WO2018037324A1

WO2018037324A1 - System using hybrid solar-fossil sources for power generation

Info

Publication number: WO2018037324A1
Application number: PCT/IB2017/055030
Authority: WO
Inventors: Shahid Khan; Divyanand GUPTA
Original assignee: Shahid Khan; Gupta Divyanand
Priority date: 2016-08-25
Filing date: 2017-08-21
Publication date: 2018-03-01

Abstract

The present disclosure relates to a combination of solar and fossil fuels for power generation by converting thermal energy into electrical energy, wherein heat transfer fluid is directed to any or combination of a heliostat solar power, a fossil and a thermal power plant to increase temperature of the received heat transfer fluid and releases heat from heated heat transfer fluid in a molten salt tank that is further feeds molten salt tank released heat to an Stirling engine based electric generator to generate electricity.

Description

SYSTEM USING HYBRID SOLAR-FOSSIL SOURCES FOR POWER GENERATION

FIELD OF THE INVENTION

[0001] The present disclosure generally relates to the field of power generation. In particular, present disclosure pertains to a method for effectively using combination of solar and fossil sources for power generation.

BACKGROUND

[0002] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Steam engines are widely used to generate electric energy by executing various energy conversions such as conversion of thermal energy from a fuel to steam, conversion of thermal energy of steam to mechanical energy in a turbine and conversion of mechanical energy to electrical energy by a rotary generator/alternator.

[0004] FIG. 1 illustrates an existing mechanism for generating electricity from heat in a commercial thermal power plant. FIG. 1 illustrates conversion of heat within a heat chamber at 102 to a superheated steam 104, wherein superheated steam 104 is provided as input to a turbine and rotary alternator 106 to convert superheated steam 104 into electricity 108.

[0005] FIG. 2 illustrates a design of an existing power tower. As illustrated in FIG. 2, a plurality of heliostats 202a, 202b... .202n upon receiving incident sunlight, focuses the received sunlight to a receiver 206 mounted on a power tower 204 to raise the temperature of heat transfer fluid (a nitrate salt) stored in the receiver 206, which thereby generates steam, which in turn can be used to produce electricity. FIG. 3 illustrates an exemplary flow path in an exemplary existing molten salt solar power plant. As illustrated, power plant includes a cold storage tank 302, a hot salt storage tank 308, a receiver 306 mounted on power tower 304, a steam generator 310, a steam turbine and electric generator 312, a substation 314, a grid 316, a condenser cooling tower 318 and a heliostat 320. The heliostat 320, upon receiving incident sunlight, focuses sunlight to a receiver 206 that raises the temperature of heat transfer fluid (nitrate salt) stored in receiver 206, and thereby, raises temperature of a liquid salt pumped from cold storage tank 302 to receiver 206 and directs a hot liquid salt of receiver 206 to hot salt storage tank 308. The hot salt from hot salt storage tank 308 is pumped to steam generator 310 to generate superheated steam for a steam turbine and electric generator 312, wherein steam turbine and electric generator 312 generates power that can be distributed to a transmission line 316 through a substation 314. The steam generator 310 then returns the salt to cold salt storage tank 302 where it is stored for its subsequent pumping to receiver 206.

[0006] Such molten salt solar plants operated with the nitrate salt with a drawback that the nitrate salt is solid at room temperature and hence, minimum temperature of about 150 °C to about 280 °C need to be maintained at all times to keep it in liquid state (both in hot salt storage tank and cold salt storage tank). In case the minimum temperature is not maintained, the nitrate salt in storage tank is converted into solid salt and pipelines will be jammed and in severe cases, the pipelines may break. Especially in winters and rainy seasons, this problem gets aggravated. In such cases, extra fuel/gas is required to convert the nitrate salt present in such a huge storage tank and pipelines into liquid phase, which is cost prohibitive. Further, it leads to considerable wastage of energy.

[0007] Further, existing plants are only operative with the solar systems. Hence, the entire system goes off in the absence of low or no solar input and this limits the success of concentrated solar power (CSP), both economically and commercially. Continuously storing solar heat energy at high temperature is quite expensive and maintenance of such system is also a complex task.

