As summer rolls around once again, many electrical contractors and facility managers are preparing for power grid problems similar to what we experienced last summer – costing businesses approximately $6 billion in lost revenue, productivity and damage. One might think this is an isolated event not likely to happen twice. Think again. Over the past decade, national demand for electricity has increased 30 % percent , while transmission capacity has expanded by only 15%. Secretary of Energy Spencer Abraham has recognized that it will likely be a bumpy ride stating that “ ...our nation's transmission system over the next decade will fall short of the reliability standards our economy requires and will result in additional bottlenecks and higher costs to consumers.”
The hefty price tag of upgrading the infrastructure is one reason that change has come slow. The North American Electric Reliability Council (NERC), the group charged with monitoring the power grid, has estimated that improvements will cost $56 billion. Meanwhile, the Electric Power Research Institute (EPRI), a nonprofit energy research consortium, puts a preliminary estimate at more like $100 billion.
While the utilities and politicians try to figure out this problem, we must deploy our own defense against the damaging and very costly effects of unsteady and poor power quality. Currently, there are many power protection and reliability solutions available that protect critical processes from power surges and blackouts. Battery-based uninterruptible power supply (UPS) systems, micro turbines and diesel engine generators are common solutions. However, these conventional systems have posed a number of performance, cost and reliability challenges to users seeking reliable operation of their equipment and processes.
The valve-regulated lead-acid (VRLA) batteries that provide temporary power for the UPS as well as start up power for generators are the most unreliable and most costly element of conventional power quality and reliability solutions. For applications that need relatively high power delivery over a short period of time, battery-free systems, such as those using Active Power's CleanSource® flywheel-based technology, now offer an attractive alternative or complement to battery-based systems for many key applications with any of the following requirements:
- Continuous power;
- Power quality improvement; and
- Battery isolation and redundancy.
Real World Applications
Nufern, a Connecticut-based designer of optical fiber for telecommunications, put the innovative flywheel system to the test during last summer's devastating blackouts. Nufern's application-specific optical fiber is produced from pure glass rods, or preforms, that are melted at 3,000 ° Celsius to create fibers smaller in diameter than a human hair and as long as one mile. Making optical fiber requires precision machinery with the highest level of clean consistent power. One blip on the electrical line can cause serious problems for Nufern's delicate processes.
Because battery-based power systems were not an option due to the exacting nature of their critical processes, Nufern worked with local Caterpillar dealer, H.O. Penn and purchased a redundant solution including an 800kW Caterpillar generator and two 300kVA Cat ® Uninterruptible Power Supply (UPS) systems (using Active Power's CleanSource ® technology) to handle their demanding electrical loads.
During last summer's blackout, Nufern was completely unaffected due to the quick response of the battery-free UPS. When the power dropped, the flywheel UPS seamlessly transferred the load to the generator in only 13 seconds. “At first, we didn't know there was a blackout. Our lights didn't even flicker. The only way we knew something was going on was that our generator was on and our power monitoring systems were telling us we were on backup power,” commented Alan Laverdure, senior engineer/facilities for Nufern and former manager at a local utility. “The flywheel UPS did exactly what it was designed to do. We were in the process of producing a glass preform at 3,000 degrees. If we had lost power even for an instant, the glass rod would have broken, chlorine glass would be exposed and at least a week's worth of painstaking work and thousands of dollars in materials would be scrapped.”
Critical manufacturing processes are not the only application requiring precise power quality. For television broadcasters, such as ABC News, a continuous on-air signal is quite literally the lifeblood of their business. Additionally, in the event of an emergency, broadcasters are required to fulfill an important public safety service through their participation in the national EAS (Emergency Alert System). Therefore, ensuring continuous power availability under any conditions is an absolute necessity.
Incoming electric power disturbances can easily take a broadcast transmitter off the air. Even a few seconds of outage can wreak havoc on a high-tech newsroom like ABC, resulting in a lost signal, stranded viewers and potential loss in commercial revenue.
Additionally, an unexpected power outage can cause some transmitters to undergo a hard shutdown, which can damage transmitter components due to the sudden loss in cooling or other control malfunctions. Given the high costs and risks of a power failure, ABC's Director of Systems Services, Phillip Durante, has turned to Active Power's CleanSource flywheel technology for back-up power solutions since 1998.
Two CleanSource DC energy storage systems provide ABC with continuous power protection for their microwave uplinks. With CleanSource DC in place, the network is assured of a reliable source of backup power to ride through utility disturbances.
A battery-based back-up power solution would have taken up too much space, been more expensive to maintain, and required a temperature controlled atmosphere. Given the small footprint, low maintenance requirements, and unlimited lifespan of the CleanSource DC system, it was the natural choice from both a system reliability and business value perspective for ABC.
