Patent Publication Number: US-2022228276-A1

Title: Fuel cell energy circulative utilization system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuel cell energy circulative utilization system, and in particular to a system applicable to a combination of an SOFC (solid oxide fuel cell) cell and an SOEC (solid oxide electrolysis cell) cell and including at least one energy circulation and switch system to switch the SOEC cell to supply at least one for example energy product of hydrogen for feeding back to the SOFC cell for use as energy input. 
     2. The Related Arts 
     Green energy is the focus of the century in respect of electricity generation or energy reuse. Particularly, all the countries around the world have been fully devoted themselves to the development of green energy policy and also due to the influence of waking of environmental protection in respect of the urgent need for improving air pollution, electric vehicles, such as electric motorcycles and electric cars that are of the greatest numbers, have been gradually increased in respect of the number thereof year by year. Thus, circulative utilization of the green energy is apparently of vital importance. This is because, in addition to the household electricity consumption, there is also a need for generation and supply of electricity for charging the electric vehicles or energy storage. However, if this results in insufficiency of electricity supply and a vicious cycle begins due to reliance on fossil fuel power generation that causes high pollution or natural gas power generation, the effectiveness and expectation of green energy would deteriorate. 
     The most commonly used ways of green energy electricity generation include nuclear energy, hydraulic energy, wind energy, solar energy, geothermal energy, or tidal energy. Taking nuclear energy as an example, although the capacity of electricity generation is relatively great and no requirement for frequent supply of energy, the nuclear wastes produced by the nuclear electricity generation plants would cause expensive costs for storage of such wastes and the used equipment and facility after the unclear electricity generation plants are shut down. Further, nuclear pollution issues, such as Fukushima Daiichi nuclear disaster of Japan, are extremely hard to handle. As such, nuclear energy is still of a great concern in respect of safety, and is virtually impossible for development and use in certain green and anti-nuclear area. This limits the industrial use of nuclear energy. 
     Concerning other green energy electricity generation, such as hydraulic energy, wind energy, solar energy, geothermal energy, and tidal energy, they are subject to severe limitations in respect of geographic locations, weather, temperature, seasons, or sea bed terrains, and are not easy to install. Thus, such green energy electricity generation modes of hydraulic energy, wind energy, solar energy, geothermal energy, and tidal energy provide electricity generation capacity that is very limited, and can only serve as an auxiliary system of electricity generation, and cannot be used as a primary system of electricity generation. Thus, the major electricity generation systems that are currently used are limited to thermal power generation or nuclear power generation, which are of high environmental pollution or high risk to health. Further, such green energy electricity generation modes of hydraulic energy, wind energy, solar energy, geothermal energy, and tidal energy provide only one single function of electrical energy output and does not have a synergic effect involving production of other types of energy products and circulative utilization of energy. Further, such green energy electricity generation modes of hydraulic energy, wind energy, solar energy, geothermal energy, and tidal energy require a great cost for maintenance. For example, a dam that is used for hydraulic electricity generation may quickly get sedimentation and thus shortening the service life thereof; the high-rise wind electricity generation facility is hard to maintain; the solar panels require constant and frequent cleaning to ensure an expected power conversion rate; the geothermal electricity generation facility has to severely control instantaneously jetting of a large amount of geothermal energy; and the tidal power generation facility virtually lasts long for service. These are all factors that limit the development and use of the green energy electricity generation modes. 
     Further, concerning the new generation of known solid oxide fuel cell (SOFC) serving as a primary electricity generation system, it requires constant supply of a large amount of hydrocarbon or hydrogen resources, such as natural gas, into the SOFC to maintain uninterrupted generation of electricity in the SOFC. Electricity generation based on SOFC is such that even in a time interval of off-peak hours requiring just a low load capacity, cutting off the supply of hydrocarbon or hydrogen source does not result in an immediate reduction of performance of the SOFC, and instead, electricity generation will maintain until the chemical reaction that generates electricity in the SOFC gradually slows down. This would lead to a great waste of electricity generated thereby. Further, if such an extra amount of electricity has to be stored, additional facility must be built up for storage of electricity. This requires additional costs of installation and human labor. If consideration is made in respect of cutting off the supply of hydrocarbon or hydrogen source in advance before the off-peak hours for the purposes of avoiding such an extra amount of electricity so generated, there would be an issue of insufficient supply of electricity if incorrect calculation of the timing of cutting off the supply of the hydrocarbon or hydrogen source into the SOFC is made due to the loading resulting from user end power consumption being variable day after day, and this would cause an embarrassing situation of blackout in a local region or even in the whole area. This deteriorates the utilization performance and practical value of SOFC based electricity generation, and leads to lacking of economic value of industrial use. This is an issue that has to be handled in respect of electricity generation based on solid oxide fuel cells. 
