Modeling and experiments on a high-temperature heat pump for district heating using Data Center waste heat

This thesis has been developed within the framework of the Horizon Europe THUNDER project, which aims to develop sustainable waste heat recovery solutions for district heating. The work focuses on the modelling and experimental validation of a high-temperature heat pump (HTHP) designed to upgrade waste heat from a data centre cooling system to the high temperature levels required for charging a thermochemical seasonal storage. The main objectives are to develop and validate a predictive model capable of simulating the HTHP operation under varying source and sink conditions, and to carry out experimental tests and performance analysis of the system. Experimental tests were conducted in Hiref’s laboratory using a prototype specifically developed for this project and operating with the refrigerant R1233zd(E), which has a low global warming potential (GWP), belongs to the A1 safety class, and is capable of condensation temperatures up to 140 °C. The tests reproduced operating conditions representative of the demonstration site in Varna, Bulgaria, including the source and sink temperature levels expected during real operation. Model outputs—thermal capacity, performance, and operating parameters—were compared with measurements, showing good agreement but highlighting deviations at certain load points. A sensitivity analysis was performed to assess the influence of key parameters, including economizer performance and compressor behaviour. The results confirm the validity of the model while emphasising the need for extended experimental campaigns to improve accuracy and broaden its applicability.