Sodium thermal electrochemical converter coupled with organic Rankine cycle and thermochemical heat storage for power-heat-power application

Abstract

The inherent intermittency of solar PV and wind sources makes the power supply from renewables unstable. To mitigate this issue, power-heat-power (PHP) systems have been developed in which surplus/cheap electricity can be stored in the form of high-temperature heat, and whenever needed it can be used for electricity generation using a power cycle. The present work focuses on the integration of an innovative combined cycle consisting of a sodium thermal electrochemical converter (Na-TEC) in combination with an organic Rankine cycle (ORC) as a bottoming cycle, with a redox oxide-based thermochemical heat storage (TCHS) system for PHP application. A Multiphysics model is developed to simulate and analyze the performance of the proposed combined cycle. Parametric optimization is performed to achieve optimal system performance. The proposed Na-TEC/ORC achieved a maximum power density of 0.98 W/cm2 and a maximum conversion efficiency of 40 % which is 21.2 % higher in comparison to a standalone Na-TEC device. A maximum exergetic efficiency of 53 % can be achieved while keeping the evaporator temperature at 1150 K and the condenser temperature at 550 K for this cycle. For the maximum conversion efficiency of Na-TEC, a round-trip-efficiency of 36.1 % is calculated for the proposed PHP system provided the TCHS system is 95 % efficient.