WO2013066331A2

WO2013066331A2 - Method for controlling cell-presssure balance and separator liquid level in an electrolyzer and apparatus thereof

Info

Publication number: WO2013066331A2
Application number: PCT/US2011/059138
Authority: WO
Inventors: Martin A. Shimko; Paul M. Dunn; Steve R. WEISS; David Mauterer
Original assignee: Avalence Llc
Priority date: 2011-11-03
Filing date: 2011-11-03
Publication date: 2013-05-10
Also published as: WO2013066331A3

Abstract

The present invention relates to for an improved apparatus that facilitates the controlling of the cell pressure balance, and separator liquid level as well as provides for a method for circulation of electrolyte through the individual cells by passive means,, thereby reducing the need for manually monitoring the cell pressure balance and the electrolyte level in an electrolyzer for producing high pressure hydrogen at pressures up to 10,000 psig or higher.

Description

METHOD FOR CONTROLLING CELL-PRESSSURE BALANCE AND SEPARATOR LIQUID LEVEL IN AN ELBCTROLYZER AND APPARATUS THEREOF FIELD OF THE INVENTION

The present invention relates to an improved electrolyzer apparatus that provides an improved method for controlling cell-pressure balance and separator liquid level in an electrolyzer for producing high pressure hydrogen at pressures up to 10,000 psig or highe r by means of electrolysis of water.

BACKGROUND OF THE INVENTION

Alkaline electrolyzers using liquid electrolyte to generate hydrogen operate in the following way. Two electrodes are placed in a bath of liquid electrolyte of optimally 25% to 28% KOH by weight, and separated by a membrane that selectively allows liquid but not gas to pass through. When a voltage of approximately 2 volts is impressed across the electrodes, current flows through the electrolyte between the electrodes. Hydrogen gas is produced at the cathode and oxygen gas is produced at the anode. The separation membrane keeps the hydrogen and oxygen gasses separated as the generated gas bubbles rise through the electrolyte driven by buoyant forces. There is a disengaging space above the electrolyte bath that has a solid barrier between the generated gasses. It is in this region that the generated gasses are removed for storage or venting. This instant invention improves upon the US Patent # 7,510,633 which describes an electrolyzer cell with a coaxial anode/cathode configuration wherein anode, cathode and separation membrane in the apparatus are configured coaxially as shown in Figure 1. The outer containment shell acts as the cathode i.e. hydrogen generation electrode while the central rod (or tube) acts as the anode i.e. the oxygen generation electrode. This configuration creates annular regions for the liquid electrolyte preferably 28% KOH between the electrodes and the separation membrane. Individual gas generation cells are formed in this manner. This eliminates the requirement of a separate compressor component for high pressure gas storage.

The existing electrolyzers present a problem with regard to their ability to balance the pressure of the electrolyte across the separation membrane during operation at pressures greater than 15 bar (200 psi) and the problem increases with the increase in operating pressure. Even small pressure imbalances, in terms of percentage, can cause improper gas migration through the separation membrane or worse cause fracturing and catastrophic failure of the membrane itself. The basic electrode configuration using high speed feedback control circuits and high speed variable control valves prove inadequate and also fundamentally incompatible with high pressure oxygen operation (as found in balanced, high-pressure hydrogen systems). The unique configuration of the proposed system allows a gentle yet effective approach to balancing the pressures to be implemented, as described in this patent. SUMMARY OF THE INVENTION

In order to overcome the drawbacks of the existing state of art, the instant invention provides for an improved apparatus that facilitates the controlling of the cell pressure balance, and separator liquid level as well as provides for a method for circulation of electrolyte through the individual cells by passive means, thereby reducing the need for manually monitoring the cell pressure balance and the electrolyte level in the electrolyzer. The unique configuration of the electrolyzer according to the present invention allows a gentle yet effective approach to balancing the pressures to be implemented.

