Wind power system for energy production

A wind power energy system includes a compression system that produces pressurized air with a first temperature that is received by a storage system at a second temperature that is approximately equal to the first temperature. The wind power energy system is insulated with about ten centimeters of glass-wool insulation to create an essentially adiabatic system. The pressurized air is utilized by a generator and generate electricity for a power grid. The generator also includes a combustion engine input. A control system detects fluctuation in wind power and commands the combustion engine to provide an appropriate amount of input energy to the generator such that the sum of the wind energy and combustion engine inputs produces a predetermined amount of electrical output by the generator.

BACKGROUND OF THE INVENTION

This invention relates to wind power energy and, more particularly, to a wind power energy system that produces a generally constant pressurized air pressure with modest heat energy loss to generate reliable electrical output.

Wind power is a rapidly growing segment of the electric power generation industry. A “dedicated generator” design utilizes a wind turbine to input rotational energy directly into an electric generator to generate and supply electricity to a power grid. The wind turbine is connected to a gearbox that converts the typical fifteen to thirty revolutions per minute of the wind turbine to 1500 to 3600 revolutions per minute required for an electric generator. The gearbox is a noisy, heavy, and expensive component of the wind tower and it is generally desirable to eliminate it from the wind tower design.

Another type of wind tower design utilizes a wind turbine to drive a compressor that produces pressurized air, which is stored in a tank. Pressurized air rotates a turbine attached to an electric generator to supply electricity to the power grid.

In particular, several drawbacks exist for conventional wind power systems with regard to electricity generation. For one, the amount of energy produced by conventional wind towers varies. One contributing factor to the variation is natural variation in wind speed. For the dedicated generator design, wind speed variation leads directly to spikes in the amount of electricity that the generator produces. For pressurized air storage designs, wind speed variation leads to variation in the pressure of the stored pressurized air. More importantly, in conventional designs the varying amount of electricity supplied to the power grid makes wind generated power difficult to sell in the energy market, which requires selling power more than twenty-four hours in advance.

Some conventional wind power systems utilize supplemental power input. When the amount of electricity generated by a conventional wind power system fails to meet the required demand, additional electricity from a remote off-site generator is transmitted to the wind power site to supplement the wind power electricity. This introduces significant additional costs, infrastructure, and inefficiencies to the system.

Other conventional wind power systems utilize two types of wind towers. One tower generates electricity for immediate use and another type of tower produces pressurized air to store energy for later generation of electricity. When wind conditions are inadequate for the first type of tower to immediately meet electricity demands, the pressurized air produced by the second type of tower can be utilized to generate supplemental electricity. Although this type of wind power system addresses variation in electricity generation, there is still demand for more efficient wind power systems.

In the power industry in general, a dual input generator utilizes the input of a first combustion engine to generate electricity and the input of a second combustion engine to supplement the first combustion engine when additional electrical output is desired. Combustion engines, however, utilize conventional hydrocarbon fuels and therefore suffer considerable expense and environmental impact.

Another drawback for conventional pressurized air wind power systems is inadequate operational efficiency. The percent of wind energy that actually results in electric energy produced is typically less than forty percent for conventional wind towers. The considerable loss in efficiency can come from a variety of sources. For one, the loss of heat energy when air is compressed accounts for approximately fifty percent of the total energy lost. The compression ratio produces pressurized air having an extremely high temperature, for example 600° C. The extreme temperature and heat exceeds a maximum temperature limit of the materials making the wind power system and must therefore be dissipated in order to avoid failure of the system. Dissipation occurs through intercooling in the compression system and loss of heat to the outer surrounding environment.

Another source of operational efficiency loss in conventional pressurized air wind power systems is waste of potential power from turbine rotation when the wind speed varies from a pre-selected design point. The rotational speed of the wind turbine scales linearly with wind speed, but the power generated by the wind turbine scales with the cube of the wind speed. This forces either the air compressor compression ratio to vary strongly with wind speed or the wind turbine to operate far away from peak aerodynamic efficiency in order to dissipate or forego a portion of wind power. The resulting inefficiencies lead to higher expense to produce wind generated electricity.

Despite dual input generators and existing conventional wind power systems, a demand remains for a wind power system that is reliable, efficient, and cost effective. Accordingly, it is desirable to provide a wind power system with low variation in the amount of electricity generated and high operational efficiency.

