Management of the part-load operation of a heat pump-based low enthalpy district heating and cooling network in a university campus with photovoltaic generation

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ABSTRACT Low-enthalpy district heating and cooling networks offer a promising pathway for integrating renewable electricity and decentralized thermal generation, particularly when coupled with high-efficiency heat pumps. This paper presents a comprehensive partial load operational optimization framework for a heat pump based low-enthalpy district heating and cooling network, combined with a photovoltaic surplus thermal load shifting strategy, in which building thermal inertia is explicitly exploited through temperature setpoint modulation to shift heat pump operation toward periods of photovoltaic surplus generation. The approach combines alternative building setpoint control strategies with a mixed-integer nonlinear programming formulation to optimally allocate thermal demand among multiple heat pumps while accounting for partial-load operation. Results obtained for the University of the Balearic Islands campus network show that the proposed methodology enhances the operational efficiency of the heat pumps system by steering each unit toward its most favourable partial-load region and avoiding inefficient ON/OFF cycling, resulting in a reduction of more than 8% in the energy consumed by the heat pumps compared to sequential dispatch strategies. While the use of building thermal inertia enables an additional annual reduction of more than 5.7 MWh of grid electricity consumption, adding an operational flexibility that allows a substantially more homogeneous distribution of running hours among heat pumps from strongly unbalanced operation (over twice the operating hours difference) to approximately 1300–1465 hours per unit, without incurring any additional energy cost.

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