OBJECT OF THE INVENTION

An object of the present invention is to provide an improved electrolyzer apparatus that provides an improved method for controlling cell-pressure balance and separator liquid level in an electrolyzer for producing high pressure hydrogen at pressures up to 10,000 psig or higher, by means of electrolysis of water.

Another object of the present invention is to provide a method for controlling cell-pressure balance and separator liquid level in an electrolyzer for producing high pressure hydrogen.

Yet another object of the present invention is to provide a method for circulation of electrolyte through the individual cells by passive means. Yet another object of the present invention is to provide an electrolyzer with a unique configuration that allows effective balancing of the cell-pressure. Accordingly the present invention relates to an improved electrolyzer apparatus that provides an improved method for controlling cell-pressure balance and separator liquid level in an electrolyzer. The present invention relates to a method for controlling the cell pressure balance, and separator liquid level. The present disclosure also relates to a method for circulation of electrolyte through the individual cells by passive means.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a cross-sectional view of the electrolyzer cell depicting the deployment of the cathode, anode and the separation membrane with the liquid electrolyte.

Figure 2 is a schematic representation of the longitudinal section of the electrolyzer cell of the instant invention.

Figure 3 relates to the schematic representation of the novel system of this invention wherein a plurality of electrolyzer cells are connected in parallel to the common separation chambers for oxygen and hydrogen collection. Figure 4 is a representation of a float level sensor.

Figure 5 depicts a schematic representation of a continuity probe level sensor. DETAILED DESCRIPTION OF THE INVENTION AND SPECIFIC EMBODIMENTS THEREOF :

Before proceeding with the description, the reference numerals indicated in the drawings are described herein. Referring to Figure 1, there is shown an electrolyzer cell EC comprising an anode A; a cathode C; the electrolyte chamber EL comprising the Anode sub-chamber EL(A) and the Cathode sub- chamber EL(C); a separation Membrane SM; the anode side separation membrane SM(A); and the cathode side separation membrane SM (C). Referring to Figure 2, there is shown an Electrolyzer cell EC comprising the anode A; the cathode C; a hydrogen connecting line also referred to as the hydrogen separator liquid return CL(H); an oxygen connecting line also referred to as the oxygen separator liquid return CL(O); a source of DC Power DC; electrolyzer cell hydrogen production chamber EC1; electrolyzer cell oxygen production chamber EC2; the electrolyte chamber EL comprising the Anode sub-chamber EL(A) and the Cathode sub-chamber EL(C); the anode active electrode surface ES(A); the cathode active electrode surface ES(C); the hydrogen gas outlet also referred to as the hydrogen gas take-off connection GO(H); the oxygen gas outlet also referred to as the oxygen gas take off connection GO(O); lower (electrically insulated) region of anode LR(A); the lower (electrically insulated) region of cathode LR(C); the separation membrane SM; the anode side separation membrane SM(A); and the cathode side separation membrane SM (C). Referring to Figure 3, there is shown a system wherein plurality of electrolyzer cells are connected in parallel, the system shows the following components namely the oxygen connecting line CL(O); the hydrogen connecting line CL(H); a check valve CV; the electrolyzer cell EC; the electrolyte in hydrogen separation chamber EL(H); the electrolyte in oxygen separation chamber EL(O); the hydrogen gas outlet GO(H); the oxygen gas outlet GO(O); the hydrogen separation chamber, also referred to as a hydrogen separator HSC; a level sensing device LSD on the hydrogen separator, a pump for injecting water P; the oxygen separation chamber, also referred to as an oxygen separator OSC; and a valve for venting accumulated oxygen V.

