HYDROGEN RECUPERATION FOR VEHICLES

Abstract

The invention relates to a method (100) for converting and/or storing electric energy E obtained from mechanical energy M in a vehicle comprising a motor (1), in particular a motor vehicle. In the method, a) mechanical energy M obtained when braking and/or during an overrun operation of the vehicle is converted into electric energy E in a first step using a generator (2), b) the electric energy is stored in an intermediate energy store (3) in a second step, c) the stored electric energy E is discharged to an electrolysis module (4) in a third step, d) the module converts the electric energy E into chemical energy C in a fourth step at least by splitting water (H.sub.2O) into hydrogen (H.sub.2) and oxygen (O2), and e) the chemical energy is conducted into a gas tank (5) of the vehicle for temporary storage and/or is supplied to the motor (1) and/or a fuel cell (10) of the vehicle in a fifth step.

Claims

1. A method for converting and/or storing electric energy E obtained from mechanical energy M in a vehicle comprising a motor (1), wherein the mechanical energy M is obtained when braking and/or during an overrun operation of the vehicle, the method comprising a) converting the mechanical energy into electric energy E in a first step using a generator (2), b) storing the electric energy in an intermediate energy store (3) in a second step, c) discharging the stored electric energy E to an electrolysis module (4) in a third step, d) having the module convert the electric energy E into chemical energy C in a fourth step at least by splitting water (H.sub.2O) into hydrogen (H.sub.2) and oxygen (O.sub.2), and e) conducting the chemical energy into a gas tank (5) of the vehicle for temporary storage and/or supplying the chemical energy to the motor (1) and/or a fuel cell (10) of the vehicle in a fifth step.

2. The method (100) according to claim 1, characterized in that the hydrogen (H.sub.2) is compressed by a compressor (6) prior to temporary storage in the gas tank (5).

3. The method (100) according to claim 1, characterized in that the voltage of an on-board power supply (15) of the vehicle is increased in order to increase the power density of the intermediate energy store (3) for the electric energy E.

4. The method (100) according to claim 1, characterized in that the hydrogen (H.sub.2) reacts with the carbon dioxide (CO.sub.2) present in the exhaust gases and/or carbon monoxide (CO) in a reactor module (14) to form methane (CH.sub.4) and water (H.sub.2O), wherein the methane (CH.sub.4) is conducted into the gas tank (5) of the vehicle and/or supplied to the motor (1).

5. The method (100) according to claim 1, characterized in that the water (H.sub.2O) required for the conversion of electric energy E into chemical energy C comes from a water tank (7) and/or a reactor module (14) and/or the fuel cell (10) and/or from exhaust gas (11) of the motor (1).

6. The method (100) according to claim 1, characterized in that the chemical energy C converted in the form of hydrogen (H.sub.2) and oxygen (O.sub.2) from the electric energy E is supplied to the fuel cell (10), which converts the chemical energy C into electric energy D under reaction of the hydrogen (H.sub.2) with oxygen (O.sub.2) to form water (H.sub.2O).

7. The method (100) according to claim 6, characterized in that the water (H.sub.2O) obtained during the reaction of hydrogen (H.sub.2) and oxygen (O.sub.2) is conducted into the water tank (7) and/or discharged to the electrolysis module (4).

8. The method (100) according to claim 1, characterized in that the compressor (6) is driven electrically and/or via exhaust gases (11) of the motor (1).

9. A mobile system for converting mechanical energy M via electric energy E into chemical energy C, which system is connected to a motor system and/or a fuel cell system of a vehicle, said mobile system comprising a water tank (7), an electrolysis module (4) which is at least connected to the water tank (7) and to which electric energy E is supplied from an intermediate energy store (3) of the motor system and/or of the fuel cell system, and a compressor (6), which is at least connected to a gas tank (5) of the motor system and/or the fuel cell system in order to compress at least the hydrogen (H.sub.2) converted in the electrolysis module (4) from the water (H.sub.2O) prior to being introduced into the gas tank (5).

10. A mobile system for converting electric energy E obtained from mechanical energy M into chemical energy C while carrying out the method of claim 1, the mobile system being is connected to a motor system and/or a fuel cell system of a motor vehicle, said mobile system comprising a water tank (7), an electrolysis module (4) which is at least connected to the water tank (7) and to which electric energy E is supplied from an intermediate energy store (3) of the motor system and/or of the fuel cell system, and a compressor (6), which is at least connected to a gas tank (5) of the motor system and/or the fuel cell system in order to compress at least the hydrogen (H.sub.2) converted in the electrolysis module (4) from the water (H.sub.2O) prior to being introduced into the gas tank (5).

