High utility rates and recurring reliability issues, particularly in urban areas, are driving the need for more effective and efficient power quality innovations for equipment such as data servers and medical treatment systems. Such applications tend to be more sensitive than ever before to minuscule power glitches.
Uninterruptible power supply (UPS) systems ensure that critical loads never see a blip. Most consist of arrays of lead acid batteries. But as increasingly power hungry data servers and other vital equipment grows in number, so does the challenge of finding enough space with sufficient weight-bearing capacity to support dozens – and perhaps hundreds – of lead-acid batteries.
It’s also paradoxical that while UPS systems must be able to dependably supply continuous power to vital loads, batteries are notoriously unreliable. Every time they are cycled, UPS batteries become less capable of responding properly, even when called upon to operate for only a split second. A single cell failure in one battery may bring down the entire string and the entire critical load with it. Other issues include the need to vent toxic and explosive gases, fire and hazardous materials (hazmat) permitting, acid spill containment, onerous testing and replacement schedules, disposal problems and more.
Issues of battery maintenance and reliability have spurred development of energy storage alternatives that are more reliable and less costly to operate. In the late 1990s, commercially viable flywheel energy storage systems hit the market. Cautious UPS users were intrigued, but hardly lined up to buy the new and somewhat unproven technology. Now, a decade later, recent flywheel advances – combined with a proven track record – have accelerated their deployment.
“Our orders last year were 25 times that of the previous year,” said Frank DeLattre , senior vice president of sales and service for Pentadyne Power Corp., which specializes in flywheel systems.
Early designs that are still being sold today use a heavy steel disk to store energy kinetically. The disk is kept spinning by a motor-generator, which, along with ancillary systems, draws 3,000 Watts. When a building’s utility voltage falls below a set point, the flywheel motor-generator instantly fills the void, carrying the load throughout a power disturbance – mostly lasting less than a second – or until the backup generator comes online several seconds later.
The most recent advances in flywheel technology use carbon-fiber composites that are lighter, stronger and safer than massive steel flywheels. This enables more energy to be stored in a smaller, lighter package, eliminating much of the footprint and weight issues of conventional solutions. The newer designs are also far more energy efficient, using only 10 percent of the standby energy required by steel puck systems, which saves thousands of dollars in utility costs annually for each unit. Carbon-fiber pucks are 90 percent lighter than steel pucks, so magnetic levitation within a factory-sealed high vacuum increases efficiency and eliminates the costly and relatively frequent needs of steel puck designs for bearing and vacuum pump service.
In addition to reliability and operational improvement compared to battery solutions, modern flywheels are far more cost-efficient. Over a 20-year design lifespan, cost savings from a hazmat-free flywheel compared to a five-minute valve-regulated lead acid battery bank ranges from $100,000 to $200,000 per flywheel deployed.
Commercial flywheel suppliers include Active Power, Emerson Network Power/Liebert, Pentadyne and Socomec Sicon. Customers who have made the transition from UPS batteries to flywheels have reported favorable results and relief from worry about reliability for ride-through backup power quality supply. Scripps Green Hospital in La Jolla, Calif., installed flywheels in conjunction with their UPS to ensure power continuity to their heart catheterization laboratories.
“Dealing with batteries is especially problematic and costly,” said Alan Beyea, who heads the hospital’s engineering services department. “Even in the first year, several cells in our battery bank went bad. I’ve been very impressed with the flywheel technology.” He recently ordered another flywheel. “In our circumstances,” he said, “we just can’t take risks.”
A nonprofit organization has been created to promote onsite energy technologies. The technologies integrate power, heat and cooling to hospitals and other critical facilities in Texas, especially during natural and man-made disasters. The Texas Combined Heat and Power Initiative (TXCHPI) will promote the use of combined heat and power (CHP) technologies as the most reliable, economic and environmentally-friendly solution to energy security for the state’s businesses and essential service facilities.
“Considering power outages brought by hurricanes such as Rita, as well as rolling black-outs, Texas must act now to ensure power continuity to the state’s critical infrastructure,” said board member and the group’s executive director, Rich Herweck. He is founder of CleanEnergy, LC, which develops potential clean energy prospects in Texas. “CHP provides onsite or near-site power generation to ensure that vital institutions, such as hospitals, schools and critical government offices, can always operate, no matter the circumstance,” he said. Other board members include Joe St. Pierre of Solar Turbine and Ray Deyoe of Integral Power. Members of the initiative include CHP users from industrial, institutional and commercial applications, as well as equipment manufacturers, engineers and project managers, utilities and public interest groups.
About 30 percent of CHP capacity in the U.S. is in Texas – about 16,000 MW. The group believes that with the right policies, that number could double by 2015 through development at large and medium-scale industrial and commercial facilities. The group also says the state would benefit from reduced emissions, conservation of natural resources, deferred investment in grid strengthening and alleviating grid congestion.
CHP technologies use engines, turbines and fuel cells to produce power at a customer’s site. Heat recovery technologies boost efficiency by trapping the thermal energy from exhaust streams to operate equipment for cooling or heating or to control humidity. By capturing the waste heat, CHP uses less fuel and reduces air emissions for the amount of useful work performed compared with a utility power generation station. While the typical efficiency of a central generation is in the 30 percent range, CHP can be as much as 90 percent energy efficient.
The group plans to meet monthly to educate prospective users about the benefits and potential of CHP. The group also plans to meet with elected officials to advocate policy changes that recognize CHP benefits. “CHP technologies can make a tremendous impact on the Texas energy situation,” said Dan Bullock, director of the Gulf Coast CHP Applications Center, a group funded by the U.S. Department of Energy. “Promoting these technologies can benefit the state of Texas’ disaster readiness as well as its economy.”