GB2301699A

GB2301699A - Method and apparatus for power generation

Info

Publication number: GB2301699A
Application number: GB9605388A
Authority: GB
Inventors: Yuji Ando; Tadayoshi Tanaka; Takuya Doi; Takumi Takashima
Original assignee: Agency of Industrial Science and Technology
Current assignee: National Institute of Advanced Industrial Science and Technology AIST
Priority date: 1995-05-30
Filing date: 1996-03-14
Publication date: 1996-12-11
Anticipated expiration: 2016-03-14
Also published as: JPH08329994A; GB9605388D0; GB2301699B; JP2708094B2

Abstract

Thermal decomposition of a reactant XY proceeds thermally on a negative catalytic electrode 1 to form products X and Y. The product Y is a cellular reaction product which seperates into ions Y+ and electrons e- on the catalytic electrode. The ions Y+ having moved through a solid electrolyte 3 the electrons e- having passed through an external resistor 6, and the product X formed on the catalytic electrode 1 reacts on a positive catalytic electrode 2 reproducing the reactant XY. The positive electrode 2 is heated e.g. by solar heating to promote reproduction of the reactant XY.

Description

METHOD OF AND AN APPARATUS FOR POWER GENERATION The present invention relates to a method of and an apparatus for power generation intended to convert various thermal energies, such as waste heat, into electric energy via chemical reactions.

A reactant reproducible type heat fuel cell has thus far been used as a device for converting thermal energy into electric energy via a chemical reaction without involving the exchange of materials between a power generating apparatus and the outside. This device reproduces the reactants by causing a reaction reverse to the cellular reaction to proceed thermally by use of a catalyst. This type of device is, for example, disclosed in Report of the Govt. Industrial Research Inst., Tohoku, Vol.

17, pp. 39 - 56, (March 1984) by Tamio Ikesyoji.

This is shown in Fig. 1.

In Fig. 1, the numerals 10 and 11 represent reactant inlets on the negative electrode side and the positive electrode side, respectively; 12 and 13, product outlets on the negative electrode side and the positive electrode side, respectively; 14, a negative electrode; 15, an electrolyte; 16, a positive electrode; 17, a catalytic reactor; and 18, an external resistor. The symbols A and B signify reactants for a cellular reaction; and C and D, products from the cellular reaction. Hydrazine (N2H4) is exemplified as A, oxygen (02) as B, nitrogen (N2) as C, and water (H20) as D. If hydrogen (H2) is used as A, and oxygen (02) as B, there is no product corresponding to C, and water (H20) is formed as D. In Fig. 1, a heating means for applying heat energy to be converted into electric power is omitted.

As shown in Fig. 1, the reactant A is introduced from the negative electrode-side reactant inlet 10, and the reactant B from the positive electrode-side reactant inlet 11, whereafter the products C, D, respectively, are formed. During this process, electrons migrate from the negative electrode 14 to the positive electrode 16, obtaining electric energy. The resulting products C, D pass the negative electrode-side product outlet 12 and the positive electrode-side product outlet 13, respectively, entering the catalytic reactor 17.

There, the products C, D form the reactants A, B upon the reverse reaction to the cellular reaction.

The reactants A, B reproduced are introduced into the negative electrode-side reactant inlet 10 and the positive electrode-side reactant inlet 11, and used for the cellular reaction again.

This system is advantageous in that electric energy is obtained from heat energy without any materials exchanged between the power generator and the outside.

In the conventional reactant reproducible type heat fuel cell, however, a solid catalyst was used for the catalytic reactor 17. Thus, at low reaction temperatures, even when the reactants A, B were reproduced on the catalyst, they were not easily released. To promote their release, it was necessary to employ a somewhat high reaction temperature.

This necessity was ascribed to the independence of the fuel cell portion and the catalytic reactor 17 from each other. Because of this independence, the reactants A, B had to be introduced into the negative electrode-side and positive electrode-side reactant inlets 10, 11 after being reproduced in the catalytic reactor 17 and released therefrom.

