Power plants – Combustion products used as motive fluid – Process
Reexamination Certificate
2002-06-04
2004-03-30
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
Process
C060S039511, C165S004000, C165S010000
Reexamination Certificate
active
06711902
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to power systems and, more specifically, to an integrated cycle power system and method for producing a power system having an elevated thermal efficiency curve throughout a broad band of power settings. The present invention is particularly useful in, although not strictly limited to, gas turbine electric power-generation systems such as utilized for ship powering and propulsion, and for utility power supply.
BACKGROUND OF THE INVENTION
Power systems are utilized in a multitude of applications, wherein power and/or converted electricity is needed. For instance, notwithstanding gravity, any moving object (i.e., vehicle, plane or ship) requires power to facilitate its movement. In addition, power systems are often utilized to convert mechanical energy into electrical energy, wherein this electrical energy is thereby utilized to power a proximal system or subsystem, or can be transferred via electrical power lines to provide electrical power for remote facilities such as homes and businesses.
Several types of power systems are known and widely used. For instance, internal combustion piston engines are typically used to power land vehicles, small machinery and some water craft. Turbines are typically utilized, however, for larger ships and utility power facilities because of the overall need for increased efficiency and large power demands.
A turbine is a device that converts enthalpy and kinetic energy of a moving fluid into some form of mechanical energy, which subsequently can be converted into electrical energy. A basic turbine generally consists of a series of rotors, wherein the rotors comprise a plurality of airfoil-shaped blades connected to a disk, wherein the disk is connected to shaft. The angle of attack, between the chord line of the blade-airfoil and the relative wind of the gas flow, generates a lift vector at the blade root, thereby causing the shaft to rotate. The rotating shaft can then be used to turn a generator to produce electrical current.
The most widely utilized turbine is the gas turbine. In a simple gas turbine cycle, low-pressure air is drawn into a compressor, wherein the air is compressed to a higher pressure. Fuel is then added to the compressed air followed by the mixture being burned in a combustion chamber. The resulting hot product from the combustion chamber enters a turbine and is expanded therethrough. The thermal efficiency of a gas turbine is equal to the net power output divided by the heat input. As such, to increase the thermal efficiency of a gas-turbine cycle the net power output must be increased and/or the heat input must be decreased per unit of power output.
Because of the enormous utilization and reliance on gas turbines for generating power, even the slightest improvement in its thermal efficiency can provide a substantial economic benefit. For instance, even a one percent increase in thermal efficiency can result in millions of dollars in energy savings per year for a single power plant. More specifically, based on the present average fuel cost, the cost to produce 100 MW of electric power for a typical power plant having a Rankine steam bottoming cycle and operating at 47% efficiency is approximately $4000 per hour for the fuel cost alone. This results in a cost per 24-hour period of approximately $96,000. Only a three percent increase in thermal efficiency for the production of 100 MW of power results in a fuel savings of approximately $8000 per 24-hour period, thus yielding approximately a $2,920,000 savings per year. It is widely known within the art that fuel costs are the largest expense for power plants, often amounting to greater than 70% of total operating and maintenance expenditures. These costs are typically passed on to the consumer.
Moreover, an overall plant operating efficiency of 47% is, traditionally, only achieved by coupling a Rankine steam bottoming cycle to the exhaust outlet of the base, simple-cycle gas turbine prime mover. The Rankine steam bottoming cycle, in a customary installation, will routinely occupy 10-15 times the volumetric expanse of the gas turbine and its immediate support equipment. This extreme space-and-mass profile renders such systems impractical for any type of mobile/impermanent application such as: ship, rail, barge, or limited duration fixed-base assignment. Because of the excessive amount of equipment and machinery that makes up a Rankine steam bottoming cycle, the costs of manufacture and operation-and-maintenance (O&M) are substantial. Generally stated, (1) the relatively low thermal efficiency of prior-art electric power generation systems results in overall high costs of acquisition and O&M expenditures, while (2) undue system size and mass foreclose product market applications beyond those of the traditional land-based power station.
Moreover, because of the worldwide energy crises and universal demand for more efficient power sources, prior-art power systems have proved to be disadvantageous, causing many to search for alternative energy sources such as solar, hydro and electrochemical. Although many of these types of energy sources are inexpensive, they fail to provide sufficient power for high-load, utility-level capacities, thereby rendering them uneconomic for all but the most modest of markets.
Consequently, it is readily apparent that there is a need for a thermally efficient power system and method that can provide energy for high-load applications at all power demand levels and that can operate at equal or higher thermal efficiency levels than prior-art systems without the need for arbitrarily complex combined-cycle thermal management strategies. It is to such an improvement that the present invention is directed.
BRIEF SUMMARY OF THE INVENTION
Briefly described, in a preferred embodiment, the present invention overcomes the above-mentioned disadvantages and meets the recognized need for such a device by providing a thermally efficient integrated-cycle power system and method, wherein the Rankine steam bottoming cycle of typical power plants is eliminated.
According to its major aspects and broadly stated the present invention in its preferred form is an integrated-cycle power system and method. More specifically, the present invention comprises a thermal transfer assembly, a recuperating heat exchanger assembly, a heat integrator, a thermal conduit assembly and a gas turbine. The thermal transfer assembly receives heat emitted from the effluent of a preferably external, independent augmenting heat source, such as a fuel cell, wherein the heat is preferably in the form of high temperature gas. Within the thermal transfer assembly, the energy of the high temperature gas is transferred to a conductive medium carried within a thermal conduit assembly. Due to a thermal potential between the augmenting heat source effluent and the heat integrator, the augmenting heat-source energy is transferred to the heat integrator, wherein energy from a novel recuperating heat exchange assembly is combined therewith and introduced into the combustion chamber of a gas turbine.
The recuperating heat exchanger assembly receives exhaust heat from the gas turbine and recuperates this energy via the heat integrator back into the combustion chamber of the gas turbine.
The novelty of the present invention lies not only in the overall system and method, but in many individual elements such as, for exemplary purposes only, the transfer media, the thermal conduit assembly, the heat integrator, the recuperating heat exchange assembly, the branch isolation assemblies and the facilities by which to integrate an independent augmenting power source such as a fuel cell, as is more fully described herein.
A feature and advantage of the present invention is to provide a power generating system having a high thermal efficiency without the excess space requirements of a Rankine steam bottoming cycle.
A feature and advantage of the present invention is its design system that enables the efficient engineering-adaptation of the invention to a broad powe
Freay Charles G.
Myers Joel D.
Myers & Kaplan LLC
Patel Ashish D.
LandOfFree
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