TECHNICAL FIELD

The present invention relates to power generator systems, and particularly to a geothermal energy generator system that provides maximal conversion of geothermal heat into useable power with minimal environmental impact.

BACKGROUND ART

The need for power in the form of, e.g. electricity, is ever increasing due to increasing demands. Limited natural resources and potential environmental harm limits meeting of these demands. These concerns provide the impetus for other areas of energy or power production.

One area of alternative power production deals with geothermal power plants. Most conventional geothermal plants generally employ heat from a heated medium, such as steam, hot water, CO ₂ and other gases, of an underground, geothermal reservoir, to drive power generating turbines and/or provide additional heating for residences. While effective, these geothermal power plants tend to be inefficient. For example, many geothermal plants do not fully utilize the available potential energy of the hot medium. Use of the heated medium in these power plants, is generally not utilized for any other additional work. There is still much more work that can be obtained from the exiting medium.

In light of the above, there is still a need for a more efficient geothermal power plant that can more fully utilize the available heat for power production. Thus, a geothermal energy generator system solving the aforementioned problems is desired.

DISCLOSURE OF INVENTION

The geothermal energy generator system is a closed loop, binary cycle power generating plant that utilizes heat from a geothermal heat well to convert a working medium of gas, e.g., CO ₂ , and liquid, e.g., H ₂ 0, into steam to produce energy. The geothermal energy generator system includes a medium preparation subsystem that cools recycled working medium to a predetermined temperature. The cooled working medium is selectively fed to a carbonation subsystem that permits gas to dissolve into the liquid at the predetermined temperature. The carbonated working medium flows through a heat exchange pipe section in the geothermal heat well to produce high pressure steam and gas or hot medium. The hot medium passes through a power generating subsystem containing a primary power generating assembly, a secondary power generating assembly, and a tertiary power generating assembly arranged in series to maximize usage of heat from the working medium and produce energy.

These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is schematic diagram of a geothermal energy generator system according to the present invention.

Fig. 2 is a detailed schematic diagram of a medium preparation section of the geothermal energy generator system shown in Fig. 1.

Fig. 3 is a detailed schematic diagram of a medium conversion section of the geothermal energy generator system shown in Fig. 1.

Fig. 4 is a detailed schematic diagram of one of the spherical containers in the medium conversion section shown in Fig. 3.

Fig. 5 is a sectional view of a geothermal heat well in the geothermal energy generator system shown in Fig. 1.

Fig. 6 is a detailed schematic diagram of a power generating section of the geothermal energy generator system shown in Fig. 1, as seen from the top.

Fig. 7 is a sectional view of one of the vertical columns in a secondary chamber of the power generating section shown in Fig. 6.

Fig. 8 is a detailed schematic diagram of the power generating section of the geothermal energy generator system shown in Fig. 1, as seen from the side.

Similar reference characters denote corresponding features consistently throughout the attached drawings. BEST MODES FOR CARRYING OUT THE INVENTION

The geothermal energy generator system, generally referred to by the reference number 10 in the Figures, provides efficient energy production by maximizing utilization of heat from a geothermal heat well. The geothermal energy generator system 10 includes several subsystems for preparing and circulating a medium through the geothermal energy generator system 10 and generating power or energy, such as electricity, for distribution. Unlike most conventional geothermal power plants, the geothermal energy generator system 10 does not utilize the existing hot medium in a geothermal reservoir. Instead, the geothermal energy generator system 10 uses the heat from the geothermal reservoir to heat an external working medium.

The geothermal energy generator system 10 is a type of binary cycle power plant configured in a closed loop to recycle the medium being processed for power production. As best seen in Figs. 1 and 2, the geothermal energy generator system 10 includes a medium preparation subsystem 20. The medium preparation subsystem 20 recycles the medium exiting from a power generating subsystem 50 to cool and store the medium. In an embodiment, the medium is a solution of water (H ₂ O) and carbon dioxide (CO ₂ ). This combination will flash steam at relatively low geothermal temperatures. Other gases and liquids with similar characteristics can also be used.

