Flywheel energy storage tech at a glance

Scientists from the Siksha ‘O' Anusandhan Deemed to be University in India have conducted an extensive review of all flywheel energy storage systems (FESS). In “Flywheel energy storage systems: A critical review on technologies, applications, and future prospects,” which was recently published in Electrical Energy Systems, the researchers explain that FESS are an optimal mechanical storage solution under high energy and power density, higher efficiency, and rapid response.

“With the potential of 500 MJ storage and power range of kW to GW, FESS operates many applications, among which most common are for power quality enhancement, uninterruptible power supplies (UPS), and flexible AC transmission system (FACTS),” they said. “For such applications, BESS is unlikely to last longer, even for 10 years, due to its short lifecycle since the number of cycles for these applications is frequently too high.”

Compared to other mechanical energy storage technologies such as pumped hydro and compressed air, flywheel storage has higher values for specific power, specific energy, power and energy density, lifecycle, efficiency, self-discharge rate, and energy capital costs. By contrast, it has lower values for lifespan, scale, maintenance and power capital costs. Its impact on the environment is described as “extremely low,” while that of pumped hydro and compressed air is presented as “medium to low” and “high to medium,” respectively. The scientists said extremely high self-discharge rates and safety are the main shortcomings for FESS.

The study reviews all components used in FESS in terms of different rotor configurations, motor/generator (M/G), rotor bearings, various power electronic interfaces, and housing. It also presents a state-of-the-art survey of different applications for uninterrupted power supply (UPS), transportation, solar and wind energy storage, flexible-AC-transmission-system (FACTS) devices, marine, space, power smoothing, and frequency regulation.

In addition, the paper looks at FESS costs and assesses various control approaches. It also looks at stability and maintenance.

“Modern technology advancement and investigation reveal that the FESS is an assuring candidate for administering ancillary benefits, promoting the incorporation of renewable energy generation, and delivering a promising future in commercialization,” the academics said. “FESS holds many merits compared to other ESSs units such as modular, recyclable, quick response, larger peak power, long life-cycle, highly efficient, eco-friendly, and high energy density.”