A popular size and style domestic refrigerator-freezer was altered to reduce energy use 50 percent, from 2 kilowatt hours per day to 1 kilowatt hour per day. This reduction in energy use exceeds the decrease called for in a new rule announced by the federal government April 24. The rule requires refrigerators sold in 2001 to use 30 percent less electricity than those on the market today.
"Last week, I announced efficiency standards for the 'fridge of the 21st century,' and this week Oak Ridge is helping us meet these standards through public-private partnerships," said Energy Secretary Federico Pena. "Top quality appliances save money on power bills and protect the environment for future generations."
This laboratory prototype is the product of joint research and development by ORNL researchers and refrigerator manufacturer engineers in a cooperative research and development agreement (CRADA). The CRADA between ORNL and the Appliance Research Consortium (a subsidiary of the Association of Home Appliance Manufacturers) achieved a dramatic energy reduction in a standard 20-cubic-foot refrigerator with a freezer on top. More than 60 percent of the refrigerators sold in the United States are "top-mounted" refrigerators like the lab model.
"Some 125 million refrigerators in the United States consume approximately 1.5 percent of the energy used in the country," says Ed Vineyard, a researcher who worked on the project with his ORNL colleagues Jim Sand and Randy Linkous in the Efficiency and Renewables Section of the Energy Division. "If the energy used in units presently in homes was reduced to 1 kilowatt hour per day, refrigerators would consume only about one half of one percent of the nation's energy, saving almost 6.5 billion dollars annually. The accompanying decrease in demand for electricity from coal-fired power plants would also significantly reduce greenhouse gas emissions."
The CRADA's high-efficiency refrigerator, which exceeds the goal of government standards scheduled to go into effect in 2001, is more efficient because of several changes. Vacuum insulation panels were used around the freezer section to reduce heat gain. In addition, polyurethane foam was added to the doors, doubling their thickness.
Three motors that operated on alternating current to drive two fans and the compressor were replaced with three direct-current electrically commutated motors; because of reduced energy losses from magnet windings, DC motors use less electricity and release less waste heat that must be removed from the cabinet of the refrigerator, further decreasing its power requirements.
Finally, the automatic defrost control, which daily removes ice from refrigerant coils to improve their heat transfer, was replaced with adaptive defrost. It relies on refrigeration circuit sensors to ensure that defrosting occurs only when needed - perhaps every other day in summer and once a week in winter - depending on the humidity and number of refrigerator door openings.
ORNL and its CRADA partners - Amana, General Electric, Maytag, Sub-Zero, Sanyo, W. C. Wood, and Whirlpool - also developed a second model which is more cost-effective than the initial prototype. It has all the extra features except for the vacuum insulation around the freezer and increased evaporator area. This second model would result in savings of approximately 4.5 billion annually.
The work was performed under a CRADA between the Department of Energy's Office of Building Technologies, state and community programs and the Appliance Research Consortium of the Association of Home Appliance Manufacturers.
ORNL, one of the Department of Energy's multiprogram national research and development facilities, is managed by Lockheed Martin Energy Research Corporation.
(photo available upon request) .