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Title:
MULTI-TRIGGERED ELECTRODES IN ELECTROCHEMICAL SYSTEMS
Document Type and Number:
WIPO Patent Application WO/2019/098824
Kind Code:
A1
Abstract:
The present invention is in the field of an electrochemical hydrogen storage system for forming a chemical fuel, such as by electrolysis of water thereby forming hydrogen, and for storing electricity, such as during daylight, and for delivering electricity and/or hydrogen during night, as well as to a method of operating said electrochemical hydrogen and/or oxygen storage system, a battery with cells of the system, and a chemical production unit.

Inventors:
WENINGER, Bernhard (Postbus 5, 2600 AA Delft, NL)
Application Number:
NL2018/050749
Publication Date:
May 23, 2019
Filing Date:
November 12, 2018
Export Citation:
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Assignee:
TECHNISCHE UNIVERSITEIT DELFT (Stevinweg 1, 2628 CN Delft, NL)
International Classes:
C25B15/02; C25B1/02; C25B9/18; H01M10/42; H01M16/00
Domestic Patent References:
WO2016178564A12016-11-10
WO2015065957A12015-05-07
WO2016178564A12016-11-10
WO2016178564A12016-11-10
Foreign References:
US20060088739A12006-04-27
EP2781624A12014-09-24
Other References:
F. M. MULDER ET AL: "Efficient electricity storage with a battolyser, an integrated Ni-Fe battery and electrolyser", ENERGY & ENVIRONMENTAL SCIENCE, vol. 10, no. 3, 14 December 2016 (2016-12-14), Cambridge, pages 756 - 764, XP055402364, ISSN: 1754-5692, DOI: 10.1039/C6EE02923J
Attorney, Agent or Firm:
VOGELS, Leonard Johan Paul (Weteringschans 96, 1017 XS Amsterdam, NL)
Download PDF:
Claims:
CLAIMS

1. Electrochemical storage system comprising

a multi cell-array with [2,n] cells electrically connected in series,

each cell comprising

a membrane, a first cell compartment and a second cell compartment, and electrolytes,

at least one Hydroxyl Storage Electrode (HSE) with at least one appendant Hydrogen Evolution Electrode (HEE) to gether forming a negative electrode,

at least one Oxygen Evolution Electrode (OEE) form ing a positive electrode,

at least one first electrical connection to the pos itive electrode and at least one fourth electrical connection to the negative electrode,

wherein the fourth electrical connection at the cell side is split into a fifth electrical connection to the at least one HSE and a sixth electrical connection to the at least one HEE,

wherein the negative electrode of cell m is in electrical connection to the positive electrode of cell m+1,

wherein hydrogen evolution (IHE) currents between HSEi and HEEi and optionally oxygen evolution (IOE) currents OEEi (ie[l,n]) are independently controlled with at least one controller,

wherein electrical connections provide a multi-trig gered electrode, and

wherein the at least one first electrical connection of the first cell is adapted to be electrically connected to a first terminal of an external DC power source/sink and wherein the at least one fourth electrical connection of the last (nth) cell is adapted to be electrically connected to a second ter minal of the DC power source/sink.

2. Electrochemical hydrogen storage system according to claim 1, wherein the positive electrode comprises at least one appendant Proton Storage Electrode (PSE) , and wherein the first electrical connection at the cell side is split into a second electrical connection to the at least one PSE and a third electrical connection to the at least one OEE.

3. Electrochemical hydrogen storage system according to any of claims 1-2, wherein the controller is a DC/AC controller with an individually controllable lAc/ioc current ratio in use, wherein the DC is provided at the electrode side of the controller .

4. Electrochemical hydrogen storage system according to claim 3, wherein the controller has at least one AC current for controlling oxygen evolution (IOE) currents and inde pendently at least one AC current for controlling hydrogen evolution (IHE) currents, preferably one AC current for con trolling all oxygen evolution (IOE) currents and one AC current for controlling hydrogen evolution (ΪHE) currents.

5. Electrochemical hydrogen storage system according to any of claims 1-4, wherein the controller comprises a trans former .

6. Electrochemical hydrogen storage system according to any of claims 1-5, wherein the HSE, HEE, optional PSE, and OEE electrodes are each independently selected from Ni, Fe, Cd,

Co, W, Mo, Pt, Ru, Ir, C, and combinations thereof.

7. Electrochemical hydrogen storage system according to any of claims 1-6, wherein ne [3-1000].

8. Electrochemical hydrogen storage system according to any of claims 1-7, comprising k multi cell-arrays in parallel, wherein ke [2-250] .

9. Electrochemical hydrogen storage system according to any of claims 1-8, comprising per cell each individually 2-100 Hydroxyl Storage Electrode (HSE) with each individually 2-100 appendant Hydrogen Evolution Electrode (HEE) together forming a negative electrode, and each individually 2-100 optional Proton Storage Electrode (PSE) with each individually 2-100 appendant Oxygen Evolution Electrode (OEE) forming a positive electrode,

wherein preferably at least one of a number of HEE's is equal to a number of hydrogen evolution currents, a number of OEE' s is equal to a number of oxygen evolution currents, a number of HSE's is equal to a number of controllable bidirectional HSE currents plus 1, and a number of PSE' s is equal to a number of controllable bidirectional PSE currents plus 1.

10. Electrochemical hydrogen storage system according to any of claims 1-9, wherein at least one HSE electrode is adjacent to at least one HEE electrode, preferably wherein all HSE electrodes are adjacent to at least one HEE electrode, and/or wherein at least one optional PSE electrode is adjacent to at least one OEE electrode, preferably wherein all optional PSE electrodes are adjacent to at least one OEE electrode.

11. Electrochemical hydrogen storage system according to any of claims 2-10, wherein the at least one HSE electrode and at least one HEE electrode form an array of electrodes, and/or wherein the at least one PSE electrode and at least one OEE electrode form an array of electrodes.

12. Electrochemical hydrogen storage system according to any of claims 1-11, wherein electrolytes are selected from 0H and H2 for the HEE side, preferably at a concentration of 0.1- 12 mole/1, and from 0H~/02 for the OEE side, preferably at a concentration of 0.1-12 mole/1.

13. Electrochemical hydrogen storage system according to any of claims 1-12, wherein electrolytes are dissolved in wa ter, preferably de-ionized water, preferably with a conductivity of < 0.5 mS .

14. Electrochemical hydrogen storage system according to any of claims 1-13, comprising in fluidic connection with the storage system at least one of a refill unit and a storage system.

15. Electrochemical hydrogen storage system according to any of claims 1-14, comprising at least one liquid-level sensor .