     Further, patent documents in the related field are known, such as Japan laid open patent No. 2018-174115, which discloses an electrochemical component, electrochemical module, an electrochemical device, an energy system, a solid oxide fuel cell, and a method for manufacturing an electrochemical component, in which a solid oxide fuel cell structure of which the electrochemical mechanism is complicated and the cost is high is disclosed for improving the electrochemical performance. However, the solution of the document still suffers the same issue and problem as that of the prior art fuel cell that the timing of cutting off the supply of energy is hard to control. Such a Japan patent document teaches, in paragraph [0031], based on the characterizing features discussed above, due to the inclusion of an electrochemical device and a discharged heat utilization portion for reusing the heat discharged from the electrochemical device, it is possible to provide an energy system that realizes durability/reliability and excellent performance and also achieves excellent energy efficiency, and further, a combination with an electricity generation system that generates electricity by using combustion heat of unused fuel gas discharged from the electrochemical device, a hybrid system that has excellent energy efficiency can be formed. It also teaches, in paragraph [0098], in place of the discharged heat utilization portion, a reaction waste gas utilization portion can be arranged to use a reaction waste gas discharged *without burning) from the electrochemical module M, and the reaction waste gas contains residual hydrogen that has not been used in reaction in the electrochemical component E, and the reaction waste utilization portion uses the residual hydrogen to achieve effective utilization of energy according to use of the burning heat or according to electricity generation of fuel cell. Based on such disclosure, the Japan patent document provides circulative utilization of fuel gas, such as residual hydrogen from reaction inside the SOFC; however, the effectiveness of circulative utilization of the entire resources is not good at all. Further, using a non-traditional, special fuel cell having a complicated structure and expensive cost to trade for circulative utilization of the residual fuel gas of hydrogen of a small amount and low circulative utilization efficiency is not of economic value for industrial use, and would oppositely causes a concern in respect of such a redundant structure occupying valuable space of the fuel cell, this being of no value at all. 
     Further, Japan patent No. 5738983 provides a method for operating a high-temperature fuel cell stack, in which a method for protecting an anode of a high-temperature SOFC or molten carbonate fuel cell (MCFC) included in an electricity generation system from oxidization by applying an external voltage to the fuel cell is provided, for the purpose of keeping the electromotive force of the fuel cell in a safe range. Similarly, in addition to the issues and problems of the known solid oxide fuel cell in respect of resources waste for electricity generation and unexpected blackout resulting from timing of cutting off supply of hydrocarbon or hydrogen source being hard to handle, such a fuel cell needs application of an external voltage to offer protection to the fuel cell, this requiring consumption of additional energy, so that in addition to being incapable of fully exploiting the energy of the fuel cell in the entirety thereof, extra electricity resources and cost must be consumed, and this makes it not of value for industrial use. 
     PCT Patent No. WO2016000957 A1 discloses an efficient AC-DC electrical power converting unit configuration, in which a stack of the same type solid oxide electrolysis cells or a stack of the same type fuel cells is simply used to make AC-DC or DC-DC conversion and output for extra electricity. The PCT document still suffers the problems and drawbacks of the known solid oxide fuel cell or solid oxide electrolysis cell that it is necessary to make conversion and conveyance of electricity to other DC loading or energy storage, in case of extra electricity produced. Further, the conversion process of DC-DC or AC-DC conversion adopted in the PCT document needs additional installation cost, making it not economic. Further, the DC-DC or AC-DC conversion process also causes additional loss of energy, making the entire energy utilization poor. Further, utilization of energy achieved with the SOEC stack or the stack of the same type fuel cell according to the PCT document is generally limited to use of extra electrical energy, and this constrains the value and scope of industrial use thereof. 
     In addition, Taiwan Patent No. 1559610 that provides a solid oxide electrolysis fuel cell test device, Taiwan Patent No. 1708955 that provides a solid oxide electrolysis fuel cell test device and a hydrogen generation device, U.S. Pat. No. 10,494,728 that provides a process for producing CO from CO2 in a solid oxide electrolysis cell, and Japan patent No. 2019-507718 that provides a method for optimized generation of carbon monoxide based on SOCE, all relate to methods for generation of resources of hydrogen, carbon dioxide, and carbon monoxide by using solid oxide electrolysis cell. The solutions of such patent documents require additional supply of electrical energy for conversion and generation of resources, such as hydrogen, carbon dioxide, and carbon monoxide. Such resources are used to fill into hydrogen storage canisters, carbon dioxide storage canisters, and carbon monoxide storage canisters and are generally one-way resources generation of hydrogen, carbon dioxide, and carbon monoxide, making it not possible to fully exploit all resources provided in SOECs, thereby limiting the industrial use and application of the SOCEs in only a narrow scope of resources generation. This does not suit the need of economic value of industrial use. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide a fuel cell energy circulative utilization system, which helps eliminate the problems and drawbacks of the prior art technology and those of the patent documents discussed above that the known solid oxide fuel cells might cause waste of resources or potential issue of unexpected power failure due to being incapable of effective control in respect of timing for cutting off input sources of hydrocarbon or hydrogen resources at off-peak hours of power generation, and also helps to eliminate the problems and drawbacks of the above patent documents that the known solid oxide electrolysis cells may generate single type of resources of for example hydrogen, carbon monoxide, and carbon dioxide, but do not enable such single type of resources of resources that are produced as unidirectional resources generation to be used in wide applications in the industry. 
