Proof of concept of a latent heat thermal energy storage system based on the Rotating Drum Heat Exchanger for on-demand steam supply

To provide a cost-effective and CO2-free solution for the on-demand provision of process steam for industrial application, the storage of thermal energy from fluctuating renewable energy sources enables the efficient decoupling of energy supply and demand. In this study, a latent heat thermal energy storage system for the provision of process steam was designed, built and experimentally demonstrated. A custom-designed Rotating Drum Heat Exchanger, which is the key component for steam generation during discharge of the storage system, was experimentally investigated. At this heat exchanger a Phase Change Material (PCM) solidifies on the outer surface of the rotating drum, which is partially immersed into liquid PCM, while the released phase change enthalpy is transferred to water that it is fed through the inner wall of the drum, evaporating and exiting the drum as saturated steam. The technology is experimentally investigated using a drum with a total outer surface area of 1.1 m2 and 400 kg of the eutectic mixture of sodium nitrate and potassium nitrate, with a melting point of 222 C as PCM. The setup described in detail in this study, successfully demonstrates process steam generation at a pressure of up to 8 bar abs and a thermal power of up to 70 kW. The experimental methodology is validated, providing a foundation for a further comprehensive characterization and development of this technology.