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Emerging UPS Standby Power Sources Four Promising Alternatives to the Lead Acid Battery

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Emerging UPS Standby Power Sources Four Promising Alternatives to the Lead Acid Battery Thought leadership White paper Emerging UPS standby power sources Four promising alternatives to the lead acid battery Ed Spears Executive summary Product manager, Eaton Power Quality, Eaton Though an uninterruptible power supply (UPS) performs many important functions, most users value them chiefly for the emergency energy they provide during a power outage. UPSs give IT personnel the time they need to protect sensitive equipment and data from the effects of an electrical service interruption by starting a backup generator, shutting down systems in an orderly fashion, or moving data and processing to a disaster recovery site. Today, most UPS products use lead acid batteries to store emergency standby power. A proven technology with many decades of successful service in a variety of industrial settings, the lead acid battery is usually the most cost-effective energy storage solution as measured by dollars per minute of backup time. Yet despite these merits, lead acid batteries can be unpopular among data center managers due to their size, weight, maintenance requirements, toxic contents and relatively short service life, among other issues. As a result, UPS makers have long been searching for an alternative standby power technology that’s smaller, more reliable, and “greener” than lead acid batteries, yet no more expensive to operate. Today, that hunt is nearing its end. Several exciting new standby power solutions, all rapidly approaching mainstream commercial viability, appear poised to give the lead acid battery a run for its money. This white paper will explore the strengths, weaknesses and future prospects of four such technologies: Lithium-ion batteries, flywheels, ultracapacitors and fuel cells. Figure 1: Lead acid battery Traditional choice: Lead acid yet still provide a reasonable Disadvantages: – Disposal: The batteries service life in float or idle mode. • Form factor: Lead acid in an average UPS could Lead acid batteries are hardly • Backup time: Lead acid batteries are bulky and contain up to several hundred a cutting-edge technology. batteries deliver relatively high extremely heavy. Indeed, the gallons of highly toxic dilute In fact, the first one was amounts of backup time— batteries in a typical medium- sulfuric acid. As a result, invented some 150 years ago. typically five to 15 minutes. sized UPS weigh five to eight disposing of them is legally Yet they remain the standby tons. As a result, lead acid required, expensive and a energy storage solution of • Price: Lead acid batteries are tightly-regulated process. available at a relatively low batteries offer lower energy-to- choice in UPS products today, weight and energy-to-volume Most UPS owners ship their and with good reason: No price, making them the most used batteries back to the cost-effective standby power ratios than some other battery other mainstream technology types. manufacturer for recycling, handles the unique demands storage solution currently which entails covering of the data center as available but now that is • Costs: Between maintenance, freight costs for several effectively or affordably. changing rapidly, as other replacement and disposal, tons of extremely hazardous technologies have ‘caught up’ lead acid batteries have a Unlike the batteries in a forklift cargo. Disposal costs should in affordability. Competitively much higher lifecycle costs always be included in the or hybrid gas-electric car, which priced alternatives exist today. associated with them. get regular and steady use, battery replacement cost the batteries in a UPS spend • Battery monitoring systems: – Maintenance: The sealed estimates and specifically most of their time idle. Then, Several commercial systems lead acid batteries typically reference proper disposal perhaps two or three times a are available to constantly used in today’s UPS products process based on the country year, a power outage occurs, measure individual battery are often referred to as requirements for battery causing the UPS to discharge performance and provide real- “maintenance free.” In fact, disposal and recycling. its batteries very rapidly and at time reports and alarms when however, they should be • Reliability: The only sure way high current. When power is batteries may need attention or inspected at least twice a to confirm that a lead acid restored, the UPS recharges replacement. Newer ones can year to ensure that they’re battery is ready to provide the batteries, which then enter proactively detect and mitigate tightly connected, free of emergency backup power is another extended waiting period. thermal runaway, a dangerous corrosion and in good working to conduct a test discharge. Thus, while UPS batteries aren’t condition. These are fairly order. Hiring specialists to Unfortunately, however, every used often, when they are used sophisticated tools, and can perform such work might time you test-discharge a lead it’s usually fast and hard. be costly and require a user to cost $2,000 per year or acid