DE102016202259B4 - High-temperature electrolysis apparatus and method for performing a high-temperature electrolysis - Google Patents

Abstract

High-temperature electrolysis apparatus (10) for splitting water into hydrogen and oxygen, comprising a high-temperature electrolyzer (12), a parabolic mirror (14), at the focal point of which a receiver (16) is arranged to receive one, the receiver (16) having a Stirling engine (18), the expansion cylinder (20) is supplied to the heat generated by the concentrated solar radiation, wherein by the Stirling engine (18) is a conversion of heat energy into electrical energy, which is the high temperature electrolyzer (12) supplied, characterized in that the receiver (16) has a burner (22) for burning a fuel, the heat of which can also be supplied to the expansion cylinder (20) of the Stirling engine, the high-temperature electrolysis device (10) having an evaporation of water, which is part of the burner ( 22) resulting heat energy can be supplied, wherein the supply of water vapor indirectly with the Hochtemperaturele ktrolyseur (12) is connected, wherein the output of the evaporator (24) for further heating of the water vapor with at least one heat exchanger (26, 28) is connected, the heat supply line (26 a, 28 a) with an output line (12 b, 12 c) is connected, supplying the heated hydrogen and / or oxygen from the outlet of the high-temperature electrolyzer (12) to it.

Description

The invention relates to a high-temperature electrolysis apparatus and to a method for carrying out high-temperature electrolysis.

In recent years, the use of hydrogen as an alternative energy supplier has been increasingly investigated. Today, hydrogen is mainly obtained by thermal processes from fossil fuels (natural gas, heavy oil, coal) or as a by-product in the chemical industry. Another possibility for hydrogen production is the electrolysis process, that is the electrochemical splitting of water into hydrogen and oxygen. In this process, at high temperatures, part of the energy required for water splitting can be coupled in as high-temperature heat, so that the demand for electrical energy can be reduced. In this case one speaks of a high-temperature electrolysis. Here is a mix of electrical energy and heat energy necessary to split water vapor at a temperature of 700 - 1,000 ° C.

The thermal energy requirement for high-temperature electrolysis can also be provided by concentrating solar systems, for example. For this purpose, for example, a parabolic mirror can be used, which focuses the solar radiation to a focal point. Concentrating solar systems have the disadvantage that they are heavily dependent on the weather. This leads to a fluctuating energy form that does not allow continuous operation of the plant for high-temperature electrolysis. Furthermore, the energy fluctuation leads to a mechanical load of the high-temperature electrolyzer, so that its life is reduced. This was shown, for example, in the framework of the EU project Adel. In the prior art, an energy storage device is thus used to avoid this disadvantage, which is associated with high investment costs.

Furthermore, a high-temperature electrolyzer on a very high electrical energy consumption.

describes the use of a parabolic mirror in conjunction with a Stirling engine to provide electrical energy for a high temperature electrolyzer.

DE 10 2009 036 005 A1 describes the use of waste heat from thermodynamic processes to heat water for high-temperature electrolysis.

The object of the invention is to provide an apparatus and a method for performing a high-temperature electrolysis, which allows a more efficient provision of the required electrical energy.

The object is achieved according to the invention by the features of claims 1 and 8.

The high-temperature electrolysis device according to the invention for splitting water into hydrogen and oxygen has a high-temperature electrolyzer. Furthermore, it has a parabolic mirror, at the focal point of which a receiver for receiving concentrated solar radiation is arranged.

The receiver has a Stirling engine whose expansion cylinder is supplied with the heat generated by the concentrated solar radiation.

By the Stirling engine, a conversion of heat energy into electrical energy, which is supplied to the high-temperature electrolyzer. Stirling engines have long been known in the art. A suitable Stirling engine, for example, the model V160 / V161 which was developed by Schlaich Bergerman and Partner together with SOLO. The basic operation of a Stirling engine is known from the prior art.

The device according to the invention thus combines for the first time a solar receiver for receiving a concentrated solar radiation with a Stirling engine and a high-temperature electrolyzer. As a result, the electrical energy required for the high-temperature electrolyzer can be provided in a particularly efficient manner.

The receiver has a burner for burning a fuel, in particular biogas, whose heat can also be fed to the expansion cylinder of the Stirling engine.

It is envisaged that a part of the heat energy produced in the burner can be supplied to an evaporator, through which an evaporation of water takes place, whereby a supply of the water vapor to the high-temperature electrolyzer takes place.