16. Method of operating an electrochemical hydrogen stor age system according to any of claims 1-15, comprising loading the system during daytime by a total system current iTsc and discharging the system during night-time.

17. Method of operating according to claim 16, wherein a fraction of power available for loading is used for storing hydrogen .

18. Method according to any of claims 16-17, comprising charging in daytime at least one cell by providing a part of an XTSC current to at least one HSE and through a cell to at least one PSE, and providing electrolysis in daytime by providing a part of an iTSc current to at least one HEE and through a cell to at least one OEE,

discharging at least one cell during night time by providing an iTsc current to at least one PSE and through a cell to at least one HSE and providing electrolysis in a cell by a current from at least one OEE to at least one PSE and electrolysis in a cell by a current from at least one HEE to at least one HSE.

19. Method according to any of claims 16-18,

(A) wherein in at least one cell, preferably in all cells, in daytime 75-100% of the ITSC current is provided to the at least one HSE, and independently 75-100% of the ITSC current is pro vided to the at least one PSE, and/or

wherein in night-time 75-100% of the ITSC current is provided to the at least one HSE, and independently 75-100% of the ITSC current is provided to the at least one PSE, or

(B) wherein in at least one cell, preferably in all cells, in daytime 75-100% of the ITSC current is provided to the at least one HEE, and independently 75-100% of the ITSC current is provided to the at least one OEE, and/or

wherein in night-time no current iT$c is provided and electrolysis is performed by providing a current from the OEE to the PSE and from the HEE to the HSE, or

(C) wherein in at least one cell, preferably in all cells, in daytime 15-90% of the iTsc current is provided to the at least one HSE, and independently 10-85% of the iTsc current is provided to the at least one HEE, and independently 1-50% of the ITSC current is provided to the at least one PSE, and independently 50-99% of the iTsc current is provided to the at least one OEE, and/or

(D) wherein in night-time 80-1000% of the iTsc current is pro vided to the at least one HSE, and independently a current IHE is provided from the HEE to the HSE, and independently 75-100% of the ITSC current is provided to the at least one PSE.

20. Method according to any of claims 16-19, wherein cur rents are switched on during a first period of time and are switched off during a second period of time.

21. Battery with [l,n] cells according to any of claims 1-15 with a controller for regulating power distribution.

22. Chemical production unit comprising at least one electrochemical hydrogen storage system according to any of claims 1-15, wherein hydrogen or oxygen is supplied.

23. Chemical production unit according to claim 22, com- prising at least one of a biogas production unit, a cement production unit, an ammonia production unit, a urea production unit, and a syngas production unit.

Description:
Multi-triggered electrodes in electrochemical systems

FIELD OF THE INVENTION

The present invention is in the field of an electrochemical hydrogen storage system for forming a chemical fuel, such as by electrolysis of water thereby forming hydrogen, and for storing electricity, such as during daylight, and for delivering electricity and/or hydrogen during night, as well as to a method of operating said electrochemical hydrogen and/or oxygen storage system, a battery with cells of the system, and a chemical production unit.

BACKGROUND OF THE INVENTION

The present invention Is In the field of an electrochemical hydrogen storage system for forming a chemical fuel, such as by electrolysis of water thereby forming hydrogen. Alternative approaches relate to forming hydrogen also a hydrocarbon, syn gas, ammonia, urea, and an alcohol may be formed. Based on readily available fluids these chemical fuels can be produced.

A source for e.g. the electrolysis may be solar radiation.

Electrolysis of a species as water relates to decomposition of the species (water) into its constituents (oxygen and hy drogen) by providing an electric current through said species. Thereto the species is typically in fluid form. In case of water an objective is to produce hydrogen. Electrolysis can be used to skim off excess power, such as from wind energy.

It is noted that at this point in time production of hydro gen from water is considered not competitive. There are vari ous production methods, such as steam reforming, production of hydrogen from hydrocarbons, biological production, various forms of electrolysis, photo electrochemical water splitting, by concentrating solar energy, catalytic production, etc.

A good example of a suitable electrochemical storage cell is given in WO2016/178564 A1 of the present applicant.

However, standard assemblies in electrochemistry typically consist of a working electrode, a counter electrode, a sense electrode and a reference electrode. Advanced equipment for electrochemical research comprises bipotentiostat and multi channel potentiostats . Bipotentiostats are commonly used in rotating disk setups and possess a second working electrode which can be set to a voltage offset with respect to the sense or reference electrode allowing for the detection of reaction intermediates at low currents. Multichannel systems allow for testing multiple working electrodes versus a common counter electrode or for testing multiple electrode pairs within one electrochemical system. However, these configurations cannot be assembled to multi-cell arrays.

The present invention therefore relates to an improved electrochemical storage system for generating chemical fuels, which solve one or more of the above problems and drawbacks of the prior art, providing reliable results, without jeopardiz ing functionality and advantages.

SUMMARY OF THE INVENTION

The present invention relates to an electrochemical storage system for forming a chemical fuel, and for storing electric ity, and a method of operating said electrochemical hydrogen storage system, a battery with cells of the system, and a chemical production unit. The present system can be used for storage (and generation) of hydrogen of oxygen, and both hy drogen and oxygen. The present system provides various ad vantages. The present system is balancing redundant. In an ex emplary embodiment it typically has at least one proton and at least one hydroxyl storage electrode, wherein at least one electrode is for hydrogen production and at least one electrode is for oxygen production. In an exemplary embodiment wherein one electrode is capable of battery functionality and electrolysis functionality one can reduce the system; this works only with the present electrodes which have shown double functionality. Overall the ¾ and 0 2 production is preferably stoichiometric . The electrode assembly may be arranged in a way to benefit from convection caused by gas production to de crease diffusive losses. The multi-dimensional ion-flow inside the structure can to be optimised to reduce over-potentials.

The concept of multi-triggered electrodes can be applied in electrochemical systems. The control system for multi-trig gered electrodes can be applied in multi-cell bipolar arrange ment with just one control-unit to control all HEE (resp. OEE ) electrodes, such as with an isolated connection using a AC transformer (with a controllable and preferably fixed current ratio under ideal conditions) together with a AC/DC converter {with a controllable and preferably defined current ratio) .

