JPS60143575A - Conversion device of heat to electricity - Google Patents

Abstract

PURPOSE:To efficiently convert heat energy to electric energy with a simple device by supplying hydrogen to a gas diffusion electrode by heating metal hydride. CONSTITUTION:A gas diffusion electrode 6 is formed by fixing on one side of a proton ion conductor 5, and a gas diffusion electrode 7 is fixed on the other side of the conductor 5. Gas chambers 8 and 9 are installed on each back of electrodes 6 and 7. Metal hydrides 12 and 13 are accommodated in heat exchangers 10 and 11 installed in cases 1 and 2. When this device is placed on a heated metal plate 14, the lower part of the device becomes high pressure and its upper part becomes lower pressure, hydrogen gas is transfered from the lower part to the upper part and electric power is obtained. After discharge of hydrogen is completed, when the device is placed upside down on the heated plate, electric power is obtained again. By this simple construction, heat energy is efficiently converted to electric energy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a device that efficiently converts thermal energy directly into electrical energy. It is widely available where it exists.

Conventional configuration and its problemsAs a method of converting thermal energy into electrical energy,
There are thermal power generation, nuclear power generation, geothermal power generation, ocean temperature difference power generation, etc. that convert mechanical energy, and many of these have been widely put into practical use. However, the energy conversion efficiency of these devices is about 40% at most, and even higher efficiency is desired.

On the other hand, thermoelectric power generation and thermionic power generation are methods that directly convert electricity into electricity without using mechanical energy.

Although MHD power generation has been studied for a long time, it has not yet been achieved with high efficiency enough to be implemented industrially on a practical scale.

Another method is an electrochemical cell.

Unlike ordinary secondary batteries, this battery is regenerated into a dischargeable state by applying thermal energy such as heating or cooling instead of being charged electrically.

Examples of this type of battery include a high-temperature operating type battery using a combination of an alkali metal such as lithium and hydrogen, and an aqueous solution battery using a redox couple of Fe3+-Fe2+ or Fe(CN)j"f Fe(ON)j+. However, in the former case, the open circuit voltage is relatively low at 2 V/-v, and the thermal energy conversion efficiency is low at 10% or less.

Furthermore, the latter has a conversion efficiency of 0.05 to 0.07 V/-U, which is very low at 0.1%.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a device that has a relatively simple configuration and efficiently converts thermal energy into electrical energy in a continuous or continuous manner.

Structure of the Invention The device of the present invention has independent gas diffusion electrodes on both sides of a proton ion conductor, and a gas chamber for supplying hydrogen to these gas diffusion electrodes or storing hydrogen gas generated by the gas diffusion electrodes. A metal hydride is housed in at least one of the gas chambers, and a heat exchanger is provided to heat or radiate heat from the metal hydride as necessary. Then, by heating this metal hydride and supplying hydrogen gas to the gas diffusion electrode communicating with it, the gas diffusion electrode f becomes a positive electrode and the other gas diffusion electrode becomes a negative electrode, and electric power is extracted between the two. It is.

If a metal hydride is stored in each gas chamber, after the hydrogen gas has moved in one direction, the metal hydride on the opposite side is heated and the other side is cooled, and the positive and negative electrodes of the battery are reversed, but the same effect occurs. You can get electricity.

Further, although electric power is obtained intermittently, a bypass may be provided between both chambers as a path for returning hydrogen to its original direction. The feature at this time is that by lowering the equilibrium pressure of the metal hydride on the positive electrode side than on the negative electrode side, the amount of electricity obtained in one cycle is increased at a higher voltage.

The reaction formula occurring at the positive and negative electrodes is as follows.

Negative electrode (high pressure side) H2-2H" +2 e Positive electrode (low pressure side) 2H++2e→H2 Here, protons pass through the electrolyte and move from the negative electrode side to 51\-
move to the positive side.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows an example of the configuration of an apparatus according to the present invention. Reference numeral 1 designates an upper case that also serves as a positive electrode terminal, and 2 a lower case that also serves as a negative electrode terminal.The flanges provided at the opening edges of both are integrally connected by bolts 4 through an insulator 3 to form the outer casing of the device. are doing. Reference numeral 5 denotes a proton ion conductor having a thickness of 0.5 mm and made of a fluororesin ion exchange membrane having sulfone groups, and is placed in the center of the outer casing. 6 is a gas diffusion electrode provided in close contact with one surface of the proton ion conductor 6, 7 is a gas diffusion electrode provided in close contact with the other surface, and a gas chamber 8° is provided on the back of each of these electrodes. 9 is the setting.

Reference numeral 10.11 denotes a fin constituting a heat exchanger provided integrally with the cases 1 and 2, and a metal hydride 12.13 is housed here.

When this device is placed on a heated metal plate 14 as shown in the figure, the lower half of the device is on the high pressure side (negative electrode side).

The upper half becomes the low-pressure side (positive electrode side), and electricity is obtained while hydrogen gas moves from the bottom to the top. When the six discharge vanes are completed, the device is turned upside down, the direction of hydrogen movement is reversed, and electric power can be obtained again.

