Pyroelectric Effect - New Thermal to Electric Energy Converter
Source: UFTO
Date: 3/21/97    Record No.: 10435
Contact: Fred Jaeger, President
Thermodyne, Inc.
Salt Lake City, UT
801-583-2000, fax 801-583-6245,

Pyroelectric Effect - New Thermal to Electric Energy Converter
Thermodyne, a small company in Salt Lake City, has what it believes to be a new type of Thermal to Electric Converter which is based on a combined piezoelectric pyroelectric effect. The device promises to have high energy density, operate at lower temperatures and with smaller temperature differences, and be far more efficient and cost effective than any existing thermoelectric device.

History: In 1990, a British group announced a new type of converter consisting of hundreds of layers of thin piezoelectric polymers coated with bi-metal electrodes. They hypothesized that the device was working on some kind of transverse thermoelectric effect, however the device degraded after a few hours of operation, and no convincing explanation of the phenomena was forthcoming.

Some time later the Thermodyne group, aware of the British work, came up with a different explanation for what had been observed, and quickly developed a better choice of materials and geometry to go with their theory.

Piezoelectric ceramics emit electrical impulses when compressed. Similarly, when an electric field is applied to a piezoelectric material, it changes volume. This reversible action is used today in loudspeakers and sonar devices. Hundreds of materials exhibit the piezoelectric effect.

The Pyroelectric effect is a lesser known thermal cousin of the Piezoelectric effect. When a sample is heated or cooled, it emits electrical impulses, and its temperature changes when a field is applied. About one third of piezoelectric materials are also pyroelectric.

A pyroelectric converter was proposed in 1980, but the effort failed because of poor performance due in part to the use of mechanical cycling of pyroelectric plates from hot to cold region.

The Thermodyne approach allows a converter to be built without moving parts that can be used for cooling/heating (heat pump) or to make electricity, with a theoretical efficiency of 50% of the ideal Carnot efficiency. A sandwich of ceramic plates resonate electronically to cause a pumping action from heat to mechanical to electrical energy via the combined action of the piezo and pyro effects.

With power densities of hundreds of watts per square centimeter, it should enable a wide variety of practical products such as coolers, air conditioners and refrigerators, and waste heat utilization. Thermodyne has received notice from the U.S. patent office that its initial patent has been allowed and international rights are being pursued. The company is seeking a modest amount of seed development funding (equity or non-equity) to build a first milestone of a one watt, 5% efficient demonstration device within the next 5-6 months by a 10 watt, 10% prototype 6 months later. Sufficient interest already expressed by some major companies suggests that the program could become self-funding thereafter.