[0008] There is therefore, a need in the art to utilize a hybrid power station that uses both solar energy and fossils to convert heat into electricity so that the entire plant can run even in the absence of solar energy. Need is also felt for improved systems that can alleviate the problem of utilization of extra fuel/gas/energy to maintain nitrate salt present in both cold salt storage tank and hot salt storage tank in the liquid state.

[0009] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. [0010] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term "about." Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0011] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[0012] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0013] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION

[0014] An object of the present disclosure is to overcome one or more disadvantages associated with conventional power generation mechanisms and methods thereof.

[0015] Another object of the present disclosure is to provide a system that enables low cost heat storage.

[0016] Another object of the present disclosure is to a system that enables uninterrupted power supply.

[0017] Another object of the present disclosure is to provide a method that provides environment protection with minimal emission of harmful gases such as carbon dioxide (C0₂) and sulfur dioxide (S0₂).

[0018] Another object of the present disclosure provides a system that utilizes solar power. SUMMARY

[0019] Aaspects of the present disclosure provides a power generation system including at least one heat transfer fluid tank configured to hold a first heat transfer fluid (HTF); a molten nitrate salt tank configured to hold a nitrate salt in a molten state therewithin; and one or more Stirling engine based generators operatively coupled to said molten nitrate salt tank; wherein, the first HTF is circulated through one or more thermal energy sources to collect thermal energy therefrom and transfer said thermal energy to elevate and maintain a pre-defined temperature of said molten nitrate salt tank, and wherein said molten nitrate salt tank is further configured to extract thermal energy from the first HTF to be conveyed to said one or more Stirling engine based generators. In an implementation, the thermal energy extracted from said first HTF is conveyed to said one or more Stirling engine based generators using a second HTF. In an implementation, the first HTF and said second HTF are same. In an implementation, the first HTF and said second HTF are different. In an implementation, the first HTF is Therminol-1. In an implementation, the first HTF is Therminol-2. In an implementation, the one or more thermal energy sources are selected from a group consisting of heliostat solar field, fossil fired furnace and thermal power plant boiler.

[0020] In an implementation, any or combination of the heliostat solar power, the fossil and the thermal power plant receives heat transfer fluid at 300°C. In an implementation, the heliostat solar can be any of any or combination of a parabolic trough system, a linear Fresnel system, a parabolic dish system and a power tower. In an implementation, Stirling engine can use any or combination of Steam Rankine engine, an Organic Rankine Engine, a Stirling Engine and a Brayton Cycle Engine. In an implementation, the generator generated power is distributed to one or more transmission lines.

[0021] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF DRAWINGS

[0022] FIG. 1 illustrates an existing mechanism for generating electricity from heat in a commercial thermal power plant.

[0023] FIG. 2 illustrates an exemplary power tower in accordance with the embodiments of the present disclosure.

[0024] FIG. 3 illustrates an exemplary schematic diagram for flow paths in a molten salt solar power plant in accordance with the embodiments of the present disclosure

[0025] FIG. 4 illustrates an exemplary schematic diagram of heat storages from different medium in accordance with the embodiments of the present disclosure.

[0026] FIG. 5 illustrates exemplary schematic diagram of transfer of superheated fluid to a generator in accordance with the embodiments of the present disclosure.

[0027] FIG. 6 illustrates an exemplary cooling tower in accordance with the embodiments of the present disclosure.

[0028] FIG. 7 illustrates an exemplary block diagram of transmission of generator produced electricity to a transmission line in accordance with the embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0029] One should appreciate that the disclosed techniques provide many advantageous technical effects including, but not limited to, efficient communication between local users.

[0030] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

[0031] The present disclosure relates to the field of power generation. In particular, present disclosure pertains to a system and method for effectively using combination of solar and fossil sources for power generation.

[0032] Aaspects of the present disclosure provides a power generation system including at least one heat transfer fluid tank configured to hold a first heat transfer fluid (HTF); a molten nitrate salt tank configured to hold a nitrate salt in a molten state there within; and one or more Stirling engine based generators operatively coupled to said molten nitrate salt tank; wherein, the first HTF is circulated through one or more thermal energy sources to collect thermal energy therefrom and transfer said thermal energy to elevate and maintain a pre-defined temperature of said molten nitrate salt tank, and wherein said molten nitrate salt tank is further configured to extract thermal energy from the first HTF to be conveyed to said one or more Stirling engine based generators. In an implementation, the thermal energy extracted from said first HTF is conveyed to said one or more Stirling engine based generators using a second HTF. In an implementation, the first HTF and said second HTF are same. In an implementation, the first HTF and said second HTF are different. In an implementation, the first HTF is Therminol-1. In an implementation, the first HTF is Therminol-2. In an implementation, the one or more thermal energy sources are selected from a group consisting of heliostat solar field, fossil fired furnace and thermal power plant boiler.

