I-UPS aims to develop and validate a first-of-a-kind (FOAK), cost-effective and reliable high-temperature industrial heat pump fully integrated in a flexible energy system for industrial medium temperature (~400°C) heat decarbonisation. I-UPS validate up to TRL 5 a first-of-a-kind high-temperature heat pump (HTHP), based on Stirling cycles and exploiting a non-toxic, inert, zero ozone depletion potential (ODP) and zero global warming potential (GWP) fluid, able to deliver decarbonized heat up to 400°C. No other commercial alternatives are available achieving this heat delivery temperature at efficiencies higher than 100%. The developed heat pump provides enhanced performance thanks to the optimization of key subcomponents, such as optimized static and dynamic sealing solutions and compact heat exchangers enabled by genetic algorithm based design optimization and additive manufacturing techniques. I-UPS provides also a seamless integration of the developed high temperature heat pump in flexible energy systems including molten salts based thermal energy storage (TES) for on-demand decarbonized industrial heat based on RES electricity. This effective integration will be attained thanks to the design and development of purposely-optimized compact heat exchangers (pressurized gas to molten salts) which will ensure reliable high temperature operation and fast ‘plug-and-play’ installation. The integrated heat pump configuration proposed by I-UPS will enable higher modularity, flexibility, and efficiency for heating decarbonisation also leveraging waste heat recovery and contributing to the circularity of the industrial sector. I-UPS will contribute to heating flexible electrification, permitting a broader penetration of RES and facilitating and maximizing the market penetration of heat pumps in industrial contexts.