The medium preparation subsystem 20 includes a gas pre-cooling tank 21 and a liquid pre-cooling tank 22, in fluid communication with a corresponding gas outlet line 84 and liquid outlet line 85, respectively. The gas pre-cooling tank 21 receives and holds CO ₂ until the CO ₂ reaches ambient temperature. The liquid pre-cooling tank 22 similarly receives and holds H ₂ O that has been condensed and distilled until the H ₂ O also reaches ambient temperature. A feed gas outlet line 21a and a feed liquid outlet line 22a extends from the respective gas pre-cooling tank 21 and liquid pre-cooling tank 22 to selectively feed the contents of the tanks to a cooling bath tank 23. The selective feeding is facilitated by a pre- cooled gas feed pump 21b and a pre-cooled liquid feed pump 22b coupled to the respective feed outlet lines 21a, 22b.

The cooling bath tank 23 cools the CO ₂ and the H ₂ 0 down to a predetermined temperature prior to pumping the cold CO ₂ and H ₂ O to a carbonation subsystem 30. In an embodiment, the predetermined temperature is about 4° C. The cooling bath tank 23 contains water or water bath maintained at the predetermined temperature by a first refrigeration unit 24 coupled to the cooling bath tank 23. The cooling bath tank 23 can be insulated to preserve and maintain the temperature of the contents therein. A first refrigeration loop or coil 24a extends from the first refrigeration unit 24 into the cooling bath tank 23 to enable circulation of a refrigerant or coolant through the first refrigeration coil 24a. The circulating refrigerant cools the water and maintains the temperature at the predetermined level.

The pre-cooled CO ₂ from the gas pre-cooling tank 21 flows through a gas cooling coil 23a immersed inside the cooling bath tank 23. Similarly, the pre-cooled H ₂ O from the liquid pre-cooling tank 22 flows through a liquid cooling coil 23b immersed inside the cooling bath tank 23 (Fig. 2). Both the gas cooling coil 23a and the liquid cooling coil 23b enable cooling of the respective pre-cooled gas and liquid, e.g., CO ₂ and ¾0, down to the predetermined temperature of the cold water inside the cooling bath tank 23 through heat exchange therewith. It is noted that the ¾0 being cooled and the cold water for cooling in the bath tank 24 are separate and different sources of water. As such, the ¾0 being introduced into the cooling bath tank 23 from the liquid pre-cooling tank 22 may also be referred as a "working H ₂ O," "working water," or "working liquid," which is a component of the working medium in the geothermal energy generator system 10, unless otherwise indicated.

A cold gas outlet line 23c extends from the gas cooling coil 23a and out of the cooling bath tank 23 to connect with the carbonation subsystem 30. A cold gas supply pump 23e is coupled to the cold gas outlet line 23c to facilitate selective feeding of the cold CO ₂ to the carbonation subsystem 30.

The medium preparation subsystem 20 also includes a cold liquid outlet line 23d extending from the liquid cooling coil 23b and out of the cooling bath tank 23. A cold liquid supply pump 23 f is coupled to the cold liquid outlet line 23 d to selectively feed the cold ¾0 to a cold liquid storage tank 25. The cold liquid storage tank 25 collects and holds the cold H ₂ O until needed by the carbonation subsystem 30. Some warming of the cold ¾0 can occur during idle periods of operation. To maintain the cold temperature, a second refrigeration unit 26 can be coupled to the cold liquid storage tank 25. A second refrigeration loop or coil 26a extends from the second refrigeration unit 26 into the cold liquid storage tank 25 to enable circulation of a refrigerant or coolant through the second refrigeration coil 26a. The circulating refrigerant maintains the cold temperature of the working H ₂ 0. A working liquid outlet line 25a extends from the cold liquid storage tank 25, and the working liquid outlet line 25a is provided with a working liquid pump 25b to selectively feed the cold ¾0 from the cold liquid storage tank 25 to the carbonation subsystem 30.

As best seen in Figs. 1, 3, and 4, the carbonation subsystem 30 includes one or more spherical carbonation tanks 32, 33, 34, 35, 36 where the cold ¾0 and cold CO ₂ accumulate to enable the cold CO ₂ to dissolve into the cold ¾0 until a desired level of saturation has been reached, preferably full saturation. The resultant carbonated solution is the working medium, and the carbonated solution exhibits suitable volatility to rapidly form steam, i.e., flash steam, when exposed to high heat. Each carbonation tank 32, 33, 34, 35, 36 is preferably spherical in shape so as to provide a durable structure for withstanding and containing the internal pressure loads experienced during the carbonation process and dispensing of the working medium. It is contemplated that other shaped tanks can be used, such as elongate oblong-shaped tanks and cylindrical tanks. However, the sphere can provide a more even distribution of pressures which reduces probability of structural failure stresses over the long term.

