Once used primarily in emergency facilities, uninterrupted power supply (UPS) systems are becoming more commonplace as many types of companies seek to maintain the performance of mission-critical functions in the event of an emergency power loss. UPS systems are no longer reserved for emergency centers or hospitals, but are being sought out for financial service organizations, pharmaceuticals, information technology companies, and many others.
Traditionally, the vast majority of UPS systems deployed in the United States utilize various technologies based on converting Utility AC power to DC power, and then back again to AC power. This technology requires DC batteries to provide back-up power during utility outages.
Some of the new opportunities in UPS technologies available provide owners significant advantages, while virtually eliminating batteries and the associated environmental impacts and costs of maintenance and replacement.
Following is a snapshot of the new opportunities being developed for UPS systems:
- The first alternative would be to utilize a UPS system with a flywheel energy storage device backed up by a separate diesel generation system. The flywheel UPS system is similar to a static battery type system, except that the DC battery plant is replaced with a flywheel kinetic energy device.
The inertia and energy of a rotating flywheel is used to provide uninterrupted power ride-thru capability in the event of a normal power loss for the 10 to 15 seconds it takes to start the on-site back-up standby generator system. This system has a 25-second ride-thru capability to allow time for a generator (plant) to start and parallel sufficient units as appropriate. The 25-second ride-thru capability can be achieved using multiple flywheel units.
- Another alternative would be to utilize the flywheel-energy-concept UPS with the back-up engine generator directly coupled to the system. This UPS system is a development of the flywheel energy concepts mentioned previously, with the back-up engine-generator directly coupled to the system and closely integrated in its operation and control. The unit provides three to five seconds of ride-thru kinetic energy and is directly linked to the engine-generator unit mounted in-line with the output generator.
While oftentimes a standard approach to replacing, upgrading, or installing new UPS technology seems most appropriate and comfortable, there are new solutions and technologies that can provide significant benefit to owners, operators, and "benefactors" of UPS systems - especially when the entire lifetime of the equipment is considered and not just the initial start-up costs.
The mentioned options provide a snapshot of the alternatives being developed today. Additional choices, such as fuel cells and micro-turbines, have also made a significant impact in the market and warrant consideration. When considering UPS systems, the replacement costs and environmental issues associated with battery replacement will continue to play a significant role in total cost of ownership of UPS technology: Leveraging the alternatives can be a real benefit for today's facility owners.
Thomas E. Reed is principal and director of projects at Philadelphia-based Kling (www.kling.us).