Not much noise, but lots of buzz

By Henry Vere

Most people who know anything about flywheels probably know that they work through the acceleration of a rotor to a very high speed while energy is maintained in this system as inertial energy. Commercially available flywheel energy storage (FES) systems have traditionally been used for small uninterruptible power supply (UPS) systems operating at 4,000 rpm or less and are made of metal.

More advanced FES systems feature high-strength, carbon-composite filaments that spin at speeds from 20,000 rpm to 100,000 rpm in a vacuum enclosure. Magnetic bearings are used in this case due to the buildup of friction—proportional to speed—in conventional mechanical-bearing FES systems. (Friction would be high enough to cause such a great energy loss as to defeat its purpose of energy storage.) Rapid charging of a system occurs in less than 15 minutes.

A long lifespan for most flywheels, high-energy densities, and large maximum power outputs are some of the nuts-and-bolts reasons that flywheels make sense in a growing number of applications. The technology has continued to evolve since the 1950s, when early flywheel-powered buses called gyrobuses began driving through Yverdon, Switzerland. As manufacturers and developers will attest, flywheel systems are growing in industrial applications and distinctive settings.

Sticking to What Works
Austin, TX–based Active Power holds over 42 patents on the technology supporting its integrated flywheel UPS, developed over the past 15 years. The company is a main player in battery-free UPS systems and has offers flywheel products and compressed-air products alike. The company’s chairman, Joe Pinkerton, is the inventor and patent holder on Active Power’s technology. The flywheel system contains an integrated flywheel-UPS system all in one box, making the machine very efficient from a space perspective.

“In today’s environment, where the data-center market is starting to boom again, companies want to use their floor space for selling space to their customers, not for rooms full of batteries,” says Lisa Brown, Active Power’s vice president of marketing and service. “We can put twice the power in half the space, which is a great selling feature for us. Also, the energy-efficiency factor is important. Our customers save much on their utility bills.”

The machinery is manufactured in Active Power’s 120,000-square-foot operations and manufacturing facility in Austin. The company’s equipment is now installed in over 40 countries worldwide.

“We’ve been at this a long time and are undoubtedly the world leader in our field, which is medium-speed flywheels, just under 8,000 rpm,” says Ian Bitterlin, Active Power’s vice president for Europe, Middle East, Asia, and Asia Pacific operations. “We’ve built 1,400 flywheels and are tracking 1,050 of them in the field today with a wide variety of applications.”

Those applications are split currently at about 60% industrial (hospitals and airports) and 40% information technology (IT) uses. “There really aren’t any downsides to our flywheel technology, aside from perhaps the fact that they are nearly always associated with a diesel-generator system,” says Bitterlin. “We effectively have the bridge between the mains failing and the generator starting. A battery gives five to 10 minutes of backup power, while one of our flywheels would be giving 15 to 20 seconds of backup.”

A very small footprint and an efficient UPS system are Active Power’s biggest draw. In an IT application, most UPS systems run at about 50%–60% load, or 40%–50% typically, especially if they’re in a parallel redundancy application, according to Bitterlin.

“In a super-critical application, this ensures that in case one flywheel fails, the other one will be there to pick up the load,” says Bitterlin. “Our system is up to 98% efficient. Whereas many other systems may only be 90% to 93% efficient, the extra percentage points do add up—both for the environment and in real utility costs.”

Active Power is currently shipping the system for an 8-MW project in Algeria and has provided systems for highly critical computer centers. It is the original equipment manufacturer and technology provider for Caterpillar, branding many of its products with the Caterpillar name after doing all the engineering work.

The mix is gradually changing as Active Power grows direct distribution capability in various markets and sells more products under its own brand name, according to Brown.

Active Power systems have recently been installed in a major runway light project at the Mexico City Airport, in a green system for Queen Margaret University in Scotland, and in a large African sugar refinery. The company has recently announced a new 11-MW project for a major data center in the southeastern United States, through Caterpillar. This shopping mall–size center is close to a half-million square feet. “Our system was chosen for power density for one of the largest IT companies in the world,” says Brown.

