The government commitment to reduce emissions (Climate Change Act 2008 and now the Clean Growth Strategy 2017) and the resulting ambitious targets for renewable energy production requires novel approaches towards efficient production of non-intermittent electricity from renewable sources that can compensate for the closure of fossil fuel power plants around the UK. Reverse electrodialysis (RED) is a "blue" non-intermittent energy technology involving salinity gradient energy, with importance to the UK's future renewable energy mix. RED has been relatively neglected to date, hence, a systematic evaluation of its potential based on innovative materials is urgently needed. Electricity is generated when waters of different salinities (saltiness) are mixed inside an electrochemical RED cell stack (can involve industrial waste streams). A recent conservative assessment of global salinity gradient power (SGP) potential indicates that 625 TWh per year of electricity is practically extractable from river mouths globally (3% of global electricity consumption).

RED cells contain multiple pairs of anion-exchange membranes (AEM) and cation-exchange membranes (CEM). The materials development aspect of this project will focus on the development of high performance AEMs and their application in RED cells (including those supplied with real-world, non-sterile waters). These will be compared to commercial benchmark AEMs. The project will focus on AEMs because CEMs (intended for RED application) were developed as part of a previous EPSRC grant [EP/I004882/1]; there is also less diversity of chemistries available for CEMs, compared to AEMs, which is why the latter requires a more dedicated research project. A wide range of AEMs will be synthesised using the electron-beam radiation-grafting technique. We will also explore the use of sonochemistry during the grafting stage, both in combination with and without the use of the electron-beam.

The RED cell performance data will also be compared to single ion-transport data (experimental and modelling) as well as data from modelling of RED cell engineering configurations. Accurate modelling of the RED stack is crucial in order to estimate the realistic potential of RED in a future UK energy mix. The modelling activities will be further extended to take into consideration the real scalability of the process in terms of potential contribution to the UK energy demand. The integration of data on the availability and locations of fresh water and saline waste streams (e.g. waste streams from industry) with the accurate model of the RED system will produce a precise map of the technology potential at different sites. This activity will then lead to the identification of potential integrations of the process according to the available streams: i.e. once you know where you have fresh water (and how much) you can calculate how much electricity you can actually produce. Furthermore, when an alternative (e.g. industrial) saline waste stream is located close to a fresh water body, this avoids the limitations when using seawater (in terms of coastal location and the magnitude of the salinity gradient).

For cost effectiveness, this project will fully utilise membrane characterisation and RED cell testing equipment that have been purchased/established using funds from prior related EPSRC and EU projects. For maximum transparency, all resulting open access publications (CC-BY) will include DOI locators to facilitate open access to the project's (non-IP-protected) raw data. The project will be used to establish new intra-UK and UK-Dutch research collaborations that should lead to additional links to other UK and EU networks.