Figure 4 shows a level sensing device based LSD on float level sensing mechanism comprising a detector D; a high level of electrolyte in the hydrogen separation chamber EL(H)h; a low level of electrolyte in the hydrogen separation chamber EL(H)(1); the exterior side of the hydrogen separation chamber HSC(e); the interior side of the hydrogen separation chamber HSC(i); a magnet MG; a polymer float PF; and a plurality of reed switches RS(1,2,....n) wherein RS(1) is the highest placed reed switch and RS(n) is the lowest placed reed switch. Figure 5 shows another form of a level sensing device LSD based on continuity probe sensing level sensing mechanism in the hydrogen separation chamber HSC comprising the continuity probe ends PR1 and PR2; the hydrogen connecting line CL(H); a check valve CV; the electrolyte in hydrogen separation chamber EL(H); a high level of electrolyte in the hydrogen separation chamber EL(H)h; and a low level of electrolyte in the hydrogen separation chamber EL(H)(l). Access to 6500 psi hydrogen is key to dispensing compressed hydrogen gas for fuel cell powered vehicles at acceptable volume-to-weight ratios to facilitate on-board storage. The production of high purity levels of oxygen and hydrogen gas required for safe operation of the electrolyzer at these high pressures involves addressing 2 critical features.

The first of these features involves the control of the differential pressure across the gas separation membrane SM in the electrolyte region where oxygen and hydrogen gas are generated, while simultaneously controlling and maintaining the liquid level in the electrolysis chambers without the need for differential pressure measurement or any form of high speed, feedback control loop. Performing this control function at electrolyzer operating pressures of up to 6500 psi in this manner has never been performed.

The second critical feature involves maintaining the continuity of circulation of the electrolyte in the separate hydrogen and oxygen production chambers from the bottom to the top by passive means. This is accomplished by using the oxygen and hydrogen gas generated in the individual electrolysis cells to drive the circulating flow. The level control system (above) and the specific electrolyzer cell configuration enable the unique tubing configuration that achieves this function.

Both of these features are critical for enabling the direct production of ultra high-pressure hydrogen (up to 6500 psi), by means of electrolysis. Implementation of these 2 features are achieved by modifying the electrolyzer cell configuration to create long cylindrically shaped electrolysis cells as shown in Figure 2. The lower regions of the electrodes at the bottom of the cell LR(A) and LR(C) are covered so that no gas is generated in this region. This allows the electrolyte from the oxygen and hydrogen separation chambers to be connected directly to the gas generation chamber.

Accordingly, the present invention also provides for a plurality of electrolyzer cells EC, which are connected to the common separation chambers for hydrogen gas HSC, and oxygen gas OSC in parallel as shown in Figure 3. The said separation chambers provide separate catchment areas for the collection of hydrogen and oxygen.

Water is added to the hydrogen separation chamber HSC in order to maintain the balance of pressure across the separation membrane SM within the individual cells to within 2 inches of water (less than 1/10 of a psi). This is critical to maintaining product purity because the separation membrane SM cannot seal against gas leakage at pressure differentials exceeding a few inches of water. Additionally the amount of water disassociated during electrolysis must be replenished in the electrolyzer EC.

During the process of electrolysis, the gases produced include hydrogen and oxygen in the ratio of 2:1. The hydrogen that is generated flows to the hydrogen separation chamber HSC and is released for storage through a check valve CV. The check valve CV is opened allowing for the flow of hydrogen every time the pressure in the electrolyzer is marginally greater than the storage pressure. This occurs at a relatively continuous rate during gas production operation. Oxygen is vented from the oxygen separation chamber OSC through a valve V that is set to vent a specific flow rate when opened.

The method for controlling the cell pressure balance, and separator liquid level which is central to this invention,_is achieved by taking advantage of the unique configuration of the electrolyzer cell EC as shown in Figures 1, 2, and 3. Because the oxygen and hydrogen electrolyte chambers HSC and OSC are directly connected at the bottom of the cell (below the covered sections of the electrodes LR(A) and LR(C)), the pressure across the separation membrane SM at the bottom of the cell will be inherently balanced in the absence of flow in the connecting region. The pressure differential higher up the cell can only vary by product of height and the density difference between the gas/liquid mixtures on the two sides of the membrane SM(A) and SM(C). Density difference will only be a small fraction of the fluid density due to slightly different gas production rates and bubble rise time in the cell prior to exiting the electrolyte fluid (EL(H), EL(O)) in the separator. For a 4 foot cell length this will only be a couple inches of water at the most.

