DE102008002698A1 - Electrical and/or mechanical energy producing device i.e. gas cell system, has compressor arranged upstream to reactor, and storage provided between compressor and reactor for intermediate storage of compressed gaseous initial substance - Google Patents

Abstract

The device i.e. i.e. gas cell system (10) has a compressor (24) compressing a gaseous initial substance e.g. oxygen, and arranged upstream to a reactor (12). A storage (34) is provided between the compressor and the reactor for intermediate storage of the compressed gaseous initial substance. A pressure sensor (40) is integrated into the storage, and a turbine (30) is provided for recuperation of the compression energy in direction of flow of the gaseous initial substance, where the turbine is arranged downstream to the reactor. An independent claim is also included for a method for operating a device for producing electrical or mechanical energy.

Description

The The present invention relates to a device for generating mechanical or electrical energy and a method for Operation of the same according to the preamble of the independent Claims.

State of the art

In Fuel cell systems are experiencing an increasing trend recently greater attention with regard to possible Applications as a drive unit for vehicles as well as for environmentally friendly provision of electrical energy.

Your Mode of action is based on the electrochemical reaction of particular gaseous fuels such as hydrogen, natural gas, methanol or Gasoline vapors. These in a so-called half cell of the Fuel cell reactions taking place with a second Coupled half-cell reaction, in which an electrochemical reduction of Oxygen takes place.

Usually Such fuel cell systems are compared with one Atmospheric pressure operated at elevated pressure to achieve a higher overall efficiency of the fuel cell. For this purpose, however, the fuel cell supplied fuel-containing or oxygen-containing gas streams are compressed.

While the fuel-containing gas stream usually in gas pressure accumulators is carried along and thus naturally a has correspondingly increased pressure, the fuel cell supplied oxygen-containing gas stream (usually air) be compressed first. The required electrical Power is often more than 2 kW.

Farther it comes in particular in the operation of fuel cell vehicles with large load spread in the case of a low load too Operating conditions on the fuel cell, in which a Degradation of cell components can occur. This is for example then the case when the fuel cell is operated at idle. To avoid this damage, the fuel cell stack artificially electrically charged, this in turn affects negatively affect the system efficiency of the fuel cell system.

To keep the energy required for the compression of the oxygen-containing gas stream supplied to the fuel cell as low as possible, is for example in the DE 10 2005 009 674 A1 proposed to mechanically or electrically couple the energy released during the expansion of stored hydrogen in a compressed gas storage with a compressor, which serves for the pre-compression of oxygen-containing gases for the fuel cell. However, this proposed system does not solve the idling problem already described.

Disclosure of the invention

task The present invention is an apparatus for producing mechanical or electrical energy to be provided during an increased internal pressure can be operated and still has a sufficiently good overall efficiency.

These Task is based on a device for generating electrical or mechanical energy, as well as a method of operation same with the distinguishing features of the independent ones Claims solved in an advantageous manner.

This is based in particular on the fact that between a reactor, the Implementation of at least one gaseous starting substance to release the mechanical or electrical energy, and a compressor for the compression of the gaseous starting substance a memory for temporarily storing the compressed gaseous Starting substance is provided.

Of the particular advantage of this arrangement is that in particular in operating states that are idling the device correspond to the generation of electrical or mechanical energy, the possibility exists, by means of the compressor, the mentioned to compress gaseous starting substance and to buffer them. In this way, even when idling the device a ensures basic electrical load through the compressor be so that it does not come to a degradation of the device can, but subjected to a sufficiently high base load becomes.

The cached compressed gaseous starting substance in turn is available for operating states, in which a maximum load to the device for generating electrical or mechanical energy is applied. Upon reaching such Operating conditions, the compressor in its performance throttled or at least temporarily switched off completely and the device for generating electrical or mechanical energy partially or completely with the cached in the memory be supplied compressed gaseous starting substance. In this way, maximum performance of the device for generating electrical or mechanical energy can be realized without it loss of performance due to continuous compression the gaseous starting substance comes.

One Another advantageous aspect is the fact that in particular in abrupt load changes, eg. In a so-called Kick down, for a high output of a fuel cell For example, needed air in a short time available can be made. While in conventional fuel cell systems during a load change process, the compressor first accelerates must be, with a time delay of about 500 ms may occur the present device for generating electrical energy in this Period from the integrated memory with intermediate enriched Air are supplied as a starting substance.

Further advantageous embodiments of the present invention emerge from the dependent claims.

