Thermal energy conversion system

A power generation system includes a first vessel having a generally constant volume and a second vessel having a variable volume. Thermal energy is supplied to an ideal gas within the first vessel in order to raise its temperature and pressure. The thermally compressed gas is then released into, and expands the volume of, the second vessel. The expanding volume of the second vessel expands raises a mass and/or strains an elastic member, thus storing gravitational and/or elastic potential energy. This stored potential energy can be released on demand by evacuating the second vessel, typically into a third vessel, and used to power a generator. Preferably, the potential energy is used to coupled to the generator using a planetary gear drive, such that a relatively small number of input rotations yields a relatively large number of output rotations.

BACKGROUND OF THE INVENTION

a. Field of the Invention

The instant invention relates to power generation. In particular, the instant invention relates to the generation of electrical power from thermal energy.

b. Background Art

Electricity, and its ready availability, are very important to the modern lifestyle. Power generation systems produce electricity from other energy sources, such as fossil fuels (e.g., coal, petroleum, natural gas) or nuclear materials.

Many power generation systems attempt to harness thermal energy, such as solar energy or geothermal energy, for conversion to electrical energy. For example, U.S. Pat. No. 6,374,607 to Takabu discloses an apparatus that includes facing high- and low-temperature sections with a bimetallic strip interposed therebetween. The bimetallic strip is attached to a rotary member. As the bimetallic strip is heated by the high-temperature section, it flexes towards the low-temperature section, where it cools and flexes back to the high-temperature section, thereby inducing reciprocating motion that causes the rotary member to turn and generate electricity.

Extant power generation systems, however, are subject to numerous disadvantages. For example, to generate appreciable electricity, a solar farm must occupy a very large surface area (that is, it has a very large physical footprint). Other power generation systems have undesirable carbon footprints. Still other power generation systems exhibit low output and/or low efficiency.

BRIEF SUMMARY OF THE INVENTION

It would be desirable to provide a power generation system that addresses the shortcomings of extant power generation systems.

It is therefore an object of the present invention to provide a power generation system that converts thermal energy to electrical energy with greater efficiency than extant power generation systems.

Another object of the present invention is to provide a more compact system to generate electricity from thermal energy.

Disclosed herein is a power generation system that includes: at least one thermal energy accumulation vessel containing a gas; a potential energy generation system, including at least one battery vessel connected to the at least one thermal energy accumulation vessel and having a variable volume; a thermal energy dissipation vessel connected to the at least one battery vessel; and an energy conversion system, preferably including a planetary gear drive, coupled to the potential energy generation system. The potential energy generation system generates and stores potential energy via expansion of the volume of the at least one battery vessel when a quantity of the gas moves from the at least one thermal energy accumulation vessel to the at least one battery vessel after increasing in temperature while in the at least one thermal energy accumulation vessel. In turn, the energy conversion system converts potential energy stored by the potential energy generation system into electrical energy when a quantity of the gas is evacuated from the at least one battery vessel to the thermal energy dissipation vessel after expansion of the volume of the at least one battery vessel.

According to one aspect of the present invention, the at least one battery vessel includes a movable mass, such that the expansion of the volume of the at least one battery vessel raises the movable mass, thereby generating and storing gravitational potential energy. In another aspect of the present invention, the at least one battery vessel comprises a spring or other elastic element, such that expansion of the volume of the at least one battery vessel changes the length of the spring (e.g., places the spring in either tension or compression), thereby increasing the strain on the spring and generating and storing elastic potential energy.

To facilitate sealing the at least one battery vessel, it is contemplated that the at least one battery vessel can include a bellows or bellows-like structure.

To increase the rate at which the gas is thermally compressed within the at least one thermal energy accumulation vessel, it is contemplated that the thermal energy accumulation vessel can include a plurality of thermal energy accumulation chambers and/or a plurality of successive thermal energy accumulation stages.