The control units for all HEE (resp. OEE) can be connected in series. Therefore all HEE and OEE can be triggered by the same AC current which leads to a defined I HE ( resp. I OE ) for all con nected electrodes. The storage electrodes are typically not limited to one set of gas production electrodes. There may be multiple subsets of gas production electrodes, as in addition to controlled 0 2 and H 2 production it might be beneficial to locate extra gas production electrodes at suitable locations inside the storage electrodes to generate a convective flow inside the electrodes to reduce diffusive losses. Typically all electrodes in one compartment are isolated from one and another. A complete and independent control of H 2 and Oz pro duction is possible as well as to decouple the electrolysis process typically involved. Also a postponed electrolysis may be provided. Actually, most of the work required for electrol ysis is required when electricity is abundant. Through the concept of storing and releasing the hydrogen/oxygen at a later moment less electrical storage capacity is required (de crease by 80% compared to independent battery and electrolyser operation. This concept is demonstrated using ammonia produc tion. The multi-triggered electrodes-concept can be expanded, such as to batteries (only storage electrodes, e.g. Li/Na cathodes and anodes; only fuel cells electrodes and other electrochemical systems. With the present storage system it is possible to decouple oxygen and hydrogen production and to store protons and hydroxyl ions in storage electrodes. Both gasses can be released on demand in a controlled way. The con cept of multi-triggered electrodes can be applied in various other electrochemistry applications. Examples are large bat tery stacks with multiple electrodes adjacent to one and an other and fuel cell systems with controlled reaction rates at different locations of the surface. Also electro-chemical CO 2 reduction with controllable electrodes with different selec tivity is possible. The present multi-electrode electrochemi cal system is easily expandable such as by using a series con nection between the cells. For instance, in batteries, fuel cell systems, and electrolysers typically only one anode and one cathode per subsystem are used. The present system allows for multiple cathodes and multiple anodes within a cell. An easy control of all individual cell-electrodes is obtained.

The current of the individual electrodes is controlled by ap plying a total stack current and by redirecting parts of the current to other electrodes. In an example hydrogen and oxygen storage and controlled hydrogen and oxygen production is shown.

The present system can be fed by intermittent energy input and can provide electricity output (as battery) and controlla ble hydrogen and oxygen output, typically at the same time.

Such may be a requirement for large-scale chemical producers, such as for ammonia, such as to replace steam methane reform ing (H 2 input) with renewable electricity sources. The present system can also be applied in combination with oxyfuel cement production. The device can provide oxygen on demand for the production process. It is considered that the output of the cement production process is a highly concentrated C0 2 stream used for Carbon sequestration. This waste stream is also a good carbon source for C0 2 reduction (usually above 95% which is much higher than waste streams from e.g. fossil fuel power plants, which is usually around 35%) . So in addition to renew able H 2 production also carbon based fuels can be produced, with a negative carbon footprint

(Cement absorbs C0 2 , hence the negative carbon footprint) . Controlled hydrogen output is also desirable for integration of renewable ¾ for upgrading biomass related processes. Usually all this processes include a water-gas shift step, adding ¾ shift the equilibrium for CO 2 towards CO => higher carbon uti lisation of biomass processes.

It is noted that the present chemical fuel can in principle be any fuel that can be made from fluids by electrolysis; the fuel provides energy when it is oxidized.

With the term "fluid" any gaseous or liquid is indicated. With the term "adjacent" it is implied two elements that are adjacent are in direct or indirect contact with one and an other. With the term "appendant" it is implied that elements, such as the electrodes, form an alternative to one and an other, i.e. can be used as subsidiary to one and another, and are additional to one and another, i.e. can be used both at the same time.

Details of a for the present invention exemplary suitable cell can be found in WO2016/178564 Al, which document and its contents are incorporated herein by reference. Especially fig ures 1A and IB, and the description thereof provide details, as well as methods of operation such a cell and boundary conditions thereof. Some details are that each cell may at least comprise an opening for introduction of the respective aqueous liquids. The aqueous liquid used is especially a basic aqueous liquid, such as comprising one or more of KOH, LiOH, BaOHt, and NaOH. The cell aqueous liquid within the cells are preferably alkaline, such as at least 0.1 mmole/1 OH-, especially at least 3 mole/1 OH , even more especially at least 3 mole/1 OH , such as at least about 6 mole/1 OH . The concentration of the hy droxide in water is typically in the range of 4.5- 8.4 mole/L (20-32 wt . % for KOH) . Each cell may also comprise a further opening, especially configured for removal of the aqueous liquid and/or for removal of gas. Both may escape from the same opening. In an example the first cell gas comprises ¾ gas and the second cell gas comprises O 2 - The gas flow may be in the range of about 0.1 ml/cm 2 /min- 100 ml/cm 2 /min, such as 1-10 ml/cm 2 /min, whereas refill of water may be in the order of 0.1- 10 g/cm 2 /h, such as 0.3-0.5 g/cm 2 /h (@25 °C, 10 5 kPa, 1 A/cm 2 ) . Each cell also comprises electrodes. Exemplary embodiments of said electrodes and methods of making the same can be found in the above publication. Typically a first compartment comprises a Fe-based electrode, and the second compartment a Ni-based electrode, also in view of the electrolysis. The Ni-based electrode may comprise at least one of Co, La, Li, Fe, Ba, Pr, and combinations thereof. In an embodiment the amount of

Ni(OH)2 material is reduced significantly with respect to the nominal capacity of a Fe-based electrode. The Ni-based cathode can have a capacity of 50% or of even only 10% of the Fe based electrode. So the relative capacities of the electrodes (cath ode and anode) can be varied, such as a Ni-based electrode having a capacity in the range of 10-80% of a Fe-based elec trode. A pressure in a compartment may be as high as 20*10 3 kPa-80*10 3 kPa, which pressure may be controlled. Fig. la and lb of WO2016/178564 schematically show a functional unit com prising a first compartment, a second compartment, and a mem brane. The first compartment comprises a first electrode, such as an iron based electrode. The second compartment comprises a second electrode, such as a nickel based electrode. The mem brane is for blocking transport of one or more of e.g. 0 2 and H 2 over the membrane. The membrane is preferably permeable for electrolytes, such for OH , Na + , Li + , Ba 2+ , and K + . A cell may be substantially entirely enclosed by pressure containment.

Fig. lb schematically depicts an embodiment of an energy apparatus having an electrical energy storage functionality and an electrolysis functionality. The first and second compartment comprises one or more openings for a liquid and for a gas.

Further, electrical connections are provided.

In the present system an array of cells is provided. If one row of cells is provided these cells are connected electri cally in series. If more than one row is provided these rows may be connected in series, in parallel, or both. Standardized cells may be used, as well as varying cells, though using largely the same cells is preferred in view of simplicity of operation. Each cell comprises a membrane for separating liq uids being present in a first and second compartments. The liquids of each compartment comprise electrolytes, typically dissolved in an aqueous medium, which are separated by the membrane. Each compartment comprises at least one electrode.

