Abstract

Solar thermal energy provides a sustainable alternative for electricity generation and heat supply across various sectors. While photovoltaic (PV) systems are widely recognised for electricity production, solar thermal systems offer broader applicability by directly generating heat or enabling thermodynamic cycles for power and cooling applications. Key applications include concentrated solar power (CSP) for electricity and solar heat for industrial processes (SHIP) for heating and cooling. Traditionally, these systems use thermal oils as heat transfer fluids. However, their limitations on maximum temperature and efficiency necessitate additional heat exchangers. Here, we explore the Direct Vapour Generation (DVG) concept, wherein fluids as organic fluids generate vapour directly within the receiver tubes, achieving higher efficiencies. Our findings reveal optimal pressure and mass flow ranges that favour the annular flow pattern, minimising dry-out risks and enhancing heat transfer coefficients. Compared to conventional direct steam generation, DVG with organic fluids expands its utility, enabling integration with organic Rankine cycles (ORC) and SHIP applications. This study’s parametric insights contribute to designing efficient, solar-powered heating and cooling systems, highlighting DVG’s potential to advance CSP and SHIP systems in the transition to low- and medium-temperature solar thermal technologies.