Each carbonation tank 32, 33, 34, 35, 36 is coupled to or in fluid communication with the cold gas outlet line 23c and the working liquid outlet line 25a to enable selective feeding of the cold CO ₂ and the cold ¾0 into the respective carbonation tank 32, 33, 34, 35, 36. The carbonation subsystem 30 also includes a third refrigeration unit 31 in fluid communication with each carbonation tank 32, 33, 34, 35, 36 via a refrigeration line 31b extending from the third refrigeration unit 31 and terminating in a third refrigeration coil 31c in each carbonation tank 32, 33, 34, 35, 36. The third refrigeration unit 31 facilitates selective cooling of the respective carbonation tank 32, 33, 34, 35, 36 in their cycle of operation.

Each carbonation tank 32, 33, 34, 35, 36 undergoes a multiphase cycle in producing the carbonated working medium. In an embodiment, the operational cycle is divided into five phases, stages, or steps, and the following description is directed toward the operation of the carbonation tank 32 for brevity and clarity. It is to be understood that all the carbonation tanks 32, 33, 34, 35, 36 operate in a similar fashion, and the features specific to each has been distinguished by corresponding alphanumeric reference numbers in the Figures.

As best seen in Fig. 4, the initial or first phase of the operating cycle for the carbonation tank 32 begins with cooling of the carbonation tank 32. Various valves such as a working liquid valve 32a, a cold gas valve 32c, and a cooling valve 32b are coupled to the respective working liquid outlet line 25a, cold gas outlet line 23c, and refrigeration line 31b to regulate flow of the media contained in the lines into the carbonation tank 32. Each carbonation tank 32 also includes a working medium outlet line 38 with a working medium valve 38a to regulate outflow of the carbonated water to a geo thermal heat well 40. During this cooling phase, the cooling valve 32b is open while the cold gas valve 32c, working liquid valve 32a, and the working medium valve 38a are closed. Opening of the cooling valve 32b allows refrigerant or coolant to circulate through the third refrigeration coil 31c and cool the interior of the carbonation tank 32 down to a predetermined temperature, the predetermined temperature being preferably about 4°C.

The second phase of the cycle requires filling of the carbonation tank 32 with cold H ₂ O. The second phase begins when the carbonation tank 32 reaches the predetermined temperature. At this point, the working liquid valve 32a is opened and the working liquid pump 25b pumps the cold ¾0 into the carbonation tank 32 till full. The cooling valve 32b can remain open or closed to assist in maintaining the predetermined temperature. The working medium valve 38a remains closed during this time.

The third phase of the cycle introduces CO ₂ into the filled tank to enable carbonation. When the carbonation tank 32 has been filled with the working water, the working liquid valve 32a is closed and the cold gas valve 32c is opened. The cold gas supply pump 23e pumps cold CO ₂ into the carbonation tank 32 to dissolve the CO ₂ into the working water. The cold gas supply pump 23e continues to pump CO ₂ until the working water is fully saturated resulting in a highly carbonated solution. The cooling valve 32b can remain open or closed to assist in maintaining the predetermined temperature. Colder temperature assists in increasing, thus maximizing, the capacity of CO ₂ that can be dissolved in the water. The working medium valve 38a remains closed during this time.

