CONTINUOUS SUPPLY OF POWER TO AN ELECTROLYSIS PLANT
A method for continuously supplying power to an electrolysis plant with a replacement power supply following failure of the power supply and an electrolysis plant with an electrolysis stack. The method includes supplying the electrolysis plant with power from an energy potential present in an electrolysis stack of the electrolysis plant, the energy potential being convertable into power, and reducing the energy potential present in the electrolysis stack of the electrolysis plant in a controlled manner. An electrolysis plant with an electrolysis stack includes a control unit configured for activation of at least one load of the electrolysis plant for consuming power from an energy potential of the electrolysis plant.
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The invention relates to a method for continuously supplying power to an electrolysis plant with a replacement power supply following a failure of a power supply and to an electrolysis plant with an electrolysis stack.
Electrolysis plants are electro-chemical plants for conversion of water and electric current into hydrogen and oxygen.
Electrolysis plants are of an increasingly important technical significance, in particular for obtaining energy from regenerative energy sources. For example surplus wind or solar energy can be used to produce hydrogen by means of electrolysis. The hydrogen can be used hereafter on-demand and independent of wind or sun conditions as an energy carrier for energy recovery. This enables a stabilization required for technical and economic reasons of the naturally discontinuous regenerative energy production to be achieved.
What all variants of the method of water electrolysis have in common is that the electrolysis plants used can enter an uncontrolled operating state in the event of a power failure. This is the case for example if equipment necessary for operation, such as pumps, control devices, rectifiers or electric components, are no longer supplied with power and suddenly shut down.
This is to be avoided for reasons of technical safety in order to protect the plant, the environment and the operating personnel. For example a continuous supply of power to the electrolysis plant can be implemented for this purpose, which then continues to supply this plant with power after a failure of the actual power supply.
Various methods for continuous supply of power to an electrolysis plant after a power supply failure are known from the prior art.
In a known method, such as in WO 2005/031039 A2 for example, the electrolysis plant is supplied with power after a failure of the power supply by a battery-backed energy source or power source. In another known method, instead of the battery-backed energy source, a capacitor-backed energy source is used for continuous supply of power to the electrolysis plant.
An object of the invention is to specify an advantageous teaching for continuous supply of power to an electrolysis plant after a power failure. In particular the underlying object of the invention is to realize a continuous supply of power to an electrolysis plant that is favorable in terms of outlay and maintenance as well as advantageous in terms of safety.
This object is achieved, in accordance with the invention, by a method for continuous supply of power to an electrolysis plant with a replacement power supply after a power supply failure and an electrolysis plant with an electrolysis stack with the features of the respective independent claim. Useful embodiments and advantages of the invention emerge from the further claims and the description and relate to the method and to the electrolysis plant.
In the method the electrolysis plant is supplied with power in the replacement power supply as an alternative after the failure of the power supply of the electrolysis plant from an energy potential present in an electrolysis stack of the electrolysis plant and able to be converted into power, wherein the energy potential present in an electrolysis stack of the electrolysis plant and able to be converted into power is reduced in a controlled manner.
The invention is based—expressed in simple terms—on the idea that, at the point at which the power failure of the electrolysis plant occurs, an energy potential present in the electrolysis stack of the electrolysis plant itself and able to be converted into power is used in order to maintain the power supply of the electrolysis plant (continuously if possible). The energy potential present in the electrolysis stack of the electrolysis plant and able to be converted into power is used in this way in a controlled manner for further power supply of the electrolysis plant, wherein this energy potential is reduced in a controlled manner by this method.
The energy potential present in the electrolysis stack of the electrolysis plant and able to be converted into power can be reduced in a controlled manner such that an energy is taken from the potential and used explicitly for supply of power to the electrolysis plant or to parts of said plant. In a controlled manner can also mean that the energy potential is reduced with the ability to be influenced technically according to time, amount, location or origin. The controlled reduction occurs for example according to a predeterminable sequence of the different types of energy potential, according to a predeterminable amount of energy consumed or according to a predeterminable time, until there is an almost complete reduction of the energy potential.
