The Energy SuperStore is formed of nine Work Packages: one for each technology and a few which address cross-cutting issues in energy storage research.
Work Package 1 (WP1): Redox Flow Batteries
WP1 is led by Professor Nigel Brandon of Imperial College London. Redox Flow Batteries (RFBs), also termed regenerative fuel cells, are an electrochemical storage technology, but one which decouples power and energy, unlike a usual battery, offering power and capacity from kW/kWh to MW/MWh for grid scale applications. Electrical energy is stored via the generation of a physically separated reductant and oxidant, and electrical energy generated when required by the re-combination of this redox couple. Vanadium flow batteries (VFBs) are the most mature today, being commercially available and can achieve a response time of under half a millisecond for a 100% load change. However, VFBs suffer some challenges due to their low power and energy density, and further improvement is needed to reduce cost. This work package aims to design structured electrodes to optimise flow battery performance, to explore alternative chemistries that offer lower cost and higher energy density, and to apply additive manufacturing methods to flow battery fabrication.
Work Package 2 (WP2): Li- & Na-ion battery
WP2 is led by Professor Clare Grey of the University of Cambridge. The UK has seen the advent of pioneering materials for lithium-ion batteries, in particular the positive electrode LiCoO2 used in the first generation of lithium-ion batteries for electronics, as well as the LiMn2O4 cathode used in today’s electric vehicle batteries. The challenge now is to adapt batteries for grid storage and future EV requirements. Many of the materials used in the battery are too expensive, unsafe and toxic; in addition, the power densities, and in some cases energy densities, are inadequate. Therefore, new materials and new approaches must be developed. We combine materials synthesis with structural techniques to understand the process of intercalation and any associated structural changes on cycling. We focus on low cost, safe materials that can deliver high energy storage alongside long calendar and cycle life. The abundance and distribution of sodium makes Na-ion technology an attractive candidate for low cost, grid-storage devices. We will also seek to explore new Na+ ion intercalation cathodes to develop cheap, sustainable sodium-ion batteries for static storage systems.
Work Package 3 (WP3): Lithium-air Batteries
WP3 is led by Professor Peter Bruce of the University of Oxford. The lithium-air battery has a theoretical energy density that exceeds current devices and could revolutionise energy storage, extending the range of electric vehicles. The potentially low-cost chemistry may prove attractive for grid storage applications. However, a number of challenging problems have to be solved. The battery typically consists of a Li metal anode, separated from a porous cathode by an organic electrolyte. The air-cathode breathes oxygen, which is reduced and combines with Li+ ions to form lithium peroxide. The work package focuses on the formation of stable porous cathodes and novel methods of fast recharging and improved round-trip energy efficiency, three of the key problems that must be addressed.
Work Package 4 (WP4): Supercapacitors
WP4 is led by Professor Patrick Grant of the University of Oxford. Supercapacitors consist of two electrodes separated by an ion permeable membrane and store electricity from the reversible adsorption of ions onto these two porous electrodes. Supercapacitors are electrochemical devices that can deliver high power density but usually have a relatively low energy density per unit cost compared with batteries, which is the primary reason for their limited market penetration. This work package focuses on: (a) the manufacture of new electrode materials based on lower cost carbons, transition metal oxides and their novel combinations to increase energy density; (b) interface control and separators minimising the electron resistance at current collectors and to promote ion mobility across separators; and (c) the meso-scale electrode architecture and novel arrangements of different materials and porosity. The outcome of this work package will be a range of new electrode process-material-design combinations for potential applications in portable electronics, electric vehicles and grid storage.
Work Package 5 (WP5): Thermal Energy Storage
WP5 is led by Professor Yulong Ding of the University of Birmingham. Thermal Energy Storage (TES) refers to a collection of technologies that store excessive energy in thermal forms (heat and/or cold) and use the stored thermal energy either directly or indirectly through energy conversion processes when needed. TES is usually classified into three categories of sensible heat storage (SHS), based on temperature differences, latent heat storage (LHS), based on the so-called phase change materials and thermochemical energy storage (TCES), based on adsorption/ desorption, absorption/desorption, or reversible chemical reactions. Our work seeks to (a) formulate novel high performance TES storage materials covering the temperature range of -200 to +1000 °C, while developing manufacturing technologies for the materials, (b) design and fabricate TES components and devices and (c) study the relationship between materials properties and system level performance.
