Concerns about climate change and urban pollution have prompted a shift from our current over-reliance on energy derived from oil, coal and gas. Technological advances have made it easier to extract energy from "renewable " sources - solar, wind, tidal - however a defining feature of such sources is their intermittent nature, so they can only be reliably exploited if there are ways to store that energy. Electricity cannot be stored, but electricity can be used to drive electrochemical reactions which store the electrical energy as chemical energy. This is the basis of a battery - achieving efficient energy storage, using electrochemical means, is therefore one of the most prominent technological challenges facing the UK and, indeed, all advanced economies. Small scale devices based on lithium ion battery (LIB) technology have revolutionised power requirements for mobile devices over the last decade. In the current decade, a shift in energy storage methods for electric vehicles is underway with increasing interest (and sales) of LIB powered cars . The next challenge is to "scale up" the energy storage process to the scale of the electrical grid - can we develop large scale batteries which would enable us to store large amounts of electricity to power houses, schools and factories? The UK is blessed with ample (potential) wind, tidal and wave resources: although there are technical challenges involved in harnessing these resources, there is also a need to develop cheaper batteries which would not necessarily be based on LIB technology - because the batteries themselves would be stationary, so their mass and size becomes less important than their cost and lifetime. This proposal seeks to develop the basis of an alternative battery technology called the redox flow battery which is designed for large-scale storage. The proposal does not seek to develop a battery which would be ready to deploy at the end of the project, further optimisation and engineering studies would be required to achieve such a goal. Rather we seek to develop the fundamental scientific principles which could lead to better performing (in terms of energy, cost and lifetime) redox flow batteries - based on two advances we propose: one which develops a "membrane-free" flow battery, the other develops novel types of materials to be used as the battery membranes.

This project evaluates the potential of Seasonal Thermal Energy Storage (STES) systems to facilitate the decarbonisation of heating and cooling while at the same time providing flexibility services for the future net-zero energy system. The Committee on Climate Change's recent report highlighted that a complete decarbonisation of the building, industry and electricity sectors is required to reach net-zero. Current estimates are that 44% of the total energy demand in the UK is due to heat demand which has large seasonal variations (about 6 times higher in winter compared to summer) and high morning peak ramp-up rates (increase in heat demand is 10 times faster than the increase in electricity demand). Currently, around 80% of the heat is supplied through the natural gas grid which provides the flexibility and capacity to handle the large and fast variations but causes large greenhouse gas emissions. While cooling demand is currently very small in the UK, it is expected to increase significantly: National Grid estimates an increase of up to 100% of summer peak electricity demand due to air conditioning by 2050. In countries such as Denmark, district energy systems with Seasonal Thermal Energy Storage (STES) are already proving to be affordable and more sustainable alternatives to fossil fuel-based heating that are able to handle the high ramp-up rates and seasonal variations. However, the existing systems are usually designed and operated independently from the wider energy system (electricity, cooling, industry and transport sectors), while it has been shown that the best solution (in terms of emissions reduction and cost) can only be found if all energy sectors are combined and coordinated. In particular, large STES systems which are around 100 times cheaper per installed kWh compared to both electricity and small scale domestic thermal storage, can unlock synergies between heating and cooling demand on one side, and industrial, geothermal and waste heat, and variable renewable electricity generation on the other side. However, the existing systems cannot be directly translated to the UK due to different subsurface characteristics and different wider energy system contexts. In addition, the multi-sector integration is still an open challenge due to the complex and nonlinear interactions between the different sectors. This project will develop a holistic and integrated design of district energy systems with STES by considering the interplay and coordination between energy supply and demand, seasonal thermal storage characteristics, and regulation and market frameworks. The results and models from the individual areas will be combined in a whole system model for the design and operation of smart district energy systems with STES. The whole system model will be used to develop representative case studies and guidelines for urban, suburban and campus thermal energy systems based around the smart integration of STES systems. The results will enable the development and deployment of low carbon heating and cooling systems that provide affordable, flexible and reliable thermal energy for the customers while also improving the utilisation of the grid infrastructure and the integration of renewable generation assets and other heat sources.