Thus an especially advantageous continuous power supply in terms of safety can be realized, since a hazard potential usually present for the environment or the operating personnel after the power supply failure, for example in the form of a voltage or an overpressure, can be reduced in a controlled manner. Especially advantageously an adverse effect or endangering of the operating personnel or of the environment can be avoided in this way.
The power supply failure can be an intended or an unintended interruption of the power supply. The failure of the power supply is typically caused by an AC mains failure, by a power supply failure caused by some other kind of fault or by a maintenance or operation-related switching off of the power supply of the electrolysis plant or of at least one electrolysis stack of the electrolysis plant.
An energy potential present in the electrolysis plant can be a chemical, electro-chemical, electric, mechanical or pressure-based energy potential or can be composed of a number of such different types of energy potentials.
For example an energy potential is present in an electrolysis stack or in another part of the electrolysis plant, advantageously in a pressure container, in the form of pressurized operating gases (hydrogen, oxygen). A further energy potential can be present in the form of an electro-chemical or chemical potential in the electrolysis plant. The electro-chemical or chemical energy potential is present for example in the form of a gas cushion of an operating gas, especially hydrogen, capable of reaction, which adheres to an electrode or to a polymer electrolyte membrane of the electrolysis plant and by reversing a functional principle of the electrolysis plant (i.e. operation as fuel cell) is able to be converted into an electric current. An energy potential can also be present in the form of electric energy in electric or electronic components of the electrolysis plant, for example in a rectifier or in its capacitive elements.
After the power supply failure the electrolysis plant is supplied with power as an alternative from the energy potential present in the electrolysis stack and able to be converted into power, i.e. a replacement power supply is obtained. The electrolysis plant is preferably supplied continuously with power from the existing energy potential. Continuously in the given context means at least almost continuously. Between the power supply failure and an onset of the continuous power supply an unavoidable interruption of the power supply in terms of operation and safety for a limited time can occur. Expediently the power is supplied after a conversion of the energy potential into electric energy.
Especially advantageously an inexpensive continuous power supply can be realized in this way, since battery or capacitor-backed energy sources usually used for continuous power supply of electrolysis plants and the maintenance or replacement by rotation of such sources can be dispensed with.
Also advantageously a fire risk usually emanating from a battery-backed continuous power supply can be excluded. Of further advantage is that in this way a capacitive power supply usually restricted in its energy potential can at least be dimensioned with lower output, which brings with it cost savings. Also advantageously in this way an especially easy-to-maintain power supply is realized, since no additional high-maintenance plant components are needed to bring it about. Also advantageously no comprehensive additional plant components for realizing continuous supply of power are needed, so that an especially space-saving solution can be achieved. A complementary presence of two power supplies, for example one capacitive power supply and one power supply fed from the energy potential of the electrolysis plant is likewise possible.
The invention also makes provision for an electrolysis plant with an electrolysis stack and a control unit. The electrolysis plant is configured to carry out the method for continuous power supply of an electrolysis plant with a replacement power supply after a power supply failure. The control unit is configured for activation of at least one load of the electrolysis plant to consume power from an energy potential of the electrolysis plant.
Expediently the load is an electric or electronic component that is relevant for operation or further operation that is non-critical in safety terms or also for a controlled shutdown of the electrolysis plant. For example the at least one load is an electrically-actuated drain valve for reducing a pressure within the electrolysis plant. The load can also be a display element for visualization of the energy potential present in the electrolysis plant or a hazard potential of the electrolysis plant. Thus a more controlled pressure reduction and enhanced safety for the operating personnel and the environment can advantageously be achieved.
Preferred developments of the invention also emerge from the dependent claims. The developments relate both to the inventive method and also to the inventive electrolysis plant.
The invention and the described developments can be realized both in software and also in hardware, using a specific electric circuit for example.
Furthermore it is possible to realize the invention or a described development through a computer-readable storage medium, on which a computer program that carries out the invention or the development is stored.
The invention and/or each described development can also be realized by a computer program product, having a storage medium on which a computer program that carries out the invention and/or the development is stored.
In an advantageous embodiment the replacement power supply is fed at least partly from an electro-chemical energy potential, which is present in an electrolysis stack of the electrolysis plant, wherein the electrolysis stack is operated at least partly as a fuel cell for replacement power supply and for reducing the energy potential.
