27 May 2014 — Commercial buildings can cut HVAC energy use by an average 57 per cent through energy-efficiency control systems, a US government study has found – much more than expected.
The year-long trial of HVAC control systems in malls, shopping centres and other commercial buildings by the US Department of Energy’s Pacific Northwest National Laboratory found savings much higher than the 38 per cent reduction computer simulations had predicted.
“We’ve long known that heating and cooling are among the biggest energy consumers in buildings, largely because most buildings don’t use sophisticated controls,” said study lead researcher Srinivas Katipamula. “But our tests of controls installed at real, working commercial buildings clearly demonstrate how much more energy efficient airconditioning systems can be.”
Katipamula and colleagues at PNNL in 2011 set out to adapt controls found in air handling units for use in packaged rooftop HVAC systems. The goal was to enable packaged units to automatically adjust their operations based on conditions inside and outside a building. Using sensors and variable-speed motors, the advanced controls decide when and how fast ventilation fans should run, and if the units can use fresh air instead of mechanically cooling indoor air.
The study used a commercially available system by a company called Transformative Wave, due to its resemblance to the advanced controls PNNL had envisaged.
Compared with standard operations, HVAC units using advanced controls cut energy use by an average of 57 per cent, with savings ranging from 20 to 90 per cent, depending on building type and use.
Larger buildings like malls, which need bigger HVAC units, saved more energy than smaller buildings. And buildings that required more ventilation tended to save more energy.
Using the national US average electricity cost, the researchers found average annual cost reductions of $1489 a unit, with a payback of three years. Commercial buildings often have multiple HVAC units, so savings would depend on the number of units, the researchers said.
“I’m proud to see the advanced controls my colleagues and I evaluated not only work in the real world, but produce significant energy savings,” Dr Katipamula said. “We hope commercial building owners will be inspired by these tangible savings and install advanced controls in their rooftop HVAC units.”
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