The introduction of lithium-ion batteries for UPS systems has been much debated in recent times. Advances in technology have now reached the point where Li-ion is a safe and commercially viable option to protect the power for critical installations.
Ahead of last year’s Data Centre World London, Centiel’s design team announced the launch of its Li-ion UPS solution, which is already being installed by forward-thinking clients looking to capitalise on the advantages Li-ion has compared with lead-acid batteries – namely: smaller, lighter, high power density, a longer life and operation at higher temperatures.
Centiel anticipates that a significant industry changeover to Li-ion will most likely happen in the next five years. However, unlike Centiel’s technology, not all UPS systems on the market are Li-ion ready but they need to be.
One of the main drawbacks of switching to Li-ion until now has been the cost.
Prices are being increasingly driven down by the automotive industry and have reduced significantly in the past 10 years.
Increasingly we are being asked to provide comparative quotes for lead acid versus Li-ion batteries for UPS installations. Depending on the project, we are generally finding the initial capex cost of buying Li-ion compared with lead acid batteries works out at about twice as expensive.
However, Li-ion lasts twice as long and so considerations relating to total cost of ownership (TCO) have now started outweighing concerns about the initial investment.
Li-ion batteries had their origins in the early 1970s. Continued growth and development has been driven by laptops, then mobile phones because we all want our electronics to be smaller, cheaper, more powerful and operate for longer periods. These days, progression is such that Li-ion is being used to power electric cars.
There are some publicised stories about the fire risk of Li-ion technology over recent years. Any technology that is not managed correctly is potentially hazardous. If the proper procedures are not followed it is dangerous to drive a vehicle, fly a plane or even just cross the road.
Li-ion batteries are more sensitive to how they are charged and discharged and therefore need to be linked to a monitoring and control device. Centiel’s Li-ion battery monitoring system collects and reports data in real time. This system provides early warning alarms ahead of any issues and automatically shuts down faulty cells if necessary.
With lead acid, you may only know there is a battery problem when you need to use it and, if it doesn’t work, then it is too late. In addition, the more modern Li-ion batteries have been developed with a ‘belt and braces’ approach and can include numerous safety features such as: steel containers and internal separators that melt at high temperatures to shutdown conductivity. The current collects from the opposite end of its pack ensuring there are no hotspots at high current density areas, while improvements to the cathode material have also been achieved, which is more stable during overcharge.
Every battery, including lead-acid batteries, is a potential hazard. However, Li-ion technology has now been developed to be safe, if managed correctly, for use in data centres and other facilities requiring critical power protection. Li-ion batteries typically require less than half the physical space of the equivalent lead acid blocks and less than 25% of the weight. Commonly, above ground-floor installations can require structural strengthening of the building simply to house the required battery systems.
Logistically, moving many tonnes of equipment in and out of an upstairs comms room, when batteries need replacing, can also present challenges. For data centres looking to increase their power density within the same footprint, Li-ion promises a practical solution.
One of the main benefits of Li-ion is length of life. Ten-year design life lead acid batteries are normally replaced every seven or eight years. With Li-ion this is 13-15 years.
Switching to Li-ion could also improve the overall efficiency of the comms room. This is because a further advantage of Li-ion is that it can work at a higher temperature, therefore requiring less cooling, reducing the amount of overall energy consumed. Most IT systems work at >250°C and the UPS technology itself can work well up to 400°C. By contrast: an industry standard estimate is that for every 10 degrees above 200°C the operating life of a VRLA battery is halved.
With growing concerns about reducing the carbon footprints of data centres, being able to decrease and remove the electricity requirement for cooling could become an increasingly attractive and important consideration.
The uptake and roll-out of Li-ion across the datacentre industry will not happen overnight. Not all systems are Li-ion ready. Manufacturers of UPS equipment need to ensure their technology is compatible and can ‘talk’ to the Li-ion battery monitoring system.
Interestingly, the adoption of Li-ion within UPS systems so far has been greater in developing countries in Africa and the Middle East, where the main power grid is less reliable than in the UK and frequent power problems are more commonplace. In these instances, the UPS and battery systems are required to be cycled several times per day.
This greater adoption is primarily due to the higher cycling life of Li-ion: typically, 2,500 power-up and down cycles compared with about 300 for VRLA technology.
Over time, we believe, there will be an inevitable shift towards Li-ion batteries as further cost reductions driven by developments in the automotive industry flow through to the standby power sectors. Incorporating Li-ion will inevitably reduce the size and weight of UPS systems overall, and the longer useful working life of Li-ion will mean fewer costly replacements. This will benefit customers with reductions in both capex and opex.
As Centiel’s technology is already Li-ion ready, existing lead acid battery installations will have the option to upgrade to Li-ion in the future without needing to replace the UPS.