How Does a Flywheel Work?
Flywheel energy storage systems (see Figure 1), store kinetic energy (i.e. energy produced by motion) by constantly spinning a compact rotor in a low-friction environment. When utility power fluctuates or is lost, the rotor's inertia allows it to continue spinning and the resulting kinetic energy is instantly converted to electricity. The motor, which uses electric current from the utility grid to provide energy to rotate the flywheel, spins constantly to maintain a ready source of kinetic energy. The internal generator then converts the kinetic energy of the flywheel into electricity.
Figure 1. The CleanSource flywheel incorporates a patented magnetic bearing technology that enhances efficiency and reliability
Continuous Power configurations that incorporate the flywheel UPS with a diesel generator, offer a space-saving, low-maintenance, high reliability alternative to battery-based UPS systems. During a power failure, the flywheel assures a seamless transition to generator power for virtually unlimited backup time (See Figure 2). Critical computer/network infrastructure, process control and broadcast transmitters are typical applications for this configuration.
Reserve Time Requirements
When properly integrated and maintained, standby diesel generators can and will reliably power a load in 10 seconds or less. Thus, in continuous power applications, use of flywheel technology entirely eliminates the need for banks of lead-acid batteries and extended backup time. Flywheel UPS systems actually provide a reliability advantage over the traditional 15-minute backup system even though flywheels provide 15 seconds of energy ride-through. In fact, 15 seconds is enough time to monitor the power to minimize unnecessary diesel starts and further reduce genset dependency in the availability equation.
In many circumstances, end users with this type of critical power need to eliminate the requirement for batteries due to maintenance concerns or limited space, as was the case at Nufern. By not relying on batteries, Nufern doesn't have to worry about their reliability, maintenance, temperature sensitivity, replacement or disposal. “Battery-based UPS systems were not viable for us. For our operations, we'd need a large room just to house battery banks, not to mention the inherent reliability problems and their environmental unfriendliness. We just can't trust batteries. They fail,” commented Laverdure.
Figure 2. Flywheel-based Continuous Power Configuration coupled with a diesel generator ensures a smooth transition to long-term power backup
A recent report on Flywheel Energy Storage from the U.S Department of Energy's Federal Energy Management Program (http://www.eere.energy.gov/femp/pdfs/fta_flywheel.pdf - Sept 2003) notes that batteries "suffer from a significantly shorter equipment life and higher annual operation and maintenance expenses" compared to flywheel technology.
Power Quality improvement can be assured with a standalone flywheel system that will eliminate the most common power problems: voltage surges, spikes, sags and other disturbances. Because the vast majority of power quality events fall into this category and last only a few seconds, many applications will benefit from the use of a flywheel-based UPS alone (See Figure 3) that will eliminate more than 96% of power disturbances. Batch or process manufacturing sites with a history of short-term power glitches or sags are ideal applications for high-power flywheel systems. “ Not only does the flywheel UPS provide instant power backup, it also provides constant voltage regulation – a must for Nufern's operations. Receiving voltage swings and transients can be just as damaging to our equipment and processes as blackouts,” further commented Laverdure. “The flywheel UPS made sure we had clean output at the proper voltage.”
Figure 3. In its simplest form, a flywheel-based UPS – with no batteries or generator – provides power protection from more than 96% of power disturbances.
Battery Isolation and Redundancy configurations are another ideal application for flywheel technology. Flywheel energy storage is an effective means of isolating chemical battery strings from harmful power faults. By eliminating more than 96% of common power disturbances, the flywheel minimizes battery charge/discharge cycles, prolonging battery life while adding an additional layer of redundancy. This configuration can be used to maximize reliability of DC systems without generator backup.
Benefits of Flywheel Technology
From 65kVA to 3600kVA, 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 and space available. In any of these configurations, the user will benefit from the many unique benefits of flywheel-based systems including:
- High power density - small footprint;
- Parallel capability that allows for future expansion;
- Fast recharge (under 150 seconds);
- Up to 99% efficiency for reduced operating cost;
- Low maintenance;
- Long useful life;
- Simple installation;
- N+1 Redundancy options;
- Quiet operation; and
- Wide temperature tolerance.
Flywheel implementations such as those offered by Active Power and Caterpillar comply with the highest international standards for performance and safety including those from UL and CE. They also incorporate advanced features that users expect to make the systems easy to use, maintain and monitor such as self-diagnostics, event logs, adjustable voltage settings, RS-232/485 interface, alarm status contacts, soft-start precharge from the DC bus and push-button shutdown. Available options include DC disconnect, remote monitoring, Modbus and SNMP communications and real-time monitoring software.
Coupled with several million hours of proven field operation in a wide variety of environmental conditions, these features and benefits make battery-free flywheel technology worthy of consideration for critical power protection needs.
