Tailings dam material could be one of the waste materials that could be used to create high-density fluids (HDF) that would enable a new-generation and much more capable form of pumped hydro-energy storage system. This technology is being developed by UK company RheEnergise, in partnership the Universities of Exeter and of Greenwich, in England. And on Thursday the company announced that it had won a £1-million (roughly R21-million) grant from the UK Government’s Energy Entrepreneurs Fund (EEF) Net Zero Innovation Portfolio.

“The opportunities presented by the EEF grant are phenomenal,” enthused RheEnergise CE Stephen Crosher. “We are delighted to be able to lead and partner with two outstanding universities – Greenwich and Exeter. The project has the potential to solve three huge questions that affect people daily and globally: those of climate change mitigation, delivering firm power supply from renewables and how to use [locally-sourced] waste from other industries for new purposes, creating truly circular economies. … [O]ur research team will be closely examining waste and tailings from various sources but in particular from mines and quarries.”

The company describes HDFsas an “environmentally benign” replacement for water in conventional pumped hydro-power storage schemes. (South Africa currently has four such water-based systems: national electricity utility Eskom’s Drakensberg, Ingula and Palmiet, and Metropolitan Cape Town’s Steenbras, with a reported total installed capacity of 2 912 MW.)

The HDF used in RheEnergise’s system has 2.5 times the density of water, giving it a viscosity similar to that of cream. As a consequence, it can store 2.5 times the energy that a water-based system could. This, in turn, allows an HDF-based system to be deployed at lower elevations than a water-based system has to be: as the company puts it, “hills rather than mountains”. This massively expands the geographical footprint where pumped energy storage technology could be used.

“This funding will see the next generation of energy pioneers drive forward cheap and sustainable low-carbon technologies,” affirmed UK Energy Minister (equivalent to Deputy Minister in South Africa) Graham Stuart. “This will not only deliver green jobs and lower the costs of energy to businesses but also foster world-leading solutions to net-zero and economic growth.”

The company will start the construction of an HDF hydro-power storage demonstrator system later this year. Announced last November, it will be located near Plymouth in south-west England and have a capacity of 250 kW/1MWh (four hours). The current plan is to have grid-scale system in commercial operation in three to five years from now; that would have a capacity of 5 MW.