The electro-chemical energy potential can be contained in a hydrogen-water mixture present at an electrode or at a polymer electrolyte membrane of the electrolysis stack. After the power supply failure an electric current can be generated in this way by an electro-chemical reaction of the hydrogen-water mixture at the electrode or polymer electrolyte membrane for feeding the replacement power supply. I.e. the electrolyte stack is operated temporarily as a fuel cell, until the hydrogen-water mixture present is depleted. In this way an especially inexpensive and easy-to-maintain continuous power supply in the form of a so-called self-maintenance of the electrolysis plant can be achieved. A further advantage is that in this way a hazard potential emanating from the hydrogen-water mixture, which is a result of the danger of explosion of the mixture, can be minimized. Consequently it is of particular advantage that enhanced safety is achieved for the operating personnel, the environment and the electrolysis plant itself.
In a further embodiment the replacement power supply is fed for at least some of the time from a pressure-based energy potential that is present in the electrolysis stack of the electrolysis plant, and/or from an electric energy potential that is present in the electrolysis plant.
The electric energy potential can be contained as so-called residual potential in a rectifier or in its capacitive components or in other capacitive electric elements of the electrolysis plant.
The pressure-based energy potential can be contained in a pressurized working gas or working gas mixture of the plant.
In an advantageous development the replacement power supply is fed for at least some of the time from the pressure-based energy potential which is present in an electrolysis stack of the electrolysis plant, wherein the pressure-based energy potential is converted into electric energy by means of a turbine unit for supplying replacement power and for reducing the energy potential.
The turbine unit can comprise a turbine and a generator. Turbines and generators are well proven and widely used technical means. In this way a conversion of the pressure-based energy potential into electric energy for feeding the replacement power supply that is simple-to-realize and reliable can be achieved.
Advantageously a longer-lasting continuous power supply of the electrolysis plant can be achieved in this way. It is also of advantage that in this way a hazard potential emanating from the electric and/or pressure-based energy potential can be minimized and consequently enhanced safety for the operating personnel, the environment and the electrolysis plant itself can be achieved.
In accordance with a preferred development, initially an electro-chemical energy potential is reduced, subsequently an electric energy potential and finally a pressure-based energy potential.
For example the energy potential contained in the hydrogen-water mixture can initially be reduced, subsequently the energy potential of the capacitive electric elements of the electrolysis plant and finally the pressure-based energy potential of the oxygen can be reduced. However a different, predetermined sequence of potential reduction is also conceivable. Thus, in a simple manner, a staged reduction of the overall energy potential in accordance with the levels of the hazard potentials emanating from the various energy potentials can be achieved and a hazard-free state of the electrolysis plant can be explicitly achieved.
As an alternative or in addition, a pressure-based energy potential can also be present in a pressure container of the plant.
In an advantageous form of embodiment the replacement power supply is fed at least some of the time from an electric energy potential of a rectifier unit of the electrolysis plant, wherein the rectifier unit is operated for at least some of the time as an energy source for replacement power supply and for reducing the energy potential.
As an alternative or in addition the electric energy potential can be present in any given capacitive electric elements of the electrolysis plant. Especially advantageously, after the power failure, hazard potential emanating from rectifiers of the electrolysis plant can be explicitly reduced in this way.
Expediently the energy potential present in the electrolysis plant can be reduced to a hazard-free level within between 1 minute and 20 minutes, especially within from 2 minutes to 15 minutes, preferably within from 6 minutes to 8 minutes.
Through the reduction of the energy potential within between 1 minute and 20 minutes, for example within from 2 minutes, an especially timely reduction of the accompanying hazard potential than with less long-lasting power supply of the electrolysis plant can be achieved. By reducing the energy potential within from 2 minutes to 15 minutes, for example within 5 minutes, a timely reduction of the accompanying hazard potential can be achieved during a moderately long-lasting continuous power supply of the electrolysis plant. By reducing the energy potential within from 6 minutes to 8 minutes, for example within 7 minutes, a sufficiently timely reduction of the accompanying hazard potential can be achieved during an especially long-lasting continuous power supply of the electrolysis plant. Advantageously in this way on the one hand a sufficiently rapid reduction of the energy potential to a hazard-free level can be achieved, on the other hand a sufficiently long-lasting continuous power supply of the electrolysis plant can be provided.
