Advanced Refrigerator/Freezer Technology

The "Fridge of the Future"

Reverse instrumentation in test refrigerator

To meet the government's new energy standard for refrigerators — a 30% reduction for units manufactured after July 2001 — ORNL researchers have designed and demonstrated a "fridge of the future" that uses half as much energy as today's refrigerator-freezers (RFs) and one-fifth as much as 1972 models: the 1 kilowatt-hour per day refrigerator.

In a cooperative research and development agreement (CRADA) with the Appliance Research Consortium (ARC), a subsidiary of the Association of Home Appliance Manufacturers, researchers adapted a standard 1996 baseline 20-ft³ RF cabinet (shown as unit A in the table below) by adding various features that would improve energy efficiency.

The changes involved

addition of vacuum insulation panels around freezer section to reduce heat transfer,
addition of polyurethane foam to the doors to double insulation thickness,
replacement of AC motors with more efficient DC motors, and
replacement of automatic defrost control with an adaptive defrost that operates only when needed.

These improvements, shown as unit C in the table below, cut power consumption to 0.93 kWh/day, a performance that exceeds the 2001 energy standard and that would save $6.5 billion annually if all the 125 million RFs in the U.S. operated as efficiently.

Because the addition of vacuum insulation panels results in a significant cost increase to RF units, researchers also tested the unit without the vacuum insulation. This modified unit (unit B in the table) would still be about 44% more efficient than the 1993 standard and would save $4.5 billion annually in the United States.

**Energy consumption of ARC baseline and advanced refrigerator/freezers**
Refrigerator/ freezer		Energy consumption (kWh/d)	% run time*	Manufacturer cost increase ($)	Simple payback time (years)
A	Baseline unit	1.68	44.2	—	—
B	Unit A with 2-in.-thick doors, high-efficiency compressor, low-wattage condenser fan, and adaptive defrost scheme	1.16	47.6	53.38	6.6
C	Unit B with vacuum insulation around freezer section and larger evaporator	0.93	36.5	134.33	11.4
*Percentage of time compressor runs each hour.

The minimum energy use achieved by unit C, 0.93 kilowatt-hours per day (kWh/d), is 45% lower than the energy use of the baseline unit and 54% lower than the DOE-mandated maximum of 2.01 kWh/d for this size of RF. Estimated manufacturing costs increased by $134 for this system, resulting in an 11.4 year simple payback, assuming the consumer's cost is twice the manufacturer's cost. Prototype B achieved a minimum energy use of 1.16 kWh/d, with an estimated manufacturing cost increase of $53 and a simple payback of 6.6 years.

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