Additives May Save Energy for Cooling Big Buildings

December 22, 2005

A National Institute of Standards and Technology (NIST) researcher discovered a method that may improve the energy efficiency of water chillers that cool the nation's large commercial buildings. The technique, if confirmed through experiments with full-scale chiller systems, could save as much as 1% of the 320 billion kWh of electricity used annually by chillers or an equivalent 5.5 million barrels of oil per year, according to Mark Kedzierski, the NIST mechanical engineer who developed the technique.

The advance builds on NIST research to optimize mixtures of chiller refrigerants with lubricants. Researchers discovered that some lubricants, when injected in small amounts, can significantly enhance evaporator heat transfer, increasing the efficiency of chillers. They found the most efficient heat transfer occurred when the added oil's surface tension, viscosity, composition and chemical characteristics complemented those of the chiller's base lubricant.

Kedzierski developed rules for the selection of the different types of oil additives according to the type of chiller lubricant, making successful energy enhancement less of a hit-or-miss proposition. Laboratory work testing the energy-enhancing potential of several oil and lubricant combinations identified by the rules is under way.

"The leap from a successful laboratory experiment to an everyday large-scale cooling application is a big one. NIST wants to see this theory translated into products germane to manufacturers as soon as possible," Kedzierski said. "We welcome private-sector interest in the theory and its application."

Source: National Institute of Standards and Technology (NIST).