Advantageously the hazard-free level of the energy potential is achieved in a voltage-free and/or current-free and/or overpressure-free and/or reaction gas-free operating state of the electrolysis plant.
Especially advantageously a reduction of a danger of explosion, a danger of short circuit and a danger of bursting is achieved in this way. In addition in this way a non-hazardous recommissioning of the electrolysis plant for the operating personnel and the environment can be achieved after the reduction of the energy potential and the restoration of the power supply.
In an advantageous development, after the reduction of the energy potential present in the electrolysis plant, the electrolysis plant is supplied continuously with power by means of a capacitive energy store.
Especially advantageously in this way an extension in time of the continuous power supply—beyond the reduction of the energy potential present in the electrolysis plant—can be achieved. This is especially of advantage if the energy potential present in the electrolysis plant is not adequate for a sufficiently long continuous energy supply. Furthermore capacitive energy storage units for continuous power supply are well-proven and cost effective, so that a reliable and inexpensive extended continuous power supply is achieved.
In accordance with a preferred embodiment a continuous power supply of at least one load of the electrolysis plant is provided.
Expediently the load is a safety-relevant load, for example an electrically-actuated valve or a pump, which is necessary for controlled further operation or for controlled shut down of the electrolysis plant. Advantageously the power supply in the given context is provided continuously in the sense that the load does not experience any operational or safety-relevant interruption of the power supply.
In an advantageous development the method is used to control the reduction of the energy potential present in the electrolysis plant to a hazard-free level.
Advantageously in this way a control intervention by the operating personnel in the sequence of the reduction of the energy potential can be achieved.
In accordance with a preferred embodiment the control unit is prepared for activation of at least one load of the electrolysis plant for consuming power from an electro-chemical energy potential of the electrolysis stack.
Expediently the electro-chemical energy potential is present in a hydrogen-water mixture present at an electrode or a polymer electrolyte membrane of the electrolyte stack. Advantageously a flowing away of a current generated as a result of an electro-chemical reaction within the electrolysis stack can be achieved by this type of activation.
The description given above of advantageous embodiments contains a plurality of features, which in some cases are reproduced in the subclaims in a number of combinations. These features can however expediently also be considered individually and combined into further sensible combinations. In particular these features are able to be combined individually and in any given suitable combination with the inventive method as well as the inventive arrangement in accordance with the independent claims.
The characteristics, features and advantages of this invention described above, as well as the manner in which these are achieved, will become clearer and easier to understand in conjunction with the following description of the exemplary embodiments, which are explained in greater detail in conjunction with the drawings. The exemplary embodiments serve to explain the invention and do not restrict the invention to the combination of features specified therein, also not in relation to functional features. In addition suitable features of a given exemplary embodiment can also be considered specifically in isolation, introduced into another exemplary embodiment to supplement it and/or be combined with a given claim.
In the Figures:
During normal operation of the electrolysis plant 2 the electrolysis stack 4 and the load 16 or the entire electrolysis plant 2 are supplied with operating energy via the power supply 10.
The electrolysis stack 4 is supplied with direct current or DC voltage by the rectifier unit 12. In the electrolysis stack 4 water is split up into hydrogen and oxygen under the influence of the direct current by an electro-chemical reaction at the polymer electrolyte membrane 6 and the electrodes 8. The hydrogen can be used hereafter as an energy carrier or reactive intermediate product. The oxygen can be discharged into the environment or supplied to a pressurized container. Typically, because of the aggregate state-related expansion of the reaction medium of water, not inconsiderable pressures in the range of between 30 bar and 50 bar occur within the electrolysis stack 4.
During normal operation the load 16 is also supplied with power by the power supply 10. The load can be a safety-relevant load, for example an electrically-actuated pressure-relief valve or a cooling device to avoid overheating of the electrolysis plant 2. During normal operation the safety-relevant function of the load 16 is maintained by the power supply 10.