Preferably, the at least one thermal energy accumulation vessel is connected to the at least one battery vessel via at least one one-way valve. Likewise, it is preferable for the at least one battery vessel to be connected to the at least one thermal energy dissipation vessel via at least one one-way valve. Optionally, these one-way valves may be automatically actuated. For example, an electronic controller can be programmed (1) to open the valve(s) connecting the thermal energy accumulation vessel to the battery vessel the when the gas in the at least one thermal energy accumulation vessel increases in temperature by a preset amount; (2) to close the valve(s) connecting the thermal energy accumulation vessel to the battery vessel when the potential energy generation system has generated and stored a preset amount of potential energy; (3) to open the valve(s) connecting the battery vessel and the thermal energy dissipation vessel when the potential energy generation system has generated and stored a preset amount of potential energy; and/or (4) to close the valve(s) connecting the battery vessel and the thermal energy dissipation vessel when a preset amount of the generated and stored potential energy is converted to electrical energy.

In some embodiments of the invention, gas is recycled throughout the system. Thus, the thermal energy dissipation vessel can be connected to the at least one thermal energy accumulation vessel, preferably via at least one one-way valve, which can optionally be automatically actuated. The power generation system can also include a reserve gas vessel, which will typically be connected to the at least one thermal energy accumulation vessel via a pressure regulator, in order to maintain a preset baseline pressure in the at least one thermal energy accumulation vessel.

It is contemplated that electrical energy can be stored in one or more electrical storage devices, for example in batteries or capacitors, that can be coupled to an output of the energy conversion system.

In another embodiment, a power generation system according to the present invention includes: a first vessel having a fixed volume and containing a gas; a second vessel including a movable element that allows for a volume of the second vessel to vary; a pressure line including a one-way valve coupling the first vessel to the second vessel; and an energy conversion system. The energy conversion system includes: a rotating input shaft; a rotating output shaft; a planetary gear drive coupling the rotating input shaft to the rotating output shaft; and an electrical generator. The rotating input shaft is coupled to the movable element such that, when the movable element moves to reduce the volume of the second vessel, the rotating input shaft rotates and the energy conversion system generates electricity. For example, a pulley system can be used to couple the rotating input shaft to the movable element. A decoupling mechanism can also be provided to decouple the movable element from the rotating input shaft when the movable element moves to increase the volume of the second vessel (e.g., when storing potential energy) and to couple the movable element to the rotating input shaft when the movable element moves to decrease the volume of the second vessel (e.g., when releasing potential energy).

Also disclosed herein is a method of power generation, including the following steps: thermally compressing a gas that obeys the ideal gas law in a first vessel having a constant volume; releasing the thermally compressed gas from the first vessel into a second vessel having a variable volume to increase the volume of the second vessel and store at least one of gravitational potential energy and elastic potential energy; releasing the gas from the second vessel, thus allowing the volume of the second vessel to decrease; and using a planetary gear drive to convert the stored potential energy into electrical energy as the volume of the second vessel decreases.

An advantage of the present invention is that converts over 80% of input thermal energy to electricity.

Another advantage of the present invention is that it is more compact than existing systems to convert thermal energy to electrical energy, particularly when compared to solar power systems.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic diagram of a power generation system10that converts thermal energy to electricity according to the teachings herein. Power generation system10generally includes at least one thermal energy accumulation vessel12, a potential energy generation system including at least one battery vessel14, a thermal energy dissipation vessel16, and an energy conversion system18that converts potential energy generated and stored by the potential energy generation system into electrical energy. Thermal energy accumulation vessel12is connected to battery vessel14, which is in turn connected to thermal energy dissipation vessel16, which is itself connected to thermal energy accumulation vessel12via a series of one-way valves.

Power generation system10is charged with a gas, such as air, that obeys the ideal gas law, PV=nRT. Specifically, thermal energy accumulation vessel12, which will typically have a constant volume VA, is charged to an initial pressure PA1with an amount nA1of such a gas at a temperature TA1. One of ordinary skill in the art will recognize, of course, that only two of these three quantities (e.g., nA1and PA1) can be independent, while the third (e.g., TA1) is dependent upon the other two.