By the said device is thus an uninterrupted and constant operation of the high-temperature electrolyzer possible. In particular, it is possible to constantly supply the high-temperature electrolyzer with energy and electricity. If, for example, the heat generated by solar radiation decreases as a result of changes in the weather, the output of the burner can be increased so that the high-temperature Electrolyzer on the Stirling engine is still enough electricity can be supplied.

At the same time, a separate energy source for supplying heat energy to the high-temperature electrolyzer is not necessary, since evaporation of the water takes place through part of the heat produced in the burner. This water vapor is fed to the high-temperature electrolyzer.

It is further provided according to the invention that the output of the evaporator is connected to further heat the water vapor with at least one heat exchanger, the heat supply is connected to an output line which supplies him heated hydrogen and / or oxygen from the outlet of the high-temperature electrolyzer. The heat supply line of the heat exchanger is the line through which the heat-emitting fluid is supplied to the heat exchanger. By said feature, it is possible to use the energy contained in the heated hydrogen and / or oxygen from the high-temperature electrolyzer for further heating of the water vapor. This can thereby preferably heat to a temperature of 700-1,000 ° C.

Furthermore, it is preferred that the outlet of the evaporator for further heating of the steam is connected to a first heat exchanger whose heat supply line is connected to an oxygen outlet line which supplies it with heated oxygen from the outlet of the high-temperature electrolyzer. Furthermore, the outlet of the evaporator is connected to a second heat exchanger whose heat supply line is connected to a hydrogen outlet line, which supplies it with heated hydrogen from the outlet of the high-temperature electrolyzer. The heated in the first and second heat exchanger water streams are then fed to the high-temperature electrolyzer. This makes it possible to use both the heat energy present in the heated hydrogen and in the heated oxygen.

It is further preferred that the device has a condenser which is connected to the hydrogen outlet line of the high-temperature electrolyzer. The condenser serves to remove the unreacted water from the hydrogen stream.

Alternatively, this condenser may be connected to the discharge line for discharging the heat-generating fluid of the second heat exchanger.

Furthermore, the device preferably has a compressor, which is connected downstream of the high-temperature electrolyzer. This serves to compress the hydrogen from the high-temperature electrolyzer.

• Konzentrieren von Sonnenstrahlung durch einen Parabolspiegel zu einem in dessen Brennpunkt angeordneten Receiver,
• Zuführen der durch die konzentrierte Sonnenstrahlung erzeugten Wärme zum Expansionszylinder eines im Receiver angeordneten Stirlingmotors,
• Zuführen der durch den Stirlingmotor erzeugte elektrischen Energie zu einem Hochtemperaturelektrolyseur.

The invention further relates to a method for carrying out a high-temperature electrolysis, using a device as has been described so far. The method comprises the following steps:

• Concentrating solar radiation through a parabolic mirror to a receiver arranged in its focal point,
• Supplying the heat generated by the concentrated solar radiation to the expansion cylinder of a Stirling engine arranged in the receiver,
• Supplying the electrical energy generated by the Stirling engine to a high temperature electrolyzer.

• zusätzliches oder alternatives Zuführen einer durch einen Brenner erzeugten Wärmeenergie zum Expansionszylinder des Stirlingmotors,
• Zuführen eines Teils der im Brenner entstandenen Wärme zu einem Verdampfer, durch den ein Verdampfen von Wasser erfolgt, wobei ein Zuführen des Wasserdampfs an den Hochtemperaturelektrolyseur erfolgt.

the procedure the following additional steps:

• additionally or alternatively supplying heat energy generated by a burner to the expansion cylinder of the Stirling engine,
• Supplying a portion of the heat generated in the burner to an evaporator, through which an evaporation of water takes place, wherein a supply of water vapor to the high-temperature electrolyzer takes place.

In a preferred embodiment, the heat energy supplied to the expansion cylinder of the Stirling engine by the burner is increased when the heat energy generated by the solar radiation falls below a defined threshold value and / or is insufficient for the operation of the high-temperature electrolyzer.

The method according to the invention can have all the features which have been described in connection with the device according to the invention and vice versa.

In the following, preferred embodiments of the invention will be explained with reference to figures.

• 1 eine schematische Darstellung einer Ausführungsform der erfindungsgemäßen Hochtemperatur-Elektrolysevorrichtung,
• 2 eine Ausführungsform eines Parabolspiegels,
• 3 eine Ausführungsform eines Receivers.

Show it:

• 1 a schematic representation of an embodiment of the high-temperature electrolysis apparatus according to the invention,
• 2 an embodiment of a parabolic mirror,
• 3 an embodiment of a receiver.

