extracting energy through heat pumps and chillers at demand. The project studied a fictional district and compared multiple variations of a TSN to a traditional district heating and cooling (DH/DC) or geothermal base case. The fic tional district consisted of four buildings, both residential and commercial, and used a supermarket as a waste heat source. The heating and cooling demand for the fictional district was 1 448.2 MWh and 860.2 MWh, respectively. Resulting in an remaining heating demand of 588.0 MWh or as a 1.7:1 ratio between the heating and cooling de mand. The study concluded that the DH/DC solution has the lowest investment cost but the highest operational cost and CO2 emissions. As a result of an improved co efficient of performance (COP), the TSN was found to have a lower operational cost and CO2 emissions than both the DH/DC solution and the geothermal solution, but at a higher investment cost. The optimized iteration of the TSN case study, using net work temperatures adjusted to a geothermal storage of boreholes, was deemed to be the most realistic. Compared to the DH/DC solution, the optimized iteration resulted in an increase of 107% in investment cost, a reduction of 84% in operational cost and a reduc tion of 23% for CO2 emissions. A result that also can be presented as a payback time of 2.6 years. Compared to a geothermal base case, the investment cost for the optimized iteration was 17% higher, the operational cost was 4% lower and the CO2 emissions were reduced by 14%. Resulting in a payback time of 91.0 years, a consequence of the assumed redundancy investment of a DH/DC connection. If this connection is omitted and redundancy is achieved in another way, the TSN might result in a lower investment cost than the geothermal base case.