The at least one electrode may form a negative electrode or a positive electrode, one located in the first compartment and the other in the second compartment. The negative electrode comprises at least one Hydroxyl Storage Electrode (HSE) with at least one appendant Hydrogen Evolution Electrode (HEE) , typically an array of appendant electrodes, whereas the posi tive electrode comprises at least one Oxygen Evolution Elec trode (OEE) and optionally at least one appendant Proton Stor age Electrode (PSE) , typically an array of appendant elec trodes. Cells are electrically connected to one and another. Amongst others thereto at least one first electrical connec tion to the positive electrode and at least one fourth electrical connection to the negative electrode is provided. The negative electrode of cell m is in electrical connection to the positive electrode of cell m+1. The fourth electrical connection at the cell side is split into a fifth electrical con ¬ nection to the at least one HSE and a sixth electrical connection to the at least one HEE. The hydrogen evolution (I HE ) currents between HSEi and HEEi and optionally oxygen evolution (i oE ) currents, such as between optional PSEi and OEEi (ie

[l,n]), are independently controlled with at least one controller; typically one controller per current is provided. The electrical connections and controller therewith provide a multi-triggered electrode. E.g. for power storage and power provision the at least one first electrical connection of the first cell is adapted to be electrically connected to a first terminal of an external DC power source/sink and wherein the at least one fourth electrical connection of the last (n th ) cell is adapted to be electrically connected to a second ter minal of the DC power source/sink; energy generated by a power source can be stored as such in the present system.

With the present system chemical fuels can be generated using electrochemical reduction and oxidation. The most common example thereof is the oxidation and reduction of water, where hydrogen and oxygen are evolved. As an alternative, CO 2 can be reduced, together with water oxidation, to obtain carbon mon oxide. As a third example, the combination of these reactions can yield hydrocarbons, which can be used as fuel.

In a second aspect the present invention relates to a method of operating an electrochemical hydrogen storage system according to the invention, comprising loading the system dur ing daytime by a total system current i T sc and discharging the system during night-time. As such e.g. imbalances in energy generation and consumption can be accommodated as well as electrolytic species such as hydrogen and oxygen can be pro vided .

In a third aspect the present invention relates to a bat tery with [l,n] cells, such as [2,n] cells, according to the invention with a controller for regulating power distribution. The present layout is equally applicable to small systems, such as to batteries with one or more cells. In a fourth aspect the present invention relates to a chemical production unit comprising at least one electrochemi cal hydrogen storage system according to the invention, wherein hydrogen or oxygen is supplied, preferably at a con stant flow rate.

Thereby the present invention provides a solution to one or more of the above mentioned problems and drawbacks.

Advantages of the present description are detailed through out the description.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to an elec trochemical hydrogen storage system.

In an exemplary embodiment of the electrochemical hydrogen storage system the positive electrode comprises at least one appendant Proton Storage Electrode (PSE) , and wherein the first electrical connection at the cell side is split into a second electrical connection to the at least one PSE and a third electrical connection to the at least one OEE. As such a more versatile system is provided, in which also energy for night-time hydrogen production can be provided.

In an exemplary embodiment of the electrochemical hydro gen storage system the controller is a DC/AC controller with an individually controllable and preferably I AC /I DC current ratio in use, wherein the DC is provided at the electrode side of the controller. Such a controller is capable of addressing all individual electrodes independently and controlling stor age of energy and hydrogen and oxygen, as well as production thereof .

In an exemplary embodiment of the electrochemical hydro gen storage system the controller has at least one AC current for controlling oxygen evolution (I OE ) currents and inde pendently at least one AC current for controlling hydrogen evolution { IHE) currents, preferably one AC current for controlling all oxygen evolution (I OE ) currents and preferably one AC current for controlling hydrogen evolution (I HE ) currents. Therewith all evolutions are controlled very well.

In an exemplary embodiment of the electrochemical hydro gen storage system the controller comprises a transformer. The transformer typically comprises a coil and optionally a magnetic element, such as a ferrite core.

In an exemplary embodiment of the electrochemical hydro gen storage system the HSE, HEE, optional PSE, and OEE electrodes are each independently selected from Ni, Fe, Cd, Co, W, Mo, Pt, Ru, Ir, C, and combinations thereof. These electrodes can be manufactured, such as identified in the WO2016/178564 A1 and are very suited for the present system.

In an exemplary embodiment of the electrochemical hydro gen storage system ne [3-1000], preferably n [4-100], such as ne [5-50] ; i.e. a relatively large number of cells in the multi cell array can be provided.

In an exemplary embodiment the electrochemical hydrogen storage system comprises k multi cell-arrays in parallel, wherein ke [2-250], preferably k [3-100], more preferably ke[4- 75], such as ke[5-50]. In addition to or as an alternative to a large number of cells in an array, also multi cell-arrays may be provided in parallel, therewith significantly increas ing a storage and production capacity. Such an increase may be relevant for large industrial scale plants.

In an exemplary embodiment the electrochemical hydrogen storage system comprises per cell each individually 2-100 Hy droxyl Storage Electrode (HSE) with each individually 2-100 appendant Hydrogen Evolution Electrode (HEE) together forming a negative electrode, preferably 5-50 HSE and 5-50 HEE, such as 10-30 HSE and 10-30 HEE, and each individually 2-100 op tional Proton Storage Electrode (PSE) with each individually 2-100 appendant Oxygen Evolution Electrode (OEE) forming a positive electrode, preferably 5-50 PSE and 5-50 OEE, such as 10-30 PSE and 10-30 OEE. For good control and efficiency a large number of electrodes may be provided.

In an exemplary embodiment of the electrochemical hydro gen storage system at least one HSE electrode is adjacent to at least one HEE electrode, preferably wherein all HSE elec trodes are adjacent to at least one HEE electrode, such as in an intermittent mode.

In an exemplary embodiment of the electrochemical hydro gen storage system at least one optional PSE electrode is ad jacent to at least one OEE electrode, preferably wherein all optional PSE electrodes are adjacent to at least one OEE elec ¬ trode, such as in an intermittent mode.

In an exemplary embodiment of the electrochemical hydro ¬ gen storage system the at least one HSE electrode and at least one HEE electrode form an array of electrodes.

In an exemplary embodiment of the electrochemical hydro gen storage system the at least one PSE electrode and at least one OEE electrode form an array of electrodes.

In an exemplary embodiment of the electrochemical hydro gen storage system at least one of a number of HEE's is equal to a number of hydrogen evolution currents, a number of OEE's is equal to a number of oxygen evolution currents, a number of HSE' s is equal to a number of controllable bidirectional HSE currents plus 1 (#HSE=#i H s E +l) , and a number of PSE' s is equal to a number of controllable bidirectional PSE currents plus 1.

