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Why SunGard uses flywheel UPSes in its data centers

For its data centers, SunGard has chosen flywheel uninterruptible power supplies. A SunGard executive explains why the company chose flywheels over battery-based backup.

For data centers, a concern with flywheel-based uninterruptible power supplies (UPSes) is their ability to transition the data center load from primary utility power to backup generators. So the question is why a company like SunGard – where uptime is crucial to its disaster recovery business – has decided to use flywheel UPSes despite the shorter ride-through time. Karl Smith, the head of critical environments at SunGard Availability Services, explains.

For more on data center backup power:
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How long has SunGard used flywheel UPSes?
Karl Smith: The first installation of the VYCON flywheel was approximately three years ago as part of a trial to understand how the system performed over a period of time.

When did SunGard first consider using flywheels, and why?
Smith: For several years now, but at that time they were new in the market, so we wanted to gain some experience with them over time. We liked the VYCON solution, as we see it as the next-generation flywheel utilizing high-speed technology and full magnetic bearing that totally removed the need for maintenance of any mechanical bearing used in older designed flywheels.

The driver for utilizing flywheels is to reduce the lifecycle cost and maintenance requirements when installing large banks of batteries. In addition, the space savings by using flywheel and fewer batteries means lower construction costs and allows for optimum space utilization.

If you have a mix of flywheels and battery UPS, how prevalent are the flywheels? Are there some in every SunGard data center?
Smith: Our legacy data centers still have batteries, but as it becomes necessary to replace the batteries, we would like to reduce the number of strings of batteries and complement them with a string of flywheels as well. For future data center builds, we are planning on having a combination for short-run time batteries, in parallel with a bank of flywheels.

One of the concerns often cited for flywheels is they don't have as much ride-through time that a string a batteries can have. Has this been an issue, and if so, how do you deal with it?
Smith: It is true that batteries provide much longer ride-through time, but the most important ride-through time is in the first 30 seconds. We don't need much more than this to have our stand-by generators come online. In most cases, our generators are online and loads are switched over in 30 to 40 seconds. The flywheels will be our first line of defense, but should we need a few extra minutes to get a redundant generator online, then the battery can be utilized. Having the flywheels discharge first means the batteries are not discharged in normal operation, thus their life can be extended.

What is the maintenance/upkeep schedule for flywheels? How does it compare with battery-based UPS?
Smith: Flywheel maintenance is simply the changing of the vacuum pump oil every year, which only takes about 10 minutes. The useful life of the flywheel is around 20 years. Batteries, on the other hand, need to be checked every three months and then replaced typically every six to seven years. Every interconnection between the 32 to 40 batteries also must be checked for loose connections.

The nice feature on the flywheel system is you always know the "state of charge" of the energy storage. If the flywheel is spinning, then energy is available. While you can have battery monitor systems on the battery, you really don't know how much energy you have until the battery is under load, which typically only happens when there is an outage.

Let us know what you think about the story; email Mark Fontecchio, News Writer. Also, check out our blogs: Data Center Facilities Pro, Mainframe Propeller Head, and Server Farming.

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