Liquid piston based on molecular springs for energy storage applications

Liquid piston is a method for pressure transmission used in a wide range of technologies. Currently, liquid piston is a passive element solely used to apply pressure to a working body. In this work, the concept of liquid piston based on molecular springs - an active element, which can store a considerable amount of mechanical energy, apart from its main function, which is pressure transmission is proposed. To demonstrate the concept, the {Cu-2(tebpz) MOF + H2O} molecular spring was characterized by employing high-pressure intrusion-extrusion cycling, atomistic simulations, in situ neutrons scattering, scanning electron microscopy and X-ray diffraction. Using compressed air energy storage (CAES) as a case study, it is demonstrated that energy density for this technology can be enhanced similar to 5 times by replacing water with a water-based molecular spring. Apart from increased energy density, liquid piston based on molecular spring improves thermal management of CAES systems, enables narrow operational pressure ranges and provides an anti-vibration feature to mitigate undesired vibrations or impacts. The liquid piston based on molecular spring concept can be useful for a broad range of technologies, where pressure transmission is implemented through fluids.