The deployment of lithium-ion batteries in UPS applications

Schneider shared its insights into the sustainability impact - and the trends for future deployment - of Li-ion batteries in data centre UPS applications

Across the board, the pursuit of sustainable energy solutions is rapidly increasing pace. But, for an industry that represents between 1-2% of global electricity consumption, this search could not be more pressing. 

Running in parallel to sustainability demands, the European energy crisis is forcing data centres - regardless of their attitudes towards sustainability - to place sustainable energy solutions among their top priorities.

"Customers are looking for highly energy efficient equipment. Energy efficiency used to be something 'nice' to have, and customers were only looking at it for energy savings, in terms of monetary purposes," explains Mustafa Demirkol, Vice President of Data Centre Systems at Schneider Electric.

"When the cost of energy is not that high, customers put this into a secondary, 'nice to have' criteria. But, we are going through a serious energy crisis in Europe now, and nobody knows when it is going to be over."

Due to the combination of these factors, two of the most prevalent industry trends are energy efficiency improvements and the deployment of lithium-ion (Li-ion) batteries.

"Batteries are a big part of the game. The market is moving more and more towards Li-ion batteries. Around five or ten years ago, it was questionable. But now, the market is pretty convinced," Demirkol states. 

Li-ion batteries have developed significantly since their first introduction in 1985. The case for their use as a substitute for valve-regulated lead-acid (VRLA) batteries within data centre uninterruptible power supplies (UPS) has been well documented during this time. But now, VRLA batteries are largely considered to be an inferior solution, with this traditional choice being increasingly being replaced by Li-ion batteries. 

"The battery which underpins any UPS is a major consideration for any data centre owner or operator," adds Marc Garner, VP, Secure Power Division for Schneider Electric UK & Ireland. 

"Traditionally, the market has utilised VRLA batteries to ensure power continuity and continuous operation of the IT equipment and services they support. However, there are challenges with this technology in terms of their operating life, environmental requirements and monitoring."

A greener energy solution - what makes Li-ion batteries more sustainable? 

By deploying Li-ion batteries, data centres are striving towards the lowest level of carbon dioxide production across not only their products and supply chains, but also the operation of the equipment. One of the key reasons for Li-ion batteries' high sustainability is their extended lifespan. 

"Although the components of the system are more complex, Li-ion batteries have a far longer lifespan and therefore require servicing and replacement less often than lead-acid systems," explains Garner. 

"For the data centre operator, a battery which does not meet the design requirement of the load presents a major risk to service continuity. The alternative is that operators will sometimes oversize the system, with all the environmental impacts present in manufacture, installation and operations. By contrast, the characteristics of Li-ion cells mean that none of this will apply to it over the same 10-year period, and the longer lifespan of a Li-ion battery is perhaps its major advantage in terms of sustainability and TCO."

A typical lead-acid battery will have a service life of between three to five years. In comparison, Li-ion models achieve ten or more. This improvement in performance helps the sustainability (and reduces the associated costs) of the site's manufacturing, transportation, installation and operations. In fact, over a typical UPS lifecycle, a VRLA cell would need to be replaced within the system at least twice in ten years.

"The weight of a Li-ion battery is one-third of a regular battery, but with the same backup time. So, when you reduce the weight by that much, you reduce the carbon dioxide emissions dramatically. Secondly, because the lifecycle of the batteries is much higher, this gives you significant operational advantages," Demirkol explains.

"You don't have to perform operational shutdowns every three or four years, and you don't need to recycle the batteries every three or four years. So the cost of a battery was really high, but with the advancement of Li-ion batteries, it went down significantly."

Alongside this, the energy consumption of a Li-ion battery is also considerably less. 

"During its operational life, a Li-ion battery typically consumes less energy than a VRLA alternative because its internal chemistry makes for a slower self-discharge rate. As such, they do not need the same amount of recharging, and over its lifetime, a lead-acid battery will typically lose 0.2% of its rated capacity, roughly double that of a Li-ion battery which typically loses only 0.1%," Garner adds. 

Implementing Li-ion batteries while prioritising lifecycle management

However, data centres need to note that if they do decide to implement Li-ion batteries, this needs to be done in a way that successfully manages the full lifecycle of the technology. Namely, through a sustainable end-of-life strategy. 

"As a mature battery technology, lead-acid cells are supported by a long-established recycling ecosystem designed to minimise waste and repurpose components. In fact, lead-acid batteries have a return for recycling rate of up to 99.3%," Garner illustrates.

"As a newer technology, Li-ion still relies mainly on mining extraction for raw materials as the necessary recycling practices are still being developed."

As a result, e-waste management is particularly critical with Li-ion batteries, and successful end-of-life requires a lot more sophistication than other battery alternatives. Thankfully, however, the second-use market offers a very promising solution. 

"Most of these batteries work perfectly well, just not in a data centre environment. But, say in residential energy storage units, they are perfectly suited to working in that environment. After all, you don't need that level of high performance in a house, you just need a backup power," Demirkol explains. 

New technologies are constantly being developed to improve the recyclability of these batteries. But in the meantime, the second life market is rapidly expanding in scope. 

"What we see is that the market is going to move towards secondhand solutions. After all, why would you even waste that totally fine battery? Why are we even recycling it?," poses Demirkol.

"A commitment to best practices with regards to taking back defective and end-of-life batteries is helping reduce the environmental impact of Li-ion, whilst its recycling processes continue to be established and mature," adds Garner.

Interestingly, the electric vehicle market is paving the way for second-use applications. Alongside this, other examples of second-use Li-ion cells being utilised include microgrid applications, and hospitals to support emergency lighting. 

Looking forward, recycling technologies are also set to improve dramatically. Established pyrometallurgical techniques are already being applied to Li-ion batteries at end of life to recover the cobalt and nickel elements. Alongside this, newer hydrometallurgical techniques are being developed, which could recover over 95% of all constituent materials.

Given the high sustainability performance of these batteries, and the ongoing innovations in their manufacturing and recycling that market demand is driving, Li-ion batteries will hold a key role in the green data centres of the future. 

"Although there are inevitable environmental impacts emerging with the growth of this resilient and energy-efficient technology when evaluated holistically, it's clear that Li-ion batteries offer a more sustainable solution for UPS systems," Garner asserts. 

"When combined with the characteristics of more compact design, lighter weight, longer lifecycle and more reliable performance, they make a compelling case for use in an industry where both space and uptime are at a premium."

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