     As such, the present invention provides a fuel cell energy circulative utilization system, which comprises: 
     at least one input energy, which is an energy source containing hydrocarbons or hydrogen; 
     at least one first electric cell, the first electric cell comprising at least one energy input terminal, an electricity output terminal, and at least one energy output terminal, the energy input terminal being connected with the input energy, so as to have the electricity output terminal generating and outputting electricity and to have the energy output terminal generating and outputting thermal energy and water; 
     at least one second electric cell, the second electric cell comprising at least one electricity input terminal, an energy input terminal, and an energy output terminal, the electricity input terminal and the energy input terminal being respectively connected with the electricity output terminal and the energy output terminal of the first electric cell to respectively input the electricity and the thermal energy and water output from the first electric cell so as to have the energy output terminal of the second electric cell output at least a hydrogen source; and 
     at least one energy circulation control device, the energy circulation control device being connected among the energy input terminal, the electricity output terminal, and the energy output terminal of the first electric cell and the electricity input terminal, the energy input terminal, and the energy output terminal of the second electric cell, in order to manipulate and control the hydrogen source output from the energy output terminal of the second electric cell for feeding back to the energy input terminal of the first electric cell, the energy circulation control device being operable for controlling and switching the first electric cell and the second electric cell between working modes as a solid oxide electrolysis cell (SOEC) or a solid oxide fuel cell (SOFC). 
     Further, in the above fuel cell energy circulative utilization system according to the present invention, the input energy the input energy is formed of a natural gas source. 
     In the above fuel cell energy circulative utilization system according to the present invention, the input energy is formed of a biogas source. 
     In the above fuel cell energy circulative utilization system according to the present invention, the input energy is formed of a blue hydrogen source. 
     In the above fuel cell energy circulative utilization system according to the present invention, the input energy is formed of a green hydrogen source. 
     In the above fuel cell energy circulative utilization system according to the present invention, the input energy comprises a source containing hydrocarbons and is connected with at least one reformer, the reformer comprising a first output terminal and a second output terminal, wherein the reformer is operable to separate the input energy that contains hydrocarbons into hydrogen and carbon dioxide to be respectively output through the first output terminal and the second output terminal, the first output terminal of the reformer being connected with at least one input control valve, the input control valve having an end connected with one end of the energy circulation control device connected with the energy input terminal of the first electric cell to control the hydrogen output from the first output terminal of the reformer to flow through the energy circulation control device and the energy input terminal of the first electric cell to input into the first electric cell or not, one energy output terminal of the first electric cell outputting carbon dioxide, the second output terminal of the reformer being connected with the energy output terminal of the first electric cell that outputs carbon dioxide to jointly output carbon dioxide. 
     In the above fuel cell energy circulative utilization system according to the present invention, the first electric cell is formed of a SOFC, and the first electric cell is operable in the SOFC working mode. 
     In the above fuel cell energy circulative utilization system according to the present invention, the electricity output terminal of the first electric cell is connected with at least one microgrid. 
     In the above fuel cell energy circulative utilization system according to the present invention, the energy output terminal of the first electric cell outputs carbon dioxide. 
     In the above fuel cell energy circulative utilization system according to the present invention, each energy output terminal of the first electric cell is connected with at least one greenhouse to supply sources of water and carbon dioxide output through the energy output terminal into the greenhouse to be used therein. 
     In the above fuel cell energy circulative utilization system according to the present invention, the second electric cell is formed of a SOFC and the second electric cell is operable in the SOEC working mode. 
     In the above fuel cell energy circulative utilization system according to the present invention, the electricity input terminal of the second electric cell is connected with at least one commercial electricity source. 
     In the above fuel cell energy circulative utilization system according to the present invention, the electricity input terminal of the second electric cell is connected with at least one renewable energy source. 
     In the above fuel cell energy circulative utilization system according to the present invention, the renewable energy source with which the electricity input terminal of the second electric cell is connected is formed of at least one of solar panel generated electricity source, wind power generation electricity source, hydraulic power generation electricity source, geothermal power generation electricity source, and tidal power generation electricity source. 
     In the above fuel cell energy circulative utilization system according to the present invention, the energy input terminal of the second electric cell is connected with at least one water storage tank, and the water storage tank is provided with a control valve to control supply of water to the energy input terminal. 
     In the above fuel cell energy circulative utilization system according to the present invention, one energy output terminal of the second electric cell outputs oxygen, and the energy output terminal is connected with at least one greenhouse to supply the oxygen source output from the energy output terminal to the greenhouse to be used therein. 
