Power Without Interruption: Flywheels, large UPS, and battery testing
November 26, 2014
The importance of having an Uninterruptible Power Supply (UPS) is underscored by John Steele, inside sales manager for Mitsubishi Electric Power Products Inc. “Power can go out or have a fluctuation at any given point,” he says. “The question is how much do you stand to lose if your critical loads go down? A UPS does more than just bridge the gap for power fluctuation. It also protects your critical loads from surges, spikes, switching transients, or other power anomalies that can potentially damage the servers themselves.” Once the server or a component in the data center gets damaged, it may take days to get a new piece of equipment installed, he adds.
Climate change, against the backdrop of an aging electricity grid, means there may be an even greater need for providing such protection.
Severe weather is the number one cause of power outages in the United States, costing the economy billions of dollars a year in lost output and wages, spoiled inventory, delayed production, inconvenience, and damage to the grid infrastructure. Those are the findings of “Economic Benefits of Increasing Grid Resilience to Weather Outages” a 2013 report prepared by the President’s Council of Economic Advisers and the US Department of Energy’s Office of Electricity Delivery and Energy Reliability, with assistance from the White House Office of Science and Technology.
The report’s researchers make the point that the aging nature of the grid—much of which was constructed over a period of more than 100 years—has made Americans more susceptible to outages caused by severe weather. Between 2003 and 2012, roughly 679 power outages—each affecting at least 50,000 customers—occurred due to weather events, according to the US Department of Energy.
Additionally, the report finds that the number of outages caused by severe weather is expected to rise as climate change increases the frequency and intensity of hurricanes, blizzards, floods, and other extreme weather events. In 2012, the US suffered 11 billion-dollar weather disasters—the second-most for any year on record, behind only 2011.
Those who run data centers are keenly aware of the criticality of the situation.
As a company that provides co-location and Cloud services, EasyStreet, based in Beaverton, OR, uses a great deal of energy and is dependent upon that energy to be available without interruption.
System uptime and availability are prime concerns. “Making sure that customer’s computing systems have available power is paramount to not only keeping systems up and running at high nines of availability, but for us to keep operating as a viable company,” points out Jon Crowhurst, director of EasyStreet’s technical services.
Power outages can cost organizations thousands, and even hundreds of thousands, of dollars every minute computing systems go down. “If EasyStreet can’t maintain power integrity, customers will go elsewhere,” notes Crowhurst.
EasyStreet also has a commitment to being as green as possible and has won many accolades for its business and green initiatives, including being an EPA Green Power Partner.
Through several initiatives, both of EasyStreet’s data centers are now zero-carbon footprint energy consumers. To get to that point, EasyStreet has utilized wind power and flywheel energy storage to meet its needs in a sustainable fashion.
EasyStreet recently built a new SAS 70 (The Statement on Auditing Standards No. 70) Type II audited data center, and completed an energy-saving retrofit to its first data center. Both data centers operate on power that is 100% generated from wind as part of the Portland General Electric Wind Program.
Crowhurst says the company started buying wind offset credits three years ago for its first data center, initially purchasing 50% of its utilization offsets by wind. “We gave our co-lo [co-location center] customers the opportunity to participate in that program and pay a small up-charge to be able to put a
Portland General Electric Wind Program logo on the website, which means that we’re all participating in the program together,” he notes.
EasyStreet’s data center project is the first to qualify for funding through the Oregon Department of Energy’s State Energy Loan Program due to the energy efficiencies gained compared to conventional data center designs. Assisted by the Energy Trust of Oregon, EasyStreet played a pioneering role in developing the Oregon Department of Energy’s expertise in the area of efficient data center design, says Frank DeLattre, president of VYCON Energy.
“Through careful planning and implementation of energy smart technologies and systems, EasyStreet estimates that it will be able to save 524,000 kilowatts a year—enough energy to power 52 average households,” says DeLattre.
In a data center, the cooling system consumes the majority of power. With that in mind, Crowhurst and his team extended the company’s green design throughout the data center to include the purchase of energy-efficient UPS systems and energy-efficient transformers.
Reliability was the primary factor in choosing from among the available green technologies. Crowhurst looked to VYCON to learn more about its clean flywheel energy storage systems. The flywheels had to be able to work with double-conversion UPS systems. VYCON’s VDC-XE units fit the criteria.
“I visited the VYCON factory and looked at how the flywheels were made,” he notes. “VYCON’s experience and history in the marine and rail industry is a fairly impressive use of the technology and shows how rugged they are.”
VYCON’s VDC flywheel systems store and deliver a reliable source of direct current (DC) power, utilizing the kinetic energy of a high-speed flywheel. They are designed to be compatible with major brands of three-phase UPS systems. The systems interface with the DC bus of the UPS, just like a bank of batteries, receiving charging current from the UPS and providing DC to the UPS inverter during discharge, says DeLattre.
