Pilot-scale hybrid district heating substation integrated with adsorption heat pump

This paper reports the first cooling-season operating experience of a pilot hybrid district-heating substation installed in an office building in Ostrołęka (Poland), combining a district-heating–driven adsorption chiller with three latent-heat storage units using phase-change materials located in the hot, chilled, and heat-rejection circuits. Measurements were collected every 30 s from mid-May to early September 2023. During the test season, the district-heating supply temperature was highly stable (63.6 °C on average, and a standard deviation of about 1.0 °C for 10-min averages) and rarely fell below 62 °C, which enabled reliable chiller operation despite the typically small district heating side temperature drop (≈3–5 °C) characteristic of adsorption cooling under Polish summer conditions. Night-time cooling provided by the dry cooler proved valuable for pre-charging the phase-change-material storage units, achieving up to about 12 kWh of stored cooling in the chilled-water storage unit (denoted as Latent Heat Thermal Energy Storage 2), and up to about 15 kWh in the heat-rejection storage unit (denoted as Latent Heat Thermal Energy Storage 3) during a single free-cooling period. A full 12 kWh charge of the chilled-water storage unit corresponds to a reduction of about 34.3 kWh in the required driving heat, assuming an average energy efficiency ratio of about 0.35. In addition, a 4-h night-time chiller run stored up to about 14 to 16 kWh in the chilled-water storage unit at a 20 °C setpoint. Using a phase change material storage unit (denoted as Latent Heat Thermal Energy Storage 3) lowered the chiller heat-rejection inlet temperature by about 2–3 °C, which the authors estimate can increase cooling power by ∼2 kW for a 3 °C reduction at representative operating points. The results confirm the technical feasibility of district-heating-driven cooling with phase-change-material-based hydraulic decoupling and highlight practical commissioning challenges as well as control and measurement issues relevant to wider deployment.