SUMMARY OF THE INVENTION

The wind power energy system of the present invention includes a wind turbine that rotates in response to wind and powers a compression system that produces pressurized air with a first temperature. The compression system includes insulation to slow the rate of heat loss, creating an essentially adiabatic system. A storage system including a wind tower storage portion receives the pressurized air at a second temperature that is approximately equal to the first temperature of the pressurized air produced by the compression system. A nozzle transfers the pressurized air from the wind tower storage portion to a primary storage portion. In the primary storage portion, the pressurized air flows through a conduit and a flow control valve and impinges on a generator turbine. The generator turbine rotates a shaft and a rotor of a generator to generate electricity. The electricity generated is supplied to a power grid. A second input in the form of a combustion engine is coupled to the generator. The generator uses the combustion engine energy when the first input energy provided by the wind power energy system fluctuates to continue producing a predetermined amount of electrical output. The combustion engine further includes an exhaust conduit that directs hot exhaust from the combustion engine to an air-to-air heat exchanger located on the conduit of the primary storage portion.

In one example, the second temperature is at least 50% of the first temperature. Even though 50% represents an improved conservation of the temperature component of the potential energy compared to the prior art, even greater temperature conservation can be required.

In another example, the second temperature is about 85% of the first temperature. To achieve 85%, the insulation is a glass-wool insulation that has a heat conductivity of about 0.04 W/(m·K) and a thickness of about 10 cm.

In another example, the second temperature is lower than a maximum temperature limit of the material making the wind power energy system. The maximum temperature generated by the compression system is controlled by the compression ratio of the compression system.

In another example, the compression ratio is 8:1. An 8:1 compression ratio yields a pressurized air temperature of about 300° C. and is preferred in order to allow the inexpensive materials typically used in a wind power energy system to operate within a desired temperature range.

In another example, the wind power energy system includes thirty-three wind towers that are each capable of generating 1.5 MW of maximum power. The entire wind power energy system is capable of generating approximately 50 MW of power. The wind tower storage portion of each wind tower contributes a volume of approximately 900 cubic meters to the primary storage portion and is maintained at a pressure of about 7.5 bars. The primary storage portion holds approximately 10,000 cubic meters and has a pressure between 7.0 bars and 8.0 bars.

In another example, the compression system includes a plurality of clutches and air compressors. The air compressors are arranged in a parallel relation to each other such that each air compressor has an independent, or mutually exclusive, air inlet. A control logic circuit communicates with the wind turbine and the plurality of clutches and closes or opens a predetermined number of clutches to engage or disengage the associated air compressors in response to changing wind conditions. The number of air compressors engaged at any one time is determined by the power being extracted by the wind turbine.

In another example, the wind power energy system thereby operates in a steady state air pressure condition. The control system communicates with the flow control valve and the compression system and commands the flow control valve to allow a predetermined amount of compressed air to be used to rotate the generator turbine. The control system determines the predetermined amount of compressed air such that the amount of compressed air used for rotating the generator turbine is about equal to the amount of compressed air produced by the compression system.

In another example, a plurality of air compressors is arranged in a series relation such that a conduit fluidly connects the air outlet to the air inlet of the next air compressor in the series. A control logic circuit communicates with the wind turbine and each valve and determines how many air compressors to employ depending on the wind speed. A constant pressure of pressurized air is produced.

In another example, the wind turbine blades include cylinders and pistons Rotation of the wind turbine and turbine blades causes the pistons to stroke in the cylinders and pressurize air. The pressurized air is stored in a wind tower storage portion.

The wind power system according to the present invention provides low variation in the amount of electricity generated and high operational efficiency.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1illustrates a schematic view of a wind power energy system10. The wind power energy system10includes a wind tower11with a wind turbine12connected to a power distributor14. The power distributor14supports the wind turbine12and transmits power from the wind turbine12, in response to wind, to a compression system16that produces pressurized air with a first temperature. The pressurized air has potential energy, including a pressure component and a temperature component. Loss of pressure and/or loss of temperature (heat) reduces the total amount of potential energy stored in the pressurized air. It is to be understood that the wind power energy system10typically includes multiple wind towers11to produce pressurized air.

A nacelle18houses the compression system16. Both the compression system16and nacelle18are disposed on a yaw orientation system19. The yaw orientation system19allows the nacelle18and wind turbine12to be oriented in the most favorable direction in relation to a wind direction.

The inventive compression system16includes insulation20that sheaths the periphery22to slow the rate of heat loss across the periphery22. A conduit24transfers the pressurized air from the compression system16to a storage system23. The storage system23includes a wind tower storage portion26that receives pressurized air from the compression system16. The pressurized air received is at a second temperature that is approximately equal to the first temperature of the pressurized air produced by the compression system16. A nozzle28transfers pressurized air from the wind tower storage portion26to a primary storage portion30of the storage system23.

