Techno-economic assessment of a solar heat pump system with pit thermal energy storage for industrial steam generation

This study proposes and evaluates a solar-assisted high-temperature heat pump system in which pit thermal energy storage (PTES) acts as a large-scale, low-temperature solar heat buffer on the heat-pump evaporator side for continuous industrial steam generation at 150°C. The main contribution is the assessment of this configuration for achieving high annual heat fractions using representative industrial load profiles derived from measured data from 22 facilities. The study also contributes a systematic three-step methodological framework comprising; (a) derivation of representative industrial load profiles using k-means clustering based on real data from 22 industrial facilities, (b) development of a Python-based pre-sizing optimisation tool to explore the design space and identify near-optimal system configurations, and (c) detailed simulations of the selected configuration from the previous step using a dynamic model developed in TRNSYS. To capture a broad range of solar irradiation and operating conditions, simulations were performed for three European climates: Davos (Switzerland), Würzburg (Germany), and Seville (Spain). The analysed hybrid system supplied 83–99 % of the annual heating demand in all cases. The most competitive case was obtained in Seville, with a levelised cost of heat (LCOH) of 71 €/MWh at a 5 % discount rate and a 15 year economic lifetime. This corresponds to a 7.5-year discounted payback period at a baseline natural-gas heating cost of 70 €/MWh, including a CO₂ tax of 100 €/tCO₂. Electricity price strongly influenced system economics; achieving a 10-year payback in Würzburg and Davos requires electricity prices below 60 €/MWh and 100 €/MWh, respectively. CO₂ reduction, relative to a natural gas baseline, ranged from approximately 34 % to over 90 %, with the highest benefits achieved in Davos due to its low-carbon electricity mix. The results demonstrate that integrating pit thermal energy storage with solar collectors and a high-temperature heat pump enables high renewable fractions and cost-competitive decarbonisation pathways for industrial steam.