     In the above fuel cell energy circulative utilization system according to the present invention, the energy circulation control device comprises: 
     at least one first flow direction controller and second flow direction controller, the first flow direction controller and the second flow direction controller being arranged pairwise and connected in parallel between the energy input terminal and the energy output terminal of the first electric cell and the energy input terminal and the energy output terminal of the second electric cell, the first flow direction controller and the second flow direction controller being operable to control flow directions in opposite directions so as to control flow directions at the energy input terminal and the energy output terminal of the first electric cell and the energy input terminal and the energy output terminal of the second electric cell for inputting or outputting; 
     at least one electricity direction control unit, which is connected between the electricity output terminal of the first electric cell and the electricity input terminal of the second electric cell, in order to control a flow direction of electricity to be a flow direction of electricity (electrical current) between the electricity output terminal of the first electric cell and the electricity input terminal of the second electric cell; and 
     at least one central control unit, which is electrically connected with the first flow direction controller, the second flow direction controller, and the electricity direction control unit, in order to control flow directions of energy of the first flow direction controller, the second flow direction controller, and the electricity direction control unit for inputting or outputting and a flow direction of electricity, so as to individually control and switch the first electric cell and the second electric cell to the SOEC or SOFC working mode. 
     In the above fuel cell energy circulative utilization system according to the present invention, the first flow direction controller of the energy circulation control device comprises at least one first electromagnetic valve and a first non-return valve connected in series. 
     In the above fuel cell energy circulative utilization system according to the present invention, the second flow direction controller of the energy circulation control device comprises at least one second electromagnetic valve and a second non-return valve connected in series. 
     In the above fuel cell energy circulative utilization system according to the present invention, at least one pairwise arranged and parallel connected first flow direction controller and second flow direction controller of the energy circulation control device that is connected with the energy output terminal of the second electric cell that outputs hydrogen has an end connected to at least one high-pressure hydrogen storage tank. 
     In the above fuel cell energy circulative utilization system according to the present invention, the high-pressure hydrogen storage tank to which the end of at least one pairwise arranged and parallel connected first flow direction controller and second flow direction controller of the energy circulation control device that is connected with the energy output terminal of the second electric cell that outputs hydrogen is connected is provided with at least one anti-explosion electromagnetic valve. 
     In the above fuel cell energy circulative utilization system according to the present invention, the pairwise arranged and parallel connected first flow direction controller and second flow direction controller of the energy circulation control device have logics of opening/closing that are opposite to each other so as to be similar to an exclusive-OR gate (XOR gate) of electronics. 
     In the above fuel cell energy circulative utilization system according to the present invention, the central control unit of the energy circulation control device is connected with at least one communication interface, and the communication interface is connected by means of at least one interconnected network to a remote control center, so as to allow the remote control center to perform remote monitoring and issuing a control instruction. 
     In the above fuel cell energy circulative utilization system according to the present invention, the communication interface to which the central control unit of the energy circulation control device is connected is formed of a wired/wireless communication interface. 
     The efficacy of the fuel cell energy circulative utilization system according to the present invention is that connection is made among the first electric cell, the second electric cell, and the energy circulation control device, and the energy circulation control device is operable to control electricity flow directions and energy input or output flow direction at the energy input terminal, the electricity output terminal, and the energy output terminal of the first electric cell and the electricity input terminal, the energy input terminal, and the energy output terminal of the second electric cell, so as to set the first electric cell and the second electric cell to a configuration in which one of the two is set as a solid oxide fuel cell, while the other one is set as a solid oxide electrolysis cell, whereby during the course of generating and supplying electricity for the solid oxide fuel cell, in case of off peak hours or occurrence of requirement for load lowering in respect of regulation of electricity, an extra amount of electricity and thermal energy resulting from loading lowering can be fed to the solid oxide electrolysis cell to have the second electric cell that is set as a solid oxide electrolysis cell outputting multiple types of resources or energies, such as hydrogen and oxygen, through the energy output terminal thereof. Further, such resources of hydrogen may be fed back to the first electric cell that is set as a solid oxide fuel cell through the energy input terminal thereof, or may alternatively be stored for subsequent use, so as to greatly reduce the supply amount of the input energy to which the energy input terminal of the first electric cell is connected. Further, the hydrogen that is fed back to the first electric cell to be used thereby is a type of green hydrogen, so as to achieve a further effect of energy saving and carbon reduction and enhancing the operation performance of the solid oxide fuel cell. Further, the first electric cell and the second electric cell can be controlled by a remote control center operable to control the energy circulation control device for adjusting and switching the first electric cell or the second electric cell in respect of the quantity thereof to be set as solid oxide electrolysis cells, or for adjusting and switching the first electric cell or the second electric cell in respect of quantity thereof as being set as the solid oxide electrolysis cell according to cost variation and value of electricity and hydrogen resources in the energy market, so as to effectively and flexibly regulate the generation, storage, and sales of electricity and hydrogen resources to thereby enhance the economic effect of industrial use and applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a fuel cell energy circulative utilization system according to a first embodiment of the present invention; 
         FIG. 2  is a diagram illustrating a first flow direction controller and a second flow direction controller of an energy circulation control device of the fuel cell energy circulative utilization system according to the present invention; 
         FIG. 3  is circuit block diagram of the energy circulation control device of the fuel cell energy circulative utilization system according to the present invention; 
         FIG. 4  is a diagram illustrating a fuel cell energy circulative utilization system according to a second embodiment of the present invention; 
         FIG. 5  is a diagram illustrating a fuel cell energy circulative utilization system according to a third embodiment of the present invention; 
         FIG. 6  is circuit block diagram of an energy circulation control device of the third embodiment shown in  FIG. 5 ; and 
         FIG. 7  is a diagram illustrating a preferred example of application of the fuel cell energy circulative utilization system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring first to what depicted in  FIG. 1 , a first embodiment of a fuel cell energy circulative utilization system  100  is provided according to the present invention, in which the fuel cell energy circulative utilization system  100  comprises at least one source of input energy  10 , which can be formed of an energy source containing hydrocarbon or hydrogen, such as a natural gas source, a biogas source, blue hydrogen, or green hydrogen, and in the first embodiment of the present invention, a hydrocarbon based natural gas source is taken as an example for illustration. 
