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Flywheels: Data Centers’ Green Superheroes

The title data center manager implies a host of responsibilities including overseeing technical and IT issues such as server operations, security, cloud data, networked communications, and much more. Due to the critical nature of these systems and the need to keep operations up and running, policies and proven strategies are implemented to maintain a secure and efficient data center. One of these strategies is to incorporate highly reliable power protection to assure constant uptime of the data networks.

Power problems can be the result of Mother Nature, think polar vortex, a local transformer outage on the grid, or an electrical issue within the building facility. Another common problem is the reliability of the batteries that are used in uninterruptible power systems, or more commonly known as UPSs.

Lead-acid batteries can be costly and undependable. For instance, one non-functional cell in a strand of 40 batteries can prevent the UPS from protecting against a power outage or under-voltage situation. Batteries also necessitate monitoring, overseeing, and supporting to avoid such incidents. These continual maintenance procedures can bog down IT activities.

According to research conducted by the Ponemon Institute, battery storage systems have not proven to be reliable. The Ponemon study found that 55% of respondents blamed battery failure as the root cause of an outage due to a primary power failure. 

In addition, UPS batteries are noxious with dangerous chemicals and need exacting disposal techniques. From an environmental standpoint, these potential hazards can easily deter managers who wish to implement a clean, green power system. Space and cooling requirements are also important considerations.

Flywheel energy storage systems have gained substantial traction in replacing lead-acid batteries due to their reliability, smaller form factor, minimal maintenance, and ecological advantages. A typical battery plant is about three times the size of a similar-sized flywheel. If less space is allocated to power equipment, there is then more room for income-producing computer servers and other computing assets. Also, batteries must be kept in a temperature- controlled environment; conversely, flywheels do not require expensive cooling as they have a wide tolerance to heat and cold conditions.

Today’s data centers demand more than 10 to 30 minutes of backup power as they require continuous power to ensure the protection of large amounts of data, as well as the hardware supporting them.  As such, these data centers are designed to the highest degree of operational uptime, incorporating a redundant power infrastructure that is supported by multiple UPSs and generators.  Thus, data center managers must evaluate various options for maximizing energy efficiencies while ensuring operational success. The challenge, of course, is implementing more energy-efficient technologies without disrupting the high percentage of availability (99.999%), while achieving a low total cost of ownership. This is where the flywheel energy storage system presents a reliable alternative.

How Flywheels Work

Flywheel diagramThe flywheel clean energy storage system is a green substitute for lead-acid batteries. Flywheels have been used for centuries to mine kinetic energy. Now, with new rapid motor technology and dynamic electronic systems, highly efficient flywheel systems provide instant energy for a variety of critical applications. Acting as a “mechanical” battery, the flywheel stores energy kinetically in the form of a rotating mass. During a utility outage, the energy stored by the rotating mass is converted to electrical energy through the flywheel’s integrated electric generator. The system provides the DC energy to the UPS until a stand-by emergency diesel generator can be started. Once either the utility is restored or the genset provides power to the input of the UPS, the flywheel system will be re-charged by taking some current from the DC bus of the UPS until it is back up to full charge speed.

During a power interruption, the flywheel will render backup power easily and quickly (Figure 1). When the flywheel is used alone (not with batteries) the system will provide instant power to the connected load. When using the flywheel along with batteries, the flywheel protects the batteries from short duration outages extending battery life for longer power disruptions. If a power event lasts longer than 10 or 15 seconds, the flywheel will quickly transform to the facility’s generator. To achieve longer run times, additional flywheels can easily be integrated. The Electric Power Research Institute’s (EPRI) research shows that 80% of all utility power anomalies/disturbances last less than two seconds, and 98% last less than 10 seconds.  This real-world scenario gives the flywheel system plenty of time to smoothly transfer to the facility’s generator.

From 40kVA to megawatts, flywheel systems are deployed to achieve the highest level of power quality and reliability in a diverse range of mission critical applications. Move over Superman, flywheels are the superhero’s of today’s data centers.

By Frank DeLattre, president of VYCON, Inc.

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