In the example shown in FIG. 2, a heat exchanger 10' is provided instead of the fin 1o to exchange heat with the metal hydride by flowing a heat medium such as oil, and a bypass pipe 16 is provided between both gas chambers.
A check valve or valve 16 is provided here. Then, by heating the lower half and cooling the upper half, electricity is extracted in the same way as in Figure 1.Then, by heating the upper half and cooling the lower half, the hydrogen pressure in the upper half is reduced. becomes higher. At this time, hydrogen moves to the lower part through the check valve or pulp 16. After the movement is complete, the lower half is heated again, which generates electricity, and the cycle repeats.

Next, in FIG. 1, 100 g of Mq-MqH2 metal hydride is placed in each of the upper and lower portions. The temperature below is 400℃ (10 atm), and the temperature above is 77℃ (0,
0001a tm ), the open circuit voltage of both electrodes at that time was about 300 mV. This value is the theoretical value of about 60 mV per 10 times pressure difference (aomV x 5:
71・-n3oomV).

Figure 3 shows the relationship between the temperature of various metal hydrides and the Chisai new hydrogen pressure. FIG. 4 shows the current-voltage characteristics of this battery, and curve A shows the above experimental results. From this curve,
It can be inferred that the performance is determined by the electrical resistance of the ionic conductor. Also, the electric capacity that can be discharged once is 100mA/
Under the condition of crA, it is about e 0Ah (theoretical value 11oAh), and the conversion efficiency with respect to heat input is about 43% (Carnot cycle efficiency 48%), both of which can be said to be excellent values. When the device was turned upside down after the discharge was completed, power was again obtained with the above characteristics.

As another example, Mg-MgH2,
The upper part shows the case where Na--NaH, which has a lower equilibrium pressure than this, is added. When Aya MIJH2 was heated to 400°C and Na-NaH was cooled to 77°C, a pressure ratio of 108 was obtained between the compartments, and the open circuit voltage was as high as 450 mV. Further, the current-voltage curve is shown as curve B in FIG. In this case, no current was obtained during regeneration, but a higher voltage was obtained during discharge than in the case of the curve.

In order to obtain an even higher voltage from one device, we assembled a device that was exactly the same as the device of curve A, except that both poles were divided into two and these were connected in series with each other. The open circuit voltage was doubled to 600 mV. Curve C in FIG. 4 shows this discharge characteristic. The voltage is higher than curves A and B.

In addition to the above, usable metal hydrides include:
Ca-CaH2, Ti-TiH2, Ni-KH, V-VH
There are 3°La-LaH2, etc., and one with an appropriate equilibrium pressure can be selected depending on the operating temperature. Also 2
More than one species may be mixed as necessary, or metal pieces may be added to improve heat conduction.

Proton ion conductors are required to exhibit high conductivity, heat resistance, pressure resistance, etc. Metal mesh, ceramic porous bodies, etc. may be used to supplement mechanical strength.
It is also possible to increase the distance between the metal hydride and the film as a means of supplementing heat resistance.

In addition, the conduction loss of heat through the container gutter of the device is 9.
In order to suppress this, it is possible to take measures such as constructing a part of the container with a material other than metal that has low thermal conductivity, or fixing the container with a heat insulating material between the containers. desirable.

A catalyst such as platinum or palladium or carbon powder may be added to the gas diffusion electrode to improve performance.

Further, in order to improve the output characteristics, the ion conductor and the electrodes may be operated with the temperature raised to some extent.

Effects of the Invention As described above, according to the present invention, thermal energy can be efficiently converted into electrical energy with a relatively simple configuration, the operation noise is quiet, and miniaturization is possible. has.

[Brief explanation of the drawing]

FIGS. 1 and 2 are longitudinal cross-sectional views showing an example of the configuration of an energy conversion device according to the present invention, FIG. 3 is an equilibrium pressure characteristic diagram of a typical metal hydride, and FIG. 4 is a characteristic diagram of the device according to the present invention. It is. 1...Top case, 2...Bottom case, 4
...Glo 10' - Nton ion conductor, 6,7... Gas diffusion electrode,
8゜9...gas chamber, 10.10', 11.11
'・River...Heat exchanger, 12.13...Metal hydride, 16.Old...Pipe, 16...φ...Valve.

Claims (3)

[Claims] (1) In addition to providing independent gas diffusion electrodes on both sides of the proton ion conductor, a gas chamber communicating with each gas diffusion electrode is provided, and at least one of these gas chambers has a heat source that can exchange heat with the outside. A device for converting heat into electricity, characterized by having a built-in metal hydride in contact with an exchanger. (2) The apparatus for converting heat into electricity according to claim 1, wherein each of the gas chambers is connected via a check valve or a valve. (3) An apparatus for converting heat into electricity according to claim 1 or 2, wherein each of the gas diffusion electrodes is separated into a plurality of parts and these are connected in series.