In one aspect of the invention, thermal energy accumulation vessel12is a single chamber. In another aspect of the invention, thermal energy accumulation vessel12contains a plurality of chambers. In still further aspects of the invention, thermal energy accumulation vessel12is a multi-stage device; each stage can include a single chamber or a plurality of chambers.FIG. 8, for example, depicts a multi-stage, multi-chamber embodiment of thermal energy accumulation vessel12.

Thermal energy accumulation vessel12is designed to effect thermal compression of the gas contained therein. Thus, as one of ordinary skill in the art will appreciate from the instant disclosure and from well understood principles of thermodynamics and heat transfer, the design of thermal energy accumulation vessel12can vary considerably without departing from the spirit and scope of the present invention. Although certain contemplated embodiments of thermal energy accumulation vessel12are discussed in detail herein, the invention is not limited to these embodiments, and other configurations of thermal energy accumulation vessel12are equally within the spirit and scope of the present invention.

Unlike thermal energy accumulation vessel12, battery vessel14has a variable volume. For example, as shown inFIG. 2, battery vessel14may include a piston20(shown in phantom) having a mass m that can move along the longitudinal axis of the generally cylindrical battery vessel14. Alternatively, as shown inFIG. 3, battery vessel14may contain a bellows-like structure22(shown in phantom), also having a mass m, that can expand and contract along the longitudinal axis of the generally cylindrical battery vessel14.

It is desirable that the initial position of piston20or bellows-like structure22allow for at least a small volume of gas to be present within battery vessel14, such that piston20does not contact the bottom of battery vessel14or such that bellows-like structure22does not completely collapse upon itself. That is, the initial volume VB1of battery vessel14is non-zero, and there is an initial quantity nB1of gas within battery vessel14.

Because piston20is free to move upwardly or downwardly, and bellows-like structure22is free to expand and contract, the absolute pressure PBwithin battery vessel14will remain relatively constant throughout the power generation cycle described herein. Using this equilibrium state, where the sum of all forces acting on piston20or bellows-like structure22is zero, PBcan be determined from the equation mg+PatmA=PBA, where Patmis the local atmospheric pressure and A is the area over which the atmospheric pressure Patmand absolute pressures PBact (e.g., the surface area of piston20).

Generation and Storage of Potential Energy

As one of ordinary skill in the art will appreciate, raising mass m of piston20or bellows-like structure22by a height Δh will generate an increase in potential energy ΔU=mgΔh. The increase in height Δh of mass m coincides with an increase in the volume of battery vessel14from its initial volume VB1to an expanded volume VB2, where VB2=VB1+AΔh.

Mass m can be driven to undergo the increase in height Δh by supplying additional gas from thermal energy accumulation vessel12to battery vessel14via pressure line24, which includes a one-way valve25that only permits gas flow from thermal energy accumulation vessel12to battery vessel14, and that prohibits gas flow in the reverse direction. To accomplish this, the amount of gas nA1within thermal energy accumulation vessel12is subjected to a heating cycle that raises its temperature from TA1to TA2. The gas within thermal energy accumulation vessel12is preferably heated by subjecting it to solar heating. Other methods of heating the gas within thermal energy accumulation vessel12, such as subjecting it to waste heat from a manufacturing process or to geothermal heat sources, are also within the spirit and scope of the present invention, however.

The increase in temperature within thermal energy accumulation vessel12from TA1to TA2results in an increase in pressure within the thermal energy accumulation vessel12from PA1to PA2according to the ideal gas law. Specifically, because VAand nA1are constant during the heating process within thermal energy accumulation vessel12,

Opening one-way valve25connecting thermal energy accumulation vessel12to battery vessel14allows this high pressure, high temperature gas to flow from thermal energy accumulation vessel12into battery vessel14. To return piston20or bellows-like structure22to an equilibrium state (i.e., where the pressure within battery vessel14is PB), the volume in battery vessel14must increase (e.g., from VB1to VB2), as dictated by the ideal gas law in view of both the increased temperature of the gas within battery vessel14(e.g., from TB1to TB2) and the increased amount of gas within battery vessel14(e.g., from nB1to nB2).