     At least one first electric cell  20  is in the form of a solid oxide fuel cell (SOFC), but is not limited to any specific type. In the present invention, a solid oxide fuel cell power generation system from the BlueGen series of SolidPower company of Italy, BLOOM ENERGY company of USA, BOSCH company of Germany, or AVL company of Austria, is taken as example for illustration. Further, the first electric cell comprises at least one energy input terminal  21 , an electricity output terminal  22 , and at least one energy output terminal  23 ,  24 , and  25 , with the energy input terminal  21  being connected with the input energy  10 , so that the electricity output terminal  22  may output generated electricity  221  and the energy output terminals  23 ,  24 , and  25  respectively generate outputs of thermal energy  231 , water  241 , and carbon dioxide  251 , and the electricity output terminal  22  is connected with at least one microgrid  200  to supply the electricity  221  to the microgrid  200 . 
     At least one second electric cell  30  is not limited to any specific type, and in the first embodiment of the present invention, a solid oxide fuel cell power generation system from the BlueGen series of SolidPower company of Italy, BLOOM ENERGY company of USA, BOSCH company of Germany, or AVL company of Austria, is taken as example for illustration, and the second electric cell  30  is operable in the form of a solid oxide electrolysis cell (SOEC). The second electric cell  30  comprises at least one electricity input terminal  31 , energy input terminals  32 ,  32 ′, and energy output terminals  33 ,  34 , wherein the electricity input terminal  31  and the energy input terminal  32 ,  32 ′ are respectively connected with the electricity output terminal  22  and the energy output terminals  23 ,  24  of the first electric cell  20  to respectively input the electricity  221 , the thermal energy  231 , and the water  241  output from the first electric cell  20 , so as to have the energy output terminals  33 ,  34  of the second electric cell  30  output hydrogen  331  and oxygen  341  and the hydrogen  331  output from the energy output terminal  33  is fed back to and connected to the energy input terminal  21  of the first electric cell  20 , so that the energy input terminal  21  of the first electric cell  20  may receive the hydrogen  331  output from the energy output terminal  33  of the second electric cell  30  as resources feedback and for circulative utilization to thereby reduce the ratio of hydrogen input and loading capacity of the input energy  10 . 
     Further referring to what depicted in  FIGS. 2 and 3 , at least one energy circulation control device  40  is not limited to any specific type and an arrangement including at least one first flow direction controller  41 , a second flow direction controller  42 , at least one electricity direction control unit  43 , and at least one central control unit  44  is taken as an example for illustration, wherein the first flow direction controller  41  and the second flow direction controller  42  are arranged in a pairwise configuration as being connected in parallel between the energy input terminal  21  and the energy output terminal  23  of the first electric cell  20  and the energy input terminal  32  and the energy output terminal  33  of the second electric cell, and further, the first flow direction controller  41  and the second flow direction controller  42  are arranged to control flow in directions that are opposite directions, and the first flow direction controller  41  and the second flow direction controller  42  that are pairwise arranged and parallel connected have opening and closing logics that are opposite, namely being similar to an exclusive OR gate, so that one is open while the other is closed. 
     The above-described first flow direction controller  41  is not limited to any specific type, and in the present invention, an arrangement including at least one first electromagnetic valve  411  and a first non-return valve  412  that are connected in series is taken as an example for illustration, and also, the above-described second flow direction controller  42  is not limited to any specific type, and in the present invention, an arrangement including at least one second electromagnetic valve  421  and a second non-return valve  422  that are connected in series is taken as an example for illustration. The first electromagnetic valve  411 , the first non-return valve  412 , the second electromagnetic valve  421 , and the second non-return valve  422  are all formed of anti-explosion valve devices. 
     The electricity direction control unit  43  is connected between the electricity output terminal  22  of the first electric cell  20  and the electricity input terminal  31  of the second electric cell  30 , so that a flow direction of electricity is controlled to be an electricity (current) flowing direction between the electricity output terminal  22  of the first electric cell  20  and the electricity input terminal  31  of the second electric cell  30 . 
