An evaluation and innovative coupling of seawater heat pumps in district heating networks

Seawater heat pumps present promising solutions for the decarbonization of the heating sector by utilising seawater as a renewable heat source. This study explores their integration into district heating networks in cold climate regions, focusing on case studies in Estonia, and Norway. A main challenge lies in the freezing threat of seawater during winter, prompting investigations into innovative solutions. This research evaluates two proposed strategies: coupling seawater heat pumps with an additional heat source and locating them far off the shore where water temperatures are more stable. The study employs a multifaceted approach, considering technical, economic, and environmental factors. The research assesses and models seawater heat pumps in two case studies, exploring 10 MW heat supply scenarios. Performance indicators include Coefficient of Performance (COP), Electricity consumption, CO2 emissions, and Levelized Cost of Heat (LCOH). Results highlight the feasibility and advantages of coupling free heat sources with seawater heat pumps in district heating networks. In the Norwegian case, coupling waste heat and seawater heat pumps significantly reduces electricity consumption, CO2 emissions, and LCOH by 88 %, 65 %, and 76 %, respectively. In Tallinn, where seawater freezing is a concern, installing far-off the shore seawater heat pumps maintain year-round operation with a seasonal COP of 3.5 and a 34 % reduction in CO2 emissions compared to electric boiler coupling. Economic assessments suggest the feasibility of integrating far-off the shore seawater heat pumps in low-power price scenarios.