The key to mamtaining the balanced pressure is to limit the rate at which liquid flows between the chambers at the bottom of the cell near LR(A) and LR(C). This rate of flow of liquid is set by limiting the rate at which the liquid levels in the separators EL(H) and EL(O) can change, either through liquid addition or gas venting, which in turn will limit the rate of flow induced in the connecting lines CL(O) and CL(H)) and between the electrolysis chambers ECl and EC2. Thus the invention provides for an intricately timed system of level sensing, fluid addition, and controlled gas venting to control the pressure differential across the membrane in the cell and add fluid to replenish the liquid inventory.

The liquid Level Sensing system that senses the liquid level in the hydrogen separator HSC can be embodied by a number of methods. One example of this is shown in Figure 4. The device consists of a polymer float PF having a density less than that of the electrolyte wherein the said polymer float PF contains imbedded magnets MG. This float PF rises and falls with the level of electrolyte EL(H) in the hydrogen separator HSC. On the exterior of the separator HSC(e) a vertically oriented series of magnetically sensitive reed switches RS(1,2,....n) are placed. The float PF will rise and fall with the level of the liquid EL(H) in the separator HSC and activate the reed switch (RS) at the vertical location across from it.

This level sensing may also be performed by a number of alternative means such as continuity probes, acoustic sensing, capacitance probes, or optical means. For example the continuity probes would operate as follows. The device consists of a pair of electrically isolated probes PR1, PR2 that extend into the separator HSC at lengths that define the minimum EL(H)1 and maximum desired liquid level EL(H)h in the separators. Electrical continuity is checked between the probes PR1 and PR2 and the separator HSC. If the conductive electrolyte EL(H) is between the two probe lengths PR1 and PR2 - continuity is found on one probe PR2 only, If the electrolyte level EL drops below the lower level EL(H)l - no continuity is found. If it is above the level of both probe tips PR1 and PR2, continuity is found in both PR1 and PR2. This embodiment is shown in Figure 5.

Electrolyte Inventory Control As the water in the electrolyte EL is consumed to produce the oxygen and hydrogen, the liquid level in the hydrogen and oxygen separators EL(H) and EL(O) will drop. When a specific lower level reed switch RS(n)) is activated by the float PF in the hydrogen separator HSC, indicating a lower liquid level EL(H)L a fill pump P is activated for injecting water into the HSC. The injection of water continues until the float PF rises and the magnetic field activates a higher reed switch RS(1) and the injection pump P is deactivated. The rate of change in the liquid level is set by the pump flow rate. This can be set at a low enough rate so that the flow induced in the connecting channel at the bottom of the cells will not impose a noticeable (less than 1 inch of water) flow induced pressure difference there.

Liquid Level in the Oxygen Separator, The gas produced in the oxygen side of the electrolyzer EC2 is not continuously vented but is normally collected in the oxygen side separator OSC. This causes a slow movement of liquid EL(O) out of the oxygen separator OSC downward, inducing a small flow in the connecting path CL(O) between the sets of cell chambers. This flow rate is very small during normal operation. When low level EL(H)1 is indicated by the float/sensor system, a valve V is opened and oxygen vented from the separator OSC. This gas can go either directly to the atmosphere or to a separate storage container for oxygen. The flow of oxygen can be easily controlled by the valve selection and setting. The rate of change in the liquid level in the oxygen side is therefore set at a rate that does not create excessive flow in the connecting path in the liquid electrolyte between chambers.

Also provided according to the present invention is a method for circulation of electrolyte through the individual cells by passive means.

