Today’s data explosion is driving data center operators to implement a variety of solutions to address the ever-increasing appetite for data. Artificial intelligence, telemedicine, self-driving cars, the Internet of Things (IoT), and automation — not to mention financial transactions and social media — are requiring ever more data capacity and bandwidth along with the massive energy consumption necessary to support them.
And now, due to the COVID-19 pandemic, consumers and businesses have quickly moved to data-intensive online meetings, streaming videos, and virtual events in keeping with social distancing. Hence, the demand for “always-on” connectivity for continuous content delivery is at the highest need in history, putting tremendous pressure on data center and colocation, infrastructure as well as facility systems and personnel.
To this end, the need for reliable and scalable power protection that is essential to protect all the servers with their associated equipment against power faults has never been as critical as now. For large companies, the cost of an outage can escalate into the millions of dollars per hour of downtime. In 2018, the DoE estimated that outages were costing the U.S. economy $150 billion annually. Now with the vast increase of remote workers, outage costs could be much higher along with increased downtime in productivity. Whether an enterprise or a large colocation facility, protecting against downed power is a priority.
UPSs and Energy Storage
Today’s UPSs have come a long way in efficiency and scalability. While 3-phase UPSs for data centers and other mission-critical applications have advanced, the energy storage component of the UPS systems requires special attention. When there’s a power outage, strings of batteries – typically lead-acid type – provide ride-through to either a second utility feed or an on-premise generator. The problem is that valve-regulated-lead-acid (VRLA) batteries need expensive cooling, ongoing maintenance, frequent replacement and require a large amount of real estate as well as environmental mitigation and spill containment.
While Lithium-ion (Li-ion) batteries are an option offered by some UPS manufacturers, lead-acid batteries are still the de facto choice due to their lower initial cost and widespread understanding of how they operate, the required maintenance and lifespan. Li-ion batteries do offer some key advantages over lead-acid type, including the ability to operate in broader temperature ranges with thousands of charge-discharges cycles over their life span. However, fire safety precautions are a crucial consideration for data center operators. According to The National Fire Protection Association (NFPA) 855 standard, Li-ion batteries must include an approved Battery Management system with thermal runaway management. In addition, there must be three feet of clearance all around the battery cabinets so fire will not spread from cabinet to cabinet. The NFPA 855 standard provides important safety guidance for the use of lithium-ion batteries in UPS systems in data centers and other mission-critical facilities.
Greening the Infrastructure
Data center and facility managers must consider various factors in the quest to increase energy efficiencies and reduce a data center’s carbon footprint. The question becomes how to implement green technologies without disrupting high nines of availability while still achieving a low total cost of ownership (TCO).
This challenge becomes even more crucial when looking at the power protection infrastructure. Data center operators need emergency power systems that are highly efficient and have reduced requirements for service, including the ability to conduct preventative maintenance without going to bypass or taking the UPS offline. Many UPS systems offer flexibility and scalability, allowing the user to add additional capability as the power load grows. However, most organizations today are looking to deploy greener and more sustainable solutions into their data centers. One of the greener approaches to energy storage involves incorporating flywheels into power protection configurations instead of heavy, toxic batteries that are environmentally unfriendly for the data center and the planet.
Due to their inherent design and functionality, flywheel systems can save a facility hundreds of thousands of dollars compared to lead-acid batteries over a 20-year life. Due to their proven reliability, low cost of ownership, small footprint – only 30 inches (depth) by 30 inches (width) – and favorable environmental characteristics, managers of data centers, hospitals, industrial systems, electric rail, and microgrid applications are reaping the benefits of clean energy storage that flywheels offer.
Real-World Experience
When the UPS batteries at DataBank’s various Tier 3 data centers were coming to the end of their useful life, Danny Allen, DataBank’s vice president of engineering, wanted to find a more reliable, affordable and greener approach to lead-acid batteries. Having previous experience with the reliability, cost and sustainable aspects of flywheels at DataBank’s other data center facilities, Allen was confident in his choice to deploy 36 of VYCON’s VDC XXE 300kW flywheel systems along with 12 VDC 450kW XXT models. The flywheels (Figure 1) are paired with Mitsubishi 9900B-750kVA three-phase, on-line double-conversion UPS systems. “The dependable reliability and very low maintenance costs of the VYCON flywheels along with their green advantages make it an easy decision to replace lead-acid batteries,” commented Allen.
Another example is Cavern Technologies that has its data center located 125-feet underground in a 3-million square-foot facility. Fortified by a natural limestone bunker that is three times stronger than concrete, the data center is protected from natural and deliberate disasters, has a consistent 68° ambient temperature and is further reinforced by best-in-class biometric and facial recognition security systems. Cavern’s fully redundant infrastructure is designed to meet the specialized power, cooling and security requirements its customers require to house IT systems that support their mission-critical business processes.
During a recent expansion, Mike McDaniel, vice president of facility engineering for Cavern Technologies, was looking for a more reliable and lower maintenance energy storage solution than lead-acid batteries offer. “All of our critical loads are now protected by four 2N-designed 300kVA dual-conversion UPSs paired with four of VYCON’s 300kW VDC flywheels,” said McDaniel. “We still have legacy UPSs that carry many of our customer’s loads, so this is only for customers online within the last two years. Going forward, all new customer loads will be on the flywheel design.”
