High-Efficiency Refrigerator with Cold Energy Storage Enabling Demand Flexibility

Household refrigerators provide a convenient and safe means of food preservation and storage. Typical household refrigerators consume 1.5–2.0kWh of electricity per day, and more than 100 million refrigerators are used in U.S. homes, resulting in significant primary energy consumption and carbon emissions. We propose a novel household refrigerator that uses advanced evaporators with phase change material (PCM)–based long-duration cold energy storage, PCM heat conduction enhancement using a metal foam material, direct-contact defrosting technology, and a low–global warming potential (GWP) alternative refrigerant to achieve flexible load demand management and transformational efficiency improvement in excess of 20%. In a conventional refrigerator, average on/off cycling time is about 30 minutes (i.e., 48 cycles per day), representing 14.3%–24.7% energy loss. The proposed novel refrigerator achieves one on/off cycle while shifting 100% of daytime load to nighttime operation. Conventional household refrigerators must be defrosted after 8–12 hours of operation, and two to three defrosting cycles per day typically account for 17.7% of the electric energy usage. The proposed refrigerator targets one defrosting daily, reducing the defrosting need by nearly 50%. In addition, we will use the low-GWP refrigerants for replacing R134a in household refrigerators to further reduce GHG emissions. This will enable a 30% reduction in GHG emissions and a nearly 100% load shift from daytime to nighttime operation. Replacing all conventional refrigerators in homes and commercial buildings with the proposed novel refrigerator would save up to 167 TBtu of primary energy consumption and reduce GHG emissions by 7.2 million t. This replacement would directly support a smooth transition toward meeting the ambitious goals of net-zero carbon emissions by 2050 while creating millions of clean energy jobs. Additionally, the novel refrigerator's load shifting capability enables approximately 0.7%–1.0% of daytime electricity demand to be shifted to nighttime operation nationwide.

Project Impact

This project will develop and demonstrate an innovative efficient household refrigerator that enables flexible load demand management and transformational efficiency improvement more than 20% compared with a commercially available 2022 refrigerator as baseline, targeting a 30% reduction in GHG emissions and a 100% reduction in peak electricity demand.