It is critical for the production of high purity electrolysis gas products that the separation membrane SM stay fully wetted. It is the surface tension of the produced gas bubbles that prevents their penetration through the wetted pores of the membrane material. In the tall, cylindrical configuration used to enable the high pressure operation the density of the bubbles increases with height in the cell. For most economically practical production rates, the natural rise rate of the bubbles (especially at elevated pressures) is insufficient to keep the top regions of the cell membrane fully wetted due to bubble density, thereby allowing an unacceptable leakage rate of gas across the membrane. A means of "flushing" the electrolyte upward through the cell is needed to increase the upward velocity of the bubbles and maintain a wetted membrane. The natural balance of the electrolyte in the cells that is used as the basis of the level control would be adversely affected by a forced pumping though the cells. Therefore a passive method that is consistent with the level control and pressure balancing system is provided. By connecting the hydrogen liquid/gas separation chamber HSC located above the electrolyzer EC with the bottom of the hydrogen production chamber ECl of the individual cells the density difference between the fluid in the production chambers EL(H) and EL(O) (filled with bubbles during operation) and the connecting line CL that does not contain any bubbles, a buouncy driven flow loop is created. This arrangement as shown in Figures 2 and 3 has demonstrated a marked increase in product purity.

Thus, in an embodiment, the present invention provides an improved electrolyzer cell EC for generating ultra high pressure hydrogen by means of electrolysis comprising:

a cathode C of tubular configuration connectable to a source of electricity DC, and defines a cathode active electrode surface ES(C), at which hydrogen is generated;

an anode A which is connectable to a source of electricity DC, defines an anode active surface ES(A), at which oxygen is generated, and is disposed within the cathode C to define therewith an annular electrolyte chamber EL disposed between the cathode active electrode surface ES(C) and the anode active electrode surface ES(A);

a separation membrane SM of tubular configuration disposed within the electrolyte chamber EL between the cathode and the anode to divide the electrolyte chamber into an anode sub-chamber EL(A) and a cathode sub-chamber EL(C), the separation membrane SM sealing against the passage therethrough of gases but permitting passage of liquid borne ions;

a hydrogen gas take-off connection GO (H) in gas-flow communication with the cathode sub chamber EL(C) for removing the hydrogen to the Hydrogen separation chamber (HSC) and an oxygen gas take-off connection GO(O) for removing the oxygen to the Oxygen separation chamber (OSC)

wherein

said Hydrogen separation chamber (HSC) is deployed with a level sensing device (LSD) to detect the level of electrolyte such that if the level sensing device (LSD) indicates low level of electrolyte then a water pump P is activated to inject water into the hydrogen separation chamber HSC at a pre-determined flow rate;

said Oxygen separation chamber (OSC) is provided with an oxygen connecting line CL(O) connecting the said chamber to the bottom of the said electrolyzer cell EC and a valve V for venting accumulated oxygen as a bye-product at a predetermined rate to prevent excessive flow of the electrolyte into the electrolyzer cell through said connecting line CL(O) In another embodiment, the present invention provides, the electrolyzer cell EC wherein the level sensing device (LSD) is selected from a group consisting of float level sensing device, a continuity probe sensing device, acoustic sensing device, capacitance probe or optical sensing device. In yet another embodiment, the present invention provides, the electrolyzer cell EC wherein said float level sensing device comprises of polymer float FF deployed inside the hydrogen separation chamber (HSC) and a detector D deployed on the exterior of the hydrogen separation chamber (HSC(e)). In yet another embodiment, the present invention provides, the electrolyzer cell EC wherein the polymer float PF is constructed from a polymer material having density lesser than the density of the electrolyte and is embedded with at least one magnet MG.

In yet another embodiment, the present invention provides, the electrolyzer cell EC wherein the detector D comprises of at least one magnetically sensitive reed switch RS.

In yet another embodiment, the present invention provides, the electrolyzer cell EC wherein the continuity probe sensing device comprises atleast a pair of electrically isolated probes PR1 and PR2 extending into the Hydrogen separation chamber HSC at lengths that define the minimum electrolyte level EL{H)1 and a maximum electrolyte level EL(H)h.