For any given Δh, VB2can be computed according to the equation VB2=VB1+AΔh. The ideal gas law further provides that

VB⁢⁢1nB⁢⁢1⁢TB⁢⁢1=VB⁢⁢2nB⁢⁢2⁢TB⁢⁢2.
Of course, TB2=TA2, and (nB2−nB1)=(nA1−nA2) (that is, the amount of gas that flows into battery vessel14is equal to the amount of gas that flows out of thermal energy accumulation vessel12, and the temperature of the gas that flows into battery vessel14is equal to the temperature of the gas that flows out of thermal energy accumulation vessel12).

Thus, it is possible to compute, for a given temperature increase from TA1to TA2within thermal energy accumulation vessel12, the amount of gas (nB2−nB1) that needs to flow into battery vessel14to achieve a desired Δh. Likewise, for any given amount of gas (nB2−nB1) that flows into battery vessel14, it is possible to compute the required temperature increase from TA1to TA2to achieve a desired Δh. Of course, the greater the increase in temperature, the less gas will be required to achieve the desired increase in volume of battery vessel14and vice versa. In effect, a known amount of thermal energy must be supplied from thermal energy accumulation vessel12to battery vessel14in order to effect the desired generation and storage of potential energy.

The relationships described above, along with other applications of the ideal gas law, can be leveraged to automatically actuate the opening and closing of one-way valve25to achieve the maximum Δh (e.g., the maximum distance piston20can travel, or the maximum expansion bellows-like element22can achieve), thus yielding the maximum generation and storage of gravitational potential energy, in a single valve open-close cycle. For example, a controller can be programmed to open one-way valve25when the gas in thermal energy accumulation vessel12undergoes a preset temperature increase or pressure increase, as measured by an appropriate sensor (e.g., a temperature sensor or pressure gauge). Likewise, the controller can be programmed to close valve25when a preset amount of gas has passed into battery vessel14or when the volume of battery vessel14has increased by a preset amount, again as measured by an appropriate sensor (e.g. a sensor of the rotational position of an element of the planetary drive, as described in further detail below).

In an alternative embodiment of the invention, rather than (or in addition to) storing gravitational potential energy by raising a mass, the volume expansion in battery vessel14from VB1to VB2compresses a spring26(exemplary arrangement illustrated inFIG. 4) or places spring26in tension (exemplary arrangement illustrated inFIG. 5), thereby alternatively (or additionally) storing elastic potential energy (e.g., UE=½k(Δx)2), where k is the spring constant of spring26and Δx is the distance by which the spring is stretched or compressed when the volume of battery vessel14increases from VB1to VB2. Spring26can be a compression spring (such as a conical spring) or any other suitable elastic element.

Although consideration of Hooke's law (i.e., F=−kx) will somewhat complicate the system of equations that must be solved to automatically control one-way valve25on pressure line24due to the changing equilibrium pressure within battery vessel14resulting from the use of spring26(e.g., the equilibrium pressure will increase as strain on the spring increases), one of ordinary skill in the art will appreciate how to solve this system of equations through application of the teachings herein in conjunction with well-understood principles of physics, engineering mechanics, and thermodynamics.

Thus, in general, power generation system10generates and stores potential energy by (1) allowing an ideal gas to increase in temperature and pressure within the fixed volume of thermal energy accumulation vessel12; and (2) releasing the high temperature, high pressure gas into battery vessel14, where it expands and raises a mass and/or changes the length of a spring as the volume of battery vessel14increases.