[0033] In an implementation, any or combination of the heliostat solar power, the fossil and the thermal power plant receives heat transfer fluid at 300°C. In an implementation, the heliostat solar can be any of any or combination of a parabolic trough system, a linear Fresnel system, a parabolic dish system and a power tower. In an implementation, Stirling engine can use any or combination of Steam Rankine engine, an Organic Rankine Engine, a Stirling Engine and a Brayton Cycle Engine. In an implementation, the generator generated power is distributed to one or more transmission lines.

[0034] An aspect of the present disclosure provides a power generation system that utilizes a single molten nitrate salt tank configured as a cheap and energy efficient heat storage instead of implementation of separate tanks for storage of hot salt (hot salt storage tank) and cold salt (cold salt storage tank) and maintaining both of them at the required temperature. FIG. 4 illustrates an exemplary schematic diagram depicting a power generation system that utilizes a single molten nitrate salt tank 412 to collect thermal energy from a plurality of sources in accordance with an embodiment of the present disclosure. As illustrated, the power generation system includes a molten nitrate salt tank 412 configured to hold nitrate salt therein and at least one heat transfer fluid tank 404 configured to store a first heat transfer fluid (HTF) that can remain in a substantially liquid state at the temperature range of about -35 °C to about +390 °C. In a preferred implementation, the first heat transfer fluid is Therminol-1. Both the tanks can be used for exchanging heat from different sources, wherein sources can be a heliostat solar field 406 (CSP), a fossil fired furnace 408, a thermal power plant boiler 410 and the like. A pump 402 can be configured to carry the heat transfer fluid (maintained at a temperature of about 300°C) to any or combination of heliostat solar field 406 (CSP), fossil fired furnace 408 and thermal power plant boiler 410.

[0035] A first portion of the heat transfer fluid received from heat transfer fluid tank 404 can be directed to heliostat solar field 406 (CSP), a second portion of the heat transfer fluid received from heat transfer fluid tank 404 can be directed to fossil fired furnace 408 and a third portion of the heat transfer fluid received from heat transfer fluid tank 404 can be directed to thermal power plant 410 to raise the temperature of the heat transfer fluid to a predefined temperature. The heated HTF coming from heliostat solar field 406 (CSP) can be combined with the heated HTF coming out from fossil fired furnace 408 and heated HTF coming out from thermal power plant 410. The combined heated HTF from heliostat solar field 406, fossil fired furnace 408 and thermal power plant boiler 410 can be directed to molten nitrate salt tank 412, wherein molten nitrate salt tank 412 extracts heat from the combined heated HTF and can then pass the extracted heat to a second HTF. In an implementation, the first HTF and the second HTF are same. In an alternative implementation, the first HTF and the second HTF are different. Preferably, the second HTF is different than the first implementation. In an implementation, the second HTF is remain in a substantially gas state at the temperature range of about -40 °C to about +650 °C. Preferably, the second HTF is Therminol-2. The second HTF can then be fed to one or more generators. In a preferred implementation, the one or more generators are Stirling engine based generators.

[0036] In an implementation, one or more valves such as 414a, 414c and 414e can be utilized to control the speed of the HTF entering into heliostat solar field 406, fossil fired furnace 408 and thermal power plant 410 for heating. In an another implementation, one or more valves such as 414b, 414d and 414f can be utilized to control the speed of the HTF exiting from heliostat solar field 406, fossil fired furnace 408 and thermal power plant 410. In an implementation, fluid and/or heat circulation can be performed via bank of vertical, horizontal and/or inclined tubes interconnecting different components of pump, molten nitrate salt tank and different sources. In an implementation, flow of heated fluid coming out from different sources can be combined periodically. In an alternate implementation, flow of heated fluid coming out from different sources can be combined continuously. It would be appreciated that any mechanism to extract heat from the combination of heated fluids can be utilized to enable implementations of the present disclosure, and all such possible mechanisms are completely within the scope of the present disclosure.

