R,D&D priorities vary according to the technology. For pumped hydro storage, the primary objectives are addressing the constraint of site availability and minimizing environmental impact by using sea-based or underground reservoirs. As a significant proportion of pumped hydro capacity is ageing and not designed to help balance variable renewable, R,D&D is also being directed at upgrading existing plants and increasing their flexibility, using variable-speed turbines, for instance.
Several compressed air energy storage concepts, which should increase efficiency by reducing or avoiding gas use, are also in development. Adiabatic compressed air involves the storage of waste heat from the air-compression process and its use to heat up the air during expansion. The isothermal design, meanwhile, aims to maintain a constant temperature. Several large-scale demonstration projects are planned or under development; these include RWE’s 90 MW adiabatic Adele plant in Germany or SustainX’s 1 MW isothermal project in the US. As with pumped hydro storage, artificial reservoirs, especially pressurized tanks, are also being developed in response to the limited availability of natural storage formations.
Battery research is focused on new materials and chemical compositions that would increase lifespan, enhance energy density and mitigate safety and environmental issues. For instance, lower-cost materials for the negative electrode of the lithium-ion battery are being tested, as are organic solutions to replace the water-based electrolytes of flow batteries. Liquid-air and liquid-metal concepts that use oxygen from the air instead of storing an oxidizing agent internally are often considered potentially disruptive, but their commercial prospects remain uncertain.
Finally, R,D&D of hydrogen-based technologies is highly active. Efforts are focused on: improving the viability of water electrolysis (by reducing the capital costs of proton exchange membranes and increasing efficiency through the use of high-temperature concepts); assessing the suitability of blending hydrogen with gas; developing methods of using hydrogen to manufacture synthetic fuels; and continuing to investigate hydrogen storage in the form of metal hydrides and in underground formations.
Despite growth in activity, funding for electricity storage R,D&D is still lagging behind that of other low-carbon-enabling technologies, such as smart grids. Most of the funding is being channeled into compressed air energy storage. Hydrogen R,D&D is also benefiting indirectly from growing interest in hydrogen-fuelled transportation.
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