Delta Dental of Michigan opened its state-of-the-art data center in July 2009 and garnered a distinction of being one of only 19 centers worldwide to earn a Tier III design rating from the Uptime Institute. They’ve also pumped a lot of “green” technologies into their data center, including outside air economizers and efficient cooling by way of overhead cabling to prevent airflow obstruction. I recently spoke with Christian Briggs, Delta Dental’s data center manager, on why the company decided to deploy flywheels as part of the backup power chain.
When did Delta Dental actually implement flywheels in its data center? How long had it been in the works?
Flywheels were part of the initial opening of the data center. They were in the design of the building [construction lasted approx. 13 months, with design at about seven months].
Could you describe the decision-making process in using flywheels?
This was something that we looked at from the beginning. We had previous bad experience with batteries even though we were keeping up with our maintenance.
In a recent case study on Delta Dental’s data center, you mentioned that batteries are front-ended with the flywheel in your data center. Did you totally phase out batteries as a standalone UPS option, or are they still individually a component of your data center?
Our UPS system will supply power to the load side using power from the flywheels first, then transition over to the batteries. This configuration is often referred to as a battery-hardening configuration. It is designed to pick up the load for short power outage situations. It also allows for a more gradual transfer of power to the batteries rather than a sudden hard drop. The slower transition is less harsh on the batteries and will extend their life span.
You also mentioned that you didn’t purchase the flywheels specifically for their green aspects. What was the main reason you decided to use the technology in your data center? Were there any disadvantages or tradeoffs in using flywheels compared to what you had in place before?
Many of the “green aspects” didn’t apply since we were also going to purchase and install batteries. The main reason was to harden the battery system. The main disadvantage with the flywheel is that systems currently on the market can only store enough kinetic energy to last for about a minute. That isn’t enough time to coordinate an orderly shutdown, but it is enough time to transfer on to generators. We have and continue to develop a very rigorous testing program for our emergency power supply chain [Delta Dental utilizes switch gear, paralleling gear and generators], but even with that, there is always the chance that the breaker that worked just fine in a test the day before trips on the day that you need it. When that happens, the data center has about 40 minutes to orderly shut down the most critical portions of our business.