The fourth phase of the cycle transfers the carbonated working medium to the geothermal heat well 40. When the working water is fully saturated with CO ₂ , the cold gas valve 32c is closed sealing the carbonation tank 32. The cooling valve 32b is also closed. The only outlet for the working medium at this point is the working medium outlet line 38. During the actual carbonation occurring in the third phase, the internal pressure of the carbonation tank 32 increases to greater than 1 atm. This pressure provides the motive force for expelling the working medium as the working medium outlet valve 38a gradually opens relieving the internal pressure and releasing the working medium through the working medium outlet line 38. When the working medium flows through the geothermal heat well 40, exposure to heat and heat exchange therein causes rapid evaporation of the H ₂ 0 and releases the CO ₂ , creating a mixture of high pressure steam and rapidly expanding volume of CO ₂ . The flow path of the working medium is confined so that the mixture of steam and CO ₂ exhausts through a main turbine 60 in the power generating subsystem 50, which will be further detailed herein. This rapid formation of steam and gas may create some back pressure. However, the confined flow path between the carbonation tank 32 and the main turbine 60 insures that such back pressure and heat can be utilized to assist in draining the contents of the carbonation tank 32. Some heating of the carbonation tank 32 can occur during this draining or transferring step. The working medium valve 38a remains open until the internal pressure of the carbonation tank 32 has normalized to about 1 atm.

The fifth phase of the cycle prepares the carbonation tank 32 for the next batch of cold H ₂ O and cold CO ₂ . Each carbonation tank 32, 33, 34, 35, 36 is provided with an air blower 37. An air cooling loop or coil 37c resides inside the respective carbonation tank 32, 33, 34, 35, 36 with an inlet end coupled to the air blower 37 and an outlet end extending outside the respective tank. The inlet end of the air cooling coil 37c includes an air inlet valve 37a, and the outlet end of the air cooling coil 37c includes an air outlet valve 37b. During this fifth phase of the cycle, the working medium valve 38a is closed when the internal pressure of the carbonation tank 32 reaches to about 1 atm. Both the air inlet valve 37a and the air outlet valve 37b are opened, and the air blower 37 is activated to blow cool outside or ambient air through the air cooling coil 37c. The circulating ambient air cools the interior of the carbonation tank 32 to ambient temperature. When ambient temperature has been reached, the air inlet valve 37a and the air outlet valve 37b are closed, the air blower 37 deactivated, and the cooling valve 32b is opened to repeat the multiphase cycle.

As noted previously, each carbonation tank 32, 33, 34, 35, 36 undergoes the same multiphase cycle. They do not, however, necessarily perform the cycle of operation at the same time. Since each carbonation tank 32, 33, 34, 35, 36 has a generally fixed capacity, it is preferable that one or more of the carbonation tanks 32, 33, 34, 35, 36 operate in a staggered pattern or out of phase with respect to each other to avoid potentially extended downtime in power production. For example, if all the carbonation tanks 32, 33, 34, 35, 36 were operating in sync and at the same phase, then there will be a lull in available working medium being fed to the power generating subsystem 50 due to empty carbonation tanks 32 requiring refill and carbonation. An asynchronous pattern of operation will ensure that a substantially continuous supply of working medium flows through the power generating subsystem 50. For example, while the carbonation tank 32 is at the first phase of the cycle, the carbonation tank 33 can be operating at the second phase of the cycle, the carbonation tank 34 can be operating at the third phase of the cycle, the carbonation tank 35 can be operating at the fourth phase of the cycle, and the carbonation tank 36 can be operating at the fifth stage of the cycle. The pattern can be varied, e.g., subsets of two, three, four tanks, etc., so long as the carbonation tanks 32, 33, 34, 35, 36 can be made to provide a substantially continuous supply of working medium.

As best seen in Fig. 5, the working medium outlet line 38 extends into the geothermal heat well 40. The geothermal heat well 40 can be a drilled, earthen hole extending into the earth to a suitable depth that provides a stable temperature range of about 150° C to 400° C. Most geothermal reservoirs contain natural steam, which is the working medium utilized by some conventional geothermal power plants. The geothermal energy generator system 10, however, only utilizes the heat from the geothermal heat well 40 to generate steam. To that end, the working medium outlet line 38 includes a heat exchange section 39 that allows heat transfer between the working medium flowing through the working medium outlet line 38 and the heat inside the geothermal heat well 40. Thus, the working medium for the geothermal energy generator system 10 is isolated from the steam that may naturally exist in the geothermal heat well 40. The geothermal heat well 40 is provided with a concrete plug 41 capping the geothermal heat well 40, which traps the heat and other contents thereof. The geothermal heat well 40 can also be provided with an auxiliary water supply line 42 extending into the geothermal heat well 40 through the plug 41 to selectively feed water into the well if the water content in the well is dry or depleted to undesirable levels. It can be seen from this configuration that the geothermal heat well 40 has negligible impact on the natural environment, and no natural resources, apart from the heat, is consumed in the process of generating energy.