The technology enables the VYCON flywheel to charge and discharge at high rates for countless cycles without degradation throughout its 20-year life. The flywheel systems’ footprint offered another benefit. “As a co-lo, space is a precious commodity,” says Crowhurst. “The more space we have, the more we can accommodate our customers’ servers and other computing assets.”
In its new data center, EasyStreet has three VYCON VDC-XE systems running in parallel with double-conversion UPS systems. If there’s a power outage, the 300-kW flywheel systems act as a bridge designed to seamlessly transfer to the facility’s diesel-engine generators. Crowhurst says backup batteries are not needed.
“Having 30 minutes of batteries is, in my opinion, pointless. If the generator doesn’t start in the first 30 seconds, there’s nothing you can do,” he says. “If you had two generator mechanics with their tools in hand standing next to the generator and said, ‘I need this fixed in 14 minutes,’ they’d both laugh at you, because there’s nothing that can be done to diagnose or repair a problem with the generator in the time allowed. A well-maintained generator plant doesn’t need 15 minutes—or even 10 minutes—of batteries.”
Pleased with the results the company had garnered to date from installed flywheel technology that had performed as planned through utility glitches, EasyStreet’s senior management team added three flywheel units, which are connected to an Eaton 9395 UPS to support the existing data center load. The flywheels are designed to work with any UPS.
EasyStreet now has three Eaton and MGE UPS systems with 18 flywheels.
“This vision with actual energy savings allows us to save money which translates to saving our customers money,” says Crowhurst. “It’s a great win-win.”
Large UPS Systems
Another option for data centers was recently unveiled by Mitsubishi Electric Power Products, which introduced its 9900C UPS for large data centers: a 1-MW scalable system designed for high efficiency—up to 97%—at all load levels. The system also is designed for a small footprint and low total cost of ownership in a true online double conversion UPS.
The 9900C three-phase UPS also is designed with improved power usage effectiveness over conventional UPS systems. Its scalability enables up to eight units for N+1 redundancy or N capacity to offer high power density per square foot of floor space.
In incorporating Digital Signal Processor and Direct Digital Control, Mitsubishi offers “smart” control of its Insulated Gate Bipolar Transistor (IGBT) technology to achieve optimal performance. Additionally, its three-level conversion design provides a 15-year lifetime on the capacitors. The 9900C provides a variety of open architecture communications methods as well as an intuitive LCD touch panel for quick access of system status, monitoring, and control.
The most important factor to consider when making a decision about a UPS is the technology, the desired size, and the types of loads on the system. “There has been a big push for transformerless types of UPS in the past 10 years, primarily because these systems have become much more reliable,” says Steele. “The technology has improved, whereas 15 years ago, everything was transformer-based until you got into the smaller 1 kilovolt-ampere to 10 kilovolt-amperes UPS.”
Steele points out that it is inadvisable to run a UPS on a 100% load.
“You want to run it closer to 30 to 50% load to optimize the performance of the UPS,” he says. “Another very critical aspect of UPS technology is how it plays in your facility: what size is your generator? What size is the utility feed coming in? What size is the distribution downstream of the UPS system?”
Additionally, the facility’s size, types of loads being powered up, and the temperature of the environment in which the UPS will be located all play a part in UPS selection. Once installed, ongoing maintenance is critical. The UPS needs an alternate power supply, such as batteries or a flywheel, says Steele.
“It’s just as important—if not more important—to maintain the alternate power supply as it is the UPS system,” he points out. “If you have batteries on the UPS system, depending on the battery technology you’re using, it’s very critical that those are looked at routinely, and over time, in comparison to how they looked on day one to be maintained properly.”
In maintaining the UPS system, it is ideal to have a trained manufacturer’s representative or an authorized service provider from the manufacturer examine the UPS system to ensure it is functioning properly, Steele adds.
First responders play another significant role. “We like to say that nothing ever goes wrong in the field, but there is training businesses look at to have somebody onsite who would be a first responder to report back to say something is going on with the UPS system,” says Steele. “They would call somebody to the site to help continue to troubleshoot, but at least they have the information needed to know on what’s happening at the site.”
A UPS system should be tested two to four times annually, Steele says. “I highly recommend batteries should be tested four times a year,” he adds.
As previous experiences in severe weather events have demonstrated, the placement of backup power is important to its operation. “Usually the UPS systems, when we get into the larger sizes over 100 kilovolt-amperes, tend to go in the utility rooms with the major transformers, the generators, the switchboards, and the switchgear,” says Steele. “If it’s 100 kilovolt-amperes, you more often see those on the data center floor or closer to the servers themselves. If it’s obviously going to be in an area that could potentially flood, you may want to consider relocating the UPS system. Electronics don’t like a lot of water.”
