Flywheels: A Power Protection Alternative

For some control applications, a brief power outage or brownout is an inconvenience. However, for the majority of computer-controlled processes, even a momentary glitch in the power supply is completely unacceptable, as well as costly. The traditional means of guaranteeing a continuous power supply has been the use of battery-based uninterruptible power systems (UPSs) along with engine gen-sets.

04/01/2010


Flywheels provide uninterrupted DC ride-through power and voltage stabilization during brief utility power disruptions and brownouts.

Flywheels provide uninterrupted DC ride-through power and voltage stabilization during brief utility power disruptions and brownouts.

LINKS

For more sustainability related information, visit the Sustainable Engineering channel at www.controleng.com

Sidebars:
Energy savings ROI
Packaging powered by fuel cell
Energy Star Awa

For some control applications, a brief power outage or brownout is an inconvenience. However, for the majority of computer-controlled processes, even a momentary glitch in the power supply is completely unacceptable, as well as costly. The traditional means of guaranteeing a continuous power supply has been the use of battery-based uninterruptible power systems (UPSs) along with engine gen-sets. While UPSs are a proven solution, their lead-acid batteries are slow to recharge, require constant maintenance, are temperature sensitive, and pose a heavy environmental cost. Proper disposal—governed by strict environmental regulations —is also an issue.

 

Battery manufacturers state that battery life can be maintained for at least four years if they are kept at a constant temperature of 75 °F and experience no excessive cycling. This can be problematic for facilities that experience frequent short duration power interruptions. Every time the batteries are called upon in such instances, the battery cycling degrades the overall life of the battery. In addition, most batteries for UPSs are connected in series, which means than one dead cell in the string can render the string useless.

 

An alternative solution—the flywheel

Acting as a mechanical battery, the flywheel stores kinetic energy in a high-speed rotating group and converts it back into electrical energy to support critical loads. Providing ride-through time to bridge power to the backup generators, the flywheel system is a space saving, near-zero maintenance, and affordable means of guaranteeing constant power for mission-critical installations. A 2006 Federal Technology Alert by the U.S. Department of Energy stated, “Flywheels appear poised to replace or supplement batteries as a backup power supply in UPS systems. ...Although the initial cost of a flywheel is typically greater than batteries it would be replacing or supplementing, its longer life and simpler maintenance will often result in lower life-cycle costs.”

 

By using two flywheels, Model 1 will achieve 26.6 seconds of run time and Model 2 will achieve 28.6 seconds of run time. In either case, the flywheel exceeds the goal of meeting a 20-second run time requirement as a minimum.

By using two flywheels, Model 1 will achieve 26.6 seconds of run time and Model 2 will achieve 28.6 seconds of run time. In either case, the flywheel exceeds the goal of meeting a 20-second run time requirement as a minimum.

Clean energy storage

Flywheel technology stores kinetic energy in a quiet, spinning disk to provide a reliable and predictable source of dc power. With recent advances that have made it more compact and able to support higher power applications, flywheel technology has emerged as a reliable, environmentally friendly power protection solution that stores energy mechanically instead of chemically, thereby enhancing dependability and reducing the carbon footprint.

 

Designed for high power, short-duration applications, a flywheel system can replace lead-acid batteries by working like a dynamic battery that stores energy kinetically by spinning a mass around an axis. Electrical input spins the flywheel rotor up to speed, and a standby charge keeps it spinning 24/7 until called upon to release the stored energy (see cut-away image). Proven technology used in the flywheel allows the flywheel hub—a high-speed permanent magnet motor/generator with contact-free magnetic bearings —to levitate 100% and sustain the rotor during operation. This configuration allows the rotor hub to spin with no metal contact, eliminating bearing wear, bearing oiling or greasing, or maintenance. As a result, no bearing replacements are required for the life of the flywheel.

 

Unlike traditional batteries, the flywheel can charge and discharge at high rates for countless cycles without degradation throughout its 20-year life. The amount of energy available and its duration is proportional to its mass and the square of its revolution speed. In the flywheel world, doubling mass doubles energy capacity, but doubling rotational speed quadruples energy capacity: E = kMω² (k depends on the shape of the rotating mass; M represents the mass of the flywheel; and ω is the angular velocity).

 

When used in conjunction with a UPS system, flywheels can provide uninterrupted DC ride-through power and voltage stabilization during brief utility power disruptions and brownout situations, preserving the battery array for use in longer-term outages. Most backup generators require six to 10 seconds to come on-line and connect with the UPS via the automatic transfer switch. Some flywheel units can provide up to 300 kW of instant ride-through power and voltage stabilization for more than 20 seconds (or other combinations of power and time), which is more than enough time for the majority of electrical disturbances. As a plus, flywheel units can be paralleled for additional power capacity, run-time, and/or redundancy.