The primary storage portion30acts as a venturi to mix compressed air from the wind tower storage portion26with compressed air in the primary storage portion30even when the pressure in the wind tower storage portion26is lower than the pressure in the primary storage portion30. Flow of compressed air in the primary storage portion30is accelerated through a throat portion32and flow of compressed air from the wind tower storage portion is accelerated in the nozzle28such that the mixing of the two flows occurs at lower pressure than either before the flow accelerations. The combined flow is then decelerated and the pressure is recovered in a downstream portion34of the primary storage portion30.

Pressurized air from the primary storage portion30flows through a conduit36and a flow control valve38. The flow control valve38regulates the mass-rate and pressurized air pressure to the generator turbine40, and is the principle means by which the pressurized air pressure in the primary storage potion30is controlled.

The pressurized air, acting as a first input for a generator42, provides a first energy by rotating the generator turbine40which in turn rotates a shaft44and a rotor46of the generator42to generate electricity. The flow control valve38regulates the amount of electrical power generated by controlling the mass flow rate and pressurized air pressure that is allowed to impinge on the generator turbine40. The electricity generated is supplied to a power grid48.

The rotor46also includes a second input in the form of a combustion engine50that is coupled to the rotor46and shaft44. A clutch52is disposed between the rotor46and the combustion engine50for selectively engaging and disengaging the combustion engine50with the shaft44. The generator42uses a second input energy from the combustion engine50to generate electricity and supply electricity to the power grid48.

The generator42utilizes wind power input energy and combustion engine input energy to generate a predetermined amount of electricity. The generator42includes a control system54that communicates with the wind power energy system10, the combustion engine50, and the generator42. When the first input energy provided by the wind power energy system10fluctuates, the control system54detects the fluctuation and commands the combustion engine50to provide the appropriate amount of second input energy to the generator such that the sum of the first energy and second energy produces the predetermined amount of electrical output by the generator42. The combustion engine50compensates for fluctuating wind conditions over a duration longer than about ten minutes and allows the generator42to supply a generally constant amount of electricity to the power grid even when the wind speed varies.

The combustion engine50further includes an exhaust conduit56with insulation20. The exhaust conduit56directs hot exhaust from the combustion engine50to an air-to-air heat exchanger58located on the conduit36of the wind power energy system10. It is to be understood that a variety of heat exchanger types may be used, including but not limited to a heat exchanger with an organic Rankine cycle system. The heat exchanger58utilizes the hot exhaust to transfer heat from the hot exhaust to the compressed air before it flows through the flow control valve38, thereby increasing the temperature component of the potential energy of the compressed air and increasing the efficiency of the wind power energy system10.

The insulation20is important in the wind power energy system10for maintaining an essentially adiabatic system. The pressurized air produced by the compression system16has a first temperature. When the pressurized air is received by the wind tower storage portion26it has a second temperature that is approximately equal to the first temperature. A loss of temperature between the compression system16and the wind tower storage portion26results in loss of potential energy in the pressurized air and ultimately to lower operational efficiency of the wind power energy system10. Unlike prior art wind power systems, the inventive wind power energy system10conserves at least more than 50% of the heat energy produced in pressurizing the air. Thus, the insulation20that generally surrounds the compression system16and primary storage portion30is a key factor of maintaining an adiabatic system.

In one example, the second temperature is at least 50% of the first temperature. Prior art wind power systems lose or dissipate large amounts of heat during compression of the pressurized air and do not achieve a 50% level. Even though 50% represents an improved conservation of the temperature component of the potential energy compared to the prior art, even greater temperature conservation can be required for commercial viability.

In another example, the second temperature is about 85% of the first temperature. To achieve 85%, the insulation20is a glass-wool insulation that has a heat conductivity of about 0.04 W/(m·K) and a thickness of about 10 cm. The insulation20preferably surrounds all portions of the wind power energy system10. This includes at least the compression system16, conduit24, wind tower storage portion26, nozzle28, primary storage portion30, and conduit36, which all provide thermal storage when insulated. It should be understood that other types of insulation having different heat conductivities and requiring difference thicknesses may be utilized.