A return on investment in UPS systems will depend on its size and number of units, Steele points out. His company is seeing two- to three-year returns on larger projects, he adds.
Steele says, “The norm five years ago were the 500- and 750-kilovolt-ampere systems, but now we are moving into the larger one megawatt-type units and taking that as high as we can go with parallel systems up to four or five megawatts. It seems like there’s a shift right now moving towards the larger systems as opposed to multiple small systems.”
More Large UPS systems
Jim Jones, director of UPS products for Staco Energy Products, says his company has taken note of requests for UPS systems with higher operating efficiencies. To that end, Staco Energy Products is introducing a larger UPS with a 480-V transformerless topology “to eliminate as much of the energy losses as we possibly can in the operation of the system,” notes Jones, who adds that containing rising utility costs is the driving factor. “We’re looking at the 480 topology in the 300-, 400- and 500-kilovolt-ampere ranges,” he states.
The company’s end users are primarily in the mid-range to large IT sector. “Most of the facilities are finding that their utility costs are continuously climbing,” points out Jones. “The only way to eliminate that cost is using more efficient equipment. Unity as a power factor is the best course, but that’s not the easiest and least expensive way to develop the technology.”
Many of the UPS units today have a 0.8 or 0.9 power factor, says Jones. “There are a lot of losses due to heat rejection because of the electronics in the UPS itself,” he says. “We need to eliminate that. We on the UPS side can help them save on their utility usage, their kilowatt demand.”
Staco Energy Products has five UPS units, not including the new one that’s currently rolling out. The line includes:
Unistar C, a 1-, 2-, and 3-kVA rack/universal mount single-phase, online double-conversion UPS
Unistar P, a 6-kVA rack/universal mount and a 6- and 10-kVA tower single-phase, online double-conversion UPS
FirstLine P, a 65- to 250-kVA three-phase, online double-conversion UPS
FirstLine PL, a 10- to 40-kVA three-phase, online double-conversion UPS
FirstLine PL 924, a 9- to 36-kW online double-conversion three-phase UL 924 central lighting inverter
The new UPS system will be part of the FirstLine P offerings, which does use transformers, notes Jones. “The next step will be going to transformerless 480,” he says.
Staco’s UPS units are user-friendly, adds Jones. “The unit can be completely controlled and monitored right at the control panel on the unit or remotely from a desk.” Maintenance is standard and includes an annual preventative maintenance check, primarily focusing on the condition of the batteries.
Staco Energy Products also manufactures power factor correction units to help facilities control high utility bills. “We look at it from the standpoint of complete savings for the data center from all aspects, from the power factor correction and a more efficient UPS to minimize the utility costs the customer is paying,” says Jones.
Utilities do not have the money to build new power plants, he adds. “The only way they’re going to improve is to put demands on their customers, which they’re doing today—increasing the kilowatt demand charges and forcing their customers to use more efficient equipment in their facilities and reduce their demand charges.”
Jones talks about a typical ROI target for the UPS units: “As long as the ROI is 13 months or less, the project is usually a go, and approved,” he says. “If it gets above that, it takes a little bit longer to justify it.”
The Move Toward Green
“Tapping the power of alternative energy sources such as solar, wind, biomass and others will help to reduce our country’s dependence on fossil fuels and foreign imports of petroleum,” notes Phil Charatz, president and CEO of Fuji Electric Corporation of America. “By achieving energy independence, we can preserve the environment around us and see a critical shift in our approach to product development.
“Right now, ‘alternative energy’ and ‘green’ remain somewhat of a trend, which means the industries that seek to advance these technologies rely heavily on government subsidies to survive,” he adds. “In order for these companies to thrive and sustain long-term success, it’s our responsibility to embrace energy-efficient products as a way of life.”
To that end, Fuji Electric manufactures products such as Electric Vehicle Charging Stations, energy-efficient UPS systems, and geothermal power generation equipment.
“With products ranging from small components such as power semiconductors to large systems that include rectifiers, transformers, and UPS systems, we strive to achieve superior efficiency levels for reductions in power consumption,” says Charatz. “With large systems, increases of even 0.1% efficiency will have a tremendous impact on the end user’s total energy usage, so our R&D [research and development] and engineering teams are constantly seeking new, innovative methods to use in Fuji Electric’s product development and manufacturing processes.”
The company’s 500-kVA UPS System is designed for 97% efficiency, achieved through a true-online double conversion UPS system.