Flywheel maintenance in general runs about one-half the cost of traditional battery UPS systems, according to Brown. The only maintenance is a basic annual preventive maintenance routine and replacing the bearings every three years, which takes about four hours. “Compare that task to changing an entire battery array every four or five years. Batteries are a huge investment in space and equipment. Also, rather than periodic testing as with batteries, our system features remote diagnostic monitoring built in as a part of the whole package.”

Active Power has released a “green” compressed air–based UPS system to meet the growing need and demand in the small- to medium-size data center market. This system is the only UPS of its kind delivering both backup power and cooling, thus addressing two of the key concerns facing data center managers today.

“We call our products ‘economically green,’” adds Bitterlin. “They are good for your business financially and for the environment, too. The green may fool you at first, but these systems can compete head to head with mainstream choices and win on their merits. The green factor adds a nice bonus.”

Specializing in Hospital and Data Center Applications
“If the application is appropriate and you only need a small amount of ride-through time, flywheel technology may be for you,” says Bill Campbell, senior product manager for power systems integration with Liebert Corp. “With the type of batteries we use for a UPS system, the shortest runtime battery that can be purchased is five minutes. Even if you only require it for 12 seconds, you’re still going to have to buy a five-minute battery. Therefore, there may be certain circumstances where it may be more beneficial to get a flywheel for that particular application.”

Carbon-fiber flywheels make use of magnetic levitation and a factory-sealed vacuum.

Carbon-fiber wheels use about one-tenth the standby power of steel flywheels.

Flywheel energy storage systems—like the Pentadyne VSS+DC marketed by Emerson Network Power as the Liebert FS—store energy in a small, rotating mass. The Liebert FS version of the Pentadyne VSS+DC is specifically designed to optimize performance when connected to Liebert Series 610 or Liebert Npower UPS systems and is 100% supported by Liebert’s Global Service (LGS) organization. Pentadyne uses a carbon-fiber composite that weighs only 25 pounds, but this is rotated at 54,000 rpm within a magnetic field. The assembly is contained within a 2-inch-thick carbon-steel vessel.

“Our product would either supplement or replace the battery arrays used with UPS systems,” says Keith Field, Pentadyne director of marketing. “We deliver a lot more reliability without all the maintenance issues, costs, and the health and safety concerns. One set of batteries in the Sacramento area actually blew the roof off a building. It’s not a common occurrence, but it has happened.”

Pentadyne recently released a next-gen-eration system rated at 190 kW for more than 12 seconds when used with a 225-kilovolt-ampere UPS. With energy storage products, the less energy drawn from them, the longer the duration. Therefore, they can produce more power for a shorter time or less for longer periods, all depending on the load at the time of the discharge.

“With this newly enhanced product and an exceptionally strong distribution channel with Emerson Network Power and our Europe affiliate, Socomec Sicon, our revenue in 2006 was more than 10-times that of 2005, validating the effectiveness and value of our technology,” says Field.

“In addition to being more reliable and more cost-efficient than batteries, flywheels are also more compact and much lighter. At an Army Corps of Engineers facility featuring a major expansion of a data center, a whole second floor was going to have to be built at the facility to house everything.

“For the number of batteries required, they would have had to do all sorts of expensive structural reinforcement of the main building to hold up the weight. Flywheels were the perfect answer for them. They’ve been using two that have operated flawlessly, and they’ve recently ordered 20 more for this military data center expansion.”

Pentadyne also has flywheel units operating at hospitals from Alaska to Ohio. Cincinnati Children’s Hospital is currently in the process of installing 16 Pentadyne units to support a data center that will be used to investigate genetic causes of diseases affecting children. Half of the dual-bus power quality system will be a regular UPS system using batteries; the other runs in parallel using Liebert FS flywheels.

Fending Off Grid Glitches
Beacon Power started out building flywheels for telecom applications. That earlier application was intended to commercialize flywheels to replace batteries in remote locations. “This is our heritage and is where the technology was first perfected,” says Gene Hunt, director of corporate communications. “Because the telecom industry wanted them buried in the ground, the system is designed for a 20-year life with no maintenance. Our system used magnetic bearings and a high-pressure vacuum to minimize friction, as well as a composite carbon fiber rim that spins at more than 22,000 rpm, storing more energy over a longer life than any other flywheels.”

