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SEALED SYSTEM REJECTION HEAT ENERGY HARVESTING

IP.com Disclosure Number: IPCOM000213129D
Publication Date: 2011-Dec-05
Document File: 6 page(s) / 138K

Publishing Venue

The IP.com Prior Art Database

Abstract

The present invention is a system comprising an appliance system, a thermoelectric generator (TEG), and a high efficiency/low operational power/high current output signal processor. This system allows for a maximization of appliance system efficiencies by converting waste, or rejected, system heat to usable electric current and voltage.

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SEALED SYSTEM REJECTION HEAT ENERGY HARVESTING

BACKGROUND

The present invention relates generally to the recovery of waste heat energy in the form of electrical output in appliances, and more particularly to the incorporation of a thermoelectric generator (TEG) in a home appliance.

Typically, appliances generate waste heat due to inefficiencies in motors, compressors and other components. For example, appliances such as refrigerators are known to utilize a compressor to compress a phase-changing fluid, which is then condensed, expanded and evaporated. Compressing the fluid generates heat, which in cooling applications is waste heat that is discharged to the ambient environment from the compressor and the condenser. Because the waste heat is not recovered, the heat is lost energy decreasing the overall efficiency of the system.

Previous attempts have been made to increase efficiency by recovering lost heat utilizing conventional thermoelectric generators (TEG). Figure 1 shows a conventional TEG. As is illustrated, the TEG may comprise: a ceramic casing, a conductor, p-type semiconductors, n-type semiconductors, a positive terminal, and a negative terminal. Typically, the output voltage will range from about 0V to about 5V and the output current will range from about 0A to about 2A.

FIGURE 1

1


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TEGs are self-sufficient energy sources that convert thermal energy into electrical energy according to the Seebeck effect. The Seebeck effect is a phenomenon whereby heat differences may be converted into electricity due in large part to charge carrier diffusion in a conductor. Electrical power may be generated under the Seebeck effect by utilizing thermocouples which are each comprised of a pair of dissimilar metals (n-type and p-type) joined at one end. N-type and p-type refers to the respective negative and positive types of charge carriers within the material. Commonly, the generator is coupled to a signal processor, such as a converter, that converts the electricity from one level of DC voltage to another prior to providing the electricity to an intended load.

Benefits associated with utilizing TEGs include the elimination of a need for moving parts, such as the motors or turbines that are generally required for power generation. Also, TEGs can continuously generate electricity until the thermoelectric material has deteriorated.

Despite the benefits associated with TEGs, their utilization as heat recovery devices in home appliances remains inefficient. The primary reason for these inefficiencies can be attributed to the signal processors that are commonly provided with the generators. Converters, such as a standard DC-DC converter, require a threshold voltage to be met in order to power up. The threshold voltage for most commercially available DC-DC converters is about 2.5V.

As is shown in Figure 2, TEG electrical output is linear with respect to the temperature gradient across the TEG, where the temperature g...