Li Song, University of Oklahoma assistant professor in the College of Engineering’s School of Aerospace and Mechanical Engineering, along with her research colleagues, Gang Wang, University of Miami assistant professor, and Mike Brambley, staff scientist, Pacific Northwest National Laboratory, have invented a method that overcomes these barriers to significantly reduce building operating costs as well as energy consumption. Nearly 95 percent of all U.S. companies don’t monitor their building energy efficiency due to a lack of awareness, existing infrastructure restrictions or the prohibitive cost of commercial monitors.
Song’s applied research has potential to reduce energy consumption in a single structure by as much as 20 percent. Depending on the building conditions, Song estimates peak savings could be as much as 30 to 50 percent. Song’s research team devised a mathematical formula using existing output data, such as pump speed and power, to monitor energy use in heating, ventilation and air conditioning units. Based on the results, the formula detects unreliable systems and faulty equipment that affects energy consumption. Song's formula creates virtual sensors to identify energy waste at the air-handling unit as well as at a whole-building level.
"Waiting until exorbitant utility bills appear may be a sign that the equipment hasn't worked optimally for years," said Song. "This method allows earlier detection of minor equipment faults, possibly preventing an overhaul of the entire system."
Besides saving companies money on utility bills, Song's formula is a low-cost option to commercial monitors, making it easier for more companies to track energy efficiency. Song estimates one ultrasonic flow meter, which monitors water pump performance, could cost as much as $5,000, and an organization would need to buy several monitors to get an accurate picture. Song's virtual process uses little to no hardware and is within ±2% uncertainty ranges compared with commercial meters.
Prior to developing virtual sensing, Song implemented the energy monitoring and operation fault detection and diagnosis manually in more than 100 buildings with cumulative savings exceeding $70 million. In one building alone, her method reduced annual electricity consumption by 53 percent, electricity demand by 21 percent and gas consumption by 49 percent in one year. In another building the structure qualified as an Energy Star building five months after the evaluation.
Song's research, which has focused on corporate efficiencies, is now entering the government sector. Her research team was recently awarded a three-year, $1 million contract from the U.S. Department of Defense to increase building efficiencies at military installations. Her first analysis focuses on Tinker Air Force Base in Oklahoma City, Okla.
"The U.S. Department of Defense spends $4 billion each year in facility operations," said Song. "They have a federal mandate to reduce building energy consumption by 30 percent by 2015. My research team thinks we can double the reduction."
Song is one of a few researchers in the United States working on improving HVAC efficiencies using virtual sensor measurements. Her next research focuses on creating wider applications for the virtual sensors using equipment data beyond "vents and pumps."
Song is also in the process of developing a smart-device that contains all the mathematical formulas so the building owner can plug it into an existing system easily and monitor energy efficiency on an ongoing basis.
"The virtual valve ï¬‚ow meter won't replace conventional ï¬‚ow meters if they are needed for utility metering for billing," said Song, "but it does offer companies an inexpensive and readily accessible solution to monitor energy consumption. Companies can use the information to create a more efficient system, saving them money while reducing energy consumption."