In an exemplary embodiment of the electrochemical hydro gen storage system electrolytes are selected from OH- and ¾ for the HEE side, preferably at a concentration of 0.1-12 mole/1, preferably 0.5-10 mole/1, such as 4-8 mole/1, and from OH-/O 2 for the OEE side, preferably at a concentration of 0.1- 12 mole/1, preferably 0.5-10 mole/1, such as 4-8 mole/1.

In an exemplary embodiment of the electrochemical hydro gen storage system electrolytes are dissolved in water, pref erably de-ionized water, preferably with a conductivity of < 0.5 mS/m, preferably < 100 pS/m, more preferably < 50 pS/m. Under laboratory conditions ultra-pure water is used with a conductivity of < 1 pS/ , such as 0.5 pS/m.

In an exemplary embodiment the electrochemical hydrogen storage system comprises in fluidic connection with the storage system at least one of a refill unit and a storage system, such as for water that may be consumed and may need to be re plenished, that may be formed, as well as a refill and storage for electrolytes.

In an exemplary embodiment the electrochemical hydrogen storage system comprises at least one liquid-level sensor, preferably a sensor per cell. Two exemplary systems may be considered. A system comparable to a bipolar alkaline electro- lyser; in this configuration all cells are filled with elec trolyte and the cells may he connected via piping to a gas/liquid-separation tank. In this configuration only one sensor in the tank is sufficient and one only needs to refill in one place. It is also possible, that each cell is a stand alone system; then a sensor for each cell may be required. To monitor a liquid level in a cell, especially in view of water consumption, a sensor is preferably provided. If the level is too low water can be replenished.

In a second aspect the present invention relates to a method of operating an electrochemical hydrogen storage system according to the invention.

In an exemplary embodiment of the present method a fraction of power available for loading is used for storing hydrogen, preferably a fraction of > 0.25, more preferably a fraction of > 0.50, such as > 0.75. Therewith a much higher efficiency and storage is obtained.

In an exemplary embodiment the present method comprises charging in daytime at least one cell by providing a part of an I TSC current to at least one HSE and through a cell to at least one PSE, and providing electrolysis in daytime by providing a part of an I TSC current to at least one HEE and through a cell to at least one OEE, discharging at least one cell during night time by providing an I TSC current to at least one PSE and through a cell to at least one HSE and providing electrolysis in a cell by a current from at least one OEE to at least one PSE and electrolysis in a cell by a current from at least one HEE to at least one HSE. Therewith energy and/or electrolytic species as oxygen and hydrogen is/are stored and released in an efficient and cost effective way.

In an exemplary embodiment of the present method in at least one cell, preferably in all cells, in daytime 75-100% of the I TSC current is provided to the at least one HSE, prefera bly 90-99.99%, more preferably 99-99.9%, such as 99.5%-99.85% , and independently 75-100% of the I TSC current is provided to the at least one PSE, preferably 90-99.99%, more preferably 99-99.9%, such as 99.5%-99.85% , and/or

wherein in night-time 75-100% of the I TSC current is provided to the at least one HSE, preferably 90-99.99%, more preferably 99-99.9%, such as 99.5%-99.85%, and independently 75-100% of the I TSC current is provided to the at least one PSE, prefera bly 90-99.99%, more preferably 99-99.9%, such as 99.5%-99.85% .

In an exemplary embodiment of the present method in at least one cell, preferably in all cells, in daytime 75-100% of the I TSC current is provided to the at least one HEE, prefera bly 90-99.99%, more preferably 99-99.9%, such as 99.5%-99.85%, and independently 75-100% of the I TSC current is provided to the at least one OEE, preferably 90-99.99%, more preferably 99-99.9%, such as 99.5%-99.85% , and/or

wherein in night-time no current I TSC is provided and electrol ysis is performed by providing a current from the OEE to the PSE {electrons flow from the OEE to the PSE) and from the HEE to the HSE (electrons flow from the HSE to the HEE) .

In an exemplary embodiment of the present method in at least one cell, preferably in all cells, in daytime 15-90% of the i T sc current is provided to the at least one HSE, prefera bly 35-75%, more preferably 50-70%, such as 60%-65%, and inde pendently 10-85% of the IT SC current is provided to the at least one HEE, preferably 20-50%, more preferably 25-40%, such as 30%-35%, and independently 1-50% of the i T sc current is provided to the at least one PSE, preferably 2-25%, more preferably 5-20%, such as 8%-12%, and independently 50-99% of the I TSC current is provided to the at least one OEE, preferably 60- 95%, more preferably 75-92%, such as 85%-90%.

In an exemplary embodiment of the present method in night time 80-1000% of the IT SC current is provided to the at least one HSE, preferably 200-750%, more preferably 400-700%, such as 500%-600%, and independently a current I HE is provided from the HEE to the HSE, and independently 75-100% of the i T sc cur rent is provided to the at least one PSE, preferably 90- 99.99%, more preferably 99-99.9%, such as 99.5%-99.85% . It is noted that a current UHE from HEE to HSE may relate to 100% of the ITSC-

The above shows that the present system can be operated in various ways, making the system versatile and applicable in various environments. Is it worthwhile to note that not only day-night fluctuations can be smoothed out by the system, but that the system can also smooth out short time variations (e.g. caused by clouds, demand peaks and so on) . In an exemplary embodiment of the present method currents are switched on during a first period of time and are switched off during a second period of time. Depending on demand and depending on supply the present system can be switched and controlled in a sophisticated way.

In a third aspect the present invention relates to a bat tery.

In a fourth aspect the present invention relates to a chemical production unit.

In an exemplary embodiment the present chemical produc tion unit comprises at least one of a biogas production unit, a cement production unit, an ammonia production unit, a urea production unit, and a syngas production unit.

The one or more of the above examples and embodiments may be combined, falling within the scope of the invention.

EXAMPLES

The below relates to examples, which are not limiting in nature .

Control of operating pressure during different operation conditions .