Conversion of Stored Potential Energy to Electrical Energy

Once a desired amount of gravitational and/or elastic potential energy has been generated and stored within the potential energy generation system (e.g., by raising the mass m of piston20or bellows-like structure22by a preset Δh and/or by changing the length of spring26by a preset Δx), the stored potential energy can be released into energy conversion system18connected to the potential energy generation system. Energy conversion system18, in turn, converts the potential energy into electrical energy. The resultant electrical energy can be used immediately to provide power to a connected electrical load, stored for later use in an electrical energy storage device28such as a battery or a capacitor, returned to an electrical power grid, or some combination thereof.

As illustrated inFIG. 6, energy conversion system18can include a rotating drum30that is connected to piston20(or, alternatively, bellows-like structure22) via a cable32running through a pulley system34. Cable32is wrapped around drum30so as to apply a torque thereto. As described in further detail below, the application of torque to drum30by cable32results in the generation of electrical energy at generator38.

To take up slack in cable32as the volume of battery vessel14expands, drum30can be driven to rotate in a cable take-up direction shown by arrow “A” inFIG. 6. In some embodiments of the invention, drum30is driven in the cable take-up direction via a power spring36coupled to drum30. Power spring36stores potential energy as mass m of piston20or bellows-like structure22descends (i.e., some of the potential energy generated and stored by battery vessel14is used to coil power spring36rather than being converted to electrical energy), and then releases this stored potential energy as mass m of piston20or bellows-like structure22rises, thereby driving drum30to take up slack in cable32.

As an alternative to power spring36, drum30could be fitted with a counterweight that is raised to store potential energy as mass m of piston20or bellows-like structure22descends (i.e., some of the potential energy generated and stored by battery vessel14is used to raise the counterweight rather than being converted to electrical energy), and that is allowed to descend to drive drum30to take up slack in cable32as mass m of piston20or bellows-like structure22ascends.

Drum30is preferably coupled to a generator38via a planetary gear drive40. The use of planetary gear drive40allows a very small number of turns of drum30, such as would be associated with the release of potential energy by battery vessel14, to be converted into a much greater number of turns within generator38, thereby increasing the electrical output of power generation system10.

As described above, power spring36drives drum30to rotate in take-up direction A as mass m of piston20or bellows-like structure22ascends within battery vessel14. A clutch mechanism can be employed to decouple drum30from generator38during the potential energy generation and storage phase of the power generation cycle by allowing “slip” in the system.

To release potential energy from battery vessel14, one-way valve42on pressure line44connecting battery vessel14to thermal energy dissipation vessel16is opened, allowing the high pressure gas within battery vessel14to evacuate into thermal energy dissipation vessel16. According to the ideal gas law, to maintain the equilibrium pressure (e.g., PB) within battery vessel14as constant-temperature (e.g., TB2) gas escapes to thermal energy dissipation vessel16, the volume of battery vessel14must decrease (e.g., return to VB1from VB2).

The decreasing volume of battery vessel14, in turn, allows mass m of piston20or bellows-like structure22to descend. As mass m of piston20or bellows-like structure22descends, cable32is paid out and drum30rotates in a payout (e.g., power generation) direction shown by arrow “B” inFIG. 6. When drum30rotates in payout direction B, however, the clutch mechanism operates to couple drum30to generator38via planetary gear drive40(i.e., no “slip” is permitted), thereby generating an electrical output.

As one of ordinary skill in the art will recognize, spring26may not have a linear force curve. As a result, the force acting on drum30via cable32will not be constant, which may undesirably affect the electrical output of generator38.

To help ensure a constant electrical output at generator38, a relatively constant torque should be applied to drum30. Torque, of course, is a product of force and distance. It is contemplated, therefore, to account for variation in the force applied to drum30via cable32by designing a drum30with a varying diameter, such that higher forces are applied at shorter distances than lower forces. Indeed, the profile of drum30can be custom-machined to match the force curve of spring26, both mathematically and physically, to achieve a desirable substantially constant torque, and thus a substantially constant electrical output at generator38.

