PTS: Blog

LinkedIn Discussion on Eliminating the Battery String

Thanks to everyone who’s participated in our Computer Room Design networking group at so far! We’re off to a great start, with over 200+ members joining in the first two weeks. I’d like to share highlights from one of our recent discussions…

Kevin Woods, Director of Business Development and Sales at i2i, asked:

Eliminating the Battery String? Does anyone have experience/opinion on the viability of the UPS/CPS systems? They incorporate a flywheel in between the generator and engine and in cases of power interruption, the flywheel uses kinetic energy to power the generator for up to 30 seconds while the engine is engaged.


• Mark Schwedel, business partner at EMC and advisor for Green Rack Systems, recommended taking a look at the patent for an improved UPS/CPS system, which employs a high-efficiency uninterrupted power supply function integrated with an engine-generator set that combines both short term protection against momentary power interruptions with longer term power generation.

• Gordon Lane, Facilities Coordinator at Petro Canada, shared his experience:

Not a direct comparison to gen/engine set up but I have a flywheel UPS system that has been in service for 23 years. Very reliable, change the bearings every 50000 hours – about 6 years – and we have just about completed a program of taking the MGs out for cleaning and re-insulation.

Obviously coming to end of life, 20 yrs was estimated life, but the serviceability has been phenomenal.

Certainly looking to replace with a similar system and I believe Caterpillar has a flywheel UPS solution that they integrate into their diesel offerings.

• Jason Schafer, Senior Analyst at Tier1 Research, explained in part:

My personal issue with flywheel solutions, aside from the reliability that both sides will argue, is that 30 seconds simply isn’t enough time when you are talking about the criticality most datacenters need. The most common argument relates to allowing time to manually start a generator; and flywheel advocates will say “if a generator doesn’t start in 30 seconds it’s not very likely that it’s going to start in 20 minutes” – I disagree with this. I’ve seen, on more than one occasion, where generator maintenance was being performed and through human error the EPO switch on the generator was mistakenly left pushed in. There’s no way anyone is going to identify the problem and fix it in 30 seconds – I’d be surprised if anyone even got to the generator house in 30 seconds after a power outage. Minutes, however, are a different story.

I’m not saying that flywheels and CPSs don’t have their place – I think they do, or rather will in large scale in datacenters, but we’re not quite there yet. When virtualization plays a part in the redundancy and fault tolerance of a datacenter, where ride-through in the event of a power outage is more of a convenience than a necessity (a-la Google’s datacenters – they can lose an entire facility and continue on for the most part), you’ll see flywheels gain more traction.

What are your thoughts on the viability of the UPS/CPS systems? Please share your experience by posting a comment here, or by continuing the discussion in the Computer Room Design Group on LinkedIn.