In another example, the second temperature is lower than a maximum temperature limit of the material making the wind power energy system10. The maximum temperature generated by the compression system16is controlled by the compression ratio of the compression system16. The maximum compression ratio of pressurized air to ambient 20° C. air from the surrounding environment is about 12:1 and results in the pressurized air having a temperature of about 375° C. The materials used to construct the wind power energy system10are inexpensive standard materials. That is, the materials are standard grade steels or other materials that are not highly specialized for high temperature performance. The standard materials have a maximum temperature limit of about 375° C. and therefore can operate without failure when the compression system16utilizes a compression ratio of 12:1 and produces pressurized air having a temperature of about 375° C.

In another example, the compression ratio is 8:1. Utilizing an 8:1 compression ratio yields a pressurized air temperature of about 300° C. A compression ratio of about 8:1 is preferred in order to allow the materials making the wind power energy system10to retain a safe amount of physical strength and structural integrity.

In another example, the wind power energy system10includes thirty-three wind towers11that are each capable of generating 1.5 MW of maximum power. The entire wind power energy system10is capable of generating approximately 50 MW of power. The wind tower storage portion26of each wind tower11contributes a volume of approximately 900 cubic meters to the primary storage portion30and is maintained at a pressure of about 7.5 bars. The primary storage portion30holds approximately 10,000 cubic meters and has a pressure between 7.0 bars and 8.0 bars. The pressure between the wind tower storage portion26and the primary storage portion30is maintained in a steady state pressure condition by the control system54. In particular, wind gusts and other variation in wind speed that can cause variation in prior art wind systems are absorbed through variation in air pressure of plus or minus 0.5 bars in the wind tower storage portions26of the thirty-three wind towers11. This allows the wind power energy system to absorb wind speed variation that occurs for a duration of less than approximately ten minutes. Larger variations in air pressure in the wind tower storage portion26can be absorbed by utilizing a lower pressure such as 6 bars instead of 7.5 bars in the wind tower storage portion26. Furthermore, the operational efficiency of the wind power energy system10is only weakly dependent on the air pressure. That is, the system operates at 82% efficiency at 8 bars and about 75% at 3 bars.

In another example, the wind power energy system10includes a single wind tower11. The generator42and the combustion engine50, such as a diesel engine are located near the single wind tower11. That is, the generator42and combustion engine50are not remote from the single wind tower11and therefore do not require separate foundations, housings, power conditioners, and the like. Therefore, certain benefits, such as lower expense, may be obtained by locating the generator42and the combustion engine50near to the wind tower11.

FIG. 2Aillustrates a schematic view of one example of the compression system16. The wind turbine12is a first source of energy producing a variable energy from harnessing the wind. The compression system16includes a power distributor68coupled to the wind turbine12to receive the variable wind energy in the form of rotational power. The power distributor68transmits the rotational power to a plurality of secondary shafts70that are coupled, respectively, to a plurality of clutches72and air compressors74.

The air compressors74each include an air inlet76for intaking air from the outside environment and a conduit78for transferring pressurized air to the wind tower storage portion26. The air compressors74generally each have an isentropic efficiency of at least 70% and preferably 85%, and are arranged in a parallel relation to each other such that each air compressor74has an independent, or mutually exclusive, air inlet76. That is, the air inlet of any one air compressor74is not in direct fluid communication with any other air compressor and each air compressor74independently supplies pressurized air to the wind tower storage portion26. Each air compressor74and conduit78also includes insulation20that sheaths the periphery79and slows the rate of heat transfer to the outside environment. It should be understood that this is but one example configuration out of many possible parallel air compressor configurations that can be utilized in employing the invention.

The compression system16further includes a control logic circuit80that at least communicates with the wind turbine12and the plurality of clutches72. When the wind speed is relatively high, the control logic circuit80closes a predetermined number of the plurality of clutches72to engage the associated air compressors74. When the wind speed is relatively low, the control logic circuit80opens a predetermined number of the plurality of clutches72to disengage the associated air compressors74.

The number of air compressors74engaged at any one time is determined by the power being extracted by the wind turbine12from a first source of energy, the wind. The power extracted changes with the cube of the wind speed. The number of air compressors74engaged increases or decreases in proportion to the power being extracted by the wind turbine12, thus yielding energy in the form of constant pressurized air with varying mass flux. The wind tower storage portion26receives the pressurized air and acts as a second source of energy supplying constant pressure pressurized air to a third source of energy, the primary storage portion30. Furthermore, when the number of air compressors74engaged is less than the maximum number of compressors, the control logic circuit80selects which of the air compressors74to engage so as to distribute the “wear and tear” evenly among all the air compressors74.

