Could Flywheels Be the Future of Energy Storage?
Flywheels are one of the world’s oldest forms of energy storage, but they could also be the future. This article examines flywheel technology, its benefits, and the research from Graz University of Technology.
Energy storage has risen to prominence in the past decade as technologies like renewable energy and electric vehicles have emerged. However, while much of the industry is focused on conventional battery technology as the path forward for energy storage, others are turning to more unique approaches.
Flywheel energy storage concept. Image used courtesy of Adobe Stock
Specifically, recent years have increased interest in flywheels. A project team from Graz University of Technology (TU Graz) recently developed a prototype flywheel storage system that can store electrical energy and provide fast charging capabilities.
Understanding the Flywheel
Flywheels are considered one of the world’s oldest forms of energy storage, yet they are still relevant today.
On a high level, flywheel energy storage systems have two major components: a rotor (i.e., flywheel) and an electric motor. These systems work by having the electric motor accelerate the rotor to high speeds, effectively converting the original electrical energy into a stored form of rotational energy (i.e., angular momentum). The flywheel continues to store energy as long as it continues to spin; in this way, flywheel energy storage systems act as mechanical energy storage. When this energy needs to be retrieved, the rotor transfers its rotational energy back to a generator, effectively converting it into usable electrical energy.
The anatomy of a flywheel energy storage device. Image used courtesy of Sino Voltaics
A major benefit of a flywheel as opposed to a conventional battery is that their expected service life is not dependent on the number of charging cycles or age. The more one charges and discharges the device in a standard battery, the more it degrades. This degradation becomes a significant shortcoming for batteries in local energy storage solutions, where charging and discharging may occur rapidly and frequently.
Flywheels, on the other hand, do not degrade proportionally with age or charge/discharge cycles. This makes them a viable short-term storage system, particularly effective when energy is frequently supplied and removed.
FlyGrid Flywheel Storage
Recently, a team of researchers led by TU Graz announced the successful development of a flywheel prototype that can store electricity and provide fast charging outputs.
The new prototype, FlyGrid, is a flywheel storage system integrated into a fully automated fast-charging station, allowing it to be a solution for fast EV charging stations. TU Graz claims that the rotor is made of high-strength carbon fiber, allowing it to withstand up to 30,000 revolutions per minute. The motor used to accelerate FlyGrid is a loss-optimized, synchronous reluctance motor, which offers levels of efficiency and sustainability to the system.
TU Graz’s FlyGrid prototype. Image used courtesy of TU Graz
After months of testing, TU Graz reports that the prototype's buffer storage can provide an energy content of five kilowatt-hours but can only last for up to 25 hours on a single charge due to the energy demand of the motor. From an output perspective, FlyGrid is also said to offer a charging capacity of 100 kW, with the potential for larger storage volumes thanks to its modular design.
According to the TU Graz researchers, FlyGrid is best as an addition to existing grid and EV charging infrastructure.
