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It is therefore important that any downtime of a data centre is avoided (the cost of which is estimated at around £7,000 per minute) to keep data safe and businesses running. Having a reliable backup system in place can help reduce the risk of outages and therefore downtime. This is essential now more than ever as data centre operators are moving towards higher levels of reliability, energy efficiency and performance, due to the growing reliance of data and tightening of environmental legislation. Every area of data centre architecture is being affected, including the UPS (Uninterruptible Power Supply).
The UPS role in a data centre is to maintain a consistent high-quality power supply throughout the unlikely event of a power outage or short-lived drop in power quality. It keeps servers running (from periods between 1-15 minutes) if either of these events occur.
In terms of UPS infrastructure, there is a major trend of adopting Lithium-ion (Li-ion) battery systems in data centres. Until recently, almost all data centres have relied on valve-regulated lead-acid (VRLA) batteries, but Li-ion is set to take at least a 10% share of the market within the coming years.
Compared to the traditional lead-acid electrochemistry, Li-ion has significant benefits – especially for UPS. Due to its high power density, Li-ion delivers more power with a lower footprint and lower weight over a longer lifetime (above 15 years) and lower maintenance. It is also compatible with electronic smart monitoring.
High reliability and availability
An important example of Li-ion technology is SLFP (Super Lithium Iron Phosphate), which is well suited to data centres as it offers the highest level of safety and power density, with a long calendar life. This is ideal for mission-critical applications such as data centres where safety is paramount.
An example of the practical applications of SLFP chemistry is the Flex’ion battery range for data centres, oil and gas and utility applications. Flex’ion batteries have high availability – there is no risk of sudden death, they have low maintenance requirements and fast discharging rates, minimising the chances of an unplanned outage.
However, if an outage does occur Li-ion technology allows the battery systems to be recharged quickly, increasing the system’s availability after an outage or discharge. Flex’ion Li-ion batteries only take 75 minutes to recharge, whereas traditional VRLA batteries require 8-12 hours recharge time. There is even a high-power version of Flex’ion that can be recharged within 15 minutes with a smart charger.
Availability is also increased by in-built intelligence known as Intelli-Connect supervision, which allows for the battery to be available even when the charger is disconnected or UPS connection lost.
It’s really difficult to know when a lead-acid battery will fail, so there is potential for a data centre failure to occur because the expected backup power is unavailable. So, when using lead-acid batteries in data centres, operators either have to accept this risk, or invest in further redundancy.
Li-ion battery systems have inherent smart monitoring, which offers the ability to tell an operator about their State of Charge (SOC) and State of Health (SOH), as well as any alarms and if any replacement components are necessary. This means that operators don’t have to waste money on replacing them too early, but also prevent a loss of critical back-up power.
Improving Power Usage Effectiveness (PUE)
The energy efficiency of a data centre is measured by Power Usage Effectiveness (PUE) and it is based on the ratio of the total energy consumed by a data centre to the energy consumed by computing equipment. Those data centres with the highest energy efficiency have the lowest PUE number.
Low PUE numbers can be achieved by Li-ion systems as they have the capability to achieve 97% energy efficiency. Traditional VRLA batteries can only reach 80% and other lead-acid batteries only 73%.
Feeling the heat
Li-ion technology also has the ability to withstand higher temperatures than VRLA batteries, so less energy is needed for cooling when a Li-ion battery system is used. Flex’ion, for example, can withstand a continuous operating temperature of 35°C at full performance for up to 20 years. Traditional VRLA technology on the other hand has a reduced calendar life and degraded performance when exposed to high operating temperatures. This means that operators have to invest in cooling equipment to overcome this issue, increasing energy consumption and reducing PUE.
As a result, by installing a Li-ion battery, system savings can be made both in terms of CAPEX and OPEX. The size of HVAC equipment can be reduced, decreasing CAPEX, and a lower energy consumption over the battery’s lifetime will occur, decreasing OPEX.
The best things come in small packages
Data centre operators can now switch to small and lightweight batteries as Li-ion has higher power density than VRLA batteries. This offers major benefits as it makes the handling of the batteries easier and minimises the amount of space they take up. This has the potential to be the key for operators to create huge infrastructure savings for enterprise and co-location data centres located in major cities.
More space would also be made available for servers or other services by implementing Li-ion technology. Flex’ion systems, for example, are up to three times more compact and six times lighter than traditional VRLA batteries.
Heavyweight VRLA battery systems also have to be supported by structural steelwork which requires more bracing and vertical support than a Li-ion battery. The cost to put this structure in place can make the cost of a Li-ion battery look minimal. Therefore it’s worth thinking in terms of the bigger picture when choosing which battery system is right for your data centre.
About the author:
Francois Danet is Li-ion Business Development Manager at Saft for the Data Centre/Big Data within Industrial markets. He is based in Levallois-Perret, France at Saft’s headquarters. After working for SKF Group as an Application Engineer, he launched and monitored International tools for Citroen as After Sales Manager. He has joined Saft in 2007 first as Railway Sales Engineer and Sales Manager. Today, he prescribes and develops channels to market, builds high level relationships with key players, supports strategic product development, potential partnerships and investments.
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