battery you permanently interpret the information and more, depending on the reduce its capacity and slightly follow through on arranging battery size. shorten its operating life. Advantages: a qualified vendor to inspect – Replacement: Sealed lead Though the battery testing • Internal chemistry: Lead acid or replace the identified acid batteries generally have programs built into most batteries are an almost ideal battery. Used correctly, battery a five to six year service life. modern UPSs reduce such fit for the unpredictable and monitoring systems can extend That means data centers battery wear, they do not inconsistent IT environment, as the useful life of sealed lead must budget to replace them eliminate it. their internal chemistry enables acid batteries and prevent two to three times over the them to provide high amounts disruptions when an individual lifespan of a typical UPS. of current on short notice, battery fails, resulting in shorter backup times. Alternative #1: Lithium-ion Advantages: Disadvantages: What the future holds: • Compact form factor: The • Higher cost: Until recently, Today’s lithium-ion batteries Most cell phones and laptops best lithium-ion batteries lithium-ion batteries cost are now able to serve as use lithium-ion batteries, currently available deliver a 60 several times as much as an attractive alternative to which have grown steadily percent weight saving and 40 comparable lead acid models lead acid UPS batteries. The smaller, lighter and denser percent footprint saving over upfront. lithium-ion cell’s small size and over the last decade. In lead acid batteries • Safety concerns: Safety high density make it the best industrial settings or data option for use in hybrid and centers, lithium-ion batteries • Improved backup time: The is a concern. If overheated batteries are not only much or overcharged, lihtium- plug-in electric vehicles. As a are capable of performing result, car manufacturers are the same functions as lead lighter and smaller, but also ion batteries have been improve backup time by 30 known to explode and burn working actively with suppliers acid batteries, while offering to develop safer, more compact significant additional benefits. percent. profusely when ignited. However, lithium chemistries and more affordable models. • Long lifespan: Lithium-ion In fact, experts now agree that batteries feature a 10-year for UPS applications use safer chemistries, and active lithium-ion batteries now offer service life and a much higher a lower total cost of ownership cycle life, which will save you management systems that disconnect a failing battery than lead acid batteries. Many money in the longrun. This observers believe lithium-ion makes them ideal for grid- long before a dangerous condition develops. batteries are likely to become sharing applications, being the preferred technology for UPS considered by some data standby power. center operators. It is worth noting that lithium- • Battery monitoring system: Leading lithium-ion batteries ion is not the only new battery have a built-in battery chemistry that holds promise management system to for UPS applications. Nickel provide automatic balancing, zinc, Sodium sulfur, and even optimization, and protection saltwater batteries are currently for temperature, voltage levels being tested with UPS systems. and current concerns. These chemistries offer excel- lent performance and an even better safety profile than either lead acid or lithium-ion. Figure 2: Lithium-ion 2 EATON Thought leadership White paper Alternative #2: Flywheels Advantages: Disadvantages: What the future holds: • Compact form factor: • Limited backup time: A Though flywheel technology is A flywheel is a mechanical Flywheels are significantly typical lead acid UPS battery improving, progress has been device typically built around smaller and lighter than lead provides 3 to 15 minutes of slow. As a result, practical a large metal disk. During acid UPS batteries. emergency power. A typical flywheels capable of generating normal operation, electrical • Low environmental impact: flywheel delivers only 15 to 30 power for significantly longer power spins the disk rapidly. seconds of standby energy. than 30 seconds are unlikely to When a power outage occurs, Unlike lead acid batteries, flywheels don’t contain Companies have the option of be available any time soon. For the disk continues to spin installing multiple flywheels, most organizations, 30 seconds on its own, generating DC dangerous and ecologically- harmful chemicals. but that still limits them to a isn’t enough time to prepare power that a UPS can use as few minutes of backup energy. critical IT systems for the impact an emergency energy source. • Long lifespan: Flywheels of a major power outage, so As the UPS consumes that typically enjoy a ten-year • Higher cost: The metal disk at the heart of most large broad adoption of flywheels as power, the disk gradually service life, versus about an exclusive source of standby loses momentum, producing five years for most lead acid flywheels usually rests on a bearing that is very expensive data center power will probably less and less energy until batteries. Moreover, while a be limited over the near term.
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