     The central control unit  44  is electrically connected with the first electromagnetic valve  411  of the first flow direction controller  41 , the second electromagnetic valve  421  of the second flow direction controller  42 , and the electricity direction control unit  43  to individually control the first flow direction controller  41 , the second flow direction controller  42 , and the electricity direction control unit  43  in respect of flow directions of energy input and output and flow direction of electricity, so as to switch and control the first electric cell  20  and the second electric cell  30  to inter-switch the working mode of a solid oxide electrolysis cell or a solid oxide fuel cell working state. For example, through control by the central control unit  44 , the second electric cell  30 , which was originally operating in a SOEC working mode, is so changed that the electricity flow direction of the electricity direction control unit  43  that is connected with the electricity input terminal  31  is changed from an input electricity (current) flow direction to an output electricity flow direction, and also, for those connected with the energy input terminal  32 , the first flow direction controller  41  that was originally in an open state is closed and the second flow direction controller  42  that was originally in a closed state is opened so as to switch to a flow direction for output; and for those connected with the energy output terminal  33 , the second flow direction controller  42  that was originally in an open state is closed and the first flow direction controller  41  that was originally in a closed state is opened so as to switch to a flow direction for input, and consequently, the hydrogen energy source of the input energy  10  can be supplied, in an opposite direction, to the energy output terminal  33  of the second electric cell  30 , so that the second electric cell  30  is switched to a SOFC working mode as that for the first electric cell  20 , and thus, the electricity input terminal  31  is switched to outputting electricity for electricity generated thereby for being connected in parallel with the electricity output terminal  22  of the first electric cell  20  to output electricity  221  to the microgrid  200 . Similarly, the first electric cell  20  is also controllable and operable by the central control unit  44  for flowing in opposite directions and electricity flow direction set for the first flow direction controller  41 , the second flow direction controller  42 , and the electricity direction control unit  43 , for switchability to a SOEC working mode, details concerning switchability and timing of working mode switch being provided in details hereinafter. 
     Further referring to what depicted in  FIG. 4 , a second embodiment of the fuel cell energy circulative utilization system  100  according to the present invention is provided, wherein the input energy  10  is shown in the form of an energy source containing hydrocarbons, such as natural gas or biogas, and the input energy  10  is connected with at least one reformer  11 . The reformer  11  is provided with a first output terminal  11 A and a second output terminal  11 B, so that the reformer  11  is operable to separate the input energy  10  that contains hydrocarbons, such as natural gas or biogas, into hydrogen  331  and carbon dioxide  251  to be respectively output from the first output terminal  11 A and the second output terminal  11 B. The first output terminal  11 A of the reformer  11  is connected with at least one input control valve  111 , wherein one end of the input control valve  111  is connected with an end of the parallel connected first flow direction controller  41  and second flow direction controller  42  that is connected with the energy input terminal  21  of the first electric cell  20 , in order to control whether or not the hydrogen  331  of the first output terminal  11 A of the reformer  11  flows through the first flow direction controller  41  and the energy input terminal  21  to feed into the first electric cell  10 , and further, the second output terminal  11 B of the reformer  11  is connected with the energy output terminal  25  of the first electric cell  20  to jointly output carbon dioxide  251 , and further, the energy output terminals  23 ,  24 , and  25  of the first electric cell  20  and the energy output terminal  34  of the second electric cell  30  are connected with at least one greenhouse  300 , for the purposes of supplying and using the multiple energy sources of thermal energy  23 , water  241 , carbon dioxide  251 , and oxygen  341  output from the energy output terminal  23 ,  24  and  25 , the second output terminal  11 B of the reformer  11 , and the energy output terminal  34  of the second electric cell  30  to and in the greenhouse  300 . Further, at least one pairwise arranged and parallel connected combination of first flow direction controller  41  and second flow direction controller  42  of the energy circulation control device  40  that is connected with the energy output terminal  33  of the second electric cell  30  that outputs hydrogen  331  has one end connected with at least one high-pressure hydrogen storage tank  400 . The high-pressure hydrogen storage tank  400  is provided with at least one anti-explosion electromagnetic valve  410  in order to control output of hydrogen  331  preserved therein. The anti-explosion electromagnetic valve  410  is similarly connected to and controllable by the central control unit  44  of the energy circulation control device  40 , in order to release the hydrogen source  331  at proper timing to feed back to the energy input terminal  21  of the first electric cell  10 , and as such, the hydrogen source  331  can be temporarily stored and fed back for circulative utilization. 
