WO2011120706A1

WO2011120706A1 - Method and device for storing energy

Info

Publication number: WO2011120706A1
Application number: PCT/EP2011/001642
Authority: WO
Inventors: Hubertus Winkler; Hans-Jürgen Maas; Peter Wasserscheid; Mathias Mostertz
Original assignee: Linde Aktiengesellschaft; Basf Se
Priority date: 2010-04-01
Filing date: 2011-03-31
Publication date: 2011-10-06
Also published as: DE102010013660A1

Abstract

The invention relates to a method and device for storing energy, wherein hydrogen (7) is produced from water (6) by means of electrolysis (E) and is synthesized (S) into a product (storage product) (10) by means of at least one further reactant (9), in which hydrogen is present in chemically bonded form, said product being fed for intermediate storage into a storage device (S2) from which said product can be removed for material or energy use. Waste heat (W1, W2) arising from the electrolysis (E) and/or the synthesis of the storage product (S) is used for heating and/or evaporating the working medium (2) of a steam turbine (D).

Description

description

Method and device for storing energy

The invention relates to a method for storing energy, wherein hydrogen is produced from water by means of electrolysis and is synthesized with at least one further starting material to form a product (storage product) in which hydrogen is chemically bound, and which is introduced for temporary storage in a storage device from which it can be taken to a material and / or energy recovery. Furthermore, the invention relates to a device for carrying out the method.

Humanity currently covers its energy needs primarily through the

Combustion of fossil fuels, such as oil, natural gas or coal. This is

Carbon dioxide released in large quantities, which is responsible for the increasingly significant warming of the Earth's atmosphere. Efforts will therefore be stepped up to use sustainable energy sources

undertaken to produce so-called renewable energy carbon dioxide neutral.

A sustainable energy source is an energy source that is inexhaustible by human standards. The largest part of sustainable

Energy sources are fed directly or indirectly by the sun. They include sunlight, wind, hydro and biomass. The earth itself is also regarded as a sustainable source of energy whose energy content can be used in the form of geothermal energy.

Often there are abundant sustainable energy sources in remote places on earth, where only a few potential customers for the energy produced there are or can be settled. This raises the problem of how energy from a remote sustainable source of energy can be brought to customers.

From the patent application US2010 / 0003184 is known to use solar energy at convenient locations to separate hydrogen from water and this with Nitrogen to synthesize ammonia. The serving as energy storage medium ammonia is then transported to distant customers where it is used to drive vehicles or to generate electricity. Due to the conversion processes, this process results in considerable exergy losses, which severely impair the overall efficiency of energy production.

Object of the present invention is therefore to provide a method of the type described above and an apparatus for its implementation, by which it is possible to overcome the disadvantages of the prior art.

In terms of the method, this object is achieved according to the invention in that waste heat arising from the electrolysis and / or synthesis of the storage product is used to heat and / or vaporize the working medium of a steam turbine.

In the steam turbine, the resulting waste heat is converted into mechanical energy with high efficiency. Usually, water is used as the working medium. However, there are also steam turbine processes in which isopentane or an ammonia-water mixture is used as working media. The inventive method, a large part of the generation of

Memory product resulting waste heat, which is lost so far, in more valuable

Energy forms are converted, whereby the efficiency of the

Energy storage is increased.

If the steam turbine is coupled to an electric generator, the mechanical energy generated in the steam turbine can be converted into electrical energy with high efficiency. A preferred embodiment of

According to the invention, at least a portion of the electrical energy thus generated is supplied to storage, whereby it is used to split off hydrogen by electrolysis of water.

Preferably, the synthesis of the storage product is carried out at a pressure which is less than the pressure of the hydrogen produced during the electrolysis. To supply hydrogen at a sufficiently high pressure of the synthesis, can on a Hydrogen compression can be omitted, which would be associated with a considerable expenditure on equipment and with a high energy consumption. The electrolysis is preferably a pressure electrolysis in which hydrogen is produced at a pressure between 15 and 150 bar.

In order that the greatest possible part of the waste heat produced in the electrolysis and / or synthesis of the storage product can be supplied to the working medium of the steam turbine at the highest possible temperature level, a preferred embodiment of the method according to the invention provides a heat pipe.

