Experimental and Numerical Assessment of a Compact Sensible Heat Storage Unit for Renewable Energy Applications

The conversion of surplus electrical energy into thermal energy represents an effective pathway for increasing the flexibility of renewable-energy systems. This study presents an experimental and numerical assessment of a compact vapor-assisted sensible heat storage unit designed to transform electrical input into stored thermal energy using a controlled evaporation–condensation process inside a vertical steel cylinder. An 800 W immersion heater was employed to generate vapor, while nine temperature sensors monitored the thermal response of the evaporator, enclosure air, and storage medium. Two operating configurations, insulated and non-insulated, were investigated to characterize charging and discharging dynamics. In parallel, CFD simulations performed in ANSYS Fluent were used to analyze coupled heat transfer and phase-change mechanisms. The results demonstrate efficient electrical-to-thermal energy conversion, with rapid temperature rise during charging driven by vapor-assisted convection following the onset of boiling. Experimental data and numerical predictions consistently reveal a transition from conduction-dominated heating to a phase-change-enhanced regime, which accelerates heat distribution and thermal homogenization within the storage unit. Comparative tests further indicate that reduced external losses improve heat retention during discharge. Overall, the combined experimental–numerical approach confirms the capability of the proposed compact system to store electrically generated heat in a stable and repeatable manner, highlighting its potential for daily photovoltaic energy buffering and small-scale renewable-energy applications.