The upgrade of the power grid will require new energy storage systems

When discussing stationary storage the common thought is towards Li-ion batteries. However, in the new report published by IDTechEx: “Potential Stationary Energy Storage Technologies to Monitor”, a new – and less new – class of energy storage technologies approaching the utility market has been investigated, showing their potential for the future power grid.

The evolving electricity grid, and related market, is demanding a growing amount of stationary energy storage to integrate an increasing installation of renewable energy sources. Although Li-ion battery is the common technology adopted, the electricity market requires different services, characterised by different technical requirements, which a new type of technologies might better, or more economically provide. The author of the IDTechEx report has investigated a promising new class of energy storage systems, including gravitational energy storage (GES), liquified air energy storage (LAES), and compressed air energy storage (CAES). IDTechEx have also interviewed companies to understand the current state of development, and the market segment which they are addressing.

The technologies analysed in the report are generally characterised by high power – from MW scale, up to GW – and long storage duration. The common specifics allow these systems to address similar segments of the stationary storage market, such as ancillary services, like frequency regulation, demand-respond (DR), and voltage control, but also utility services like energy capacity, peaker plant deferral, and grid deferral.

Some of these technologies, were initially meant to compete with pumped hydro energy storage systems, but the fast evolution of the electricity market, has offered them the possibility to address a larger spectrum of the market. Considering for example the oldest, and hence most developed of the technology investigated: Compressed Air Energy Storage (CAES). This technology has the capability to address several, if not all, the ancillary, and utility services required to support the power grid. One of the restrictions which might be faced by this system is the necessity of the underground salt caverns, although companies are developing new ways to overcome this limitation.

Similar to CAES systems, the Gravitational Energy Storage (GES) devices have large power output and the capability to store energy for (potentially) an indefinite amount of time. GES, and CAES systems and have the potential to address the same segment of the electricity. What differentiates them are the technical specifics (GES don’t have any particular installation limitation), and the business model adopted by each company.

GES systems exploit the gravitational force to store energy. Therefore, a heavy weight is usually suspended at higher altitudes when the system is “charged”. When energy is demanded by the grid the weight is released descending to lower altitudes. The speed of descending defines the power output of the system. The picture below shows the concept defined “Mountain Gravitational Energy Storage (MGES)”, published in the scientific journal ‘Elesevier – Energy’ titled: “Mountain Gravity Energy Storage: A new solution for closing the gap between existing short- and long-duration storage technologies”.

As emerging technologies, the main restriction for their adoption is their initial capital cost. At first sight, one might think these systems are uncompetitive with other existing and commercialised technologies. But from the understanding obtained by the IDTechEx report, these types of system might well support the grid, for example for long-distance energy transmission as intermediate storage, where existing technologies might not be able to be adopted. Therefore, providing an economic advantage over a long period.

Research indicates future power grid’s will require the installation of large power/large energy systems. In the German project ‘Grid Booster’, Li-ion batteries are currently being tested to deploy large amounts of electricity to improve the German power grid, this delivers power from the North side of the country (production side) to the South and West, (consumption side).

The quick adoption of renewable energy source (RES) is affecting the old concept of centralised energy grid, to a decentralised, fragmented, and more resilient power grid. The development of distributed energy resources (DER) will demand an increased installation of storage systems to optimise the existing grid infrastructure while avoiding the cost of an expensive new infrastructures, and these emerging technologies will be able to support the grid with a reduced levelised cost of storage.

By Daniele Gatti, technology analyst at IDTechEX

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