“By adopting Fuji Electric’s proprietary RB-IGBT (Reverse Blocking IGBT) technology, we have achieved conductive loss reduction and reactor loss reduction in a new three-level conversion architecture called AT-NPC (Advanced T-type Neutral-Point Clamped), compared with conventional two-level and three-level products,” says Charatz. By using RB-IGBT technology, there is a reduction in power losses and a reduction in the number of components in the system, says Charatz.
“So in addition to the technology itself achieving increased efficiency, the total cost of ownership is reduced over time since less IGBTs means higher reliability and lower operation costs,” he points out.
“For many companies, the components within their UPS systems are manufactured by third-party companies, which makes quality control a challenge,” he says, adding that Fuji Electric utilizes its own components and is one of the largest manufacturers of IGBT devices. The company also sells these components to other UPS and power electronics providers.
One significant factor in maintaining uninterrupted power for systems that include batteries is battery testing. Albér addresses that mission critical challenge by manufacturing battery monitoring systems, single cell test systems, battery multimeters, continuous load units, battery capacity test systems, and data management software solutions.
The Albér measurement method is designed to be accurate, reliable and repeatable.
According to an Albér white paper, to understand the company’s measurement technique, one must view a battery as an electrochemical generator, and the internal resistance path through which current flows as an electrical pipe. When an external load is applied to the battery, the electrochemical generator supplies current through the electrical pipe. Everything functions well as long as the generator is working and the pipe is in good shape.
As the battery ages and deteriorates, its capability to supply power becomes more limited, such as a clogged pipe. Friction in the pipe increases, causing less flow. This restriction causes the terminal voltage of the battery to drop when it's time to deliver energy to the load. The result is the battery cannot deliver the desired capacity.
The white paper makes the point that under normal operating conditions, the battery supplies DC, not Alternating Current (AC). When a battery is tested using an AC test current—which is what AC conductance and AC impedance testing does—the test current not only flows through the normal (DC) electrical pipe, it also flows through the internal capacitor (the AC path) that is also a part of the battery.
All of the parallel plates inside the battery form a gigantic capacitor, an electrical component used in a variety of electrical and electronic designs. One of the operating characteristics of a capacitor is that it allows AC to flow through it while blocking DC. The electrical path through the capacitor acts like a pipe in parallel with the normal pipe. The size of the parallel AC pipe varies depending on the size of the battery and the frequency of the test current, but it can be much larger than the normal electrical path.
When the AC test is performed, a great part of the current flows through the AC path, rather than the DC path that needs to be tested. This means as the DC electrical pipe starts to clog, the AC test current flows through the larger pipe and never recognizes any of the problems in the DC pipe. The clogging appears as a minor problem, causing the user to believe the battery is at full or near full capacity.
When the Albér Cellcorder or Battery Monitor tests the state of health of the battery, it forces the battery to supply current through the normal DC pipe and then measures the terminal voltage to see if there are any developing problems, forcing the battery to perform the way it normally should while its performance is being measured.
Since the Albér technique is a true DC resistance measurement, the capacitor in the AC path acts like a closed valve, and the Albér Cellcorder or Battery Monitor evaluates the condition of the DC pipe alone.
Ohm’s Law states that V = I x R, meaning the voltage being read across a resistor is a function of how much current is flowing through the resistor and how big it is. That’s important because if the test current used is very low, then the voltage across the resistor is so low it can’t be measured with the average test equipment, according to the white paper.
The amount of test current is an important factor when assessing a battery’s internal resistance. Large batteries have very low resistance, so, if a small test current is being used, the voltage used to calculate the result will also be very small.
Most test instruments on the market use approximately one amp of test current, which means the resulting voltage is in microvolts (0.000001). There are instruments that can measure very small voltages, but they are very sophisticated and, consequently, very costly.
A low-test current is analogous to a very small flow through the pipe. A flow of just a few drops will not fill the entire pipe and, therefore, will not indicate a clog has developed until the pipe is almost fully clogged. In mission-critical systems, time is of the essence in taking corrective action.
Ohmic test methods were developed so batteries could be tested without disconnecting them from the charger and/or the load. Online testing is much easier and cheaper, but it's not easy to design test instruments capable of handling this application. The problem with testing batteries online is that the charger and the load generate a lot of noise (ripple) that affects the accuracy of the test, according to the Albér white paper. Ripple is a low voltage AC signal that interferes with the on-line test signal if a low-current, AC-based test system is used.
The Albér white paper suggests that in determining repeatable results, end users should put available equipment to the test to evaluate technologies for online ohmic testing. Connect the different instruments to a battery where the charge voltage can be changed and vary the load to the battery while comparing test results. The superior test equipment will provide repeatable results whether the battery is off line or online with full load.
Author's Bio: Carol Brzozowski writes on the topics of technology and industry.