The 2019 pandemic taught the data center industry many lessons and confirmed the “always on” appetite isn’t going away, and, in fact, will continue to increase. The advent of Industry 4.0 encompasses advancements in everything digital — from smart cities, autonomous vehicles and aircraft, and AI to robotics, the IoT, 3D printing, genetic engineering, and quantum computing. All of this will take more computing processing and power. And, don't forget the Metaverse, which is expected to require 1,000 times more computing power than what is currently available.

"We need several orders of magnitude of more powerful computing capability that is accessible at much lower latencies across a multitude of device form factors," said Raja Koduri, senior vice president and general manager of the Accelerated Computing Systems and Graphics Group at Intel. "To enable these capabilities at scale, the entire plumbing of the internet will need major upgrades."

The challenge becomes: How do we build, integrate, and operate stronger and faster computing while lessening our burden on the planet? One way is to look at the data center power infrastructure and be open-minded to different power solutions.

Within the data center power infrastructure, uninterruptible power supplies (UPSs) are key to keeping the power flowing in the event of a power outage or momentary disruption. Most data centers are still using lead-acid batteries for ride-through — they are a known quantity; however, they have a high environmental cost. They are toxic (lead), require constant maintenance and spill containment protocols, and take up a lot of real estate that can be better utilized for compute-intensive applications. Along with the continual and expensive maintenance, they are heavy and slow to recharge. And, there's always the reliability aspect to consider.

• Are the batteries fully charged?
• Are they ready for the next power event?
• When was the last time they were tested?
• How will they react under load?
• Do they need to be replaced?
• One single dead cell in a string can render the entire string useless.

Most battery manufacturers state that battery life can be maintained as advertised for at least four years if, and only if, they are kept at a constant 77°F (typically requiring air conditioning) and experience no excessive cycling. When one considers the nature of the chemicals used, in terms of reliability, lead-acid batteries are not an optimal solution. Conversely, flywheel energy storage presents an option that does not suffer from energy degradation after each use or change based on temperature within a relatively wide operating range. They continue to maintain the same available power after each power loss cycle for the duration of an operating life measured in decades, not years.

A reliable green solution

Flywheel energy storage systems are deployed in data centers worldwide, providing instantaneous backup power when incoming electrical power fails. A prime example is The Travel Corp., a global company that supports sustainable tourism projects worldwide. When their Toronto-based data center started experiencing load increases, facility manager Craig Lee sought to find different approaches to reduce energy consumption without compromising reliability.

Lee was using three-phase UPS systems with lead-acid batteries that would switch to their two Caterpillar and Cummins diesel generators during a power outage.

"We were spending $50,000 every five years to replace the batteries, and we were not comfortable with the battery disposal cost and environmental impact,” he said. “We wanted to find a greener approach to power protection."

Looking to their technical partner, Urbacon, for suggestions, the specialists recommended replacing the dual-strings of lead-acid batteries with four flywheel energy storage systems. The flywheels are environmentally friendly and can be up to 20 times higher in reliability than lead-acid batteries. With a 20-year operational life and no bearings to replace in the current models, flywheels offer a cost-effective power solution for organizations wanting to improve reliability with a lower total cost of ownership.

Now, Travel Corp.'s data center has two 150-kVA double-conversion UPSs, each supported by two 300-kW flywheel systems connected in parallel with a maintenance bypass switch with transformers.

"When there's a power outage, we're on the flywheels and then transfer to the diesel generators,” Lee said. “We have two minutes per flywheel, so we have eight minutes before transferring to the generator. If the generators don't turn on in that time, they're not going to come online at all."

The data center has a 2N redundant A/B configuration in place with one utility supply line that splits into two separate supplies, each protected by a diesel generator for backup power.

"The flywheels have added to our reliability and lower carbon goals,” Lee said. “We have had many power failures and interruptions in the last few years, and the flywheels have worked perfectly every time, and low maintenance requirements are always a bonus."

When required 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 standby emergency generator starts.

Performing as a mechanical battery, the flywheel holds kinetic energy in the form of a rotating mass and converts this energy to electric power within the flywheel system. Some flywheels offer unique technology that includes a high-speed motor generator, active magnetic bearings used to levitate and sustain the rotor during operation, and a control system that provides vital information on system performance. These technologies enable the flywheel to charge and discharge at high rates for countless cycles, making conventional technologies like batteries obsolete. When required 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 standby emergency generator starts. Once the utility is restored or the genset provides power to the input of the UPS, the flywheel system will be quickly recharged by taking some current from the DC bus of the UPS until it is back up to full-charge speed.

Cost and environmental savings

The latest flywheel designs take advantage of higher speeds and full magnetic levitation — packing in more green energy storage into a small footprint and removing any kind of bearing maintenance requirements.

Another compelling advantage is that, over a 20-year design life span, cost savings from a hazmat-free flywheel are in the range of $100,000-$200,000 per unit — and, that’s not counting the floor space or cooling cost savings that can be achieved. Data center managers, CTOs, and CFOs tend to support flywheel investments because they typically have an ROI of three to four years.

Data centers, colos, medical facilities, and industrial plants across the globe have found that the use of flywheels — in conjunction with or instead of batteries — significantly increases power reliability and uptime. During a power outage, a flywheel provides backup power seamlessly and instantaneously, bridging the critical gap until a generator becomes operational.

When used with batteries, the flywheel is the first line of defense against damaging power outages, protecting the batteries against frequent cycling or hardening and prolonging their remaining useful life. Worldwide, companies are hardening battery strings or eliminating them by applying clean energy storage to their UPS systems. Flywheels offer an environmentally and financially sound choice in protecting critical operations.

The future

As computer workloads increase to support the many exciting applications of the digital evolution, data center power infrastructure must be ready to adapt. Flywheel technology is a smart way to protect critical electrical loads while lessening the burden on our planet.