The pressure control of systems including a HSE differ from "normal" alkaline electrolysers as the level of electrolyte may fluctuate due to fluctuations of the State of Charge (SoC) of the HSE. The following reactions describe operation conditions :

Battery operation only (PSE, Ni compound and HSE, Fe (or Cd} } :

Charge

Fe(OH) 2 + 2Ni(OH) 2 Fe + 2N100H + 2H 2 0

Discharge (1)

Charging the HSE electrode together with oxygen production :

Charge HSE/ 0 2 Electrolysis

2Fe(OH) 2 - » 2 Fe + 2H 2 0(l) + 0 2 (g) (2 )

Discharging the HSE in combination with hydrogen production :

Discharge HSE/ H 2 Electrolysis

Fe + 2H 2 0(l) - » Fe(OH) 2 + H 2 (g) (3)

Charging the PSE together with hydrogen production:

Charge PSE/ H 2 Electrolysis

2Ni(OH) 2 - > 2 NiOOH + H 2 (g) (4)

Discharging the PSE in combination with oxygen production:

Discharge PSE / 0 2 Electrolysis

4NΪOOH -I- 2H 2 0(1) - > 4Ni(OH) 2 + 0 2 (g) (5)

Electrolysi s : Electrolysis

2H 2 0(l) - > 2H 2 + 0 2 (g) ( 6)

It can be observed from reaction (1), relating to battery- operation only, that water is decomposed during discharging to form iron hydroxide and nickel hydroxide, whereas water is released during charging to form iron and nickel oxy-hydroxide . Furthermore water is consumed during electrolysis, see reac tion (6), and also during operation conditions as described by reaction (3) and (5) . On the other hand, what might not be ob vious, water is released in reaction (2) , relating to charging the HSE in combination with oxygen production. Consequently the concentration and density of the electrolyte as well as the filling level of the electrolyte may fluctuate during op eration.

Variations in filling level may influence the head pressure of the hydrogen and oxygen gas separation systems (especially under pressurized operation}. Releasing water {reaction (1) charging and reaction (2) ) can be compensated by extra toler ance in the electrolyte level in the liquid-gas separation tanks. Consuming water (discharging reaction (1) and reactions (3}, (5), (6)) can be compensated by an intelligent refill system. Refilling should not be correlated to the production of hydrogen and oxygen, the state of charge of the HSE needs to be considered.

An immediate refill is only required while discharging the battery functionality (reaction 1) to keep the operating pres sure constant. Refill cause by reactions (3), (5) and (6) can be postponed as the volume of gas produced will exceed the volume of liquid water consumed. Refill can start when the electrolyte level reaches a defined minimum level. However, refill should not exceed a maximum level for state of charge (SoC) of the HSE 0%, even when SoC of HSE equals 100% to have a possibility to refill the system and keep the pressure con stant when discharging the HSE from SoC 100% to SoC 0% and reach the max level for HSE 0% (see fig. 7) .

One might also consider the electrolyte-level with respect to a charge-discharge-electrolysis cycle. The following figure 8 shows the trend of the electrolyte level with respect to the level of charge of the HSE. For a special case with only charging and discharging the HSE under pressurized configura ¬ tion the following conclusions may be drawn:

1) In order to keep the pressure constant water has to be refilled during discharging the HSE.

2) Refilling without electrolysis will lead to successive filling of the system.

For a case of additional gas-production the following con clusions may be drawn:

3) For the case that no gas-production takes place during discharging the HSE the amount of water consumption for electrolysis previous to discharging needs to exceed the storage fluctuation caused by electrical energy storage. Then water refill can take place during discharging and the electrolyte- level and system pressure will remain.

4) For the case that gas-production takes place only during discharging the HSE, then the volume of the produced gasses can replace the liquid volume. In this case the volumetric (pressure dependent) production rate each of the both gasses, oxygen and hydrogen, needs to compensate for halve the volume reduction caused by water uptake of the electrodes.

5} For the case that gas-production takes place during charging and discharging the HSE then case 4) forms an upper limit for the individual gas-production rates. Water consump tion for electrolysis during the charging step can be brought into account to reduce gas-production rates during discharg ing. If the water consumption for electrolysis during charging exceeds the volume fluctuation caused by storage fluctuations (case (3) ) than volume change can be compensated by water re plenishment only.

Another possibility to handle fluctuations could be to keep filling at a certain set-point and to add an electrolyte buffer system to the overall system, which buffer compensates level-fluctuations caused by water uptake/release by the HSE.

As such the operating pressure of the system can be kept con stant during all operating conditions.

The storage need of a system can be calculated. For in stance, in order to store lAh of electrical energy 0.0373 mole of (e-) needs to be stored in an electrode. One Fe atom can store two electrons and one Ni atom one electron (see equation (1) ) . The amount of moles of water release during charging is equal to the amount of moles of Ni-atoms and two times the amount of Fe-atoms . This implies that for 1 Ah of electrical store 0.336 g of H 2 0 need to be stored. For 1 Ah of equivalent hydrogen storage (see equation (2) ) half the storage capacity 0.168 g H 2 O compared to electrical storage is required. Assum ing a density of water of 1 g/m1, the volume change caused by change of SoC of the HSE will cause the following volumetric changes: 0.336 ml/Ah electrical storage and 0.168 ml/Ah hydro gen storage. Assuming larger systems with about 10 kWh elec trical storage capacity (provides 10 hours one kW energy) and a hydrogen storage capacity of 50 kWh hydrogen storage capac ity (provides 10 hours of 5 kW hydrogen production) would re quire a storage capacity of 3.36 1 + 8.4 X = 11.761. This might seems small, however the system-size is still small. A kW-size is suitable for pilot-pro ects, whereas real large- scale units might have the size of MW's, thus the storage ca pacity for such large-scale projects will increase by a factor 1000.

To reduce the amount of electrolyte storage capacity a com bined system consisting of an electrolyte storage tank and an intelligent refill-system can be set in place, demonstrated by the proposed system for ammonia-production.

A balance for daytime-charging shows that in total 0.552 H 2 O is released, while 0.373 H 2 0 is consumed. This implies that the electrolyte-level will increase by 0.179 H 2 O. A combined system of consisting of an electrolyte-storage buffer and an intelligent refill system makes sense therefore. The electro lyte-storage buffer needs to be sized to about 1/3

(=0.179/0.552) of the total water release, as about 2/3

(0.373/0.552) of the water release can be handled by an intel ligent refill system.

In a to some extent simplified approach is shown in fig. 6. The system-configuration shown leads to an alkaline electro- lyser which is capable of storing hydrogen and releasing the hydrogen at any desired moment in time. An advantage is that electrodes of alkaline electrolysers are typically more efficient than battery electrodes at high rates. Without a PSE the system is less complex in configuration and an amount of Nickel for the electrode is reduced to a minimum. A disad vantage is that the system can not supply energy for night time hydrogen production by itself, and therefore for this purpose an external power supply (battery or grid connection) is required. Also in this system the Ϊ OE can not be controlled.