The working medium outlet line 38 is in fluid communication with the main turbine 60 of the power generating subsystem 50. The working medium outlet line 38 discharges the high pressure steam and CO ₂ to the main turbine 60 and drives the same. As mentioned previously, the flow path between carbonation tanks 32, 33, 34, 35, 36 and the main turbine 60 is confined in that the only outlet for the working medium is exiting through the main turbine 60. None of the working medium is redirected, and the spherical shape of the carbonation tanks 32, 33, 34, 35, 36 is well suited to endure the fluctuations of pressure and temperature as a result of this configuration.

The power generating subsystem 50 is configured to maximize energy or power production from the available heat in the hot working medium. Instead of one means of power production, the power generating subsystem 50 includes several power-generating means arranged in series. As such, the main turbine 60 can also be referred to as a primary power generator assembly. The main turbine 60 generally produces most of the power in the geothermal energy generator system 10.

As best seen in Figs. 6-8, the power generating subsystem 50 includes a secondary power generator assembly 70 downstream of the main turbine 60. The secondary power generator assembly 70 includes a relatively large first housing or chamber 71 containing a plurality of elongate, vertical secondary power generating columns 72 (Fig. 7). Each secondary power generating column 72 has a generally hourglass shape with the top end, at the ceiling, open or exposed to outside the first chamber 71 and the bottom end closed and extending through the floor of the first chamber 71.

Each secondary power generating column 72 houses a rotating common drive shaft 73 axially mounted inside the corresponding secondary power generating column 72. From the bottom as shown in the side view of Fig. 7, each secondary power generating column 72 includes a generator 74 coaxially mounted to the common drive shaft 73, a compressor 75 disposed above the generator on the common drive shaft 73, a diffuser 76 rotatably mounted to the common drive shaft 73 above the compressor 75, and a secondary turbine 77 mounted to the common drive shaft 77 near the top of the secondary power generating column 72.

Each secondary power generating column 72 generates additional power by employing the residual heat from the working medium exiting the main turbine 60 to heat and agitate air flowing through column 72. The exiting working medium from the main turbine 60 still contains an abundance of residual heat, which in most conventional systems, would be wasted or diverted to heat residential areas. In the geothermal energy generator system 10, the residual heat and the abundant potential energy thereof is exploited to obtain more work.

The generator 74, the compressor 75, and the diffuser 76 sections of the secondary power generating column 72 is preferably disposed underground or beneath the first chamber 71 so as to isolate these sections from heat exposure. Moreover, this area is cooler than an interior of the first chamber 71. The compressor 75 includes a plurality of rotating and/or fixed fans 75a mounted to a taper-ended section 75b of the common drive shaft 73. The compressor 75 draws relative cool air from the surroundings, i.e. cooler zone, or from a separate source and forces the air to flow around the taper-ended section 75b to compact and pressurize the air. This imparts increased airflow velocity to the air exiting the compressor 75.

The diffuser 76 circulates the air around a generally lower conical section 73b of the common drive shaft 73 to permit the air to flow upward towards the secondary turbine 77. The portion of the secondary power generating column 72 that extends between the floor and the ceiling of the first chamber 71 is exposed to heat from the working medium passing through the first chamber 71. Heat transfer between the relatively hot working medium and the air inside the secondary power generating column 72 heats the inside air. The heat expands the air which imparts increased convection current thereto forcing the air to rise towards and through the secondary turbine 77 and to drive the secondary turbine 77. Since all of the components are mounted to the common drive shaft 73, rotation of the secondary turbine 77 also rotates the diffuser 76, the compressor 75, and drives the generator 74 to produce additional power or energy.

It is to be noted that the arrangement of the plurality of secondary power generating columns 72 is not limited to the regular rows shown in the Figures. The arrangement of the secondary power generating columns 72 can vary such as irregular rows, staggered rows, non-uniform patterns, and the like to maximize heat exposure from the hot working medium flowing through the first chamber 71.