11. The method (100) according to claim 4, characterized in that the water (H.sub.2O) required for the conversion of electric energy E into chemical energy C comes from a water tank (7) and/or the reactor module (14) and/or the fuel cell (10) and/or from exhaust gas (11) of the motor (1).

12. A method (100) for converting and/or storing electric energy E obtained from mechanical energy M in a vehicle comprising a motor (1), wherein the mechanical energy M is obtained when braking and/or during an overrun operation of the vehicle, the method comprising a) converting the mechanical energy into electric energy E in a first step using a generator (2), b) storing the electric energy in an intermediate energy store (3) in a second step, c) discharging the stored electric energy E to an electrolysis module (4) in a third step, d) having the module convert the electric energy E into chemical energy C in a fourth step at least by splitting water (H.sub.2O) into hydrogen (H.sub.2) and oxygen (O.sub.2), and e) conducting the chemical energy into a gas tank (5) of the vehicle for temporary storage in a fifth step.

13. A method (100) for converting and/or storing electric energy E obtained from mechanical energy M in a vehicle comprising a motor (1), wherein the mechanical energy M is obtained when braking and/or during an overrun operation of the vehicle, the method comprising a) converting the mechanical energy into electric energy E in a first step using a generator (2), b) storing the electric energy in an intermediate energy store (3) in a second step, c) discharging the stored electric energy E to an electrolysis module (4) in a third step, d) having the module convert the electric energy E into chemical energy C in a fourth step at least by splitting water (H.sub.2O) into hydrogen (H.sub.2) and oxygen (O.sub.2), and e) supplying the chemical energy to the motor (1) and/or a fuel cell (10) of the vehicle in a fifth step.

14. The method according to claim 13 wherein the fifth step (e) also includes conducting the chemical energy into a gas tank (5) of the vehicle for temporary storage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The method according to the invention and the modifications thereto as well as the advantages thereof and the mobile system according to the invention, which works with the method according to the invention, and the modifications thereto as well as the advantages thereof are subsequently explained in detail with the aid of the drawing.

[0021] It goes without saying that the previously mentioned features, which are to be explained in greater detail below, can be used not only in the combination specified in each case but also in other combinations.

[0022] In the drawing:

[0023] FIG. 1 shows a block diagram of the method according to the invention.

DETAILED DESCRIPTION

[0024] FIG. 1 shows schematically a method 100 according to the invention for operating a mobile system, i.e. a mobile recuperation system which operates in a mobile motor system and/or a mobile fuel cell system. The essential elements of the motor or fuel cell system lie in the depiction of FIG. 1 to the left of the line A-A. The elements which allow for the connection to the elements of the motor or respectively fuel cell system lie in the depiction of FIG. 1 to the right of the line A-A. The arrows comprising the dashed lines, respectively the reactor module 14 depicted with the dashed lines, represent optional connections, respectively an optional module or can be used as alternatives to the elements and connections depicted with the solid lines.

[0025] The method 100 depicted in FIG. 1 is used for converting and/or storing of electric energy E obtained from mechanical energy M in a vehicle, i.e. in a mobile system comprising a motor 1 and/or a fuel cell 10. In the method 100, energy M obtained when braking and/or during an overrun operation of the vehicle is converted into electric energy E in first step a) using a generator 2. In so doing, the mechanical energy M either from the motor 1, for example via the alternator operating as a generator or else during a braking operation via a wheel 16 of the vehicle and a generator 2 connected to the wheel, for example a motor, is converted into electric energy E by means of recuperation. The electric energy E is stored in an intermediate energy store (3) in a second step b) or optionally supplied to a compressor 6. In so doing, the generator 2 and the intermediate energy store 3 can, of course, also be connected to the on-board power supply 15 of the vehicle or else to other electric consumers of the vehicle. In a third step c), the electric energy B converted from the mechanical energy M via the generator 2, i.e. the recuperation energy is discharged to an electrolysis module 4. The electrolysis module 4 is used to convert water (H.sub.2O) into hydrogen (H.sub.2) and oxygen (O.sub.2) using electric energy E. The chemical energy obtained by splitting water into hydrogen and oxygen is supplied to the compressor 6 in the form of hydrogen, which compresses the hydrogen in an optional fifth step e) and pumps said hydrogen into a gas tank 5 of the vehicle for temporary storage.

