High-Efficiency Ultra-Low-Temperature Laboratory Freezers: Field Demonstration Results

Rebecca Legett, Navigant Consulting, Inc.

Ultra-low-temperature laboratory freezers (ULTs) can be one of the most energy-intensive pieces of equipment in a laboratory, with some using as much electricity as a small house. High-efficiency models can achieve substantial energy savings, but purchasers of ULTs often must balance efficiency with other considerations such as first cost. Furthermore, few data exist to help purchasers make informed decisions where energy efficiency is concerned. The U.S. Department of Energy (DOE), through the Better Buildings Alliance (BBA), recently conducted a field demonstration of high-efficiency ULTs. At each of three demonstration sites, we evaluated a different high-efficiency ULT model alongside one or more standard-efficiency models over a period of five months. The demonstration focused on upright ULTs between 15 and 30 cubic feet—a commonly purchased ULT type in many laboratories. Energy data, temperature data, and door opening data were collected for each ULT in the demonstration.

This presentation will discuss the results of the demonstration and implications for laboratory and nationwide energy savings. As part of the data analysis, we normalized the energy data to a representative set-point, external temperature, and duration of door openings per day, and compared each high-efficiency ULT to the average standard ULT on a per-cubic-foot basis. We found that the high-efficiency ULTs used from 20% to over 50% less electricity per cubic foot than the average standard ULT over the course of the demonstration, when the data were compared at the same set of operating conditions. The demonstration results suggest that high-efficiency ULTs can save laboratories a substantial amount of energy and if implemented on a wide scale, high-efficiency ULTs have a very large energy savings potential nationwide.

Learning Objectives

  • Calculate energy and cost savings that can be achieved by selecting high-efficiency ultra-low-temperature laboratory freezers.
  • Quantify the effect of various operating conditions such as set-point, external ambient temperature, and door openings on ULT energy use.
  • Determine the energy savings potential of high-efficiency ULTs if implemented on a wide scale.

Biography:

Rebecca Legett is a Managing Consultant in the Energy Efficiency and Policy Analysis group at Navigant Consulting, Inc. Ms. Legett is supporting the Better Buildings Alliance (BBA), a U.S. Department of Energy effort to promote energy efficiency in commercial buildings. She previously worked on an ENERGY STAR test method for laboratory-grade refrigerators and freezers. Ms. Legett received her B.S.E. in mechanical engineering from Princeton University.

 

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