So it is beneficial if the memory is for caching the compressed gaseous starting substance a pressure sensor having. With this is a much more effective control of the Reactor, compressor and buffer formed system possible.

Farther is advantageous if the reactor in the flow direction the gaseous starting substance downstream of a turbine is provided for recuperation of compression energy. this makes possible the recovery of compression energy based on the increased residual pressure of the exhaust gases leaving the reactor. The compression energy in turn stands for the compression additional gaseous starting substances available.

According to one particularly advantageous embodiment of the present invention Invention, the aforementioned buffer has another Derivation for the compressed gaseous starting substance. This offers the advantage that the cached gaseous Starting substance for other applications, such as the charging of an internal combustion engine or pneumatic applications, is available.

Short description of the drawing

A Embodiment of the present invention is in the drawing shown and in the following description in more detail explained. It shows

1 a schematic representation of an apparatus for generating electrical or mechanical energy according to an embodiment of the present invention.

embodiments the invention

An embodiment of the invention is in 1 graphically illustrated. In this case, the device according to the invention for generating electrical or mechanical energy is designed as a fuel cell system. It should be noted, however, that the device for generating electrical or mechanical energy may, for example, also comprise an internal combustion engine or a gas turbine.

The fuel cell system 10 includes a fuel cell 12 for example, a first half cell 12a and a second half cell 12b includes. In this case, for example, a plurality of fuel cells 12 combined into a so-called fuel cell stack. The fuel cell 12 serves to generate electrical energy by electrochemical means. For this, the fuel cell 12 supplied with an example gaseous fuel and with an oxygen-containing gas such as air. The gaseous fuel is preferably in a corresponding pressure tank 14 saved. He can via a so-called anode path 16 , which is preferably a pressure reducer or pressure regulator 18 has, the first half cell 12a be supplied.

The means of the fuel cell 12 obtained electrical energy, for example, an electric motor 20 supplied, which may be configured, for example, as a drive of a motor vehicle. Furthermore, the fuel cell 12 with air or other oxygen-containing gas via a so-called cathode path 22 provided. Because the half cells 12a . 12b the fuel cell 12 Preferably, be subjected to a relative to the air pressure increased gas pressure, which is the second half-cell 12b supplied air previously compressed. This happens for example by means of a compressor or compressor 24 ,

In order to recover at least a portion of the applied compression energy, the half-cell is included in the 12b leaving the cathode exhaust path 28 for example, a turbine 30 integrated. This serves to recuperate the pressure energy while providing mechanical or further electrical energy. Furthermore, in the cathode exhaust gas path 28 condensed water via a return line 32 the cathode or anode path 16 . 22 for humidifying the gaseous starting substances of the fuel cell 12 fed.

To optimize the overall system efficiency is preferably in the cathode path 22 a cache 34 integrated. This is in the present example via a page path 36 with the cathode path 22 connected.

Alternatively, the cache 34 but also directly into the cathode path 22 integrated so that's in the cathode path 22 guided air completely the cache 34 happens. Here is the cache 34 in the cathode path 22 between the compressor 24 and the fuel cell stack 12 positioned. Thus, the cache allows 34 Caching already precompressed air. For a better caching control, the side path is 36 for example, via a suitable 3-way valve 38 with the cathode path 22 connected.

Here is the 3-way valve 38 preferably equipped with a non-return function, which prevents compressed air from the compressor 24 can flow in the wrong direction. Usually in the fuel cell 12 one compared to the cache 34 deviating pressure level prevails, is the 3-way valve 38 furthermore preferably provided with a suitable pressure control function. This can be ensured for example by a clock mode or by a corresponding proportional function.

Furthermore, in the cache 34 a pressure sensor 40 be provided. This serves to detect the accumulator pressure in the buffer 34 and supports an efficiency-optimized control of the device 10 for generating electrical or mechanical energy. Alternatively to positioning a pressure sensor 40 in the cache 34 may be a corresponding one for controlling the device 10 designed, not shown control unit are equipped with a functional algorithm based on, for example, the control of the 3-way valve 38 , A pressure sensor, not shown, in the cathode path 22 and based on the control of the compressor 24 an estimate of the pressure in the cache 34 calculated.

Furthermore, the cache 34 a second outlet for compressed air, not shown, which performs a function as a pressure reducer or the provision of precompressed air for pneumatic purposes or for charging a corresponding internal combustion engine is used. Other applications in the cache 34 stored compressed air can exist in the mobile supply of compressed air for machine applications or for craft equipment. The cache 34 For example, it has an internal volume of 2 to 100 liters, preferably 10 to 60 liters, and more preferably 15 to 30 liters.