Heat pipes have been state of the art and known to the person skilled in the art for many years. They contain in a hermetically encapsulated volume a heat transfer medium, which is present partly as a liquid, partly in gaseous form. Energy can be transferred to the liquid heat transfer medium via an evaporator connected to a heat source. The resulting vapor (vapors) flows to a condenser located elsewhere in the heat pipe and connected to a heat sink, where it condenses. During condensation, the energy absorbed via the evaporator is released to a large extent again and transferred to the heat sink. The now again liquid heat transfer medium is then conveyed back to the evaporator by the action of gravity, capillary force or by means of a pump.

Since the liquid and gas phase of the heat transfer medium are in the same room, a heat pipe operates in the wet steam area, in which the two phases also have the same temperature at the same pressure. Usually they are

Pressure differences in a heat pipe very low, which is why the

Temperature difference between evaporator and condenser is low. Because of the nearly isothermal nature of heat transfer, a heat pipe has an internal thermal resistance that is less than that of classic, purely metallic heat exchangers.

In the event that waste heat in the electrolysis and / or synthesis of

Storage medium is obtained at a temperature level which is lower than the minimum temperature of the working medium of the steam turbine, provides an embodiment of the method according to the invention, that the temperature of the evaporated, im Heat pipe circulating heat transfer medium is raised by vapor compression to a value that is sufficiently high to the vapors against the

Cool down working medium of the steam turbine and can condense. However, the method according to the invention is particularly advantageous

apply when the waste heat in the electrolysis and / or the synthesis of the storage product is obtained at a temperature level which is higher than the minimum temperature of the working medium of the steam turbine. The electrolysis is preferably a high-temperature electrolysis in which hydrogen is produced at a temperature of more than 70 ° C.

The storage products are in particular those containing hydrogen

Compounds in question, which can be synthesized with little effort and stored easily and inexpensively. Examples of suitable storage products are methanol and ammonia. Preferably, the hydrogen to be stored is therefore converted to methanol or ammonia.

In the event that methanol or another carbon-containing compound is produced as a storage product, an embodiment of the method according to the invention provides that the carbon required for the synthesis in the form of

Carbon dioxide is supplied. This carbon dioxide can be made from every conceivable

Carbon dioxide source come. It makes sense, however, to carbon dioxide, which arises in the material and / or energy recovery of storage product. It is therefore proposed that in the recovery of a

collected carbonaceous storage product resulting carbon dioxide and - possibly after an intermediate storage - is used in the synthesis of storage product as starting material. In order to keep the storage volume required for carbon dioxide storage low, it is further proposed that the carbon dioxide be stored liquid or in a supercritical state.

In addition to carbon dioxide, other by-products obtained in one process step, such as, for example, oxygen or water, can also be used in another process

Process step can be used as starting materials. In the event that the two

Process steps are not performed simultaneously, these by-products are expediently also cached. Depending on the nature of the storage product, it can be used in different ways. For example, it can be burned, with the released thermal energy used for heating purposes or converted into mechanical and / or electrical energy. Another possibility is to decompose the storage product to produce hydrogen, which is subsequently recycled.

The method according to the invention is further developed, in which

Decomposition of memory product gained hydrogen energetically. For this purpose, the hydrogen is preferably used as fuel of the anode

Fuel cell supplied in which he reacts with oxygen producing electrical energy to water. It is also conceivable, the hydrogen in one

Heat engine, such as a piston engine or a gas turbine to burn. The heat engine may be coupled to an electric generator, with the aid of which the generated mechanical energy is converted into electrical energy.

The decomposition of memory product will i. Gen. proceed in an endothermic reaction and thus consume thermal energy. In order to cover this energy demand at least partially, the invention provides to use in the fuel cell and / or the heat engine resulting waste heat for the decomposition of storage product. Preferably, a heat pipe is used to dissipate the waste heat from the fuel cell or the heat engine. In the operation of a fuel cell, usually not all of the hydrogen supplied to the anode can be reacted with oxygen, so that residual gas still containing hydrogen is withdrawn from the anode. To be able to use the energy contained in this residual gas, sees a variant of the

According to the invention, the residual gas is burnt and the heat released in the process, for example for heating and / or evaporation of the working medium of the steam turbine or for decomposition of storage product, is used.