1 shows the basic structure of an embodiment of the high-temperature electrolysis device according to the invention 10 , The solar radiation through the parabolic mirror 14 on the receiver 16 concentrated. The receiver 16 is the link between the parabolic mirror 14 and the Stirling engine 18 , He must absorb the solar radiation to a high extent and at the same time minimize infrared radiation. The through the receiver 16 absorbed concentrated solar radiation is used to the working medium of the Stirling engine 18 to heat. For this example, helium can be used, which reaches a gas temperature of 650 ° C at an average pressure of 150 bar. The internal energy of the working gas is converted into usable mechanical work. On the crankshaft of the Stirling engine, a generator, such as an asynchronous generator, be mounted, through which the rotation of the output shaft of the Stirling engine 18 is converted into electricity.

For a better understanding of the direction of movement of the different fluids these are in 1 marked along the lines with ascending numbers.

In the hybrid receiver 16 is a mixture of biogas (electricity biogas 2 ) and air (electricity air 3 ) burned to generate extra heat, which is the Stirling engine 18 is supplied. The combustion gas (stream exhaust 1 ) is used to water the electrolysis process in the evaporator 24 to evaporate. After evaporation, the water overheats to the operating temperature of the electrolyzer 12 (about 700 ° C) in the heat recovery system, the two heat exchangers 26 . 28 having. In order to better utilize the heat in this heat recovery system, the water flow becomes water 3 divided into two sub-streams (water 4 and water 5 ). The partial flow of water 4 gets through by the electrolyser 12 escaping stream of oxygen 1 overheated, while the partial flow of water 5 through the stream of hydrogen 1 is overheated, which consists of hydrogen and unreacted water. The two streams of water are then mixed together and the resulting stream is water 8th becomes the electrolyser 12 fed.

In the high-temperature electrolyzer 12 the splitting of water takes place with the supply of electrical energy from the Stirling engine 18 provided. From the electrolyzer 12 two streams exit:

The stream of oxygen 1 which consists of oxygen and the stream of hydrogen 1 , After leaving the heat recovery system, the unreacted water in the stream must be hydrogen 2 be separated. For this purpose, the stream becomes hydrogen 2 in the condenser 30 or cooled heat exchanger. The cooling medium is ambient air (stream of air 4 ). The product gas, which now consists only of hydrogen, is in the downstream compressor 32 compressed and can be fed into the natural gas network or stored in a tank.

Solar hydrogen production can take place centrally with several high temperature electrolyzers. In this embodiment, a plurality of high-temperature electrolyzers may be provided, for example one for each parabolic mirror.

A parabolic mirror 14 is in 2 shown. This one is about support struts 34 with the receiver 16 who made the Stirling engine 18 has connected.

The parabolic mirror 14 is tracked by a tracking system the course of the sun. This is done by a rotation about two axes.

The tracking of the parabolic mirror by the tracking system can be done either by a tracking sensor that detects the position of the sun, or by a computer program that predicts the position of the sun.

The front of the parabolic mirror can be covered with a variety of mirror segments, so that a high reflectivity of about 94% can be achieved.

The receiver 16 , the focal point of the parabolic mirror 14 is used to absorb the concentrated solar radiation as much as possible and in the form of heat the Stirling engine 18 supply. For this purpose, the receiver directly with the cylinder heads of the Stirling engine 18 be connected. The receiver 16 must be designed so that the heat absorbed the Stirling engine 18 is supplied with the least possible losses. The receiver can have very thin lines, for example, have a diameter of about 3 mm and can withstand very high temperatures. Due to the multiplicity of these lines, an approximately closed surface is formed, which acts as an absorber surface. This is where the concentrated solar radiation meets. The working gas flows through the thin lines for the Stirling engine 18 and can be heated to about 650 ° C. The solar radiation is thus due to the porous structure of the receiver 16 absorbed and absorbed heat is transferred to the working fluid of the Stirling engine 18 transfer. The internal energy of the working medium is converted into usable mechanical work in the Stirling engine.

In 3 is an embodiment of the hybrid receiver 16 shown in more detail. This has the Stirling engine 18 on, which is supplied by the left side of the receiver by concentrated solar radiation heat generated. The solar radiation hits the flat absorber element 36 , which, as already described, having a plurality of lines through which the working gas of the Stirling engine 18 runs. This absorber element 36 is with the two cylinder heads of the Stirling engine 18 connected.

Additionally or alternatively to the solar energy, the Stirling engine may 18 Heat energy over the burner 22 be supplied. This is on the outer jacket of the hybrid receiver 16 arranged where the combustion of a mixture takes place, for example, can have combustion air and biogas.