Flywheel Technology
Hardly an unproven invention, flywheels are among the oldest machines in human history. According to IEEE’s report on Flywheel technology past, present and 21st Century projections, “The origins and use of flywheel technology for mechanical energy storage began several hundred years ago and were developed throughout the Industrial Revolution. The next big milestones were during the 1960s and 1970s when NASA-sponsored programs proposed energy storage flywheels as possible primary sources for space missions. However, it was not until the 1980s when microelectronics, magnetic bearing systems and high-power density motor-generators became enabling technologies. The next decade proved that a mechanical battery could surpass chemical batteries for many applications.”
Designed for high power, short discharge applications, contemporary flywheel systems store kinetic energy in the form of a rotating mass. Magnetic bearings allow the motor assembly to rotate at very high speeds with no physical contact to stationary components, thereby taking advantage of the high efficiencies obtainable with high-speed rotation. VYCON’s patented technology incorporates a high-speed motor generator along with active magnetic bearings that levitate and sustain the rotor during operation. A monitoring and control system monitors system operations and performance via a graphic touchscreen panel as well as an advanced communication capability that includes operating parameters, alarm status and local and remote shutdown. These innovative technologies simplify operation while enabling the flywheel systems to charge and discharge at high rates for countless cycles that dramatically outperform legacy technologies like batteries.
The flywheel operates like a dynamic (mechanical) battery that stores energy kinetically by rotating a mass around an axis. Electrical input spins the flywheel rotor up to speed while a standby charge keeps it going continuously until called upon to release the stored energy. To minimize bearing power requirements and losses, the flywheel is vertically oriented, thereby only requiring the axial bearing axes to support the full rotor weight. The energy available and its duration are proportional to the flywheel’s mass and the square of its revolution speed: doubling the mass doubles energy capacity while doubling the rotational speed quadruples energy capacity.
Similar to a battery bank, the systems interface with the DC bus of a UPS, receiving charging current from the UPS itself and providing DC current to the UPS inverter during discharge. Because of this standard DC bus interface, the systems are compatible with most three-phase UPS brands. The unique magnetic bearing technology eliminates virtually all maintenance, including the need to replace or repack lubricant for a mechanical bearing system. This enables the VYCON VDC flywheel to charge and discharge at high rates for countless cycles without degradation throughout its 20-year life – unlike traditional batteries.
During a power disruption, the flywheel will provide backup power instantly (Figure 2). When flywheels are used with UPS systems (instead of batteries), they provide reliable protection against damaging voltage sags and outages.
If a power event lasts longer than 10 or 15 seconds, the flywheel will seamlessly transition to the data center’s engine-generator. For longer run times, additional flywheels can easily be integrated in the initial installation or later if needs change. When it comes to the shorter backup times, UCSD’s San Diego Supercomputer Center manager, Jeff Filliez, commented, “If the load is critical, you can’t repair it on the fly. So even if you have 15 or 20 minutes of traditional battery backup, you won’t be able to get back online in that short of time. Quickly transferring the load to the generator just makes sense.” Filliez replaced the lead-acid batteries with the highly efficient VDC flywheel units in a configuration that included a one-megawatt 9900C Mitsubishi UPS paired with three 300kW VYCON VDC flywheel units with N+1 redundancy.
Another advantage of flywheels is that they can work alongside a facility’s existing UPS lead-acid or Li-ion batteries and absorb charge-discharge cycles to preserve the life of the batteries – also known as battery hardening Every lead-acid battery discharge cycle diminishes its overall lifetime. Moreover, the flywheel provides a redundant source of DC energy storage.
From 40kW to megawatts, flywheel systems are increasingly being used to assure the highest level of power quality and reliability in a diverse range of applications. The flexibility of these systems allows a variety of configurations that can be custom-tailored to achieve the exact level of power protection required by the end-user based on budget, space available and environmental configurations.
Financial Incentives
Users of flywheel systems are experiencing huge benefits. By using a flywheel versus a five-minute VRLA battery bank, users can save $100,000 to $200,000 per flywheel deployed. And systems with a contact-free magnetic levitation system – meaning there are no bearings to replace – users will save $10,000 in bearing replacement. These figures don’t include the extra energy savings in reduced cooling as flywheels can operate up to 104ºF with no degradation in operating specifications or life expectancy.
Final Thoughts
As we enter this new age of all things digital, accelerated by the COVID-19 pandemic, we are all reminded how important our digital lives have become. We depend and expect our video conference calls, streaming videos, Internet, email, texts and a myriad of business and health systems to always be available. Flywheel energy storage is an efficient and environmentally friendly way for data centers to ensure they can keep systems operational no matter the state of the power grid.
About the Author:
John Jeter is the Director of Sales for VYCON, Inc. in Cerritos, Calif. John received his electronics training in the US Navy and holds a B.S. in Business from San Diego State University. He has been involved with power quality solutions for over 40 years with domestic and international experience.