Can anyone comment on the use of a "constant power supply" or "rotational power supply" or "diesel UPS":
http://www.hitzinger.co.uk/dieselups.htm
http://www.hitecelectric.com/en/diesel_ups/
Hitec sells them down to 25kva, but searching around, I've seen datacenters using a half-dozen or more of the 1.8mva or larger units. Do datacenters use these in lieu of battery UPSes? Or use it to back-up just the A-side or B-side power, keeping one side on traditional battery UPSes + gen-set? Or just keep using traditional batteries, but use the "diesel UPS" as an additional layer of UPS?
Any comments on how they're priced, compared to a traditional gen-set plus several UPSes?
It looks like to do maintenance, you'd have to bypass the whole gen-set; if you didn't run the power through another UPS, you might have to run on unfiltered power during the flywheel's yearly maintenance (?).