[0037] FIG. 5 illustrates an exemplary schematic diagram of transfer of second HTF to a generator in accordance with an embodiment of the present disclosure. FIG. 5 illustrates, interconnection of a pump 502, a bypass line 504, generators 506a-506n, valves 508 a-508n, a cooling tower 510 and a rectifier 512. In an implementation, the second HTF extracted from a molten nitrate salt tank 412 can be conveyed, through one or more valves, to one or more generators 506a-506n. Generators 506a-506n processes the superheated second HTF received from molten nitrate salt tank 412 and produces electricity. In an implementation, generators can be connected in series. In an alternate implementation, generators can be arranged in any fashion as per power generation is required. The generators 506a-506n can include a cold chamber and a hot chamber connected with each other, three outlets, first being connected to a cooling tower, second connected to any or a combination of molten nitrate salt tank 412 and heat transfer fluid (HTF) tank 404 and third is connected to rectifier 512. When the superheated second HTF is received by the generators 506a-506n from molten nitrate salt tank 412, temperature of the hot chamber increases to produce electricity, wherein for smooth functioning of the generator, temperature of the cold chamber can be reduced by connecting first outlet to cooling tower 510. Preferably, the system includes a cooling fluid in communication with a cooling tower to cool the cold chamber of Stirling engine generator.

[0038] In an implementation, superheated second HTF, after absorbing heat by the hot chamber of the generators 506a-506n, can be further directed from second outlet to any or combination of molten nitrate salt tank 412 and heat transfer fluid tank 404, depending on the configuration (i.e. in case the first and second HTF are same, it is redirected to heat transfer fluid tank 404, alternatively it is redirected to molten nitrate salt tank 412 again for subsequent heating). In an implementation, third outlet is connected to rectifier 512 for further processing of produced electricity.

[0039] In an implementation, one or more valves such as 508a, 508c and 508e can be utilized to control the speed of the superheated liquid while entering into one or more generators 506a- 506n for power generation. In an another embodiment, one or more valves such as 508b, 508d and 508f can be utilized to control the speed of the flow of superheated liquid (after heat extraction by chambers) to any or combination of molten nitrate salt tank 412 and heat transfer fluid tank 404. In an implementation, fluid, heat and/or liquid circulation can be performed via bank of vertical, horizontal and inclined tubes interconnecting different components of heat temperature pump, one or more generator and valves. In an embodiment, valves 508a-508f can be motorized flow control valves. It would be appreciated that any mechanism to extract heat from the combination of superheated second HTF can be utilized to enable implementations of the present disclosure, and all such possible mechanisms are completely within the scope of the present disclosure.

[0040] FIG. 6 illustrates an exemplary cooling tower in accordance with an embodiment of the present disclosure. FIG. 6 illustrates a cold water basin 602, a pump 604, a warm water inlet 606, a drift eliminator 608 and a warm water distributor 610. Upon receiving warm water from first outlet as described in FIG. 5, pump 604 can pump received water from warm water intlet 606 to fill 608 and/or a drift eliminator 610, wherein drift eliminator 610 can control water loss from a cooling tower by restricting an amount of water droplets circulation emitted with the exhaust air of the tower. A warm water distribution head 612 can be configured to distribute warm water and a cold water basin 602 can be used to store cold water for recycle purpose. In an implementation, one or more cooling towers can be configured to generate power. In an implementation, any cooling mechanism, including but not limited to, cooling tower, and the like, as may be known to a person having ordinary skill in the art. In an embodiment, cooling tower capacity can be varied according to quantity of water to be cooled.

[0041] FIG. 7 illustrates an exemplary block diagram of transmission of generator produced electricity to a transmission line in accordance with the embodiments of the present disclosure. FIG. 7 illustrates, as generators 506a-506n produce electricity, electricity can be fed into rectifier 512 which converts received electricity from AC power to DC power and further directed to a grid tie inverter 702. Grid tie converter 702 can receive DC power from rectifier 512 and inverts it to again AC power so that it can be fed into an electric utility grid. DC power output from grid tie converter 702 can be fed into a transmission line 704 to carry electricity for long distances with minimal losses. In an embodiment, grid tie converter 720 can be fed into one or more multiple transmission lines 704 simultaneously. In an implementation, rectifier 512 can be a half wave rectifier. In an alternate implementation, rectifier can be a full wave rectifier. Although not being limited to, in one exemplary implementation, DC converted electricity/power can be fed into a power inverter, including but not limited to, grid tie inverter, and the like, as known to persons ordinary skilled in the art. In an implementation, using solar power, instead of coal as fuel can be advantageous such as: solar power is free and clean, cost per generated watt is lower, zero emission of C0₂ and S0₂ continuous uninterrupted electricity production with higher efficiency, zero costing after erection of panels or turbines and solar power tower never generates waste.

