A new concept for advanced large-scale energy storage: secondary batteries with seawater as open self-replenishing cathode

World-wide implementation of renewable energy sources is substantially dependent on the availability of improved technologies for the production of efficient, safe, inexpensive and eco-friendly stationary energy storage systems. This is because the power that is produced by energy sources such as solar, wind and tidal (the latter to a smaller extent) is intermittent - implying that the peak electrical output may not coincide with peak demand. For this reason large-scale energy storage is essential to provide electrical supply when and where is needed without interruptions.
It is recognized that to meet all the requirements of modern society a portfolio of different storage technology are necessary, each one optimized for a given application. Many different battery technologies such as lead acid, metal-air, redox flow and lithium-ion have also been proposed as storage solution. They are each not without their issues due to their environmental impact or for the high capital and maintenance cost. For large scale energy storage the effective cost is determined by the life-time of the system and its environmental foot print, which will be transferred to the cost per MWh.

Within the framework of the present call "Adventures in Energy" we aim to explore a novel technology targeted specifically to large-scale energy storage coupled with marine wind, wave and tidal power production. This involves the use of sea-water as a positive electrode (cathode) in a hybrid system which is intermediate between a secondary sodium-ion battery and a fuel cell. The salt in sea-water is an inexhaustible source of sodium ions that are transferred to the negative electrode (anode) through a fast ionic-conductor membrane while charging. During discharge the sodium ions shuffle back from the anode to the sea-water. The exciting and novel aspect of this is that a natural unlimited resource is used as an active self-replenishing component of the cell. As a consequence the system offers numerous advantages: low cost, high safety and negligible environmental impact as compared to other related technologies.

The project aims to take the sea-water hybrid fuel cell from the proof-of-concept stage to a viable technology for large scale energy storage. This will be achieved through the optimisation of constituent components, development of scalable manufacturing processes and validation in a relevant environment. Our research could provide a cost-effective solution to the pressing problem of storing electricity produced in the sea by enabling the technology necessary to build large-scale semi-submerged marine energy storage parks.

Energy storage is one of the "Eight Great Technologies", identified by the government as a technology in which the UK is set to be a global leader. It is one of the most important fields of applications for the use of advanced materials and will enable the UK to gain from the global move towards new energy sources (BIS). The proposed project will lead to the development of a novel ground-breaking battery technology that will overcome the limitations for large-scale storage, adopting seawater as a self replenishing open cathode. Specifically it will provide the ideal solution to energy storage issues afflicting the current British development in renewable energy (in particular off-shore wind, wave and, to a lesser extent, tidal). By doing so, this novel technology will contribute to the development of a sustainable low-carbon economy and society. The market potential for the large-scale energy storage is impressive: greater capability to store electricity will lead to estimate savings of more than £10 billion per year in UK alone.
The uniqueness of the technology proposed by the project will reinforce UK leadership in energy storage on the global stage. The research project brings together investigators with solid track records, international leaders in their research field and strong industrial links. Given a successful outcome from the project, the partnership is in a strong position to engage with the appropriate industry partners. This will be facilitated by demonstration of an early stage prototype to industry; a first step to further collaborative research that can be supported by TSB or EU programmes that will underpin large-scale adoption of the technology.
The project will contribute to a knowledge-based society through the continued personal development of post doctoral researchers, in addition to the education of one PhD candidate and Masters Degree students. The skills acquired by these students and early career researchers will be highly sought after in the academic sector and in an expanding industrial sector