Medical Construction & Design

SEP-OCT 2017

Medical Construction & Design (MCD) is the industry's leading source for news and information and reaches all disciplines involved in the healthcare construction and design process.

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60 Medical Construction & Design | SEPTEMBER /OCTOBER 2017 | MCDM AG.COM Footprint Depending on expected system runtime and overall capacity, fl ywheels gener- ally have a reduced footprint compared to battery UPS systems with similar kVA ratings. Long battery strings are re- placed with a compact cabinet housing the rotational wheel. This reduced foot- print can lend itself to smaller UPS room requirements when space savings are a concern, particularly in renovations. Lifecycle and maintenance Across multiple system manufacturers, the typical expected lifecycle for a fl y- wheel is 15-20 years. Additionally, with any UPS system there is an associated maintenance cost. Flywheel manufac- turers recommend yearly preventive maintenance of the fl ywheel's vacuum pump and lubricating oil. Runtime A fl ywheel's runtime is relatively short when compared to its battery UPS counterpart. Flywheels typically operate in the seconds range while a battery UPS can operate for minutes at a time. This reduced runtime may not necessarily align with every facility's needs. Where longer runtimes are desired, fl ywheels can be coupled with battery strings to provide battery hardening and ride through system load spikes. Where fl ywheels are subjected to mul- tiple power losses in a short period, their available runtimes can fall below that of their full system capacity. This can be- come an issue where the transition time between normal and emergency sources is critical and much smaller, versus large battery UPS. Careful system planning and sequencing should be done to ac- count for a fl ywheel's reduced runtime. Effi ciency Like a battery-type UPS, fl ywheels have variable effi cacies based on the percent- age of system capacity being utilized. A fl ywheel becomes more effi cient as more load is placed on it (this is typical of bat- tery UPS as well) and generally ranges from 90 to 98 percent effi cient. Flywheels are quick to achieve their higher effi ciency values over a lower percentage loading range when compared to standard battery double conversion UPS systems. Environmental impact With a battery-type UPS there is an inherent need for mechanical cooling and ventilation. These requirements are both code and operational effi ciency driven. Battery UPS rooms must be ven- tilated due to hydrogen propagation that comes with battery charging; addition- ally, the UPS room needs to be kept at a consistent temperature in order not to depreciate battery life. Flywheels can operate in tempera- tures over 100 F (as well as below 0 F) and do not require mechanical cooling and ventilation the way heat-generat- ing batteries do. And fl ywheels don't contain the hazardous chemicals that make battery disposal an issue. The industry has seen new approach- es to imaging suites, operating rooms and data centers in healthcare facilities. We can surely expect more to come. Flywheel technology's emergence as a sustainable uninterrupted power source is yet another detail signifying the greater fundamental changes underway in how things are being done. Ron Parsley, P.E., LEED AP, is director of engineer- ing, Affi liated Engineers, Inc. Sean Hood, P.E., is an electrical engineer, Affi liated Engineers, Inc. From top: Upon loss of power, the rotating shaft continues to spin due to inertia. The rotational inertia transforms the fl ywheel from a motor into a generator, keeping the downstream electrical power distribution system energized long enough for an emergency generator to come online. > A fl ywheel uses the stored rotational energy from a spinning mass. In the event of a power interruption, energy is extracted from the mass, providing suffi cient emergency power prior to the standby power source.

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