In 3 is an exemplary embodiment of a receiver 16 with a Stirling engine 18 shown. This has a burner for generating additional energy 22 on, in which the combustion of a mixture of combustion air and biogas takes place. The combustion air is directed to the burner via the inlet opening 40 while feeding him the biogas through the inlet opening 42 is supplied. To increase the efficiency of the process, the combustion air is preheated by the hot combustion gas. This leaves the burner through the exhaust port 44 , The integration of the receiver 16 in the overall system can the 1 be removed. The receiver shown there 16 corresponds to the in 3 illustrated receiver 16 ,

After biogas has been supplied to the combustion air, these two components are stored in the 3 horizontal mixing pipe 46 mixed. Subsequently, the mixture through the flame holder 48 burned. The reference number 50 refers to a porous structure that absorbs the heat and to the Stirling engine 18 forwards.

Claims (7)

High-temperature electrolysis apparatus (10) for splitting water into hydrogen and oxygen, comprising a high-temperature electrolyzer (12), a parabolic mirror (14), at the focal point of which a receiver (16) for receiving one is arranged, wherein the receiver (16) a Stirling engine (18), the expansion cylinder (20) of which is supplied by the concentrated solar radiation heat, wherein by the Stirling engine (18) is a conversion of heat energy into electrical energy, which is supplied to the Hochtemperaturelektrolyseur (12), characterized in that the receiver (16) has a burner (22) for burning a fuel whose heat can also be supplied to the expansion cylinder (20) of the Stirling engine, the high-temperature electrolysis device (10) having a vaporization of water, which is part of the burner (22) resulting heat energy can be supplied, wherein the supply of water vapor indirectly with the high temperature aturelektrolyseur (12) is connected, wherein the output of the evaporator (24) for further heating of the water vapor with at least one heat exchanger (26, 28) is connected, the heat supply line (26 a, 28 a) with an output line (12 b, 12 c) is connected, supplying the heated hydrogen and / or oxygen from the outlet of the high-temperature electrolyzer (12) to it. High-temperature electrolysis device (10) after Claim 1 characterized in that the outlet of the evaporator (24) is connected to a first heat exchanger (26), the heat supply duct (26a) of which is connected to an oxygen outlet duct (12b) supplying the heated oxygen from the outlet of the high temperature electrolyzer (26). 12) and with a second heat exchanger (28) whose Wärmezuführleitung (28a) is connected to a hydrogen outlet line (12c) which supplies him heated hydrogen from the outlet of the Hochtemperaturelektrolyseurs (12), wherein in the first and second heat exchangers (26 , 28) heated water streams are fed to the high temperature electrolyzer (12). High-temperature electrolysis device (10) after Claim 1 - 2 characterized by a condenser (30) connected to the hydrogen exit duct (12c) of the high temperature electrolyzer (12). High-temperature electrolysis device (10) after Claim 2 characterized by a condenser (30) connected to the discharge line (28b) for discharging the heat - generating fluid of the second heat exchanger (28). High-temperature electrolysis device (10) after Claim 1 - 4 characterized by a compressor (32) connected downstream of the high temperature electrolyzer (12) for compressing the hydrogen from the high temperature electrolyzer. A method of performing a high temperature electrolysis using a device (10) according to any one of Claims 1 - 4 the method comprising the following steps: Concentrating solar radiation through a parabolic mirror (14) to a receiver (16) arranged in its focus, supplying the heat generated by the concentrated solar radiation to the expansion cylinder (20) of a Stirling engine (18) arranged in the receiver (16), feeding it through the Stirling engine (18) generating electrical energy to a high temperature electrolyzer (12) characterized by the further steps of: additionally or alternatively supplying heat energy generated by a burner (22) to the expansion cylinder (20) of the stirling engine (18), supplying a portion of the burner (22) heat to an evaporator (24) through which an evaporation of water takes place, wherein supplying the water vapor to the high temperature electrolyzer (12), wherein the output of the evaporator (24) for further heating the water vapor with at least one heat exchanger (26, 28) is connected, the heat supply line (26 a, 28 a) with an A Output line (12b, 12c) is connected, which supplies him heated hydrogen and / or oxygen from the outlet of the high-temperature electrolyzer (12). Method according to Claim 6 characterized by the step of: increasing the thermal energy supplied to the expansion cylinder (20) of the Stirling engine (18) by the burner (22) when the thermal energy generated by the solar radiation falls below a defined threshold and / or not for the operation of the high temperature electrolyzer (12) sufficient.

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