One suitable embodiment of energy conversion system18is shown inFIG. 9.FIG. 9Aschematically illustrates the use of multiple drums30(e.g.,30a,30b, and30c), each of which can be connected to its own unique battery vessel14, such that there can be a one-to-many relationship between generator38and battery vessels14.

Each drum30is internally coupled to a common drive shaft41via a mechanism that only couples drum30to drive shaft41when drum30is rotated in the payout/power generation direction as described further below. One suitable coupling mechanism, which employs a one-way ratchet mechanism, is shown inFIG. 10. When drum30rotates in direction A (e.g., under power of power spring36), it “slips” over the ratchet mechanism and drive shaft41does not turn. On the other hand, when drum30rotates in direction B (e.g., under power of the potential energy stored by battery vessel14), it engages the ratchet mechanism and turns drive shaft41.

Rotating drive shaft41provides an input to planetary gear drive40. As shown inFIG. 9, planetary gear drive40includes multiple stages (e.g.,40a,40b, and40c), with the output of a preceding stage (e.g.,40a) providing an input to a successive stage (e.g.,40b). The output of planetary gear drive43is the rotation of output shaft43, which serves as an input to generator38.

Each stage of planetary gear drive40includes a fixed central gear housing, an external central gear, and three compound planetary gears. Insofar as the design (e.g., selection of gear ratios) and operation (e.g., relation of input and output torques and forces) of a planetary gear drive40will be familiar to the ordinarily skilled artisan, however, it is not explained in further detail herein.

One-way valve42connecting battery vessel14to thermal energy dissipation vessel16can also be automatically actuated. For example, a controller can be programmed to open one-way valve42when a preset amount of potential energy has been stored in battery vessel14and to close one-way valve42when a preset amount of the stored potential energy has been converted to electrical energy.

In some embodiments of the invention, drum30is fitted with a sensor46that measures the rotational position of drum30. There will be a known relationship between the volume of battery vessel14(e.g., the position of mass m of piston20or bellows-like structure22) and the rotational position of drum30, determinable, for example, from the diameter of drum30and Δh and/or Δx. Thus, the output of sensor46can be used to control the automatic actuation of one-way valve25and/or one-way valve42.

FIG. 7provides a simple illustration of the use of sensor46to control the automatic actuation of one-way valve25and one-way valve42. As shown inFIG. 7, sensor46is at the 12 o'clock position when the volume of battery vessel14is at its nadir (e.g., VB1). Once one-way valve25is actuated to open (e.g., because the gas within thermal energy accumulation vessel12has achieved a preset temperature or pressure increase), drum30will rotate in direction A as the volume of battery vessel14increases from VB1to VB2. Suppose the 4 o'clock position corresponds to the maximum volume of battery vessel14(e.g., VB2). When sensor46reaches the 4 o'clock position (shown in phantom), therefore, one-way valve25can be actuated to close and one-way valve42can be actuated to open. With one-way valve42open, drum30will rotate in direction B as the volume of battery vessel14returns to VB1from VB2. When sensor46returns to the 12 o'clock position, one-way valve42can be actuated to close.

Thus, in general, power generation system10converts potential energy stored by battery vessel14into electrical energy by using the stored potential energy to drive electrical generator38.

Gas Recovery and Replenishment

Thermal energy dissipation vessel16is used to cool the gas (e.g., by opening a series of vents on the outside of thermal energy dissipation vessel16) prior to returning it to thermal energy accumulation vessel12via pressure line48, including one-way valve50, to restart the cycle. Once again, the ideal gas law provides that, as the temperature of a constant amount nDof gas within the constant volume VDof thermal energy dissipation vessel16decreases from TD1(which will be equal to TB2, and thus TA2) to TD2, the pressure thereof will also decrease (e.g., from PD1to PD2).

Of course, one-way valve50can, like one-way valves25and42, be automatically actuated. For example, a controller can be programmed to open one-way valve50when the gas within thermal energy dissipation vessel16undergoes a preset reduction in temperature or pressure or when it reaches a preset absolute temperature or pressure.

