Industrial process heat decarbonisation with hybrid concentrated solar thermal and electric heating systems

Despite being addressed as a promising route for industrial heat decarbonisation, the deployment of Concentrated Solar Thermal (CST) remains limited to low- and medium-temperature processes (50-250°C). This study investigates pathways to decarbonise medium-high temperature (300-500°C) industrial heat employing CST systems, hybridised with electric heating sustained by photovoltaic (PV) and/or wind turbine (WT) generation. A Mixed Integer Linear Programming (MILP) model is developed to optimise system design and hourly annual operation, identifying optimal renewable and storage capacities and CST/PV orientations under varying Renewable Penetration (RP) levels, with the Levelised Cost of Heat (LCOH) and the Cost of CO 2 Avoided (CCA) as key metrics against a natural gas reference case. The analysis explores the effects of hybridisation, collector orientation, temperature level and site location, yielding key insights for Southern European sites: (i) temperature of the supplied heat plays a key-role in CST competitiveness alongside land use, as CST requires nearly half the land area of PV electric heating; (ii) WT hybridisation and east-west CST/PV orientations reduce LCOH by up to 10-40% at high RPs; (iii) 70-80% RP marks a threshold beyond which further decarbonisation becomes economically less competitive, requiring large renewable generation and storage capacities; (iv) even at 100% RP, life-cycle analysis indicates total CO₂ avoidance rates of 80-90%, due to embedded emissions in renewable technologies; (v) the economic viability of decarbonisation is strongly influenced by site location: when supplying heat at 300°C with zero CO 2 emission cost, as solar irradiation decreases the break-even RP declines from approximately 70-75% in Southern Spain to 20-25% in Northern Italy.