[0042] In an implementation, one or more sterling engine based generators (SEG) utilized by the proposed invention can be advantageous over steam turbine generators (STG) as: SEG can use any or combination of a solar tower, a biomass, an agricultural waste or a coal plant boiler to raise the temperature of heat transfer fluid, SEG can be more efficient as they convert hot fluid into mechanical work and then into electricity, SEG can use Carnot cycle that is higher efficient than other mechanism such as Rankine cycle, SEG can use water for cooling, SEG can work only on heat hence easy to maintain and SEG can be of medium power to weight ratio. In an implementation, various parameters such as superheated HTF quantity, superheated HTF temperature, and the like, can be utilized by generators 506a-506n to control power of a magnetic switch and consequently speed of displacer shuttling. In an implementation, the system uses a piston-less Stirling heat engine (also interchangeably referred to as generator) that incorporates a magnetic switch. The generator can be formed of an enclosed space holding a working fluid, and divided between a hot chamber to heat a working fluid and a cold chamber to cool the working fluid such that cyclic displacement of the working fluid from hot chamber to the cold chamber and back can result in cyclic expansion and contraction of the working fluid. One end of the enclosed space can incorporate a bellow that cyclically expands and contracts due to cyclic expansion and contraction of the working fluid thereby providing a reciprocating linear motion. A displacer positioned within the enclosed space can be shuttled between the hot chamber and the cold chamber by means of a magnetic switch to displace the working fluid from one chamber to the other.

[0043] As one may appreciate, system of present disclosure is not using separate steam as power generating source to generate power, for example power plants such as thermal, nuclear, and solar power tower based power plants where water consumption is heavily required. The system of present disclosure can be used in the area where water is not available as the system only needs heat to run the Stirling based engines.

[0044] As used herein, and unless the context dictates otherwise, the term "coupled to" is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. Within the context of this document terms "coupled to" and "coupled with" are also used euphemistically to mean "communicatively coupled with" over a network, where two or more devices are able to exchange data with each other over the network, possibly via one or more intermediary device.

[0045] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C ... . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.

ADVANTAGES OF THE INVENTION

[0046] The present disclosure overcomes one or more disadvantages associated with conventional power generation mechanisms and methods thereof.

[0047] The present disclosure provides a system that enables low cost heat storage.

[0048] The present disclosure provides a system that enables uninterrupted power supply.

[0049] The present disclosure provides a method that provides environment protection with minimal emission of harmful gases such as carbon dioxide (C0₂) and sulfur dioxide (S0₂).

[0050] The present disclosure provides a system that utilizes solar power.

Claims

We Claim:

1. A power generation system comprising:

at least one heat transfer fluid tank configured to hold a first heat transfer fluid (HTF);

a molten nitrate salt tank configured to hold a nitrate salt in a molten state there within; and one or more Stirling engine based generators operatively coupled to said molten nitrate salt tank;

wherein, the first HTF is circulated through one or more thermal energy sources to collect thermal energy there from and transfer said thermal energy to elevate and maintain a pre-defined temperature of said molten nitrate salt tank, and wherein said molten nitrate salt tank is further configured to extract thermal energy from the first HTF to be conveyed to said one or more Stirling engine based generators.

2. The power generation system of claim 1 , wherein the thermal energy extracted from said first HTF is conveyed to say one or more Stirling engine based generators using a second HTF.

3. The power generation system of claim 2, wherein said first HTF and said second HTF are same.

4. The power generation system of claim 2, wherein said first HTF and said second HTF are different.

5. The power generation system of claim 4, wherein said first HTF is Therminol-1.

6. The power generation system of claim 4, wherein said first HTF is Therminol-2.

7. The power generation system of claim 4, wherein said one or more thermal energy sources are selected from a group consisting of heliostat solar field, fossil fired furnace and thermal power plant boiler.