[0026] Alternatively, the chemical energy C obtained in the form of hydrogen and oxygen can be directly supplied to the motor 1, for example an internal combustion engine or the fuel cell 10 of the vehicle as combustion gas. The hydrogen content or respectively oxygen content supplied to the motor 1 thereby reduces the consumption, i.e. the amount of the fuel to be burned, and thus the CO.sub.2 emissions of the motor 1, which is for example configured as an internal combustion engine. The chemical energy C coming from the electrolysis can, however, also be supplied to the fuel cell 10, which converts the chemical energy C into electric energy D by the hydrogen reacting with oxygen to form water. The electric energy D can, then, for example, be supplied to the on-board power supply 15 of the vehicle.

[0027] The water required for the electrolysis can come from a water tank 7 or can alternatively come via an exhaust gas treatment system 12 from the exhaust gases 11 of the motor 1 or from the reaction of the hydrogen with the oxygen to form water from the fuel cell 10. In order, however, to be able to always sufficiently provide water to the electrolysis module 4, it is advantageous to dispose the water tank as an intermediate store between the exhaust gas treatment system 12 and/or the fuel cell 10 and the electrolysis module 4. On the other hand, the water store 7 can be eliminated if it can be ensured that water is always sufficiently provided from the exhaust gas treatment system 12, i.e. from the exhaust gases 11 of the motor 1 or the fuel cell 10, to the electrolysis module for conversion of the electric energy E into chemical energy C.

[0028] In addition to the treatment of the exhaust gases 11 by the exhaust gas treatment system 12 to form water, carbon monoxide (CO) and carbon dioxide (CO.sub.2) from the exhaust gases can also alternatively be optionally supplied to a reactor module 14, in which the carbon monoxide or respectively the carbon dioxide reacts in a methanation reaction with the hydrogen obtained by splitting water in the electrolysis module 4 to form methane (CH4) and water. The methane obtained during the methanation reaction in the reactor module can also, as previously described for hydrogen, be compressed as chemical energy C via the compressor 6 and supplied to the gas tank 5 of the vehicle or be supplied as anode gas to the fuel cell 10. The water obtained during the methanation reaction can alternatively be provided to the electrolysis module 4 for electrolysis, i.e. to be used for the conversion of the electric energy E into chemical energy. Exhaust gas constituents and substances, which are not treated via the exhaust gas treatment system and are discharged back into the system, are conducted via an exhaust pipe 13 out of the system.

[0029] The hydrogen gas, or respectively the methane, introduced into the gas tank 5 via the compressor 6 is provided to the motor 1 in the form of chemical energy C, i.e. burned in the motor 1 as a combustion gas component, or as a reaction gas to the fuel cell 10.

[0030] Overall, a better pollutant balance also results from the method 100 according to the invention in addition to the improved energy balance. Said pollutant balance includes a reduction in the CO.sub.2 emissions of the motor because the combustion gas, for example the natural gas or liquefied petroleum gas, can additionally be reduced. The carbon monoxide and particularly the carbon dioxide contained in the exhaust gases 11 can additionally once again be reduced in a reactor module 14 with the hydrogen gas, which was converted in the electrolysis module 4 from electrical energy E into chemical energy, to methane and to water.

[0031] In order that the positive energy balance is not negated by the drive of the compressor 6 by using additional electrical energy, said compressor is preferably configured in the form of a turbocharger, which is driven by means of the exhaust gases 11, i.e. with mechanical energy M. The recuperation energy, namely the electric energy E converted from the mechanical energy M by means of the generator 2, can also optionally be used to drive the compressor 6.

[0032] As can be seen in the diagram, oxygen obtained from water during the electrolysis can be discharged out of the system; however, it is more energy-efficient, as already described, to either supply the oxygen as combustion gas to the internal combustion engine, i.e. supply it to the motor or supply the oxygen with the hydrogen to the fuel cell 10 in order to obtain electric energy D by forming water, said electric energy can then be provided to the on-board power supply.

[0033] In principle, the method 100 depicted as a block diagram in FIG. 1 can be used for vehicles with an internal combustion engine, i.e. preferably for gas operated vehicles which already have a gas tank 5 as well as for vehicles with electric motors, which obtain their energy from a fuel cell 10, and for hybrid vehicles, which namely have an internal combustion engine and at least one electric motor.