DISQUS

Jin · 6 months ago

Flywheel technology, by nature, has high efficiency (as high as 95%, for AC-AC), and fast response time (in milli-second). Its efficiency is the highest among all energy storage technologies. Typically, it cannot store large amount of energy. For data-center application PentaDyne is offering, the duration of storage in 10s of seconds. It has to be connected with a battery (most likely, Lead-Acid battery) or diesel generator set to be able to back up for minutes or hours. It radiates heat in motor/generator part. Large size of flywheel needs active cooling-water system.

crtoca · 6 months ago

I'm sorry but I must challenge your assertion on flywheel efficiency. Yes, they are incredibly efficient DC-DC, but the AC-DC-AC will drop their overall efficiency to much less than 95%, more like 85%.

Of course, for the tiny amount of energy they must deliver, it's probably not an important discussion. Their application is for short pulse when needed, so the energy loss is not important.

Jin · 6 months ago

AC-AC i mean on the motor/generator side, not on the grid side. Flywheel motor/generator works not on 60Hz, and has to use AC-DC-motor for charging, and generator-DC-AC for discharging. Btw, the power electronics, i.e. the convertor and invertor, the efficiency of it is not that bad for now, likely <5%. But again, it all depends on the size, vendor, working condition, etc.

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flywheelenthusiast · 5 months ago

The Pentadyne flywheel connects to the DC bus of a UPS system. While the flywheel motor is AC output, it is converted to a constant voltage DC which emulates a battery expect it designed to provide only 10-20 seconds of back-up vs minutes that a battery can provide. Because most data centers use standby diesel gen sets that only take a few seconds to start once the utility fails, the idea is to use the flywheel energy to "bridge" the time from the utility failure to the genset start. Flywheels are a great alternative to batteries, with a number of benefits. Efficiency improvement is not one of them. The flywheels take about as much energy, if not more to keep them spinning than it takes to keep batteries charged. So going from batteries to flywheels doesn't effect the overall efficiency of the delivered power to the data center.

Unfortunately Pentadyne is a poorly managed company that has burned through $80M and still not able to turn a profit. They had achieved tremendous success in commercializing the product in 2005 and growing sales in 2006 and 2007, but with a CEO change in 2007 the company has struggle with cost reduction, product reliability and now three years of flat sales.

I like Active Power's play in the field as they are seeing good traction in power quality and also Vycon who is an up and coming company who's flywheel applications includes energy re-cycling markets for electric rail and cranes, which can be much more profitable than competing against batteries in the power quality segment.

RonHumphrey · 5 months ago

Can anyone tell me if any company is working on large scale flywheel storage technology for a possible national power grid renovation? Will it work for stabilizing solar/wind sources of power generation well enough to provide power when the sun isn't shining and the wind isn't blowing?

Name · 5 months ago

Beacon Power, http://www.beaconpower.com. The current product can store 25kwh with 100kw power output. And it will be bundled into 1MW, 5MW or 20MW energy storage plant for grid storage, such as frequency regulation, which is the application Beacon Power is doing today at NEISO. Flywheel for UPS is a niche application.