Power plants – Motive fluid energized by externally applied heat – Process of power production or system operation
Reexamination Certificate
2002-04-23
2004-02-17
Nguyen, Hoang (Department: 3748)
Power plants
Motive fluid energized by externally applied heat
Process of power production or system operation
C060S655000, C060S671000
Reexamination Certificate
active
06691514
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to power generation devices, and in particular, to a method and apparatus for generating power utilizing the thermal energy provided by the temperature differential between ambient air and liquid nitrogen.
BACKGROUND AND SUMMARY OF THE INVENTION
As is known, numerous systems have been developed to meet the constantly increasing power demands of the modern world. These systems often use combustible fossil fuels such as natural gas, oil, coal and the like. Typically, the fossils fuel is burned to generate thermal energy that, in turn, is converted to mechanical energy. While fossil fuel systems are functional for their intended purpose, these types of systems have two inherent problems. First, the burning of fossil fuels may produce environmentally unfriendly by-products. Second, the supplies of the fossil fuels used in these systems are slowly becoming depleted. Consequently, it has become necessary to develop alternative sources of energy.
In order to overcome the inherent problems associated with the use of fossil fuels, various alternative-energy systems have been developed. For example, solar energy systems and systems utilizing wind power are presently in use. However, these systems also have certain limitations associated with their use. By way of example, these systems often require large energy-gathering structures such as windmills and solar panels in order for the systems to generate sufficient energy for products that have high power demands. Hence, given the size requirements, present use of such alternative-energy systems for such products as vehicles is impractical.
In addition, other types of systems have been developed that convert heat energy into mechanical energy by circulating a liquefied gas in a closed cycle. In most of these types of systems, the liquefied gas is subjected to a heat exchange with heat energy of another substance during circulation of the liquefied gas. Once again, while liquefied gas systems are functional for their intended purpose, these systems are complicated and require specialized equipment in order for the systems to function properly. By way of example, Imai, U.S. Pat. No. 3,878,683 discloses a method for power generation. The method includes the steps of disposing a liquefied gas in a closed container at a temperature and pressure less than the critical temperature and pressure of the gas. The liquefied gas is heated to the critical temperature and above the critical pressure. The pressure of the gas is regulated to a specified value greater that the critical pressure, but less than a pressure which would be detrimental to the equipment utilized. The gas is subjected to a heat exchange with another medium thereby heating the gas and cooling the medium. The gas expands to a predetermined pressure, and thereafter, valves open to allow the gas to flow into a high-pressure tank wherein the pressure of the gas is regulated. When the pressure of the gas exceeds a predetermined threshold, a valve on the high-pressure tank is opened and the gas flows to a means such as turbine that transforms the expansion of the gas into mechanical energy and that reduces the temperature of the gas below the critical temperature. It is contemplated that a portion of the power generated is used to effect the flow of all of the fluids in the system. Thereafter, the gas is liquefied and returned to the closed container. It can be appreciated that the complexity of the apparatus disclosed in the Imai '683 patent renders the device impractical for most applications. As such, a power generation system that may be used in a wide variety of applications is highly desirable.
Therefore, it is a primary object and feature of the present invention to provide a method and apparatus for generating power that is simpler and less expensive than prior power generation systems.
It is a further object and feature of the present invention to provide a method and apparatus for generating power that utilizes the thermal energy provided by the temperature differential between ambient air and liquid nitrogen.
It is a still further object and feature of the present invention to provide a method and apparatus for generating power that eliminates or severely limits the need for using fossil fuels, as required by prior power generation systems.
In accordance with the present invention, a method is provided for generating power. The method includes the steps of passing a gaseous refrigerant through a pool of compressed nitrogen such that the refrigerant is condensed and pumping the condensed refrigerant through an evaporator. Ambient air is passed over the evaporator so as to increase the temperature and increase the pressure of the refrigerant. The refrigerant is allowed to expand and to drive a power generation device. Thereafter, the refrigerant is passed once again through the pool of liquid nitrogen in order to be condensed. The condensed refrigerant is pumped through the evaporator and the process is repeated.
It is contemplated to compress the nitrogen with a compressor prior to passing refrigerant through the pool and to use the compressed nitrogen to form the pool. The compressor is positioned between the evaporator and a fan which generates a flow of ambient air. The ambient air is urged over the compressor by the fan prior to the ambient air being passed over the evaporator. It is contemplated that the nitrogen provided to the compressor is recovered from the ambient air. Alternatively, the compressed nitrogen may be allowed to expand after the refrigerant has passed through the pool. The expanded nitrogen is returned to the compressor to be compressed or released into the ambient air. The pool of compressed nitrogen is stored in a tank having a check valve. The check valve allows the compressed nitrogen to expand and to be discharged from the tank after the refrigerant passes through the pool.
The power generation device includes a turbine and an electrical generator operatively connected thereto. The refrigerant expands and rotates the turbine in order to drive the electrical generator. The electrical generator, in turn, generates electrical energy.
In accordance with a further aspect of the present invention, a method is provided for generating power. The method includes the steps of capturing nitrogen from ambient air and compressing the nitrogen with a compressor such that the nitrogen has a predetermined temperature. A gaseous refrigerant is passed through the compressed nitrogen so as to be condensed. The condensed refrigerant is passed through the ambient air having a predetermined temperature such that the temperature and pressure of the refrigerant increases. Power is generated by expansion of the refrigerant in response the difference between the predetermined temperature of the nitrogen and the predetermined temperature of the ambient air.
The step of passing the refrigerant through the ambient air may include the additional steps of pumping the condensed refrigerant through an evaporator and passing ambient air over the evaporator so as to increase the temperature and increase the pressure of the refrigerant. The step of generating power with the refrigerant may include the additional steps of providing a power generation device including a turbine and electrical generator operatively connected thereto and passing the refrigerant therethrough so as to rotate the turbine and drive the electrical generator.
A fan may be provided for generating a flow of ambient air. The compressor is positioned between the fan and the evaporator such that the fan urges the ambient air over the compressor prior to such ambient air passing over the evaporator. It is contemplated to allow the compressed nitrogen to expand after the refrigerant passed therethrough and to return the expanded nitrogen to the compressor to be recompressed. Alternatively, the expanded nitrogen may be discharged into the ambient air.
In accordance with a still further aspect of the present invention, an apparatus is provided for generating p
Boyle Fredrickson Newholm Stein & Gratz S.C.
Nguyen Hoang
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