Ensuring continuous electrical power within mission-critical facilities is top of mind for today’s facility managers, data center operators, hospital IT managers, and electrical engineers. Thoughtful planning, design, equipment selection, and maintenance of an organization’s power infrastructure is vital for continuous operations. According to U.S. Energy Information Administration findings, typical utility customers experienced nearly six hours of power interruptions in 2018 in the U.S., largely a result of severe weather or devastating wildfires. With businesses losing upwards of $150 million as a result of blackouts (according to the U.S. Department of Energy), protecting against power outages and disturbances is essential. Equally important is incorporating environmentally friendly power solutions to advance organizations’ green initiatives.

Uninterruptable Power Systems (UPS) with valve-regulated lead-acid (VRLA) batteries have traditionally met needs for instantaneous backup power during a power event. Although lead-acid batteries are a known resource, they have high environmental and operational costs. Maintenance, frequent replacement, spill containment, and environmentally responsible disposal are also considerations.

More recently, Lithium-ion batteries serve as an energy storage option with UPS. Lithium batteries have higher energy density and longer life than VRLA batteries; however, they have disadvantages, including initial cost, and may require extra floor space for potential fire spread.

The chemical nature of batteries means there is no commercially available “perfect” battery — yet. Every chemical type has considerations. But mechanical-based energy storage solutions can offer a safer and environmentally greener approach.

During a power disturbance, a flywheel system provides instant backup power to seamlessly bridge the critical gap in power until the facility’s generator comes online. A flywheel operates like a dynamic battery that stores energy kinetically, spinning a mass around an axis. Electrical input spins the flywheel rotor up to speed and a standby charge keeps it going until called upon to release the stored energy.

Figure 2. VYCON’s VDC XXT Flywheel System.

Flywheel systems connect to the UPS’s DC bus just like a battery bank, receiving charging current from the UPS and providing DC to the UPS inverter during discharge (Figure 1). Upon loss of utility power, up to 450 kW of regulated DC power per flywheel is delivered instantly to the UPS. This provides the power needed to start and transition to the generators during a prolonged outage. Multiple flywheels can be paralleled for longer run times or N+1 redundancy.

The highest-reliability flywheels offer a 20-year operational life and feature a high-speed permanent magnet motor-generator, fast recharge, magnetic levitation, no bearing replacements, and an intelligent monitoring system. For an added layer of protection, flywheels can be used in conjunction with batteries to reduce charge-discharge cycles, extend battery life, and add an extra layer of redundancy.

In a typical facility, flywheel systems require 50 to 75 percent less space than an equivalent power-rated battery bank. Also, flywheels do not require a temperature-controlled environment, as they comfortably operate from 0 to 40 °C. Microgrids and electric rail applications also demonstrate the reliability and cost benefits of flywheel energy storage. Flywheels offer an environmentally and financially sound choice in protecting critical operations.

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Tech Briefs Magazine

This article first appeared in the July, 2021 issue of Tech Briefs Magazine.

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