In some embodiments of the invention, a reserve gas vessel52is connected to thermal energy accumulation vessel12via a pressure regulator54. Pressure regulator54is set to maintain a preset baseline pressure (e.g., PA1) within thermal energy accumulation vessel12. For example, if the temperature within thermal energy accumulation vessel12drops below TA1overnight, the pressure therein would drop below PA1. To ensure that the next power generation cycle does not start at a deficit, therefore, additional gas can be supplied from reserve gas vessel52to thermal energy accumulation vessel12. Conversely, gas can also be evacuated from thermal energy accumulation vessel12back into reserve gas vessel52whenever desirable.

Typically, the gas within reserve gas vessel52will be maintained at a much higher pressure than the preset baseline pressure PA1of thermal energy accumulation vessel12. In addition, it is desirable to insulate reserve gas vessel52against thermal fluctuations, which can be accomplished by burying reserve gas vessel to a point where the ground temperature is relatively constant, which will typically be the case below the freeze line.

Example and Test Results

One example of power generation system10has been constructed and tested. In this embodiment, battery vessel14has an initial volume (e.g., VB1) of 35.2 ft3and is fitted with a piston20weighing 725 pounds.

Thermal energy accumulation vessel12was initially charged with outside air at 25° F. to a pressure of 7 psi. Thermal energy was then supplied to the air within thermal energy accumulation vessel12by moving power generation system10into a climate controlled (e.g., heated) garage. Within this environment, the air within thermal energy accumulation vessel12increased in temperature to 70° F., yielding a final pressure within thermal energy accumulation vessel12of 7.65 psi.

One way valve25connecting thermal energy accumulation vessel12and battery vessel14was then opened. As the pressure returned to the equilibrium pressure (e.g., PB), piston20ascended (i.e., Δh) 4.25 feet to achieve a final volume (e.g., VB2) of 38.2 ft3. The corresponding potential energy stored by power generation system10was 3081.25 ft-lb, or 4177.6 J.

The stored potential energy was then released to energy conversion system18and the electrical output thereof was measured. Table 1 shows the current, voltage, and electrical power outputs. In each case, power generation system10was allowed to run for 23 seconds. Distributing the 4177.6 J of stored potential energy over 23 seconds yields a maximum power output of 181.6 W.

Thus, relative to extant systems, power generation system10has a surprisingly high average output of 148.139 W for an average efficiency of 81.57%.

Although several embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention.

For example, the invention is described above with respect to a single thermal energy accumulation vessel12. The invention can be practiced, however, with any number of thermal energy accumulation vessels12. Indeed, a plurality of thermal energy accumulation vessels12can be arranged in a “farm.” Moreover, a farm of thermal energy accumulation vessels12according to the invention can be arranged in a much smaller footprint than a farm of solar panels, for example because a farm of thermal energy accumulation vessels12can be arranged both horizontally and vertically.

Likewise, although the invention is described above with respect to a single battery vessel14, the invention can be practiced with multiple battery vessels14. For example, in some embodiments of the invention, pairs of “out-of-phase” battery vessels are employed, such that, when one battery vessel in the pair is storing potential energy, the other is releasing it.

It should also be understood that the potential energy stored in battery vessels14need not be immediately converted to electrical energy. Indeed, it may be more desirable to store converted thermal energy as gravitational or elastic potential energy for later “on demand” release than to store the converted thermal energy as electrical energy.

As another example, sensors on battery vessel14can be used to actuate the one-way valves that allow the gas to move through power generation system10.

As still another example, although it is preferable that the same amount of gas move from thermal energy accumulation vessel12to battery vessel14to thermal energy dissipation vessel16and then back to thermal energy accumulation vessel12, the present invention is not so limited.

As yet another example, although the invention has been described in a context where the working fluid remains gaseous throughout the entire cycle, it is within the spirit and scope of the invention to allow for phase changes in the working fluid.

All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other.