In computing, while solid-state drives are replacing spinning hard disks for memory storage, spinning disks are starting to replace solid-state batteries for energy storage. Flywheel uninterruptible power supplies (UPS) store electric energy as kinetic energy in the form of heavy, spinning disks, which can produce electricity on demand. A flywheel UPS sitting between the data center and the grid can ensure that little power hiccups won’t knock out the system. Pentadyne, Active Power (s ACPW) and VYCON all make flywheel UPSs for data centers; in fact it’s one of their fastest-growing market segments.
Battery-based UPSs perform the same function, but flywheels offer some considerable advantages. Energy costs are a growing concern for data center managers and flywheel systems can operate at 98 percent efficiency compared to a rate of 92 percent for battery systems. Meanwhile, a battery’s efficiency will drop over time and cells often need replacing every 3-5 years. Flywheels suffer little to no degradation and are designed to last up to 20 years. Flywheel systems can also be used to complement battery systems, helping extend the life of existing battery-based backup by absorbing most of the power fluctuations that would shorten a battery’s life.
Space is also a premium in crowded data centers. The spinning discs are extremely energy dense; a 600-pound spinning steel wheel can store a lot of energy. Meanwhile, a flywheel system can have about half the footprint of comparable lead-acid battery system. While flywheels backups do cost a little more up front, Active Power tells us a 10-megawatt system could save a customer $20 million in energy and maintenance costs over those 20 years.
Active Power just signed a multimillion-dollar order with an undisclosed “global Internet search engine provider” last week for 12 1200 kVA CleanSource UPS, which will have a total capacity of 12 megawatts.
Pentadyne says it has recently surpassed Active Power to become the largest manufacturer of flywheel energy storage systems. Just this week, Pentadyne announced it closed a $22 million round of financing and will use the money to expand into new markets. Pentadyne claims that not only do its flywheels offer an order of magnitude greater reliability than batteries, but that they use 90 percent less energy than those of its competitors.
Image courtesy of Active Power.