Small demonstrator of a thermoelectric heat-pump booster for an ultra-low-temperature district-heating substation

Heating and cooling systems account for approximately 50% of global energy consumption and contribute 40% of carbon dioxide emissions. District-heating systems offer enhanced energy efficiency, diversification, independence from energy sources, and the utilization of waste and renewable energy sources. One key energy-efficiency measure in district heating is reducing the supply and return temperatures. Fourth-generation district-heating systems operate with supply temperatures of 50 to 60 °C, enabling better utilization of renewable and waste heat. Fifth-generation district-heating systems further lower the supply/return temperatures, requiring additional heat sources, such as boosters, to heat domestic hot water. Heat pumps, specifically vapour-compression heat pumps, are the most energy-efficient devices for converting fuels or electricity into heat for space and water heating. However, vapour-compression technology faces challenges related to environmentally friendly refrigerants, noise, vibration, compactness, and energy efficiency, especially for small units. In this study, we introduce a novel design of thermoelectric-based heat-pump booster. Despite its lower exergy efficiency, this technology offers advantages such as compactness, silent operation without vibration, easy power control, and longevity. We demonstrate that these thermoelectric heat-pump boosters can increase the supply-water temperature of district-heating systems from around 32 °C to 42 °C, with a heating coefficient of performance equal to 2.4 and an exergy efficiency of 9.9%. •A thermoelectric heat-pump booster for district heating is presented.•The design of the thermoelectric heat-pump booster's heat exchangers is presented.•A comprehensive experimental evaluation of performance was conducted.•A COPH of 2.4 and an exergy efficiency of 9.9% when increasing the DH supply from 32 °C to 42 °C.