Multi-Criteria Design of Industrial Process Heat Solutions, Including Concentrating Solar Thermal Collectors, High Temperature Heat Pumps, and Boilers

Industrial heat demand is a major source of CO2 emissions, making the decarbonization of this sector essential for achieving sustainability. This study explores and compares different methods for supplying useful heat to the industrial sector through a multi-criteria approach that considers technical performance, economic viability, and environmental impact. Both conventional and alternative systems are examined, aiming to develop sustainable designs. These include solar-based systems using parabolic trough collectors, supported by either electric heaters or natural gas boilers. In addition, a high-temperature heat pump (HTHP) utilizing waste heat is analyzed, also combined with either electric heaters or gas boilers as backup. For reference, a conventional natural gas boiler system is included as a baseline case. In total, five scenarios are evaluated for applications in the chemical industry. Each scenario is assessed in terms of energy and exergy efficiency, cost, and CO2 emissions. A multi-criteria analysis is then applied to determine the most sustainable option under varying electricity and waste heat price conditions. The results indicate that the configuration combining a high-temperature heat pump with electric heaters (Scenario 3) achieves the highest performance, with energy and exergy efficiencies of 0.952 and 0.666, respectively. The lowest CO2 emissions are observed in the case of using solar collectors with electric heaters (Scenario 1), reaching 4154 tons per year. From an economic perspective, Scenario 3 emerges as the most favorable option at lower electricity prices (0.10 €/kWh), with a levelized cost of heating (LCOH) of 0.0555 €/kWh. At higher electricity prices, the optimal design shifts to Scenario 2, which combines solar collectors with a natural gas boiler, resulting in an LCOH of 0.0603 €/kWh.