In one contemplated mode of operation, the ratio of pressurized air pressure to ambient air pressure inside the wind tower storage portion26is approximately 7.5:1 and the ratio in the primary storage portion30is approximately 8:1, although a more preferred condition would be equal air pressure. The control system54communicates with at least the flow control valve38and the compression system16and commands the flow control valve38to allow a predetermined amount of compressed air to be used to rotate the generator turbine40. The control system54determines the predetermined amount of compressed air such that the amount of compressed air used for rotating the generator turbine40is about equal to the amount of compressed air produced by the compression system16. The wind power energy system10thereby operates in a steady state air pressure condition.

In another example, the first source of energy producing variable energy is the wind tower storage portion26. The wind tower storage portion26stores and transfers pressurized air from the compression system16. The pressure of pressurized air in the wind tower storage portion26can vary. Preferably, the variation is not greater than plus or minus 0.5 bars from a predetermined pressure. A second source of energy, the primary storage portion30, receives pressurized air from the wind tower storage portion26and produces constant energy. The constant energy is in the form of a constant mass-rate from the flow control valve38. The constant mass-rate of pressurized air is received by a third source of energy, the generator42.

FIG. 2Billustrates another example of the compression system16having a parallel arrangement. The wind turbine12rotates the power distributor68, which includes a hub81. The hub81rotates and transmits rotational power to a plurality of rotating cylinders82that are coupled, respectively, to a plurality of clutches83and a plurality of air compressors84. The plurality of air compressors84are arranged in a parallel relation to each other such that each air compressor84has an independent, or mutually exclusive, air intake. The plurality of clutches83may be selectively controlled such that when the wind speed is relatively high, a predetermined number of the plurality of clutches83are closed to engage the associated air compressors84. When the wind speed is relatively low, a predetermined number of the plurality of clutches83are opened to disengage the associated air compressors84. The number of engaged air compressors84increases or decreases in proportion to the power being extracted by the wind turbine12, thus providing energy to the wind tower storage portion26in the form of constant pressurized air with varying mass flux.

FIG. 3illustrates a schematic of another example of a compression system16. The compression system16includes a wind turbine12that transmits variable energy from wind in the form of rotational power to the power distributor68. The power distributor68transmits the rotational power to a plurality of secondary shafts92that are coupled, respectively, to a plurality of air compressors94. The air compressors94generally each have an isentropic efficiency of at least 70% and preferably 85%. Each compressor94includes an air inlet96and air outlet98. The plurality of air compressors94are arranged in a series relation such that a conduit100fluidly connects the air outlet98to the air inlet96of the next air compressor94in the series. The conduit100also includes a one-way valve102for selectively directing compressed air from the conduit100to the conduit104or to the air inlet96, depending on a predetermined desired pressurized air level. It should be understood that this is but one example configuration out of many possible different configurations of air compressors in series that can be utilized in employing the invention.

Each air compressor94, conduit100, and valve102also includes insulation20that slows the rate of heat transfer to the outer environment. The insulation20that sheaths the air compressors94is located on the periphery103of each air compressor94.

The compression system16includes a control logic circuit106that at least communicates with the wind turbine12and each valve102. The control logic circuit106determines how many air compressors94to employ depending on the wind speed. When the wind speed is relatively low compared to a pre-selected wind speed, all the valves102are opened and the maximum number of air compressors94is employed. This results in a predetermined constant pressure of pressurized air. When the wind speed is relatively high, the control logic circuit106closes a predetermined number of the valves102to employ fewer air compressors94. This results in the same predetermined constant pressure of pressurized air, although the mass flux of pressurized air varies.

FIGS. 4A and 4Billustrate another example of the compression system16. The wind turbine12includes turbine blades114coupled to a hub116. The hub is coupled to the nacelle and rotates around an axis120. The turbine blades114include cylinders122that each houses a piston124. The piston124is coupled to a rod126that extends to and attaches to a hub128. The hub128rotates about a fixed support rod130that is attached within the nacelle118. The support rod130defines a secondary axis132that is located a distance from the axis120.

The wind rotates the wind turbine12around the axis120. The rotation of the wind turbine12and turbine blades114causes the rod126and hub128to also rotate. The rod126and hub128rotate about the secondary axis132that is a distance from the axis120, thereby causing the pistons124to stroke in the cylinders122. The stroking of the pistons124intakes air through an air intake134, pressurizes the air, and transfers the pressurized air through an outlet136to the wind tower storage portion26.