     Further referring to what depicted in  FIGS. 5 and 6 , a third embodiment of the fuel cell energy circulative utilization system  100  according to the present invention is provided, wherein the electricity input terminal  32  of the second electric cell  30  is connected with at least one commercial (electric main) electricity source  500  and at least one renewable energy source  600 , so that when the input energy  10  is of a cost that is higher than the electricity cost of the commercial electricity source  500  or the green electricity source  600 , the commercial electricity source  500  or the renewable energy  600  may directed and fed to the electricity input terminal  32  of the second electric cell  30  to allow the energy output terminal  33  of the second electric cell  30  to generate hydrogen source  331  that is blue hydrogen or green hydrogen that is of a relatively low cost. Similarly, the first electric cell  10 , when manipulated and controlled by the energy circulation control device  40  to switch to a SOEC working mode, could similarly achieve the same effect of generating a hydrogen source that is blue hydrogen or green hydrogen of a relatively low cost at the energy input terminal  21  of the first electric cell  20 . Further, the energy input terminal  32 ′ of the second electric cell  30  is connected with at least one water storage tank  700 . The water storage tank  700  is provided with a control valve  710  to control supply of water  241  to the energy input terminal  32 ′, so that when the first electric cell  20  is switched to the SOEC working mode, the water storage tank  700  supplies a necessary input of water  241  into the first electric cell  20  and the second electric cell  30  to allow both the first electric cell  20  and the second electric cell  30  to operate in the SOEC working mode to generate hydrogen source  331  of green hydrogen; or alternatively, when the second electric cell  30  is switched to the SOFC working mode, namely both the first electric cell  20  and the second electric cell  30  being in the SOFC working mode, the water storage tank  700  serves as a measure to allow water  241  output from the energy output terminal  24  of the first electric cell  20  and the energy input terminal  32 ′ of the second electric cell  30  to store and accumulate in the water storage tank  700  for circulative utilization. The control valve  710  is also controllable by the central control unit  44  of the energy circulation control device  40 . Further, the central control unit  44  of the energy circulation control device  40  is connected with at least one communication interface  441  (as shown in  FIG. 6 ), and the communication interface  441  is connected, by at least one interconnected network  800 , to a remote control center  900 , so that the remote control center  900  may do remote monitoring and issue control instructions. The communication interface  441  is not limited to any specific type, and in the present invention, an arrangement formed of a wired/wireless communication interface is taken as an example for illustration, so that connection with the interconnected network  800  can be achieved in a wired manner or a wireless manner. 
     Referring to what is depicted in  FIG. 7 , a preferred example of application of the fuel cell energy circulative utilization system  100  according to the present invention is provided, showing a configuration of connection of multiple first electric cells  20  and second electric cells  30 , wherein connection of electricity  221  among the electricity output terminals  22  of the first electric cells  20  and the electricity input terminals  31  of the second electric cells  30  and connection of hydrogen source  331  among the energy output terminals  33  of the second electric cells  30  and the energy input terminals  21  of the first electric cells  20  are schematically shown. In the application of the fuel cell energy circulative utilization system  100  according to the present invention, an example involving the first two first electric cells  20  and one second electric cell  30  as shown in the drawing is taken for illustration, but not limited to such a numeral combination of the first electric cells  20  and the one second electric cell  30 , wherein rated power generation or rated power consumption capacity for each of the first electric cells  20  and the one second electric cell  30  is 10 kilowatts (KW), and an example is provided by taking the operation performance of each first electric cell  20  as 60% and the operation performance of the second electric cell  30  as 80%, and then, the electricity output terminal  22  of the first electric cell  20  generating electricity  221  at 23.6 kilowatt-hours (KWH) would require an input of hydrogen  331  of one kilogram (Kg); and, the energy output terminal  33  of the second electric cell  30  generating one Kg hydrogen  331  requires an input of electricity  221  of 50-55 KWH, and thus, when the cost of electricity  221  available commercially is corresponding to the cost of hydrogen  331 , 100% full-load operation for generation of electricity and green hydrogen with the above arrangement of two first electric cells  20  plus one second electric cell  30  may be taken for feedback and circulative utilization; however, when the cost of electricity  221  available commercially is higher than the cost of hydrogen  331 , the central control unit  44  of the energy circulation control device  40  as described above may be used to control the electricity direction control unit  43  of the electricity input terminal  31  of the second electric cell  30  and the pairwise arranged first flow direction controller  41  and second flow direction controller  42  of the energy output terminal  33  so as to achieve a state that the flow direction of electricity  221  of the electricity input terminal  31  is switched to that for outputting and the flow direction of hydrogen  331  of the energy output terminal  33  is that for inputting, making the second electric cell  30  switched to the SOFC working mode, allowing the energy output terminal  33  of the second electric cell  30  to operate in a reversed or opposite direction for inputting of hydrogen  331  and the electricity input terminal  31  outputting electricity  221 , to thereby form parallel connection, for generation of electricity, with the two first electric cells  20  that are in the SOFC working mode for full load operation to jointly generate and output electricity  221 , and the electricity  221  may be regarded as green-energy electricity, which may be of a relatively high cost to thereby enhance the economic effect of the present invention in industrial uses. 
