Storing electricity

Energy storage technologies can help the transition to the low-carbon economy when they become better aligned with generation and system availability. From a system perspective, energy storage works exactly like load shifting.

Energy storage technologies fall into two types: electricity output and thermal output and can be classified into short-term, long-term or distributed battery storage, based on the duration of storage until delivery of the power.

For a controlled supply of electricity, long-term applications which enable electricity to be stored for periods ranging from hours to seasons are the most valuable. The technology typically used for this purpose is pumped storage hydropower (PSH), which is also today’s most mature and widespread option. The IEA estimated in 2014 that 99% of electricity storage technologies were PSH, with at least 140 GW of PSH connected to the grid worldwide. Compressed air energy storage has also been used successfully in the United States and in Europe, but on a smaller scale.

Finally, electricity output technologies such as batteries are starting to offer an additional opportunity to store electricity and make it available when needed. Although battery technologies struggle to realise large-scale deployment due to a series of challenges ranging from energy density to passing through system costs by charging capabilities, to safety and recyclability, their usage is becoming increasingly relevant with the deployment of variable renewables such as wind and solar. New models of wind turbines now include a battery application that enables short-term storage. While previous systems would have relied on expensive farm-level battery storage installations, this new technology embeds the battery in the turbine system itself. This technology is associated with software applications that enable power producers and wind turbines to access real time data and provides predictable power for the short term.

Some challenges nevertheless lie ahead for the large-scale deployment of energy storage technologies, starting with the relatively high cost of implementation, for which a form of reliable cost recovery mechanisms needs to be put in place (see Energy Technology Perspectives). Since energy storage can serve multiple purposes, large-scale deployment of these tehcnologies will require changes to the current market structure.

For more information, download the IEA publication Technology Roadmap: Energy Storage.