Eaton Corporation (http://www.eaton.com/), says:
A complete power protection solution typically includes more than just a UPS. Here are some accessories worth considering.
UPS energy storage
Most power protection solutions get their emergency standby power from either sealed batteries (also known as Valve Regulated Lead Acid, or VRLA, batteries) or flooded batteries (also known as Vented Lead Acid, or VLA, batteries). Sealed batteries tend to be less expensive, but also wear out sooner. Flooded batteries generally require specialized installation and maintenance. Deciding which kind of battery is right for you basically comes down to whether you’re willing to pay more upfront for batteries that you won’t have to replace as often.
Though lead-acid batteries are a proven technology well suited to the rigors of the data center, they’re also bulky and heavy. Furthermore, due to the toxic chemicals they contain disposing of them is an expensive and tightly-regulated process. As a result, more and more companies are supplementing lead-acid batteries with alternative standby power supplies, such as flywheels. A flywheel is a mechanical device typically built around a large rotating disk. During normal operation, electrical power spins the disk rapidly. When a power outage occurs, the disk continues to spin on its own, generating DC power that a UPS can use as an emergency energy source. As the UPS consumes that power, the disk gradually loses momentum, producing less and less energy until eventually it stops moving altogether.
On the plus side, flywheels are smaller and lighter than lead-acid batteries, easier to maintain and free of dangerous and ecologically-harmful substances. On the negative side, they typically deliver only 30 seconds of standby power. However, research shows that more than 95 percent of utility outages last just a few seconds, so using a flywheel as a complement to batteries during brief power interruptions can save data center floor space and lower maintenance costs, while also extending the life of your lead-acid batteries by reducing how often you use them.
During a utility failure, a UPS gives you the few minutes of time you need to shut down servers gracefully.
These days, however, many companies can’t afford to be without IT systems for the hours or even days that may elapse before electrical service is restored. Such organizations almost always include a generator in their power protection architecture. While UPSs provide brief periods of emergency power, generators draw on a supply of diesel fuel to keep IT systems operational for anywhere from 10 minutes to seven days or more.
When choosing a generator, look for one with 1.25 to 3.0 times the kVA rating of your UPS. The sizing process should be based on a number of factors, including UPS design, generator and fuel type, so seeking expert advice from the UPS and generator manufacturer is suggested.
In addition, be sure to maintain a supply of diesel fuel large enough to keep your data center operational for prolonged periods. During an extended power outage, demand for diesel can quickly outstrip regional supplies.
Power distribution units
An essential component of any power quality infrastructure, power distribution units (PDUs) distribute power to downstream ITE load equipment. Most companies use both floor-mount PDUs, which provide primary distribution to server racks, and rack-mount PDUs (also known as ePDUs), which distribute power to individual servers and other devices. PDUs can be equipped with optional devices like surge suppression and individual breaker (branch) monitoring systems to monitor energy use.
Businesses today invest large sums of money in their IT infrastructure, as well as the power required to keep it functioning. They count on this investment to keep them productive and competitive. Leaving that infrastructure defenseless against electrical dips, spikes and interruptions, therefore, is a bad idea.
A well-built power protection solution, featuring high-quality, highly efficient UPS hardware and appropriate accessories, can help keep your business applications available, your power costs manageable and your data safe.