The main system corresponds to the proposed solution of multi-triggered electrodes. The positive side consists only of an OEE, whereas the negative side consists of both electrodes, the HEE and the HSE. The HEE and HSE are connected as pro posed. It is noted that a system without a PSE limits the direction of the main stack current. As the OEE cannot be re versed the current needs to flow always in one direction. This does simplify the main control unit of the system. The current control for HEE will also always be one-directional.

An important consideration for the system of fig. 6 is a constant hydrogen production and hydrogen storage. During night-time also a small amount of external energy may be required to be supplied to the system to provide 1} a minimal current to the OEE to keep the electrode protected (about 5% of the maximum daytime current) and 2) production of hydrogen from the storage. The advantage of delayed electrolysis remains, only the voltage difference from HSE to HEE (about

0.25V) is required for night-time hydrogen production indicat ing that about 80% of the energy-requirement for electrolysis is already paid for at daytimes when electricity is cheap.

The invention is further detailed by the accompanying fig ures, which are exemplary and explanatory of nature and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protec tion, defined by the present claims.

FIGURES

The invention although described in detailed explanatory context may be best understood in conjunction with the accom panying figures.

Fig. la-b shows an illustration of the concept of multi- triggered electrodes.

Fig. 2 shows control of sub-electrodes and operation modes.

Figure 3a-c is a demonstration of battery and electrolysis functionality. Also demonstration of combined functionality for the purpose of ammonia production (constraints:

daily/night fluctuations for electricity input and constant hydrogen output)

Figures 4a-4d demonstrate a three electrode setup.

Fig. 5 shows an appendant multi-electrode.

Fig. 6 shows a system without PSE .

Fig. 7 shows functioning of gas-liquid separation.

Fig. 8 shows charging and discharging effects.

Fig. 9 shows an array of k parallel systems according to the invention.

Fig. 10 shows a schematic cell layout.

DETAILED DESCRIPTION OF THE FIGURES

Figure la schematically shows a prior art multi-cell array identifying that the prior art systems lack control for all cases besides the single cell system with defined superimposed electrode behaviour. For all other cases the current flow will adjust so that the voltage drop from the bulk of electrolyte of one cell to the bulk of electrolyte to the adjacent cell will be equal, path-independent. The resistances depicted in Figure 1 (top right) simplify the system, whereas in reality the functions for the resistances comprise at least rate-dependent anode and cathode reactions so that resistance control seems infeasible.

The present 'multi-triggered electrodes' enable controlling these advanced systems, see Figure lb. These advanced systems comprise electrochemical cells in series connection representing an advanced bipolar multi-electrode configuration. Each individual cell consist of a Hydroxyl Storage Electrode (HSE) with an appendant Hydrogen Evolution Electrode (HEE) together forming the negative electrode and a Proton Storage Electrode (PSE) with an appendant Oxygen Evolution Electrode (OEE) form ing the positive electrode. Each cell possesses one connection to the positive and one connection to the negative electrode defining the array current iTSC (Total stack current) . The subset electrodes HEE and OEE are fed via a side-line from the main-line. Aii grrents in t e eystem ars fixed by a superim posed ITSC, the system having controllable currents for hydro gen evolution (IHE) regulating the electron flow from the HEE to the main-line and a controllable current for oxygen evolution (i 0E) regulating the flow of electrons to the OEE from the main-line. The difference between i Tg c and i HE respectively ΪOH defines the currents form/to the storage electrode (SE) , HSE ( IHSE ) respectively PSE (I PSE ) . Expandability of this concept is provided by observing voltage and current rules.

An important issue to get the concept of multi-triggered electrodes in advanced electrochemical systems to work is con trollability of all subset electrode currents throughout the entire assembly. Two premises seem essential:

1) Isolated control: the potential of all subset-electrodes is linked to the potential of their SE hence all subset electrodes exhibit voltage offset for each other.

2) Identical currents for all sets of subset electrodes: Here we suggest control of these sub-circles through an AC current control unit.

An advantage of using a hydroxyl (resp. proton) storage electrode for hydrogen (resp. oxygen) production lays within that most of the work required for the electrolysis process is performed while electricity is abundant. Charging the storage electrodes typically takes place at potentials around 1.6V. Electrolysis typically requires extra over-potentials of around 0.1V, in total approximately 1.7V. The electrical discharge potential typically is approximately 1.25 V. The poten tial required to discharge the hydroxyl storage electrode versus the hydrogen evolution electrode is approximately 0.25V. {0.25/1.7 = 15%) which demonstrates that most of the work re quired for hydrogen production is accomplished during charging the storage electrodes. The ratio of discharge potential to hydrogen evolution potential is 1.25/0.25 = 5, which means that one electron used for discharging can power 5 electrons for hydrogen evolution. Under the assumption, that all elec trical storage capacity is used for hydrogen production 1/6 of the storage capacity is used for electrical storage while 5/6 is used for storing hydrogen. In this case, the capacity ratio for storing hydroxyl ions (for hydrogen production and elec trical Storage) to storing protons (no storage of oxygen; only electrical storage) is approximately 6. Assuming 10 hours day time with constant electricity input and 14 hours night-time with constant hydrogen output throughout the day, the daytime current for hydrogen production (I HE ) is about 37% of the total current (i T sc; I TSC = I HE * ( 1+1.4 *6/5 ) } . The current for charging the proton storage electrode is approximately (1.4*i HE /5=)

10.4% of the total current, for electrical discharging the current is approximately (I HE /5=) 7.5% of the total current.

In view of figure la the following is noted. For controlla bility the system inside a cell preferably defined in func tional components. In a given cell m the number of electrodes forming the positive electrode (a PSE' s + b OEE's) and the number of electrodes forming the negative electrode (c HSE' s +d HEE's) are preferably equal to the number of controlled current flows i to the positive electrode assembly and to the negative electrode assembly (see fig. 10) . Both the number and arrangement of electrodes a,b,c,d are independent and free of choice. In fig. 10 also electrical connections 1-6 are indi cated.

The total stack current I TSC is a controlled current. This indicates, that for the assembly of electrodes forming the positive electrode the number of controlled electrodes is equal to a+b-1; the resulting current for the "uncontrolled" electrode is the sum of all other currents. Furthermore this indicates for the assembly of electrodes forming the negative electrode that the number of controlled electrodes is equal to c+d-1; the resulting current for the "uncontrolled" electrode is the sum of all other currents.

In general it is considered that currents to storage elec trodes are bi-directional, currents to Evolution electrodes are on-directional, and all electrodes are isolated from each other .

Controllability of different HSE/PSE electrodes is an asset as different regions of the electrode' s assemblies can be charged and/or discharged. This means, that currents can be forced to electrode regions which would normally not be charged due to their unfavourable position in the electrochemical system.

