Dispelling the doubts on Li-Ion UPS battery storage
Thu 30 Aug 2018 | Leo Craig
Data centre managers still have their misgivings over the practicalities of demand-side response and energy storage.
Riello UPS’s Leo Craig argues the perceived risks are far outweighed by the potential rewards and claims its time operators learn to take advantage of the benefits of lithium-ion UPS battery storage.
Reports reveal that more than three-quarters (77%) of mission-critical organisations have an interest in participating in demand-side response (DSR), but only if it doesn’t negatively impact on its core activities.
Both parts of that statement are unsurprising. With the National Grid facing increased pressures, data centres are obviously open to the argument for a more flexible and reliable electricity network.
Li-Ion batteries operating at 30°C will have a longer life than an SLA functioning at 20°C
But when you’re dealing with sites and server rooms that demand 100% uptime, there’s clearly a natural reluctance to do anything which might weaken that must-have resilience.
As a rule, mission-critical sites such as data centres are naturally risk-adverse. And they have good reason to be so, particularly when energy-related failures can cost a business around 17% of their annual turnover.
It’s also a truism that few organisations want to be seen as ‘guinea pigs’, they want to see the hard evidence that new technologies and processes work before throwing their weight fully behind them.
It’s up to those of us who support the benefits of using uninterruptible power supplies (UPS) and batteries in data centres not just as a standby power system but as a means to generate and store green energy to champion this cause.
We need to highlight success stories. We need to offer practical solutions to the perceived problems. And we need to keep making the environmental and economic arguments.
From Lead-Acid To Lithium-Ion
Sealed lead-acid (SLA) batteries, also known as valve-regulated lead-acid (VRLA), have long been the go-to option for data centre operators. They’re reliable and relatively inexpensive, particularly their initial purchase cost.
Compared to SLA, Li-Ion provide the same power density in less than half the space.
But they’re far from faultless as optimum performance requires a temperature-controlled environment (20-25°C) with lots of energy-intensive air conditioning.
They need lots of maintenance and because their impedance increases over time – which reduces their capacity – SLA cells must be replaced fairly frequently.
Lithium-ion (Li-Ion) batteries are becoming an increasingly viable and attractive alternative.
Compared to SLA, Li-Ion provide the same power density in less than half the space.
They can operate safely in much higher temperatures (up to 40°C), recharge much faster, and have up to 50 times the cycle life.
Over the lifespan of a Li-Ion battery block (which can be between 10-15 years), lead-acid cells would in all probability require replacing two or even three times.
So although the initial cost of lithium-ion would still be higher than SLA, the total cost of ownership (TCO) over a 10-year period could be anywhere from 10-40% less.
Of course, this doesn’t mean that suddenly every UPS installed in a data centre will use Li-Ion batteries.
But in an increasingly competitive industry, it’s fast becoming an option that offers data centres an all-important edge.
Lithium-ion cells deliver the same power in less space, and as they can operate at higher temperatures could even remove the requirement for a separate battery room.
With commercial property costs high and likely to remain so, these potential floorspace and air conditioning savings will undoubtedly prove popular with data centre operators.
Add in the improved environmental performance and potential revenue streams offered by DSR, income that could be used to pass savings onto customers, and we could be looking at a significant competitive advantage.
Learn More About Li-Ion UPS Batteries
Riello UPS works closely with leading battery manufacturer Yuasa and has partnered on several recent projects using their Li-Ion cells.
Their Senior Technical Coordinator Peter Stevenson answers some of the most common queries asked about lithium-ion batteries and their use with uninterruptible power supplies.
Li-Ion batteries employ a wide range of chemistries and structures, so they can be optimised for different applications
What are the main advantages of using lithium-ion batteries with a data centre UPS?
Li-Ion batteries are about 25% of the volume and weight of an equivalent SLA battery, so that’s a big benefit in settings where space is limited.
They’re far less sensitive to temperature fluctuations, so for example, Li-Ion batteries operating at 30°C will have a longer life than an SLA functioning at 20°C. In many environments, this means fresh air cooling systems can be used, rather than expensive air conditioning, which is a significant plus in terms of total cost of ownership.
It’s also easier to predict the ageing of lithium-ion, reducing the risk of rapid loss in performance that is sometimes seen with SLA.
Finally, Li-Ion batteries typically provide up to 50 times as many deep discharge cycles as SLA. While this isn’t hugely significant in a traditional UPS, this could change if the rapid growth of solar and wind generation means a UPS’s role evolves from purely providing emergency power into an energy storage system that can generate revenue on a daily basis.
But are there any disadvantages to using Li-Ion instead of SLA?
The main and obvious disadvantage is the initial cost. Even though massive investments in automated manufacturing processes have resulted in significant cost reductions for Li-Ion over the last 20 years, the basic raw materials are still expensive compared with lead-acid.
Recycling is also an issue too. There’s still much work required to reproduce the well-developed and cost-effective recycling of lead-acid cells.
Are Li-Ion batteries in a UPS safe? Aren’t they a greater fire risk as seen with all those Samsung Galaxy Note 7s bursting into flames?
Li-Ion batteries employ a wide range of chemistries and structures, so they can be optimised for different applications. The batteries used in mission-critical systems use much more robust chemistry and packaging than the ultra-light cells found in hand-held devices.
there’s currently more than 4 gigawatts of electricity stored in Li-Ion UPS batteries in the UK
Is battery monitoring important with Li-Ion?
An advanced battery management system (BMS) is mandatory for high-voltage Li-Ion applications because each cell must be individually monitored and controlled using electronic circuits to maintain balanced states of charge.
Similar BMS are optional with SLA batteries, and although preferable in large-scale applications, they would incur significant additional capital costs.
Why haven’t data centres fully embraced the energy storage potential of lithium-ion batteries yet?
It’s more a case of ‘seeing is believing’. Examples of success in other industries will hopefully give increased confidence to the power protection sector in the next few years. The deployment of 20-megawatt grid-connected energy storage systems, which are now fairly commonplace using Li-Ion, should also provide encouragement.
Powering Ahead To The Future
Even the most conservative estimates suggest there’s currently more than 4 gigawatts of electricity stored in Li-Ion UPS batteries in the UK. That’s enough energy to power roughly 3 million typical homes.
Considering we’ve only just scratched the surface of the potential of battery storage, the future possibilities are huge. We need to do all we can to persuade more facilities with critical power protection systems in place about the benefits of both lithium-ion UPS batteries and demand-side response.
And this doesn’t just apply to data centres, it relates to other sites with on-site backup power generation too, essential infrastructure such as hospitals or utilities. If these sorts of organisations buy into the economic and environmental advantages, we’ll all reap the rewards.
Next week we’ll explore a recent project of ours, where uninterruptible power supplies with lithium-ion batteries were used to create a ‘virtual power plant’ that generates the energy required to run a busy office complex used by 40 staff.