With more renewables coming onto the grid daily, electric transportation booming, and homeowners adding battery storage to their PV arrays, how can the electricity network cope with all this.
There is an argument that we need more long-duration energy storage (LDES) to ensure grid stability in the future.
How is “Long-Duration” Energy Storage Defined?
There is no single definition of “long-duration”: the National Renewable Energy Laboratory (NREL), states that the most commonly cited number is 10 or more hours. The UK Government defines it as “Long Duration Storage with durations of over 12 hours, required for multi-day and seasonal balancing needs.” NREL also states that context around application is important when discussing what is meant by “long-duration.” For example, a 6-hour battery might be able to provide firm capacity — the ability to meet peak demand and cover any other adverse conditions like blackouts — in some situations, while in others, a storage system with up to 100 hours of duration might be what is needed.
What Types of Long-Duration Energy Storage Are There?
There are many different types of LDES around, but not many of them have been operating at a commercial scale. There is traditional Pumped Hydro, and more experimental types like Liquid air or Liquid CO2 or aqueous electrolyte flow batteries.
Much research needs to go into this field, but it seems to be necessary. Traditional Pumped Hydro, which has been discussed often on Energy Central, is difficult to site, and very capital-intensive. An electrochemical system like a metal-anode battery array is more convenient to find a location for, but currently is expensive so few have been deployed in small projects.
Liquid air is one potential contender. A UK company called Highview Power has spent fifteen years refining this technology. The company’s method cools the air and stores it in pressurized above-ground tanks. The compression equipment and power generators come from established supply chains in mature industries. The technological innovation here is using them for grid storage. It is now building LDES as part of a large-scale renewable project in the UK city of Manchester.
Many promising LDES technologies are still emerging and maturing and are not yet commercially available. Some depend on geography: for example, underground caverns to store compressed gases. So they are currently expensive and may not be supported by investors, developers, or utilities, who tend to be risk-averse. Regulatory bodies like state public utility commissions are less likely to approve costly projects with technologies that have not established a good track record.
Advantages of LDES
The main advantage of having a power grid with different LDES options is that it allows for a more diverse supply chain, potentially alleviating some supply constraints that arise when only sourcing for one specific chemistry, like lithium batteries. Lithium is rare and the batteries are expensive, despite falls in cost recently. Different storage technologies would provide resilience for the grid, and a diverse field of products for investors and utilities to choose what suits their needs most.
Overall, it is clear that there is a need for deploying LDES projects as part of the energy transition. Currently it seems that there will not be a clear “winner” in terms of cost or efficiency, which means that there should be openings for different, competing technologies. Again, government backing for early-stage projects will be important, and positive responses by regulators are needed. If that scenario comes to pass, then many technologies will flourish and utilities can look to find the ones that suit their location, power demands, resilience needs, grid congestion and other factors.