Energy storage efficiency in artificial photosynthesis – An evaluation method in engineering perspective

Abstract

In engineering perspective, energy storage efficiency is a crucial indicator for assessing economic feasibility of artificial photosynthetic energy storage systems, as it determines not only the investment return but also the life cycle of renewable energy. However, few models for evaluating the efficiency are available in the open literature. In this work, a framework for evaluating the efficiency of artificial photosynthetic energy storage systems was proposed using the synthesis of PHB (polyhydroxy-butyrate) by Cupriavidus necator and hydrogen as an example, and models for the reaction kinetics and thermodynamics of the conversion and mass transfer in the biochemical processes were proposed and checked with published experimental results. An optimization method was developed to achieve the maximum energy efficiency. It was found in the present study that continuous reactors are more efficient than batch reactors, and improving mass transfer in the reactor is a key to increasing the maximum energy storage power, which should be compromised with energy efficiency for an engineering design. It was also found that altering reaction paths with higher thermodynamic efficiency is another key to improving energy efficiency of an artificial photosynthesis energy storage system.