The positioning of the cache 34 in the cathode path 22 in particular serves to avoid critical operating states when the fuel cell is idling 12 , Normally, fuel cells are operated in an idling state either with very low gas flows, with the risk of degradation of the electrochemical half-cells 12a . 12b or the fuel cells are artificially charged with a load that causes a basal metabolic rate of the fuel cells.

In contrast, in the embodiment according to the invention, for example, in an idle operating state of the compressor 24 operated as base load and the compressed air in the buffer 34 saved. In this way, the idle operation of the fuel cell 12 generated electrical energy in the form of pressure energy for subsequent operating conditions are stored. This increases the overall efficiency of the fuel cell system. General is the compressor 24 in phases of low load on the fuel cell 12 operated and used to fill the cache 34 ,

An alternative is to idle the fuel cell stack 12 the compressor 24 at least largely out of service and take the second electrochemical half cell 12b with in the cache 34 store stored compressed air. In this way, a shutdown of the fuel cell 12 at standstill, for example, a corresponding, the fuel cell system 10 vehicle contained and the associated stack aging or shortening the life of the fuel cell stack 12 be avoided with little loss of efficiency.

During idle operation in the buffer 34 cached air, for example, the fuel cell 12 at high load requirements in addition to the already using the compressor 24 supplied air or it can be used as the sole air supply of the second electrochemical half-cell 12b serve.

Basically, a filling of the cache 34 with compressed air whenever possible by means of the compressor 24 provided amount of compressed air both the current needs of the fuel cell 12 is sufficient as well as an additional storage in the cache 34 allows.

This allows an alternate operation of the compressor 24 , Thus, in phases of low fuel cell 12 applied load of the compressor 24 switched on and in phases higher on the fuel cell stack 12 applied loads the performance of the compressor 24 shut down or turned off. The necessary pressure buildup in the cathode path 22 then takes place partially or exclusively by means of the buffer 34 ,

The device for generating electrical or mechanical energy may alternatively also comprise an internal combustion engine or a gas turbine instead of a fuel cell. So can the compressor 24 For example, also serve the charging of an internal combustion engine. Also when positioning a buffer between the compressor 24 and one instead of the fuel cell 12 provided internal combustion engine or a gas turbine, the above-described operating method can apply substantially unchanged in this arrangement. It results already on the basis of 1 explained advantages of improving the overall efficiency of the device for generating electrical or mechanical energy in an analogous manner.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102005009674 A1 [0007]

Claims (11)

Device for generating electrical or mechanical energy, comprising a reactor ( 12 ), to which at least one gaseous starting substance is supplied and reacted therein with the release of mechanical or electrical energy, and with at least one reactor ( 12 ) upstream compressor ( 24 ) for the compression of the gaseous starting substance, characterized in that between the compressor ( 24 ) and the reactor ( 12 ) a memory ( 34 ) is provided for the intermediate storage of the compressed gaseous starting substance. Device according to claim 1, characterized in that the gaseous Starting substance is air or oxygen. Device according to claim 1, that in the memory ( 34 ) a pressure sensor ( 40 ) is integrated. Apparatus according to claim 2, characterized in that in the flow direction of the gaseous starting substance, the reactor ( 12 ) downstream of a turbine ( 30 ) is provided for recuperation of compression energy. Device according to one of claims 1 to 3, characterized in that the memory ( 34 ) by means of a check-back-protected three-way valve ( 38 ) with the compressor ( 24 ) and the reactor ( 12 ) is in fluid-conducting contact. Device according to one of the preceding claims, characterized in that the temporary storage ( 34 ) has a further derivative for the compressed gaseous starting substance. Device according to one of the preceding claims, characterized in that the reactor ( 12 ) is a fuel cell. Device according to one of the preceding claims, characterized in that the reactor ( 12 ) is an internal combustion engine or a gas turbine. Method for operating an apparatus for generating electrical or mechanical energy according to one of Claims 1 to 8, characterized in that the reactor ( 12 ) temporarily at least partially from the cache ( 34 ) is supplied with a gaseous starting substance. Method according to claim 9, characterized in that the compressor ( 24 ) in phases of low on the reactor ( 12 ) is applied adjacent electrical or mechanical load. A method according to claim 9 or 10, characterized in that a power reduction or shutdown of the compressor ( 24 ) in the presence of a predetermined degree of filling of the buffer ( 34 ) he follows.