Energy storage has been touted as the enabler of high levels of intermittent renewables in the electricity system – the silver bullet or Holy Grail for solar and wind. Recent actions show positive movement in the storage industry and highlight key characteristics that will give some storage technologies a distinct advantage in the market.
As countries look for technology solutions to support increasing use of variable renewables, the advantages found with scalable electricity storage options are clear. In particular, their ability to overcome geographic constraints, reduce initial capital requirements and provide flexibility in the face of future uncertainty set them apart from other technology options.
Current estimates by the International Energy Agency show that 310GW of additional grid-connected electricity storage capacity is needed in the United States, Europe, China and India to support electricity sector decarbonisation. The vast majority of existing capacity is found in large, supply-side pumped hydro storage facilities. However, siting challenges and environmental concerns hinder future capacity growth. While opportunities exist to improve existing facilities that could allow them to better support the changing grid, these modifications will focus more on improving responsiveness and less on increasing overall storage capacity.
Scalable storage technologies use a single technology platform on largely varying scales, in essence providing system planners with a toolbox of options to fit their application requirements. In turn, these technologies can overcome the geographic constraints faced by pumped hydro and also give investors valuable flexibility in the face of uncertain future energy demand profiles and system characteristics. The latter, in particular, provides a distinct advantage over competing storage technologies and other flexibility options.
By decoupling electricity supply and demand without requiring changes in consumer behaviour, energy storage can be a less obtrusive option than demand response for system operators. Furthermore, initially smaller systems that allow for future expansions without massive cost penalties can allow investors to better hedge their future risk. In turn, they can avoid situations like that seen today in Spain, where new natural gas power plants are facing declining power demand and may soon be mothballed after only a few years of service.
Particularly in the case of batteries, cost declines and lessons learned from demonstration projects have illuminated the value of scalable storage systems compared to competing technologies and operational tools. Modular plug-and-play systems have decreased maintenance and operation challenges while allowing owners to modify their system to meet changing needs. Projects have also given a second life to batteries originally designed for mobile applications, increasing their lifetime and value.
In the United States, the Santa Rita Jail’s modular battery system aggregates smaller battery units in shipping containers. Installed from 2011 to 2012, the 4MW system currently utilises both sodium sulphur and lithium-ion batteries to support a co-located solar PV array and small wind turbine field. In the future, the modular container systems will allow the facility to increase or reduce storage capacity more easily as the jail’s population (and corresponding energy requirement) changes over time.
Earlier this year, Japan’s Sumitomo Corporation built the world’s first large-scale electricity storage system that utilises used batteries from electric vehicles (EVs). Their 600kW (400 kWh) system was built using a set of 16 used lithium-ion EV batteries to support the 10MW “Hikari-no-mori” solar farm on Yumeshima Island, Osaka. This system will help operators to learn more about the optimum storage to generation ratio and how battery storage can be used to reduce energy output fluctuations in their power systems resulting from variable renewables.
Moving forward, storage companies will increasingly look at how to capitalise on an array of opportunities across the supply, transmission and distribution, and demand portions of the energy system. While other challenges still face energy storage technologies – particularly related to market design – scalable technologies have a distinct advantage moving forward compared to competing options.
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