Work Package 6 (WP6): Compressed Air Energy Storage
WP6 is led by Professor Jihong Wang of the University of Warwick. Compressed Air Energy Storage (CAES) refers to a process of storing energy in the form of high pressure compressed air in a vessel or an underground cavern during the periods of low electric energy demand and then releasing the stored energy for electricity generation during the peak demand time. CAES has the advantages of low costs (both initial investment and recurrent), long life time and suitability to work well at both large (>100MW) and small scales (<1kW). However, its relatively low round-trip efficiency and low energy storage density are presenting major challenges for deployment of the technology. The Hub project will perform whole system modelling studies and investigate strategies for improving round-trip efficiency of CAES via reusing heat generated in the compression stage. A feasibility study will be performed on the cascading connection isothermal compression process. Also, our research will explore the potential of scroll air expanders for efficient conversion of compressed air energy to electricity. A novel compact direct air-electricity conversion device will be studied and developed for improving the air expansion process efficiency, which is expected to lead to the development of a new efficient CAES system device.
Work Package 7 (WP7): Whole System Modelling and Economic Analysis
WP7 is led by Professor Goran Strbac of Imperial College London. Energy storage technologies will play an increasingly important role in facilitating cost-effective integration of large amounts of intermittent renewables with the electrified heat and transport sectors. However, limited research has been carried out to understand the extent to which various degradation effects could potentially impact the economic case for grid scale energy storage. This is of critical importance, as grid scale storage technologies will be competing with well-established conventional electricity system technologies, such as network and generation assets with life spans exceeding 30-40 years. The key output of this activity will be a degradation-inclusive, whole-system methodology for assessing both the benefits and costs of energy storage technologies, providing various grid services within different scenarios. This will establish the impact that degradation will have on the overall economic case for storage, considering all services that storage can support. The developed models will be used to assess the impact of grid scale energy storage degradation effects and V2G techniques, in the context of UK low carbon futures.
Work Package 8 (WP8): System integration
WP8 is led by Professor Andrew Cruden of the University of Southampton. There are currently several demonstrations of grid scale energy storage systems and many powerful hybrid electric vehicles using stationary energy storage devices. The ageing and degradation performance of such massive systems, grid/vehicle integration via power electronic converters, as well as maintenance and re-cycling/re-use considerations are all areas of active research. The electrical, thermal, mechanical and cycle life characterisation and comparative demonstration of the end-use of the energy storage technologies in the Hub programme is necessary to ensure effective feedback of application test results. Therefore this work package will seek to investigate the technical issues involved with specifying, controlling and maintaining performance from the energy storage systems for both transport and grid applications. Additionally, it will develop novel methods of characterising degradation behaviour in these devices that provide more efficient and reliable results. The research will be initially based on the energy storage technologies that are investigated within the Hub, but it is expected to expand to the wider spectrum of energy storage devices.
Work Package 9 (WP9): Manufacturing and scale-up
WP9 is led by Professor Paul Jennings of the University of Warwick. The UK has a strong capability for research into future energy storage materials. Although these new materials can be demonstrated to improve performance of the battery or an energy storage device in a laboratory, scaling them up during the manufacture of cells can lead to discrepancies in capacity. There can also be significant variation in the rate of degradation, and in the overall system performance i.e. product specifications do not meet the requirements. This work package focuses on developing more effective scale up processes for cell manufacturing, and on the improvement of fault diagnosis/prognosis techniques. The learning will help to minimise the gap between the underpinning science and commercial exploitation, bringing the core science, engineering and manufacturing together, essential in the sectors of energy and transportation.