HIGH-EFFICIENCY SOLAR THERMAL ENERGY SYSTEM FOR INDUSTRIAL HEAT APPLICATIONS: DESIGN AND PERFORMANCE STUDY

Abstract

This paper examines the production and integration of low to medium temperature thermal energy for industrial and urban heating applications using solar energy, with a focus on optimizing system design, performance, and renewable energy penetration. The study proposes an optimum design methodology that accounts for key variables such as solar irradiation, system architecture, design constraints, load characteristics, operational distribution, and economic and energetic optimization criteria, while also considering the controlled contribution of fossil fuel backup systems. A synthetic combined energetic and economic utility function is introduced, in which an economic penalty is assigned to irreversibility associated with fossil fuel use, thereby enabling the solar fraction to be treated as a primary design variable that can be optimally increased beyond conventional limits. The methodology demonstrates that, compared to current practice where solar fractions typically range between 40 and 60 percent, optimized configurations can achieve levels up to 80 percent without fully excluding fossil-based support.

Building on this framework, the paper also presents a case study on the partially decentralized integration of solar thermal fields within the optimization of an existing district heating system in the city of Oradea, Romania. A deterministic approach was used to evaluate heat demand under both stationary hourly and dynamic annual regimes, and hybrid heating system configurations were simulated for urban areas with varying thermal densities, before and after thermal retrofitting of buildings. The results highlight the techno-economic benefits of decentralized renewable integration in dense urban environments, reducing heat losses associated with large centralized systems while improving efficiency, flexibility, and renewable energy uptake. Overall, the combined methodology supports strategic decision-making for enhancing solar contribution in both industrial process heat and district heating networks, promoting higher renewable penetration while maintaining operational reliability through optimized hybrid configurations.