Integration Of Heat Pumps for Enhancing Low Temperature District Heating Systems

Abstract

District heating (DH) is central to decarbonizing heating sector. Within the effort of decarbonizing the sector, the transition from third-generation district heating (3GDH) to fourth-generation low-temperature district heating (4GLTDH) systems must be performed and evaluated with care. While the feasibility of 4GLTDH systems has been studied in the technical literature, quantified comparative analyses of multiple waste heat sources under both temperature-driven (T-D) and price-driven (P-D) control within a unified dynamic framework remain rare. This thesis develops a modular MATLAB/Simulink simulation model of an integrated HP-thermal energy storage (TES)-LTDH system, parameterised on the Påtti sub-system in Vaasa. Thirteen scenarios based on three types of waste heat sources (wastewater (WW), data centers (DCs) in three configurations, and industrial waste heat (IWH) in two configurations) were evaluated in both T-D and P-D operating modes under 2024 Finnish day-ahead electricity prices, grid CO₂ factors, and ambient temperatures. Twelve performance indicators were tracked for each scenario, as well as performed a one-at-a-time sensitivity analysis on eight system parameters. Results show that WW, primary-side data center (DC-P), and air-cooled data center (DC-A) sources can be operated year-round. Secondary-side data center (DC-S) and Indus-trial waste heat (IWH) configuration at 30-40 °C (IND-B) can only be operated during part of the year. The IWH configuration at 45-50 °C (IND-A) appears to be incompatible with the requirements of 4GLTDH systems. The binding compatibility threshold is 35 °C source temperature. P-D dispatch indicated 44-50% electricity cost reduction across operationally active sources, reaching 83% for the incompatible IND-A configuration where the HP barely runs. CO₂ emissions reduced by 22-76% relative to T-D though it introduces a supply reliability penalty of 1,643-5,102 MWh, which is the largest for high-coverage sources. Overall, transitioning from 3GDH to 4GLTDH systems alone will result in a 41% reduction in CO₂ emissions; the most balanced configuration (DC-P P-D) achieves the lowest specific emissions (4.66 gCO₂/kWh) at 75 % demand coverage. These findings can provide guidance for the selection of waste heat sources for HPs in other areas with similar climates, such as in the other Nordic countries.