The Power of Compressed Air
Active Power, based in Austin, Texas, is no stranger to the $11 billion backup power industry. Unveiling the world's first commercially viable flywheel energy storage system in the late 1990s, the company made a major breakthrough in the industry with this technology, which offered customers an alternative to lead-acid UPS batteries. Although the flywheel has been successfully used as a bridging energy source for years, enabling UPSs to continue operating long enough (15 to 30 seconds) to transition to the backup generator or an alternative utility source after an interruption or event, customers wanted more — a product comparable to lead-acid batteries that would provide the equivalent of their typical 15 minutes of backup at the same price as the flywheel. After years of research and development, the company answered its customers' demands by creating the new CoolAir DC thermal and compressed air energy storage system, which just recently became available for commercial use in Q1 of this year.
CoolAir DC stores energy in the form of compressed air and heat. During an electric utility outage, the CoolAir DC routes the compressed air through a Thermal Storage Unit (TSU) to acquire heat energy. The heated air spins a simple turbine/alternator to produce 15 minutes of backup power at 85 kilowatts. Typically installed by its own company technicians, outside electrical contractors, or, in rare instances, the customer, this product also contains a small continuous-duty flywheel to support critical loads during the brief period required for the turbine to spin up to speed.
During the discovery phase of product development, Joseph Pinkerton, chairman of the board and CEO, admits the company realized an unforeseen supplemental benefit. “We set out to solve the runtime limitation problem but by the very nature of the technology we realized we could make the air coming out of that little turbine colder and colder,” he says. “In essence, if this product is sitting in a room with a bunch of IT equipment when you lose power, you generally lose air conditioning and rooms get hot very quickly. This unit not only provides backup power but also backup cooling as well.”
Especially in data center applications, Pinkerton notes that customers so far are just as interested in the controlled cooling feature as the battery-free backup draw. Although the company is initially targeting data centers and the medical community for installations, Pinkerton says interest in this product is also coming from the broadcast television industry as well as the industrial sector. Based on the success and past performance of several of Active Power's flywheel UPS units to protect critical semiconductor fabrication equipment, Freescale Semiconductor, a spinout of Motorola located in Oak Hill, Texas agreed to test the new CoolAir DC product. The unit was put into service August 1, 2005.
According to Scott Bayer, principal staff electrical engineer, site services at Freescale, the company is using a 45-kilowatt pre-production CoolAir DC unit connected to a 75 kVA Leibert UPS Model AP366. This unit contains components rated at 80 kilowatts, which is Active Power's base module, but is restricted to 45 kilowatts due to a smaller generator. The unit is serving two air handling units in an office building at the Oak Hill campus. Each has a 50-hp motor driven by a variable-frequency drive running at 40 hertz with a total peak load of 40 kilowatts.
Freescale chose this application for several reasons: to provide a non-critical, real load for the test that would not impact business operations when performing testing or if the system failed; to size the load to an existing UPS; to minimize installation costs; and to ensure no impact to business operations during installation. “I designed the ability to connect a voltage sag generator in series with the incoming power,” Bayer said. “The voltage sag generator is a test instrument that simulates voltage sags and outages while capturing the event's voltage, current, and power data through a 23-channel oscilloscope. We also used the unit's internal data acquisition capability to observe its internal characteristics of pressure, temperature, speed, and power. We characterized the performance of the CoolAir unit through extensive sag and outage testing. In every event, it carried the load as it should.”
In fact, during the last five months, the unit has protected the load through three actual voltage events, in addition to all the successful testing, notes Bayer. “The CoolAir unit has helped solve reliability and maintenance issues that are associated with battery systems,” Bayer says. “This system has real-time monitoring and provides immediate notification of any abnormal condition that may affect performance. It also provides a solution for systems needing 5 to 15 minutes of outage protection without generator backup.”
For more information, visit www.activepower.com.
Operates in temperatures from 0°C to 40°C
20-year life expectancy
Ambient noise not to exceed 70 dBA at 1 meter
Built of nontoxic recyclable materials
Supports a 100kVA UPS for 15 minutes at full load
Supports DC bus requirements for North American (480 VDC) and European (400 VDC) UPS products