Electrical generator or motor structure – Non-dynamoelectric – Thermal or pyromagnetic
Reexamination Certificate
2001-02-23
2003-09-30
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Thermal or pyromagnetic
C310S339000, C310S800000, C310S309000
Reexamination Certificate
active
06628040
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to Electro Active Polymers (EAP) that convert between electrical energy and mechanical energy. More particularly, the present invention relates to EAP polymers and their use in energy conversion devices that convert between thermal, mechanical, and electrical energy from thermal energy sources such as combustion.
In many applications, it is desirable to convert between electrical energy and mechanical energy. Exemplary applications requiring translation from electrical to mechanical energy include robotics, pumps, speakers, general automation, disk drives and prosthetic devices. These applications include one or more actuators that convert electrical energy into mechanical work—on a macroscopic or microscopic level. Common electric actuator technologies, such as electromagnetic motors and solenoids, are not suitable for many of these applications, e.g., when the required device size is small (e.g., micro or mesoscale machines). These applications include one or more transducers that convert mechanical energy into electrical energy. Common electric generator technologies, such as electromagnetic generators, are also not suitable for many of these applications, e.g., when the required device size is small. These technologies are also not ideal when a large number of devices must be integrated into a single structure or under various performance conditions such as when high power density output is required at relatively low frequencies.
Several ‘smart materials’ have been used to convert between electrical and mechanical energy with limited success. These smart materials include piezoelectric ceramics, shape memory alloys and magnetostrictive materials. However, each smart material has a number of limitations that prevent its broad usage. Certain piezoelectric ceramics, such as lead zirconium titanate (PZT), have been used to convert electrical to mechanical energy. While having suitable efficiency for a few applications, these piezoelectric ceramics are typically limited to a strain below about 1.6 percent and are often not suitable for applications requiring greater strains than this. In addition, the high density of these materials often eliminates them from applications requiring low weight. Irradiated polyvinylidene difluoride (PVDF) when combined with various copolymers is an electroactive polymer reported to have a strain of up to 4 percent when converting from electrical to mechanical energy. Similar to the piezoelectric ceramics, the PVDF-based material is often not suitable for applications requiring strains greater than 4 percent. Shape memory alloys, such as nitinol, are capable of large strains and force outputs. These shape memory alloys have been limited from broad use by unacceptable energy efficiency, poor response time and prohibitive cost.
In addition to the performance limitations of piezoelectric ceramics and irradiated PVDF-based materials, their fabrication often presents a barrier to acceptability. Single crystal piezoelectric ceramics must be grown at high temperatures coupled with a very slow cooling down process. Irradiated PVDF-based materials must be exposed to an electron beam for processing. Both these processes are expensive and complex and may limit acceptability of these materials.
As advances in microchip fabrication continue to reduce the cost and the size of logic devices while increasing their computing capabilities, new portable electronic devices using these logic devices are continually being developed. Also, these logic devices are being incorporated into existing electronic devices to increase their functionality and in some case to enable portability. Cellular phones, pagers, personal digital assistants, MP-3 players, navigational devices and locator devices are a few examples of newer portable electronic devices. These portable electronic devices along with other older portable electronic devices such as flashlights, electric tools, credit card readers and radios are utilized in many activities. All of these devices require a source of electrical energy to operate. Typically, the devices employ disposable or rechargeable batteries as an electrical power source. Performance parameters of the batteries such as cost, weight and life-time are critical element in the design and operation of these devices. In other applications, light-weight power sources are needed to power newer portable electronic devices such as minirobots and microrobots and micro-air vehicles that may be used for surveying and reconnaissance for civilian and military application. For these devices, power to weight ratios are a critical consideration.
With the portable electronics devices describe above, it would be desirable to provide portable energy sources with a high power to weight ratio that generate power over a significant time period. Hydrocarbon based fuels have a relatively high energy density as compared to batteries. For instance, the energy density of a hydrocarbon based fuel may be 20 times higher than a density of a battery. Thermo-electromechanical power generation systems that utilize a thermodynamic process such as combustion to generate mechanical energy which is converted to electricity are well known in the art. For instance, a cellular phone may be powered from a generator connected to an automobile engine. However, traditional combustion-driven thermo-electromechanical power generation systems with a reasonable high power to weight ratio tend to be quite heavy and relatively non-portable. At smaller scales, e.g. lower weights, the power to weight ratio of these systems rapidly decreases. Thus, batteries are used as the power source in most portable electronic devices. In view of the foregoing, alternative light-weight, scaleable devices that efficiently convert thermally generated mechanical energy to electrical energy would be desirable.
SUMMARY OF THE INVENTION
This invention addresses the needs indicated above by providing generators with one or more transducers that use electroactive polymer films to convert thermally generated mechanical energy to electrical energy. The generators may include one or more transmission mechanisms that convert a portion of thermal energy generated from a heat source such as internal combustion, external combustion, solar energy, geothermal energy or waste heat, to mechanical energy that is used to drive the one or more transducers located in the generator. The energy received by the transducers may be converted to electrical energy by the transducers in conjunction with conditioning electronics located within the generator. One embodiment of the present invention provides an energy conversion device with two chambers, each chamber including a diaphragm transducer that may convert thermal energy to electricity using a thermodynamic cycle such as a Stirling gas cycle. The thermodynamic cycle of the energy conversion device may be reversed to provide cooling to an external device such as a semiconductor device.
One aspect of the present invention provides a generator for converting thermal energy to electrical energy. The generator may be generally characterized as including: 1) one or more transducers where each transducer comprises at least two electrodes and a polymer arranged in a manner which causes a change in electric field in response to a deflection applied to a portion of the polymer; 2) conditioning electronics connected to the at least two electrodes and designed or configured to add and remove electrical energy from the transducer; and 3) one or more transmission mechanisms designed or configured to receive thermal energy and to convert a portion of the thermal energy to mechanical energy, where the mechanical energy results in a deflection in the portion of the polymer. The transmission may convert thermal to mechanical energy using a gas. The gas may be generated from a boiling liquid as in a steam cycle, or it may be intrinsically a gas throughout the cycle. The gas may comprise one of helium, nitrogen, carbon dioxide, air, water
Eckerle Joseph Stephen
Kornbluh Roy D.
Pei Qibing
Pelrine Ronald E.
Dougherty Thomas M.
SRI - International
LandOfFree
Electroactive polymer thermal electric generators does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electroactive polymer thermal electric generators, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electroactive polymer thermal electric generators will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3004654