 

Cut-away image of Vycon flywheel. Source: Vycon

Cut-away image of Vycon flywheel. Source: Vycon

Application sizing

Normally the sizing of UPSs and flywheels is done based on actual load. Most engineers size a UPS at 30-40% larger than the actual load to allow for growth. Once the UPS is sized, the flywheel needs to be sized to the UPS. All UPS ratings are based on kVA and kW numbers, the rating used for power applications is the kW rating. When this kW number is established, it will be labeled as the full load kW rating. For example: A 275 kVA UPS rating with a power factor (pf) rating of .9 equates to 248 kW of UPS power. Since most loads are sized to UPS at an approximately 80% load factor, along with inverter efficiency of 96%, this equates to 207 kwb. Therefore, this is the rating used to size the flywheels to assure proper power rating and proper amount of run time requirement. To make it easier to size flywheels, most flywheel manufacturers supply customers with run-time charts that match kVA with run time (see Run Time Specification Chart graphic).

 

As illustrated in the Run Time Specification Chart, by using two flywheels, Model 1 will achieve 26.6 seconds of run time and by using two flywheels, Model 2 will achieve 28.6 seconds of run time. In either case, the flywheel exceeds the goal of meeting a 20-second run time requirement as a minimum. This provides a solution that fits most facilities’ needs and ample time to transfer to an engine-genset if a longer power outage occurs.

 

Return on investment

 

When comparing the life-cycle cost of batteries with the life-cycle cost of flywheels, it’s clear which technology has a longer cost savings over the life of the technology. This return on investment (ROI) is a method used by most businesses to justify the dollars spent in purchase decisions. What most engineers have discovered is that the flywheel has been favored over batteries due the cost savings of an ROI in three to four years. However, it is important to know that the purchasing decision is not necessarily an either-or option since the flywheel can be used with or without batteries.

 

When used with batteries, the flywheel is the first line of defense against damaging power glitches because it absorbs all short-duration discharges. As a result, the flywheel reduces the number and frequency of discharges, which shorten battery life. When the flywheel is used with the UPS and no batteries, the system will provide instant power to the connected load exactly as it would with a battery string. However, if the power event lasts long enough to be considered a “hard” outage (rather than just a transient outage), the flywheel will hand off to the facility’s engine-generator.

 

Author Information

Frank DeLattre is president of Vycon. He can be reached at fdelattre@vyconenergy.com

 

Energy savings ROI

 

 

BAE Systems, a defense industry supplier, strikes a deal with Siemens and Metrus that requires it to only pay for energy savings realized from the program’s comprehensive energy efficiency improvements. Siemens is slated to manage all aspects of the project. tinyurl.com/ylz5zhr

 

 

 

 

 

Packaging powered by fuel cell

 

 

The Coca-Cola Co. will be testing fuel cells powered by biogas at its Odwalla juice packaging plant in Dinuba, CA. The core technology—solid oxide fuel cell—was developed for NASA and is reported to be highly efficient at converting hydrocarbon fuels into electricity.

 

 

 

tinyurl.com/ybpw8j3

 

 

 

 

 

Energy Star Awards

 

 

The EPA has named Cemex USA an Energy Star Partner of the Year for energy management and greenhouse gas emissions reductions. Ford Motor Company also earned its fifth straight Energy Star Award for Sustained Excellence.

 

 

 

tinyurl.com/ycuu839

 

 



No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2013 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Leaders Under 40 program features outstanding young people who are making a difference in manufacturing. View the 2013 Leaders here.
The new control room: It's got all the bells and whistles - and alarms, too; Remote maintenance; Specifying VFDs
2014 forecast issue: To serve and to manufacture - Veterans will bring skill and discipline to the plant floor if we can find a way to get them there.
2013 Top Plant: Lincoln Electric Company, Cleveland, Ohio
Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Plant Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.

Bring focus to PLC programming: 5 things to avoid in putting your system together; Managing the DCS upgrade; PLM upgrade: a step-by-step approach
Balancing the bagging triangle; PID tuning improves process efficiency; Standardizing control room HMIs
Commissioning electrical systems in mission critical facilities; Anticipating the Smart Grid; Mitigating arc flash hazards in medium-voltage switchgear; Comparing generator sizing software

Annual Salary Survey

Participate in the 2013 Salary Survey

In a year when manufacturing continued to lead the economic rebound, it makes sense that plant manager bonuses rebounded. Plant Engineering’s annual Salary Survey shows both wages and bonuses rose in 2012 after a retreat the year before.

Average salary across all job titles for plant floor management rose 3.5% to $95,446, and bonus compensation jumped to $15,162, a 4.2% increase from the 2010 level and double the 2011 total, which showed a sharp drop in bonus.

2012 Salary Survey Analysis

2012 Salary Survey Results

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.