Liquid organic hydrogen carriers for transportation and storing of renewable energy - Review and discussion

Transition to renewable energy systems is essential to achieve the climate change mitigation targets. However, the timing and the regions of the production and consumption of the renewable energy do not always match, and different energy storage technologies are needed to secure the uninterrupted energy supply. Liquid organic hydrogen carriers (LOHCs) offer a flexible media for the storage and transportation of renewable energy. These "liquid hydrogen batteries" are reversibly hydrogenated and dehydrogenated using catalysts at elevated temperatures. Commercial LOHC concepts are already available. Another flexible route to store energy is through "circular" hydrogen carriers, such as methanol and methane produced from atmospheric carbon dioxide (CO2). These fuels have a long history as fossil fuels. In this review, the chemistry and state-of-the-art of LOHCs are explored and discussed against defined criteria with comparison made to existing energy storage systems. The LOHCs and "circular" hydrogen carriers were found to be particularly promising hydrogen storage systems.