Figure 2 shows the control of sub-electrodes and effects thereof. Sets of sub-electrodes can be controlled by an AC current for control of the DC current, which is connected to the electrodes. The right hand side of figure 2 demonstrates operation modes for a negative electrode consisting of a HSE and a HEE electrode. When operating as electricity sink and when i TS c exceeds i HE charging together with hydrogen production takes place. The currents I HSE and Ϊ HE have the same direction, electrons flow to the HSE and to the HEE, the State of Charge (SoC; 0% complete discharge electrode; 100% fully charged electrode) of the HSE increases. When operating as electricity sink and when I HE exceeds iisc discharging together with hydro gen production takes place. The currents I HSE and I HE have dif ferent directions, electrons flow from the HSE and to the HEE, the State of Charge (SoC; 0% complete discharge electrode;

100% fully charged electrode) of the HSE decreases. When oper ating as electricity source the current I HSE equals the sum of I HE and i Tsc; discharging together with hydrogen production takes place. The currents I HSE and I HE have different direc ¬ tions, electrons flow from the HSE and to the HEE, the State of Charge (SoC; 0% complete discharge electrode; 100% fully charged electrode} of the HSE decreases.

Figures 3a-c demonstrate the operation principles for bat tery functionality and for the electrolysis functionality.

From figure 3b it is obvious that having only the electrolysis functionality is not sufficient. This concept works during daytime, when electricity is abundant. However, during night time the storage capacity is depleted, and needs to be regenerated in subsequent cycles. Overall stoichiometric hydrogen and oxygen production is required. Figure 3c demonstrates the discussed functionality as constant hydrogen supply for ammo nia production. Note that only 1/5 of the electrical storage capacity is required compared to a conventional solution, where a battery is applied for backing up an electrolyser stack, were 100% of the electrical storage capacity is re quired.

The suggested device for hydrogen and oxygen storage can be integrated in various other processes, e.g. as a hydrogen and oxygen supply for biomass related processes and for oxy-fuel cement production. Producing syngas from biomass usually re quires a water-gas shift reaction, feeding additional hydrogen to this process increases the carbon conversion efficiency (more CO; less C0 2} . Also integration of hydrogen to anaerobic digestion is feasible and increases the carbon conversion and product quality, in this case methane, significantly. Cement production causes significant carbon dioxide emission and car ¬ bon capture is considered one path to reduce carbon emissions. Alternative ways of producing cement may lead to high-quality carbon-dioxide output suitable for carbon capture. Here the device can serve for two purposes: controlled oxygen produc ¬ tion to be used in the oxy-fuel process and the hydrogen can be used to convert carbon dioxide to methane or syngas. The air-separation unit to produce oxygen and carbon sequestration can be replace by this device plus a carbon convert to produce carbon fuels with a negative carbon footprint. For this pro cess hydrogen production will be limiting, meaning that there will always be enough excess oxygen to drive the oxy-fuel pro cess .

Figures 4a-4d demonstrate a three electrode setup. Figure 4a shows a measured potential versus time for measurements:

HSE vs PSE (full line) HEE vs PSE (dashed line) and HEE vs. the Ni electrode at rest (central dotted line at 1.5 and 1.4 V respectively) . The HEE is switched on, off, on, off and on again. Figure 4b shows the applied test currents; in full line the current from PSE to HSE and in dashed line from HSE to HEE. The effective current the PSE experiences is equal to the dashed line; the effective current the HEE experiences is the dashed line; the effective current the HSE experiences is the sum of the full line and the dashed line meaning that the cur rent during charging is reduced when the HEE is on and the current during discharging is increased when the HEE is on.

When the HEE is on, left section, the HSE is discharging and ¾ production occurs at the HEE. Figure 4c shows the counts meas ured for m=2 indicating hydrogen production. When the HEE is off, hydrogen production occurs during charging, not during discharging. The pattern is comparable to the patterns deter mined for the battolyser. When the HEE is on there is levelled out hydrogen production during charging and discharging. The peaks during charging decrease and there is uniform H 2 production during discharging. In the central section the reduced peak indicates a better ¾ production when the HEE is on. Fig ¬ ure 4d shows the counts for m=32 indicating oxygen production. The oxygen production follows the charge insertion of the PSE. There is no effect of turning on/off the HEE visible.

Different approaches can be used for decoupled hydrogen and oxygen production. First in a setup with a redox-flow battery with extra catalytic reactors for ¾ and Oa production. Second there is a setup of applying an electron-coupled-proton buffer. And there is a setup of using one electrode for hydro gen and one electrode for oxygen evolution and producing both gasses at different times. All setups are different from the approach proposed having four electrodes, i.e. two for storage and two for gas production. Also the controllability varies.

In the proposed setup the rates are easily controllable. Furthermore the proposed setup is scalable in a bipolar setup with easy control of all sub-set electrodes.

The application of multi-triggered electrodes is not limited to the concept presented above. The concept can also be applied for a battery, a fuel-cell and other electrochemical systems. The concept of multi-triggered electrodes allows to design batteries in new ways. Currently batteries have one positive and one negative electrode. With the proposed concept, batteries can have multiple positive and negative electrodes, and all individual electrodes can be controlled. In this application all electrodes would be storage electrodes the control system needs to be arranged so that charging and discharging is possible. Advanced battery-packs are another application for the proposed concept. Batteries may consist of as many as 7104 cells, arranged in 74 parallel arrays, each consisting of 96 cells in series. During charging the same po tential is applied over parallel arrays, resulting in a light in-balance of the individual cells. Regular balancing is re quired so that all individual cells are charged to the same state of charge. The proposed configuration would allow for control of current for the individual parallel arrays making balancing redundant.

The concept of multi-triggered electrodes provides for a new design of fuel-cell systems. At present the size of fuel cell systems is limited such as due to concentrations in the fuel. The achievable potential is determined by the lowest re actant concentration . Furthermore, there is always some fuel left in the outflow. Applying multi-triggered electrodes would allow for generating a voltage profile across the electrode to benefit from higher voltages (due to higher concentrations) at the inlet and to utilize more fuel at the outlet. This together could lead to larger systems. Here it should be noted, that the direction of current flow is fixed and that the total stack current is equal to the sum of the currents of the indi- vidual electrodes.

The concept of multi-triggered electrodes can be applied in all processes were selectivity is required, e.g. in electro chemical CO2 reduction. Applying different groups of electrodes with different selectivity' s would allow to get control over the output products and to change them if required. Further more, pulsing at certain selective electrodes could lead to the production of intermediates required for the desired prod uct .

The figures have been detailed throughout the description.