A patent application, filed under number 102009037884.7 at the German Trademark and Patent Office, and the disclosure of which with its Citation is incorporated in its entirety into the present patent application, describes a process known as hydrothermal catalysis (HTK) for

Hydrogen production, which is feasible at low temperatures. The

Method is particularly suitable for the implementation of carbon and hydrogen-containing substances, such as methanol. In addition, however, it is also suitable to split off hydrogen from carbon-free substances, such as ammonia. A preferred embodiment of the method according to the invention therefore provides that hydrogen is split off from a hydrogen-containing storage product by hydrothermal catalysis.

To produce methanol or ammonia as a storage product, a number of prior art processes are known. For example, it is possible

Hydrogen with carbon dioxide by catalytically assisted reforming in a single step directly into methanol and water. However, the synthesis of methanol from hydrogen and carbon monoxide is also conceivable, hydrogen and carbon dioxide being converted by water gas shift in a preceding process step in order to obtain the carbon monoxide required for the synthesis. Furthermore, the invention relates to a device for energy storage, with an electrolyzer for generating hydrogen from water and a

Synthetic device in which hydrogen produced in the electrolyzer can be reacted with at least one further starting material in an intermediate product, as well as a

Memory device for temporarily storing the memory product.

The object is achieved device-side according to the invention that the electrolyzer and / or the synthesis device are in thermal communication with a steam turbine, so that in the electrolyzer and / or the

Synthesis waste heat generated for heating and / or evaporation of the working medium of the steam turbine is used.

Preferably, the steam turbine is connected to a generator such that the mechanical energy generated in the steam turbine can be converted into electrical energy. The steam turbine is designed so that it either with water or isopentane or an ammonia-water mixture or other suitable substance

Working medium can be operated. In order to reduce the losses in the transfer of waste heat to the working medium

Steam turbine to keep low, electrolyzer and / or the synthesis device with the steam turbine are advantageously thermally coupled via a heat pipe.

A variant of the device according to the invention provides an electrolyzer in which hydrogen can be produced at a higher pressure than in the

Synthesis device is needed. Preferably, it is a

Electrolyzer, in which hydrogen can be produced at a working temperature of more than 70 ° C at a pressure which is preferably between 15 and 150bar. The synthesis device is designed so that it can be synthesized with their help hydrogen-containing compounds that are easy and inexpensive storable. Preferably, the synthesis device is designed so that methanol or ammonia can be generated as a storage product. A preferred embodiment of the invention provides that the synthesis device comprises a reactor for carrying out a hydrothermal catalysis.

If the synthesis device is suitable for producing methanol, it expediently comprises a shift reactor in which hydrogen can be reacted with carbon dioxide to form a carbon monoxide-containing material stream.

The memory device for temporarily storing the memory product may be stationary or mobile. With that it is possible that

Storage product at the place of its production or far away from it.

Another embodiment of the device according to the invention provides that it has a device for the separation of hydrogen from the storage product, which comprises a reactor for carrying out a hydrothermal catalysis. A variant of the device according to the invention provides that they have a

Storage device comprises, in which a by-product accumulating during the production and / or utilization of storage product can be temporarily stored, wherein the storage device is arranged stationary or mobile. The invention allows the storage of energy, which is in the form of hydrogen and / or electric current, it is irrelevant from which source the energy is obtained. With particular advantage, however, it can be used to store energy generated by renewable energy sources. Frequently, energy can only be extracted from such a source in time-varying quantities, which considerably impairs the economic efficiency of this type of energy generation. As an example, solar thermal power plants are mentioned, with the help of which the solar radiation striking the earth's surface is converted into electrical energy. The electrical power of such

Power plant is dependent on the intensity of solar radiation at the site and therefore subject to the change of day and night. As a result, electrical energy can only be generated during the day, while the power plant does not provide economic returns during the night. In addition, costs are incurred in order to design a power grid for the supply of time-varying amounts of electricity from such a power plant. The invention makes it possible to store a portion of the electrical energy, which is obtained under favorable conditions from a regenerative energy source, as a storage product from which electrical energy is obtained at unfavorable times, such as during the night hours. In the following, the invention will be explained in more detail with reference to an exemplary embodiment shown schematically in FIG.