Currently, Beacon Power is working on a new design involving a matrix of flywheels grouped together for a grid-frequency-regulation function. The flywheels run in a series so that if one goes down, the system still operates. It is controlled and monitored via the Internet and set up to receive signals from the independent system operator (ISO). The flywheels are told to either absorb energy or power or to inject it, depending on what the frequency level is at that moment. It is a stabilization function that today is performed around the clock, most often by fossil-fuel-powered generators.

“What this would offer is an alternative to the conventional methods—basically two—that perform the frequency regulation function today,” says Hunt. “One of them is pumped-storage hydroelectric: good, fast, and somewhat efficient but also limited in terms of its regional availability. The rest, the grid operators must get from fossil fuel plants, either coal or natural gas–powered.

“Utilities bid into this market, setting aside some of their power plants to perform the service, just as they bid into the market for other ancillary services like voltage regulation and spinning reserve, the primary ancillary services.”

Beacon Power has one demonstration system now undergoing field trial on an industrial site in Amsterdam, NY. The system that’s there is doing two things: It’s connected to the grid at a 480-VAC line on the property, and it’s monitoring and responding to frequency regulations signals. “But it’s also been designed to provide some degree of backup power for the facility, which we may begin testing in 2007,” says Hunt. “It’s a modest manufacturing facility, but the expectation is that this particular demo could also be used to provide some minutes of backup power in the event of a power outage.”

The system, known as the Smart Energy Matrix, consists of seven flywheels with collectively about 30 kWh of power. “In theory, this could provide 5 kilowatts for six hours for this distributed generation or micro-grid application,” says Hunt. “Frequency regulation testing is now under way.”

A third application Beacon Power is looking at is that of providing “reactive” power. “Some describe this as ‘imaginary’ power needed to keep primary power stable,” says Hunt. “Like the foam on beer, it is a necessary component, but not something you want all the beer to be.”

Beacon Power’s other demonstration project, also undergoing its field trial, is in San Ramon, CA. This system is already connected to the grid and is responding to signals from the California ISO. In many ways it is similar to the Amsterdam project.

“The renewable energy market, especially wind and solar, is one that will clearly benefit from energy storage,” says Hunt. “Storage in bulk—hundreds of megawatts for these intermittent energy sources—makes for good economics. But this is a tough one; it is still relatively rare. The technologies that can do it—compressed air and pumped hydro—require unique geologic characteristics. In the meantime, our technology is designed to store megawatts of highly cyclic energy for minutes, which is perfectly suited for frequency regulation and smoothing out the intermittencies of renewable generation sources.

“In September we received a $750,000 contract from DOE [the US Department of Energy], to fund the design of a 20-megawatt flywheel plant. That would be 200 flywheels in a 20,000-square-foot building connected to the grid at a substation. It would take in energy from the grid and then recycle it. It has no direct emissions and is very cheap to operate. The flywheels are basically energy machines—mechanical batteries. That’s what makes them especially suited to this particular application.”

Flywheels can respond instantaneously, according to Hunt. They are about 85% efficient, so there is a cost associated with running them; thus, 15% of the power absorbed is used to keep them running. The only real sound to be heard when standing beside the flywheel system, despite the fact that they’re spinning at 22,000 rpm, is that of the fan used to cool the electronic equipment inside.

Beacon has built three generations of flywheel equipment. The first was a 2-kWh flywheel for telecom applications, the second a 6-kWh flywheel (about the size of a hot water heater), and most recently a larger-motor version (100 kW) of the 6-kWh model, which is what’s being used for the frequency regulation demonstrations. “As part of the Smart Energy Matrix systems, we also developed sophisticated electronics and software to control a group of interconnected flywheels as well as monitoring systems to see what’s going on,” says Hunt.

“Any of our engineers can dial up these systems in the field; they’re not staffed, and you don’t need people running them. A ‘dashboard’ comes up with seven speedometer-like gauges telling you exactly what they’re doing. Our fourth generation of flywheels, being worked on right now, will be 25 kilowatt-hours, with a 100-kilowatt-hour motor, and will contain more stored energy than any flywheel in the world. It is expected to go into production in 2007, and by the end of the year we’re looking to have a megawatt of commercial frequency regulation service available.”