The object of this invention is to provide a method of and an apparatus for power generation which do not require reactant reproduction and release steps performed in conventional catalytic reactors.

To attain this object, the method of power generation comprises constructing a positive electrode and a negative electrode from catalytic electrodes and interposing an electrolyte between both catalytic electrodes; contacting a reactant with the negative catalytic electrode while applying heat to the positive electrode and the negative electrode to form decomposition products on the negative catalytic electrode by catalytic reaction; and reproducing the reactant on the positive catalytic electrode from the decomposition products, followed by circulating the reproduced reactant to the negative catalytic electrode to make it act on the negative catalytic electrode.

The heat applied to the positive electrode and the negative electrode may be solar heat or any type of waste heat.

The apparatus for power generation concerned with the present invention comprises a negative electrode integrated with a catalyst for proceeding a reaction for producing a cellular reaction material from a reactant by catalytic reaction with heating; a positive electrode integrated with a catalyst for proceeding a reaction for reproducing the reactant from the cellular reaction material and the rest of the decomposition product; an electrolyte interposed between the negative electrode and the positive electrode; and a circulating means for transferring the reproduced reactant to the negative electrode, and also transferring the rest of the decomposition product from the negative electrode to the positive electrode.

According to the method of and apparatus for power generation of the present invention, if a heat source of a certain temperature exists, there is no need to release the reactant from the top of the catalyst, since the catalyst and electrodes are integrated to form catalytic electrodes. Thus, more electric energy than by conventional methods can be obtained.

If solar heat is used as the heat source, a clean type of power generation can be performed without requiring any special heating means.

The cellular reaction material formed on the negative catalytic electrode can be used for the cellular reaction without the need for its release from the top of the catalytic electrode. Thus, the reaction temperature of the thermal decomposition reaction of the reactant on the negative catalytic electrode can be set to be lower than that used in the conventional catalytic reactor.

Hence, heat in a lower temperature range than in the conventional method can be converted into electric energy.

The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.

Fig. 1 is a schematic structural view showing an example of a fuel cell, a conventional power generator; Fig. 2 is a sectional view showing an outlined structure of a first embodiment of the apparatus for power generation of the present invention; and Fig. 3 is a sectional view showing an outlined structure of a second embodiment of the apparatus for power generation of the present invention.

Embodiment 1 Fig. 2 is a sectional view showing an outlined structure of a first embodiment of the apparatus for power generation of the present invention.

In Fig. 2, the numeral 1 signifies a negative catalytic electrode, 2 a positive catalytic electrode, 3 a solid electrolyte, and 4 a housing covering the entire system and forming a circulation passageway 5 as a circulating means on the outer peripheries of both catalytic electrodes 1, 2. The numeral 6 represents an external resistor.

Next, the actions of the apparatus will be described. XY denotes a reactant, and X, Y signify products by thermal decomposition, of which the Y is a cellular reaction material.

On the negative catalytic electrode 1, the reactions

take place.

On the positive catalytic electrode 2, the reaction

occurs.

As a whole, the reaction

takes place, so that the cell acts as a thermally driven cell. The negative catalytic electrode 1 and the positive catalytic electrode 2 need to be different in the reaction temperature.

Embodiment 2 Fig. 3 shows an outlined structure of a thermally driven cell using solar heat as a second embodiment of the present invention. In Fig. 3, when 2-propanol (CH3CHOHCH3) is used as the reactant XY, the decomposition product X is acetone (CH3COCH3), and the cellular reaction material Y is a hydrogen atom (H). Examples of the catalytic electrodes 1, 2 and the solid electrolyte 3 are palladium carried carbon, platinum carried carbon, and NafionX, respectively. Nations which is commercially available from E. I. Du Pont de Nemours and Company is proton exchange membrane fabricated from copolymers of tetrafluoroethylene and perfluorinated monomers containing sulfonic or carboxylic acid groups.

The temperature in the vicinity of the catalytic electrode 1 is set at about the boiling point of 2propanol (82.40C). The heat source is, say, solar heat. The temperature in the vicinity of the catalytic electrode 2 is set at about room temperature.

