Rethinking energy storage to ensure long term flexibility

Delivering 24/7 carbon free energy demands battery based flexibility solutions, with vanadium flow batteries emerging as an alternative to lithium-ion, writes Matt Harper, chief commercial officer at Invinity.

Last year’s pledge by almost 120 countries during COP28 to triple renewable capacity by 2030 is tremendously encouraging. It confirms that the world has the desire to achieve a just and equitable transition from fossil fuels to renewables and paves the way for the widespread adoption of 24/7 carbon-free energy.

24/7 carbon free energy is a commitment to ensuring every kilowatthour of electricity needed for our future homes, communities and businesses can be met affordably and reliably.

The missing link between renewable generation and 24/7 carbon free energy? Flexibility.

To provide low cost, low carbon energy for all, intermittent solar and wind power will need to be stored and released at an unprecedented scale, more frequently and for longer periods than ever before.

Those sources are already the lowest cost sources of new electricity generation; delivering that energy even at night and on calm days has the potential to both decrease costs and emissions.

Our ability to architect that flexibility into our power systems by applying appropriate regulation, market design and energy technologies is what will drive the next phase of the energy transition.

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Flexibility will overcome variability

24/7 carbon free energy grids need the ability to react dynamically to intermittent renewable generation and fluctuating supply in real time to minimise the curtailment of excess renewable generation when the sun is shining and the wind is blowing and reduce the running hours of legacy fuel-based assets incrementally each year.

Working both behind and in front of the meter, energy storage technologies, like batteries, absorb excess clean energy which can then be delivered on demand.

This smooths out the intermittency in generation while also providing huge additional benefits such as maximising existing grid connection capacity or bolstering national energy security with ‘homegrown’ power generation from the sun and wind.  

With renewable generation already accessible and inexpensive, flexible energy storage is the most critical asset class now needed to unlock 24/7 carbon free energy. To date, lithium-ion batteries have proven that they can provide important flexibility to the grid.

But as we move toward the fully flexible dispatch of renewable energy, batteries will be called on more often and for longer durations. In this context, it is becoming increasingly clear that a more diverse fleet of technologies is required to provide the flexibility that will fuel the next stage of the clean energy transition.

Looking beyond lithium  

Lithium-ion batteries have long offered efficiency and compact size, so they are an excellent choice for electric vehicles and mobile devices. However, these batteries have limitations when it comes to seamlessly stepping in to fulfil demand when renewable generation drops away.

Prone to degradation, they are not appropriate for repeated, variable longer duration charge-and-discharge cycles, requiring frequent augmentation or replacement, rest periods and active management to maintain safe and efficient operation. Their usage to date has focused on providing relatively short bursts of power to the grid, typically centred on a single service rather than offering the deep, long-term, 24/7 flexibility that is now urgently required to deliver a net zero future.

The impact of this limited functionality is compounded by the sustainability of lithium-ion batteries with concerns centred on disposal, recyclability, mineral availability, insurance and ethical issues embodied in the lithium battery supply chain.

We also need to consider that flexibility exists in several dimensions. Revenue opportunities in energy markets are changing as grid demand continues to adjust and governments and regulators are beginning to incentivise longer duration storage.

For project developers and utilities looking to install projects today, having an asset that has the flexibility to deliver a range of services (which may change over time), over decades of use, is a key factor in de-risking their capital investment. This is a crucial consideration when selecting battery technologies to be able to deliver 24/7 carbon-free energy, and the answer is to look beyond lithium-ion.  

Rethinking energy storage – flexibility is key

Energy storage is not a single technology market. Segmentation is already occurring by application, notably measured by one key metric, throughput.

Throughput is the number of megawatt hours of flexibility that your asset needs to provide each year. This can be calculated by the number of cycles per year and the length of duration per cycle. Determining that will clarify what technology is most suitable for matching any gaps in renewable generation.

Battery storage throughput is already on the rise as these assets become a more integral part of the grid. For example, average daily cycling in the UK market has grown significantly over the last 18 months, driven by both grid needs and increased opportunities for operators. We now typically see more than one cycle per day across the existing fleet.

This development brings into focus the importance of using non-degrading assets that have flexibility built into their design to manage higher throughput applications.

One of the standout non-lithium technologies that is helping to deliver 24/7 carbon free energy today is the vanadium flow battery. These batteries are currently deployed globally in both standalone applications and collocated with renewable generation. Unlike lithium-ion, they do not degrade with use and do not pose a fire risk.

Importantly, they can respond as quickly as lithium-ion batteries to the needs of the grid, with no need for rest periods, and have the ability to perform services from short to long durations. This flexibility provides operators the ability to stack multiple services together or even change their operating strategy over time as markets evolve.

We must act now

A tripling of renewable capacity will only deliver a better future for people and planet if we can quickly and successfully unlock the full benefit of this clean, low-cost generation. Flexible energy storage is the key to doing so.

Looking ahead, we expect high throughput energy storage technologies to play a huge role in the establishment of green baseload power on electricity networks across the world. It is now time to build upon the momentum generated by the potential of the 24/7 carbon free energy movement.

By embracing the diverse nature of technologies at our disposal and focusing on commercially available solutions, like vanadium flow batteries, we can rapidly reduce dependency on fossil fuels while enjoying the benefits of inexpensive, reliable and clean power.