The storage of energy and the ability of flywheels to cycle energy are the things that make flywheels a good option for such highly cyclic applications as frequency regulation. Flywheels used as battery replacements in remote locations are not in a highly cyclic application.

Beacon’s research shows the vast majority of frequency regulation applications requires megawatts of power—but only for a few minutes. If you place 10 25-kWh flywheels together, you have a megawatt for 15 minutes, enough to meet 98% of the frequency regulation requirements. The other 2% are demands stemming from imbalances that would more typically be generation issues, not frequency regulation per se. This assessment is based on an analysis of actual demand from one ISO, but Beacon believes they are also typical of the other deregulated (ISO-run) grid regions.

Flywheels can be grouped together in a matrix for application in grid-frequency regulation.

Environmental Initiative
Vycon’s Technical Sales Manager Octavio Solis focuses mainly on the high-cycle applications of the company’s flywheel systems, especially in the shipyard crane industry. The Long Beach, CA–based operation has been up and running since May 2006.

California’s push for cleaner air regulations in its ports includes the Clean Air Action Plan (CAAP) released recently by the cities of Long Beach and Los Angeles. Emissions in communities surrounding the ports have become an even bigger as the economy continues to grow, according to Solis.

“With our technology we can help reduce emissions as well as reduce the fuel consumption on rubber-tired gantry [RTG] cranes,” says Solis. “We are reducing the peak power required by the generator set, and the net effect is that emissions and fuel consumption are reduced. We’re exploring many ways of installing this equipment.

“On RTG cranes, we’re now planning on reducing the size of the diesel generator set since it is no longer required to be so large with the incorporation of our Regen system. Currently, the generator set is oversized due to the hoisting function. Because we’re reducing that peak power, there’s no longer a need for such a large generator set; therefore, fuel efficiency’s increased and emissions reduced even more.”

The incorporation of a smaller genset with the company’s energy storage system is being worked on to derive additional fuel savings and an additional reduction of emissions. Vycon hopes to see greater than 35% fuel savings from this project in 2007.

A Vycon Regen system can also help with reducing peak power requirements on quay cranes that are used to load or unload container ships. Docked ships are loaded or unloaded with Quay cranes at a rate of one container per minute, and every time a container is lifted there is a large peak power requirement, normally about a megawatt. Typically, four quay cranes work on one ship, and this puts a severe demand on the utility.

Vycon’s solution can help by reducing the peak power requirement for the shipyard operations. Vycon is now in the process of developing its latest product, a 500-kW flywheel. This flywheel will be used in electric rail and quay crane applications that have large peak power requirements. The flywheel can be paralleled up to several megawatts of power to meet the specific requirements of the application.

“The biggest polluters in ports are the ships themselves,” says Solis. “Port authorities and terminal operators are exploring alternative ways of powering ships so that they’re not using their huge diesel generator sets. They are now starting to plug in the ships to utility power, also known as cold-ironing.”

One of the issues associated with cold-ironing is that the existing utility infrastructure is not ready to take on this additional demand. Vycon’s energy storage system can help by minimizing the peak power not only of the quay cranes, but of the entire port operation.

“Essentially, we can place our Regen system where it is most needed,” says Solis. “Port operators are happy because they reduce their utility costs—as they currently are penalized for peak power consumption—and utility companies are happy because we are reducing the strain on the infrastructure. It’s a win-win situation for everyone.”

The company is also now in full production of its VDC140 flywheel, used as a DC source for UPSs. This system is meant to be installed as a replacement for traditional lead-acid batteries on UPS systems below 500 kilovolt-amperes. A 750-kW unit is under development so that it can support multimegawatt UPS installations. The bearings on all of the company’s systems are magnetic and fully levitated, with no mechanical wear at all.

“A lot of people are looking for the larger machines in the UPS industry,” says Oliver Ulibas, Vycon product manager. “For us it makes good sense to get into the larger, higher-capacity units. This is where much of the demand is.”

Henry Vere is a writer specializing in science and engineering topics.

DE - May/June 2007