Next, the actions will be described.

On the negative catalytic electrode 1, the reactions

take place.

On the positive catalytic electrode 2, the reaction

occurs.

As a whole, the reaction

takes place, so that the cell acts as a thermally driven cell.

More specifically, the reactant 2-propanol is decomposed into acetone and hydrogen atoms on the catalytic electrode 1. The hydrogen atoms are divided into protons and electrons on the negative catalytic electrode 1. The protons move in the solid electrolyte 3, reaching the positive catalytic electrode 2, while the electrons pass through the external resistor 6, reaching the positive catalytic electrode 2. The acetone formed on the negative catalytic electrode 1 migrates to the positive catalytic electrode 2, where it receives the protons and electrons, reproducing 2-propanol. The resulting 2-propanol moves to the negative catalytic electrode 1, repeating the same cycle. With this cycle, a direct current is obtained as an output by supplying only heat of about 800C as an input.In this case, the resulting electric power corresponds to the change in free energy caused by the reaction in which acetone reacts with hydrogen to form 2propanol.

The above thermally driven cell enables thermal energy such as solar energy to be converted into electric energy efficiently.

Needless to say, other types of heat than solar heat may be used as the heating means. The solid electrolyte 3 has the advantage of being easy to handle, but generally any electrolyte will suffice.

Examples of the reactant XY, the decomposition product X, and the cellular reaction material Y include the following:

xY x Y Methanol Formaldehyde Hydrogen Ethanol Acetaldehyde Hydrogen Cyclohexanol Cyclohexanone Hydrogen Cyclohexane Benzene Hydrogen Ethylcyc lohexane Ethylbenzene Hydrogen Methylcyclohexane Toluene Hydrogen Benzyl alcohol Benzaldehyde Hydrogen Diphenyl methanol Benzophenone Hydrogen The power generation method and apparatus of the present invention involve integrating a catalyst for a reaction, which reproduces a reactant from the decomposition product of a cellular reaction, with an electrode to form a catalytic electrode. Thus, they can reproduce the product of the cellular reaction into the reactant thermally by the catalytic electrode on the positive side. Moreover, they are free from the necessity for releasing the cellular reaction material from the positive catalytic electrode, thus permitting production of more electric energy from a certain heat source than by the conventional method. Furthermore, they can set the decomposition reaction temperature to be lower than in the conventional method. Therefore, load on the environment is also reduced.

In addition, power generation using solar heat as a heat source has an advantage in becoming a clean type of power generation requiring no special heating device.

The present invention has been described in detail with respect to preferred embodiments, and it will now be clear that changes and modifications may be made without departing from the invention in its broader aspects, and it is our intention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS:

1. A method of power generation characterized by comprising: constructing a positive electrode and a negative electrode, from which an electric current for power generation is to be taken, from catalytic electrodes, and interposing an electrolyte between both catalytic electrodes; contacting a reactant with the negative catalytic electrode while applying heat to the positive catalytic electrode and the negative catalytic electrode to form decomposition products on the negative catalytic electrode by catalytic reaction; and reproducing the reactant on the positive catalytic electrode from the decomposition products, followed by circulating the reproduced reactant to the negative catalytic electrode to make it act on the negative catalytic electrode.

2. The method as claimed in claim 1, characterized in that the heat applied to the catalytic electrodes is solar heat.

3. An apparatus for power generation characterized by comprising: a negative electrode integrated with a catalyst for proceeding a reaction for producing a cellular reaction material from a reactant by catalytic reaction with heating; a positive electrode integrated with a catalyst for proceeding a reaction for reproducing the reactant from the cellular reaction material and the rest of the decomposition product; an electrolyte interposed between the negative electrode and the positive electrode; and a circulating means for transferring the reproduced reactant to the negative electrode, and also transferring the rest of the decomposition product from the negative electrode to the positive electrode.

4. A method according to Claim 1 or 2 substantially asz hereinbefore described.

5. An apparatus according to Claim 3 substantially as hereinbefore described with reference to and as illustrated in Figures 2 and 3 of the accompanying Drawings.