The exemplary embodiment relates to a device for storing electrical energy, which is generated via a generator driven by a steam turbine. The device is, for example, part of a solar thermal power plant in which the steam required for the steam turbine with the help of solar radiation - and therefore only during the hours of the day - can be obtained. The stored electricity is released in phases of low solar radiation - primarily at night - again, whereby a continuous power production is possible. In the steam generator F, via the line 1 energy (eg solar thermal energy) and via line 2, a working medium (eg water) are supplied, is

High pressure steam generated 3, which is relaxed in the steam turbine D. The mechanical energy obtained is transferred to a coupled to the steam turbine D generator G and converted there into electricity. A first part 4 of this stream is fed to a consumer (not shown) while a second part 5 intended for storage is fed to the electrolyzer E. The electrolyzer E is preferably a high-pressure electrolyzer in which water 6, for example at a pressure of about 50 bar and a temperature of about 80 ° C., is separated by electrolysis into hydrogen 7 and oxygen 8. The hydrogen 7 is fed into the synthesis device S. At a pressure which is lower than the working pressure of the electrolyzer E and at a temperature of about 300 ° C, the hydrogen 7 is here reacted with carbon dioxide 9, which is taken from the storage device S1, in an exothermic reaction to methanol 10. The im

The electrolyzer E and the synthesis device S resulting waste heat are discharged via the two heat pipes W1 and W2 and the steam generator F, where they are used to generate the high-pressure steam 3. Methanol 0 and oxygen 8 as well as in the synthesis of methanol resulting water are fed into storage devices S2, S3 and S4 and stored there until they are used.

If necessary - for example, during the night hours - methanol 12 can be removed from the storage device S2 and together with water 13 of the

Decomposition device Z are supplied. Here it is in an endothermic reaction, e.g. converted by hydrothermal catalysis, into a decomposition product containing hydrogen and carbon dioxide, from which hydrogen 15 and carbon dioxide 16 are subsequently separated by pressure swing adsorption DW. The carbon dioxide 16 is returned to the storage device S1 while the hydrogen 15 is introduced into a fuel cell B where it is oxidized to water 19 with oxygen 17 obtained from the storage device S3 to generate electric current 18. The fuel cell B is coupled to the decomposition device Z via the heat pipe W3, so that waste heat arising in the fuel cell can be used to maintain the endothermic decomposition reaction.

Claims

claims

1. A method for energy storage, wherein from water (6) by means of electrolysis (E) generates hydrogen (7) and with at least one further starting material (9) to a product (storage product) (10) synthesized (S) is in the hydrogen chemically is present, and for caching in a storage device

(S2) is initiated, from which it can be taken to a material and / or energy recovery, characterized in that in the electrolysis (E) and / or synthesis (S) of the storage product (10) resulting waste heat (W1, W2 ) is used for heating and / or evaporation of the working medium (2) of a steam turbine (D).

2. The method according to claim 1, characterized in that hydrogen (15) obtained by the decomposition of storage product (12) and in a fuel cell (B) to generate electric current (18) is oxidized.

3. The method according to claim 2, characterized in that in the fuel cell (B) resulting waste heat (W3) for the decomposition (Z) of storage product (10) is used.

4. The method according to any one of claims 1 to 3, characterized in that

Ammonia or methanol as a storage product (10) is generated.

5. The method according to claim 4, characterized in that methanol as

Storage product (10) by the reaction of hydrogen (7) with carbon dioxide

(9) is recovered in a catalytically assisted reforming reaction.

6. Apparatus for storing energy, comprising an electrolyzer (E) for generating hydrogen (7) from water (6) and a synthesis device (S), in which in the electrolyzer (E) generated hydrogen (7) with at least one further educt (9 ) in a product (memory product) (10) is implemented, as well as a

Storage device (S2) for temporarily storing the storage product (10), characterized in that the electrolyzer (E) and / or the

Synthetic device (S) with a steam turbine (D) in thermal connection (W1, W2) are, so that in the electrolyzer (E) and / or the synthesis device (S) accumulating waste heat for heating and / or evaporation of

Working medium (2) of the steam turbine (D) is usable.

Apparatus according to claim 6, characterized in that the electrolyzer (E) and / or the synthesis device (S) with the steam turbine (D) via a

Heat pipe (W1.W2) are thermally coupled.

Device according to one of claims 6 or 7, characterized in that the synthesis device (S) is designed as a device for producing methanol or ammonia.

Device according to one of claims 6 to 8, characterized in that the memory device (S2) for temporary storage of the memory product (10) is arranged stationary or mobile.

Device according to one of claims 6 to 9, characterized in that it comprises a memory device (S1, S3, S4) in which a in the generation and / or utilization of storage product (10) resulting by-product (8,11, 16,19 ), wherein the storage device is stationary or mobile.