Grid-scale energy storage with net-zero emissions: comparing the options

Abstract

The transition to a low-carbon economy is an enormous challenge. With increasing deployment of intermittent renewable energy, there is a recognised need for scalable options for grid-scale, long-term, high energy density, energy storage. Grid-scale energy storage combined with carbon capture and utilisation (CCU) potentially provides a high level of flexibility and reliability. However, previous power-to-gas (P2G) studies have only examined the use of synthetic natural gas (SNG) derived from electrolytic hydrogen and either biomass- or industrially-derived CO₂ for this application; making the whole power-to-power (P2P) value chain low carbon at best. Instead, our work assesses the techno-economic feasibility of using direct air capture to develop truly carbon-neutral P2P pathways. After assessing nine net-zero emission configurations using existing technologies, we found that using SNG as an energy storage carrier may be the least expensive route despite being more complex than power-to-hydrogen (P2H). P2H is currently held back by the high cost of H₂ storage and the low volumetric density of H₂ relative to SNG. Thus, bringing down the cost of H₂ storage and building more salt caverns will be imperative for P2H, whereas reducing the cost of carbon capture should be a key priority for accelerating the deployment of power-to-methane (P2M) technologies.