As one of the top 100 hospitals in the nation, Scripps Green Hospital, located north of scenic La Jolla, CA, offers a wide range of clinical and surgical services including intensive care, cancer/oncology, cardiothoracic, and orthopedic surgeries. Among the specialty services located on the campus are interventional cardiology, orthopedics, blood and bone marrow transplants, solid organ transplants, and clinical research.
Overseeing the hospital’s engineering services and operations, manager Alan Beyea has the distinction of making sure the hospital’s infrastructure is up to the task of handling the center’s myriad of medical services. Making sure power to critical load equipment is conditioned and steady is of paramount concern. Under California Title 22, in the event of one of California’s all-too-frequent power outages, hospitals are required to have generator power online in less than 10 seconds. With California’s history of rolling blackouts and the devastating effects power disruptions can have on a hospital, Beyea takes electricity issues very seriously.“In the cath lab, if the power is interrupted during a procedure, the doctors have to start the procedure all over again. This diagnostic process involves threading a small tube (or cath eter) through an artery in the arm or leg to the heart. Physicians view the procedure via X-ray to determine if a serious heart problem exists and how to treat it,” said Beyea.
Challenges
When the hospital expanded its cardiac catheterization labs, the power protection system required expansion as well. The existing 250-kilovolt-ampere (kVA) uninterruptible power supply (UPS) combined with gel-cell batteries did not have the capacity to handle the increased power needs of the new lab. The challenges were twofold: First, at a million dollars per added bed, the hospital must maximize every square foot of space—and the existing UPS room was a mere 300 square feet. Second, installing more batteries would only multiply the current battery maintenance time, costs, and headaches to which Beyea had become very familiar.“Dealing with batteries is especially problematic and expensive. Even in the first year, several cells in our battery bank went bad so we’d replace the batteries at very short intervals—way before their stated end of life. In our circumstances, we just can’t take any risks,” reflected Beyea.
Power System Maintenance
Working with GE and Scripps architectural consultant Rodriguez Park and electrical consultant, Randall Lamb, Beyea learned that advanced composite flywheel power systems manufactured by Pentadyne Power could provide the required power bridge to the generator and eliminate dependence on batteries.
GE recommended paralleling two Pentadyne VSS+DC flywheel systems to serve as the energy storage system in lieu of the battery bank. The VSS+DC is an advanced direct current (dc) flywheel power system that is fully compatible with UPS systems from leading manufacturers. Acting as a mechanical battery, the VSS+DC stores kinetic energy in a high-speed rotating group: the only moving assembly in the system. When incoming utility power sags or blacks out, the VSS+DC instantly responds to support critical loads by releasing that stored energy. To the load, the event never occurs.
Providing ride-through time to bridge power to the backup generator, the flywheel system is a safe, extremely low-maintenance, environmentally friendly alternative to UPS battery banks that improves UPS system reliability while dramatically reducing operating cost. Since Scripps requires high power, but for only a short duration to assure transfer to the backup generator, Pentadyne’s flywheel systems were the ideal solution. Pentadyne’s latest model, the VSS+DC, can provide 190 kW for 12.5 seconds (s), or longer for lower demand. This provides ample time to ride through 98% of voltage sags and outages (which are typically 10 s or less) and then seamlessly transfer to the generator in the event of a prolonged outage. Once the generator takes the load, the VSS+DC recharges rapidly, ready to immediately respond to any further disturbances. The simple, modular design of the VSS+DC enables easy paralleling for higher power, longer runtime or redundancy, all without troublesome communication links. This clearly provides quick and easy expansion capabilities. In this case, two flywheel systems in parallel easily support the customer’s load and provide more than 30 s of ride-through before transferring to the diesel generator.
“I was very impressed with the flywheel technology. Not only did it clearly demonstrate that it can reliably provide power to the load and bridge the power to the generator, but the two flywheel systems didn’t take up more room. In fact, the previous gel-cell batteries were twice the size of the old UPS system,” said Beyea.“We now have 500 kVA of capacity taking up less room than our previous 250 kVA UPS with batteries—that’s significant.”
Future Expansion
The GE UPS, automatic transfer switch, diesel generator. and Pentadyne’s VSS+DC flywheel systems complete the power components for protecting the cath labs. Each of the two flywheel systems work independently and seamlessly with the UPS and diesel generator, while the flywheels occupy a total of less than 12 square feet of floorspace. The Pentadyne VSS+DC clean energy storage systems exceeded the project’s objectives, proving themselves a superior, far more reliable alternative to batteries. Aside from providing uninterrupted power in a very compact space, the VSS+DC delivers energy-saving current adjustment, rapid recharge and an extended lifecycle a standby energy consumption one-tenth that of competing systems.
Presenting solid reliability with rapid investment return, Scripps intends to deploy additional flywheel systems in their planned expansion of two more cath labs.“When we considered the various costs of batteries, including replacement, service and real-estate compared to the costs of the flywheels, the financial equation was clear. With virtually no maintenance of the flywheels for 20 years, it makes total economic sense,” emphasized Beyea.
