Metals for energy storage : For hydrogen and power generation

Abstract: With an increase in energy demand and a transition from conventional fossil-driven energy generation, the world is facing a major challenge. This transition implies more intermittent energy sources whose reliance varies widely with time. To deal with this challenge, energy storage is one part of the solution. By storing energy when the supply is higher than the demand, it can later be used when the demand is higher than the supply. This could be done in numerous ways but this study aims to analyze the theoretical performance of metals for energy storage.  This was done for five different metals and metal-like elements. The metals studied were aluminum, boron, magnesium, silicon and zinc. The basic principle of using metals for energy storage involves a couple of steps. Firstly, energy is supplied to the metal through a reduction reaction, charging the system. After this process, the metal can be stored and thus also the energy. When the energy is needed, the energy can be released through an oxidation reaction. The products of this will be hydrogen and heat that in a later conversion process can generate electrical energy. The performance of each metal was analyzed based on round trip efficiency, energy density and CO2 emissions. To evaluate this, a model was built in IPSEpro.  The results of the study indicate that zinc performs the best in terms of round-trip efficiency while boron has the highest energy density and magnesium has the lowest amount of CO2 emissions. However, what may be more interesting is that the performance of all the metals is relatively similar to each other. The general trend is that the large advantage of using metals for energy storage is the immense energy density meaning that the storage does not take much space and can easily be transported. The results also indicate that the theoretical round trip efficiency of this technology is close to that of compressed hydrogen energy storage.  This study indicates that there is a theoretical potential for metal energy storage technology. However, the study was done purely theoretically in a best-case scenario meaning that future research, with a focus on the real-life applications of the technology, must be conducted to definitively prove if metals for energy storage is a viable option for future energy storage or not.