As best seen in Figs. 6 and 8, the power generating subsystem 50 also includes a tertiary power generator assembly 80 downstream of the secondary power generator assembly 70. The tertiary power generator assembly 80 includes a relatively large second housing or chamber 81 containing a plurality of elongate, vertical tertiary power generating columns 82. The second chamber 81 is preferably larger than the first chamber 71 mainly due to the relatively large tertiary power generating columns 82 and larger volume of air being processed thereby.

Each tertiary power generating column 82 extends between the floor and ceiling of the second chamber 81 with opposite open ends exposed to an area outside of the chamber 81. A wind turbine 83 is mounted to the top or top end of each tertiary power generating column 82. In use, the open bottom end permits ambient air to flow upward through the corresponding tertiary power generating column 82, while the working medium from the first chamber 71 flows around the tertiary power generating columns 82 to heat the air inside the second chamber 81. The heating of the inside air induces convection, and the resultant increased velocity and airflow drives the corresponding wind turbine 83 to produce additional power or energy as the air flows through the open upper end of each tertiary power generating column 82.

Each tertiary power generating column 82 is preferably tapered or frustoconical in shape to maximize airflow through each tertiary power generating column 82. The relatively larger base and the relatively narrower top funnel the air flowing from the bottom, which produces a relatively higher exit velocity of the air and, thereby, maximizes rotation of the wind turbine 83. It is also contemplated that tertiary power generating columns 82 can be constructed as straight cylinders. However, the subsequent exit velocity of the air may be less than that which can be achieved with a tapered shape. As with the secondary power generating columns 72, the tertiary power generating columns 82 can be arranged in any desired manner apart from that shown in the Figures.

After the working medium flows around the tertiary power generating columns

82 and accumulates in the second chamber 81, the CO ₂ and the H ₂ O components in the working medium pass through condensers (not shown) to be recycled back to the medium preparation subsystem 20. The second chamber 81 includes the gas outlet line 84 and the liquid outlet line 85 to pass the respective CO ₂ and ¾0 back to the gas pre-cooling tank 21 and the liquid pre-cooling tank 22 to repeat the operational closed loop circuit of the working medium. A gas feed pump 84a and a liquid feed pump 85a can be coupled to the respective lines 84, 85 to facilitate positive feeding of the components to the tanks 21, 22.

The secondary power generating columns 72 take full advantage of the available heat from the working medium exiting the main turbine 60. As the working medium flows from the working medium outlet line 38 through each power generating means, there will be heat loss and cooling of the working medium at each stage of power production, with maximum available heat at the main turbine 60 and relatively minimal available heat at the second chamber 81. However, with respect to the auxiliary power generation provided by the secondary power generator assembly 70 and the tertiary power generator assembly 80, the relatively hotter working medium in the first chamber 71 provides suitable heat energy and heat transfer to the air inside the secondary power generating columns 72 to move the internal components therein.

As a relatively larger volume of air moves inside each tertiary power generating column 82, there is not as much heat required to induce movement therein. Moreover, the wind turbines 83 do not require much wind velocity to move the blades, since most wind turbines are very efficient with respect to required wind velocities for operation.

Thus, it can be seen that the geothermal energy generator system 10 extracts as much work out of the hot working medium as possible to generate power. Depending on the available heat, some may be siphoned and distributed to heat residences. Since the geothermal energy generator system 10 only utilizes the heat from the geothermal heat well 40, this minimizes any concerns of depleting natural working medium from most conventional geothermal reservoirs over long term operation. Moreover, the closed loop and binary cycle type of operation allows for usage of relatively moderate range of geothermal heat. This eliminates some of the substantial economic investment necessary for drilling very deep into the earth. The working medium is recycled which also reduces resource costs and impact on the environment.

It is to be understood that the geothermal energy generator system 10 encompasses a variety of alternatives. For example, the operation of the various pumps and valves can be performed manually and/or automatically. The various tanks mentioned can be insulated to maintain cool temperatures. The secondary power generating columns 72 and the tertiary power generating columns 82 are preferably constructed from thermally conductive materials such as concrete, metals, composites and the like to maximize heat transfer between the working medium and the air. Moreover, the working medium can be replenished from an outside source or from a geothermal reservoir.

It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.