Flywheel Power and Energy Storage

Dan Jones

Flywheel energy storage is not a new technology, simply a somewhat forgotten technology that has suffered at the hands of our obsession with chemical storage systems such as mechanical batteries. Yet flywheel technology remains an incredibly efficient way of producing and storing energy.

Over the last half a century several successful flywheel experiments have been carried out in the last 50 years, and the flywheel’s applications ranged from acting as a UPS for a hospital to putting an entire train to movement and then to cruise speed, only by its power.

Flywheel energy storage is not a new technology, simply a somewhat forgotten technology that has suffered at the hands of our obsession with chemical storage systems such as mechanical batteries. Yet flywheel technology remains an incredibly efficient way of producing and storing energy.

Over the last half a century several successful flywheel experiments have been carried out in the last 50 years, and the flywheel's applications ranged from acting as a UPS for a hospital to putting an entire train to movement and then to cruise speed, only by its power.

The way flywheel energy storage works is very simple: Flywheels store energy mechanically in the form of kinetic energy. They take an electrical input to accelerate the rotor up to speed by using the built-in motor, and return the electrical energy by using this same motor as a generator. Flywheels are one of the oldest and most common mechanical devises in existence.

Flywheel technology

In the 1950s experimental buses called "gyrobuses" were used in Yverdon, Switzerland and prototype cars have also been built using the flywheel design principle. The development of new materials, such as carbon fibres, make them even more durable and efficient. In fact, the stronger the flywheel's material is, the higher the rotational speed and the amount of energy it can store.

Flywheels are also time-resistant. An ECE researcher, Dr. Mark Flynn, from the University of Texas at Austin, designed a flywheel system that could last 20 years of continuous usage.

"Flynn's design captures the braking energy and uses it for the next hoist. More importantly, the addition of a flywheel energy storage system lowers the peak power requirements which saves energy during idle periods. Field tests in China showed that when operators used a genset appropriate for the reduced power requirements and added a flywheel energy storage system, fuel consumption went down by 38 percent with significant reductions in emissions," said Flynn.

Flywheel Power storage systems

A flywheel energy storage solution is among the most exciting technologies available to replace conventional lead acid batteries as energy storage systems for a number of technological applications including economical rural electrification systems and remote power units.

Flywheel power storage systems could soon provide uninterruptible power supply to things like data centres as they save considerable amounts of space and are more energy efficient compared to battery systems.

This can also be highly beneficial to other buildings that cannot afford power outages such as hospitals, where lives depend on an uninterrupted flow of energy. Most outages in places like hospitals are well within a flywheel's capability but when the outage persists, the flywheel absorbs damaging power abnormalities then simply transfers to the generator - meeting emergency power regulations that stipulate gensets must be able to assume the load within 10 seconds.

Current flywheel designs

Flywheels store energy very efficiently but they also have incredibly high output potential and their durability gives them a longer life-span (they are pretty much unaffected by ambient temperature extremes).

However, even though flywheels have the potential for high-specific energy, current flywheel power systems have only low-spec energy. There are also concerns over the safety of current flywheel designs due to their high speed rotation and the possibility that the wheel breaks loose and releases all its energy at once in an uncontrolled way. Eventually flywheels will be more cost-effective than chemical batteries, but the low initial costs of traditional batteries means that flywheels cannot compete in the current market.

But a few generations down the line and after a few more experiments, we could genuinely be looking to flywheel energy storage systems as the future of the way in which we generate and store our energy.