     Further, when the cost of hydrogen  331  available from the market is higher than that of electricity  221 , in a similar way, the central control unit  44  of the energy circulation control device  40  as described above may individually control the electricity direction control units  43  of the electricity output terminals  22  of the two first electric cells  20  and the pairwise arranged first flow direction controller  41  and second flow direction controller  42  of the energy input terminal  21 , so as to achieve a state that the flow direction of electricity  221  the electricity output terminal  21  is switched to that for inputting and the flow direction of hydrogen  331  of the energy input terminal  21  is outputting, making the two first electric cell  20  switched to the SOEC working mode, allowing the electricity output terminals  22  of the two first electric cells  20  to input electricity  221 , and the energy input terminal  21  being made to operate in a reversed or opposite direction to output hydrogen  331  and thus forming parallel connection, for generation of hydrogen  331 , with the second electric cell  30  operating in the SOEC working mode, namely generating an environmental friendly source of green hydrogen, and such a hydrogen source  331  of green hydrogen may thus receive a better commercial market price, meaning this helps further enhance the present invention in respect of value of industrial use and scope of application. 
     In the preferred example of application of the fuel cell energy circulative utilization system  100  according to the present invention shown in  FIG. 7 , control of the first flow direction controller  41 , the second flow direction controller  42 , and the electricity direction control unit  43  of the energy circulation control device  40  may be achieved by means of remote monitoring and control performed by the remote control center  900  to which the central control unit  44  is connected as shown in  FIG. 6 . In other words, there only needs the minimum amount of human labor and equipment cost to do cross-region or cross-area remote monitoring and remote control for the fuel cell energy circulative utilization system  100  of the present invention as described above that involves green electricity distributive powerplants or green hydrogen production plants. Further, the fuel cell energy circulative utilization system  100  according to the present invention is applicable to for example underwater electricity-based engine propulsive system of submarines and electricity and heat supply systems of hospitals, hotels, and office buildings, regional electricity charging stations or hydrogen filling stations for electric vehicles, small-sized community distributive power generation plants that require applications of circulative utilization for green electricity and green hydrogen. 
     In addition, in the preferred example of application of the fuel cell energy circulative utilization system  100  according to the present invention shown in  FIG. 7 , the energy circulation control device  40  can be operated by the remote control center  900  to adjust, according to seasonal characteristics of electricity generation and electricity demand for the commercial electricity source  500  and the renewable energy  600  as shown in  FIG. 5  to control and adjust both of the first electric cell  20  and the second electric cell  30  both in respect of being set in the SOFC or SOEC working mode and quantity thereof, such as during summertime, electricity demand for resident household being such that electricity capacity demand for virtually full-load operation cannot be met by the commercial electricity source  500  and the renewable energy  600 , and under such a condition, the cost of electricity is expensive and is higher than the cost of the input energy  10 , then a control instruction is remotely issued from the remote control center  900  to the energy circulation control device  40  to switch a major portion of the first electric cells  20  and the second electric cells  30  to the SOFC working mode to generate, as full capacity, electricity  221 , and the electricity may be sold to a power or utility company in the area where the commercial electricity source  500  is located, meaning electricity  221  is fed, as being parallel connected thereto, for electricity supply in the microgrid  200 , and an extra amount of electricity  221  may be subject to regulation and control by the power or utility company in the area where the commercial electricity source  500  is located to feed to a neighborhood electric grid to thereby provide the best economic performance of power generation and industrial use. Further, during wintertime, the demand of electricity for the resident households drops, and under such a condition, the cost of electricity is cheap and lower than that of the input energy  10 , meaning the cost of the natural gas or hydrogen  331  for the input energy  10  is higher than the cost of electricity  22 , namely electricity  221  becomes cheap, and under such a condition, the remote control center  900  issues, from a remote site, a control instruction to the energy circulation control device  40  to switch a major portion of first electric cells  20  and second electric cells  30  to the SOEC working mode to generate, as full capacity, sources such as hydrogen  331 , and storage is made in the high-pressure hydrogen storage tank  400  for sales to the market for making more profits to thereby further enhance the present invention in respect of circulative utilization of energy and economic value of industrial use. 
     Similarly, the above-described way of the remote control center  900  issuing a control instruction from a remote site to the energy circulation control device  40  to switch the first electric cell  20  and the second electric cell  30  to the SOEC or SOEC working mode is also applicable to a user end, such as user of the microgrid  200 , for regulation and adjustment of the input energy  10  in respect of electricity  221  and hydrogen  331  so short intervals of time during peak time and off-peak time of electricity consumption periods, so as to achieve, in a precise manner, daily control and regulation of high economic performance for the input energy  10  of electricity  221  and hydrogen  331 . 
     The fuel cell energy circulative utilization system  100  according to the present invention is provided in what shown in  FIGS. 1-7 , in which the description and drawings are provided for easy explanation of the technical contents and technical measures of the present invention, and the preferred embodiments so described provide only a fraction of the present invention and are not provided as limitative examples, and further any equivalent substitute and modification of structure and component of the details of the present invention are considered failing within the scope of the present invention as defined solely by the appended claims.