Power and Energy Engineering

Renewable energy resources can deliver sustainable and secure supplies of energy in heating/cooling, transport and electricity generation. However, an electricity system based on intermittent renewable energy sources, such as solar, wind, hydropower, geothermal and marine, gives rise to new challenges concerning the storage and utilization of surplus energy, system operation, and energy supply reliability. Energy storage is essential to help cope with these challenges and facilitate a faster penetration of intermittent energy resources. This presentation reports our work on two electrochemical technologies as promising grid energy storage– electrolysers and batteries. Electrolyers provide a cost-effective and energy efficient route to clean hydrogen production. The optimal control strategies when coupling electrolyser systems with intermittent renewable energies are investigated for the first time. Control strategies considered include maximizing hydrogen production, minimizing electrolyser energy consumption and minimizing compressor energy consumption. Optimal control trajectories of the operating variables over a given period of time show

feasible control for the chosen situations. The relative merits of the optimal control strategies are revealed. Sodium ion batteries (NIB) have been considered as a promising next-generation energy storage technology, because of the natural abundance, wide availability and low cost of Na resources. We have been using molecular simulations combined with experiment for designing nanoporous carbons as negative electrode materials. Molecular simulations reveal the intercalation mechanism of Na ions into the nanoporous space with the presence of organic solvent. This is then used to guide the design of the materials for best performance in NIBs, and compared with experimental results.