In particular after a failure of the power supply 10, the electrolysis stack 4 of the electrolysis plant 2 has an energy potential 20. The energy potential 20 is made up of a diversity of elements, namely an electro-chemical energy potential 22, an electric energy potential 24 and a pressure-based energy potential 26. The pressure-based energy potential 26 can lie in a pressurized working medium of the electrolysis stack 4, preferably in oxygen with a pressure of between 30 bar and 50 bar and a volume of from 10 cm3 to 100,000 cm3. The pressure-based energy potential 26, especially after a failure of the power supply, represents a hazard risk for the environment, the electrolysis plant 2 itself and its operating personnel.
The electric energy potential 24 is produced especially from a dual-layer capacitor or residual energy of an electrode. After a failure of the power supply 10 in particular, the electric energy potential 24 represents a hazard risk for the environment, the electrolysis plant 2 itself and its operating personnel. For example operating personnel, under the influence of the electric energy potential 24, can suffer an electric shock and, as a result thereof, personal injury.
The electro-chemical energy potential 22 lies in a reaction capability of a hydrogen-water mixture present at the electrodes 8 or at the polymer-electrolyte membrane 6. In conjunction with a catalytic effect of the electrodes 8 or with specific characteristics of the polymer-electrolyte membrane 6, the water-hydrogen mixture breaks down—if the power supply from the rectifier unit 12 is not present—into water and freed-up charge carriers. Where it is possible for the freed-up charge carriers to flow away, an electric current, which is preferably used for continuous power supply of the electrolysis plant, flows. After failure of the power supply 10 in particular the electro-chemical energy potential 22 or the hydrogen-water mixture, because of its explosion potential, represents a not inconsiderable hazard potential.
After failure of the power supply 10 the electrolysis plant is supplied with power as an alternative and preferably continuously from the energy potential 20. For reasons of improved presentation in the present exemplary embodiment only the load 16 is connected to the replacement power supply fed via a supply line 28 from the energy potential 20, although electrolysis plants can usually have a plurality of loads.
In addition a further electric energy potential 25 can be present in capacitive electric elements of the electrolysis plant. In the present figure the capacitive element 14 of the rectifier unit 12 is merely shown as a representative component, although the electrolysis plant can have a plurality of capacitive elements.
To consume the power from the power feed line 28 of the replacement and preferably continuous power supply, the load 16 is activated via the control unit 18. In this way it is insured that the energy potential 20 present in the electrolysis stack 4 is reduced.
The feeding by the power supply line 28 of the replacement and preferably continuous power supply is done until the energy potential 20 is consumed. In this case the power supply line 28 of the continuous power supply can be fed simultaneously from the said different types of energy potential 22, 24 and 26 or in a predeterminable sequence from said potentials. In this way it is achieved on the one hand that the hazard potential associated with the energy potential can be reduced in a controlled manner. On the other hand any safety-relevant function of the load 16 is maintained in order to achieve a controlled further operation or a controlled shutdown of the electrolysis plant 2.
After the energy potential 20 is exhausted, the load 16 is supplied with further power from a capacitive energy storage unit 30. In this way it is achieved that, even with a premature exhaustion of the energy potential 20, sufficient energy to supply the safety-relevant load 16 is available. Especially advantageously the capacitive energy storage unit 30 can be dimensioned with significantly lower power and thus at significantly lower cost than normal. As an alternative or in addition the power can also be supplied via an electric energy potential 25 present in the capacitive component 14 of the rectifier unit 12.
At a point in time 32 the electrolysis plant 2 is operating normally. I.e. the power supply 10 has a voltage value 40, the electrolysis stack 4 has a voltage value 42, the load 16 has a voltage value 44 and the energy storage unit 30 is not exhibiting any operational activity (not in operation B=0).
