As energy grids become “smarter” and decentralised, and as renewables continue to grow as a percentage of overall generation, having solutions that ensure continual energy supply is going to be critical. One particularly positive development in this area is long-duration energy storage, or LDES.
The idea behind LDES is self-explanatory – it’s a system that is able to discharge energy continually over an extended period of time once it has been fully charged. As part of this, there’s a mind-shift in terms of what the technical priority is: traditional energy storage solutions are focused on how long energy can be stored before it needs to be used, but LDES emphasises sustained power delivery.
There is a massive openness to just what constitutes “long-duration” right now. Some bodies define it as 10 hours or longer. This number isn’t picked for arbitrary reasons, but rather represents a good window for ongoing use where power generation isn’t available – for example, 10 hours means that the lights will stay on through the night when relying on solar generation.
With that being said, 10 hours isn’t always going to be an adequate target, and there are systems that would demand 100-hour supply from the energy storage system, if not longer, to guarantee the uptime for the system that it supports.
For this reason, LDES solutions require two things – firstly, the raw technology to build a system to a target minimum duration. Secondly, an understanding of how the system uses and needs power, to properly assess what kind of duration is required for that specific system. LDES solutions, therefore, will need to be flexible and customisable – a “one-size-fits-all” approach isn’t going to work.
As wind and solar resources continue to grow, LDES will also play a vital role in preventing the curtailment of clean energy during periods of excess generation.
Curtailment occurs when the overall grid becomes overloaded, forcing a deliberate reduction in electricity output. In simple terms, when there’s too much sunlight feeding too many solar panels, and people aren’t using enough appliances in homes and offices, the amount of power being generated needs to be reduced. This is an inefficient and poor use of solar resources. LDES mitigates this by efficiently storing surplus clean energy for later use when demand outpaces supply. Homes do tend to need more power in the hours where energy generation from renewable sources is lower.
There are several different technical approaches that can produce LDES storage. The three most common types utilise thermal, electrochemical, and mechanical systems. Each technology comes with its own set of trade-offs. For instance, pumped hydro storage, a well-established technology, boasts good efficiency and relatively low costs but faces geographical constraints and manufacturers need to mitigate against environmental concerns.
On the other hand, electrochemical systems like metal-anode batteries have fewer geographical limitations but currently suffer from higher costs and limited deployment. LDES is still not a settled field of research – where Lithium-ion batteries are effectively the standard for traditional short duration batteries, research is still ongoing for determining the most promising approach to LDES. However, this is beneficial, as having a diverse array of LDES options offers more than just flexibility – it actually safeguards the energy supply chain. Part of this is the standardisation of lithium-ion batteries, too. Because the electric vehicle industry has supercharged demand for materials like lithium, nickel, and cobalt, having a range of different and more abundant materials available for LDES solutions is important.
While LDES holds immense promise, it's important to acknowledge that it's not yet the all-encompassing solution we hope for. Many of the most promising developments in LDES technology research are still in an early stage and have yet to achieve commercial viability. Many others are costly to produce and still need to earn the confidence of investors and government bodies.
The industry also needs to work on the clarity of the message. One significant challenge facing all organisations involved in LDES lies in the absence of standardised definitions and valuation methods for energy storage. Unlike solar or wind, energy storage doesn't yet enjoy uniform recognition across the energy industry, and that makes it difficult to win over the external stakeholders that will be essential in seeing LDES solutions become better integrated into the grid.
Delivering 100 per cent clean, renewable energy is a goal of most nations and businesses at this point. However, none are willing to compromise on convenience or experience to get there. While there is still work to be done on the generation side in order to be able to meet demand, the real challenge will be addressing the storage question. It’s the variability of energy generation and consumption that makes renewables challenging. There needs to be a “moderating force” on the grid to ensure that excess generation is not wasted and instead made available for the times where there isn’t enough.