Using the state described above as its starting point, at the point in time 34 a failure of the power supply 10 takes place. As a result the voltage U1 drops to the voltage value 46 or U1=0. The supply of power to the load is maintained as from point in time 34 by the electro-chemical energy potential 22 present in the electrolysis stack 4. As a result there is only a technically non-relevant adverse effect on the voltage value 44 of the load 16 at point in time 34. I.e. the supply of power to the load 16 is continued uninterrupted in the technical sense after the failure of the power supply 10. It would also be conceivable to undertake the supply of power to the load 16 by the energy potential 22 with an intentional interruption in time, for example with a supply gap of between 1 second and 100 seconds. The energy potential available or consumed for feeding the load is approximately represented by the cross-hatched area in
The supply of power to the load 16 from the electro-chemical energy potential 22 contained in the electrolysis stack 4 is continued up to point in time 36. At this point in time the voltage U2 of the electrolysis stack 4 has dropped to voltage value 48. The available energy potential is no longer sufficient for further feeding of the load 16 or for maintaining the voltage U3, so that the capacitive energy storage unit 30 is put into operation (B=1). The supply of power to the load is maintained from point in time 36 onwards by the capacitive energy storage unit 30, so that the result is only a technically non-relevant adverse effect on the voltage value 44 of the load 16 at point in time 36.
At point in time 38 a restoration of the power supply 10 occurs and the voltage U1 increases as a result to the voltage value 40. Operating energy is once again supplied to the load 16 via the power supply 10, the operating activity B of the capacitive energy storage unit is halted (B=0) and the voltage U2 of the electrolyte stack 4 rises to the original voltage value 42
Claims
1.-13. (canceled)
14. A method for continuous power supply of an electrolysis after a failure of a power supply, comprising:
- supplying as a replacement power supply the electrolysis plant with power from an energy potential present in an electrolysis stack of the electrolysis plant, with the energy potential being convertable into power; and
- reducing the energy potential present in the electrolysis stack of the electrolysis plant in a controlled manner.
15. The method of claim 14, further comprising at least temporarily feeding the replacement power supply from an electro-chemical energy potential which is present in the electrolysis stack of the electrolysis plant; and operating the electrolysis stack as a fuel cell for supplying replacement power and for reducing the energy potential.
16. The method of claim 14, further comprising at least temporarily feeding the replacement power supply from a pressure-based energy potential which is present in the electrolysis stack of the electrolysis plant and/or from an electric energy potential which is present in the electrolysis plant.
17. The method of claim 14, further comprising at least temporarily feeding the replacement power supply from a pressure-based energy potential which is present in the electrolysis stack of the electrolysis plant; and converting the pressure-based energy potential into electric energy by a turbine unit for supplying the replacement power and for reducing the energy potential.
18. The method of claim 14, further comprising at least temporarily feeding the replacement power supply from an electric energy potential of a rectifier unit of the electrolysis plant; and operating the rectifier unit as an energy source for supplying replacement power and for reducing the electric energy potential.
19. The method of claim 15, further comprising initially reducing the electro-chemical energy potential; subsequently reducing an electric energy potential; and finally reducing a pressure-based energy potential, for controlled reduction of the energy potential present in the electrolysis plant.
20. The method of claim 14, further comprising reducing the energy potential present in the electrolysis plant to a hazard-free level within 1 minutes to 20 minutes.
21. The method of claim 20, wherein the energy potential present in the electrolysis plant is reduced to the hazard-free level within 2 minutes to 15 minutes.
22. The method of claim 20, wherein the energy potential present in the electrolysis plant is reduced to the hazard-free level within 6 minutes to 8 minutes.
23. The method of claim 20, wherein the hazard-free level of the energy potential is achieved in a voltage-free and/or current-free and/or overpressure-free and/or reaction gas-free operating state of the electrolysis plant.
24. The method of claim 14, further comprising supplying the electrolysis plant with power without interruption using a capacitive energy storage unit, after reducing of the energy potential present in the electrolysis plant.
25. The method of claim 14, further comprising providing a continuous power supply of at least one load of the electrolysis plant.
26. The method of claim 14, further comprising controlling the reduction of the energy potential present in the electrolysis plant to a hazard-free level.
27. An electrolysis plant, comprising:
- an electrolysis stack having an energy potential which is convertable into power for use as a replacement power supply after a failure of a power supply; and
- a control unit configured for activation of at least one load of the electrolysis plant for consuming power from the energy potential of the electrolysis plant in a controlled manner.
28. The electrolysis plant of claim 27, wherein the energy potential is an electro-chemical energy potential of the electrolyte stack.
Type: Application
Filed: Mar 12, 2015
Publication Date: May 3, 2018
Applicant: Siemens Aktiengesellschaft (Muenchen)
Inventor: Jochen HEROLD (Weismain)
Application Number: 15/128,819