In another embodiment, the present invention provides a method for controlling cell pressure balance and separator liquid level in an electrolyzer cell, said method comprising:

sensing the level of a electrolyte in a hydrogen separation chamber HSC of an electrolyzer cell EC by atleast one level sensing device LSD configured to indicate a low level of the electrolyte EL(H)(l);

injecting water into the hydrogen separation chamber HSCat a predetermined flow rate when the level sensing device LSD indicates a low level of the electrolyte EL(H){1) ; and

opening a valve V connected to the oxygen separation chamber (CSC) when the pressure of accumulated oxygen is greater than a pre- determined pressure for venting oxygen at a rate that prevents excessive flow of the electrolyte from the oxygen separation chamber (OSC) to electrolyzer cell EC through the connecting line CL(O).

In yet another embodiment, the present invention provides a method for controlling cell pressure balance and separator liquid level in an electrolyzer cell wherein the level sensing device LSD is selected from the group consisting of a float level sensing device, a continuity probe sensing device, acoustic sensing device, capacitance probe and optical sensing means. In yet another embodiment, the present invention provides a method for controlling cell pressure balance and separator liquid level in an electrolyzer cell wherein float sensing device comprises of polymer float PF deployed inside the Hydrogen separation chamber (HSC) and a detector D deployed on the exterior of the hydrogen separation chamber (HSC(e)) which detects the rise and fall of the level of the liquid EL(H) inside the Hydrogen separation chamber HSC.

In yet another embodiment, the present invention provides a method for controlling cell pressure balance and separator liquid level in an electrolyzer cell wherein said polymer float PF is constructed from a polymer material having density lesser than the density of the electrolyte and is embedded with at least one magnet MG.

In yet another embodiment, the present invention provides a method for controlling cell pressure balance and separator liquid level in an electrolyzer cell wherein the detector D comprises of at least one magnetically sensitive reed switch RS .

In yet another embodiment, the present invention provides a method for controlling cell pressure balance and separator liquid level in an electrolyzer cell wherein the detector D comprises of a plurality of magnetically sensitive reed switches RS (1, 2, ...n).

In yet another embodiment, the present invention provides a method for controlling cell pressure balance and separator liquid level in an electrolyzer cell wherein the continuity probe sensing device comprises atleast a pair of electrically isolated probes PR1 and PR2 extending into the Hydrogen separation chamber HSC at lengths that define the minimum electrolyte level BL(H)1 and a maximum electrolyte level EL(H)h.

In another embodiment, the present invention provides a passive circulation process in an electrolyzer cell EC, said process comprising:

providing a first connecting line CL(H) between a hydrogen separator HSC and a cathode active surface ES(C) near bottom end of the cell EC;

providing a second connecting line CL(O) between a oxygen separator OSC and anode active surface ES(A) near bottom end of the cell EC; and

allowing a electrolyte to flow in the first and second connecting lines CL(H) and CL(O) such that the density difference between the level of electrolyte in the cell and the first and second connecting lines creates a buoyancy driven loop.

In another embodiment, the present invention provides an electrolyzer cell EC for direct production of ultra-high pressure hydrogen, by means of electrolysis, wherein the electrolyzer is adapted for controlling cell pressure balance and separator liquid level as described hereinabove.

In another embodiment, the present invention provides an electrolyzer EC for direct production of ultra-high pressure hydrogen, by means of electrolysis, wherein the electrolyzer is adapted with a passive circulation loop for movement of electrolyte between the separation chamber and production chamber as described hereinabove. While this invention has been particularly shown and described with references to the figures and preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

WE CLAIM,

1. An improved electrolyzer cell EC for generating ultra high pressure hydrogen by means of electrolysis comprising:

a cathode C of tubular configuration connectable to a source of electricity DC, and defines a cathode active electrode surface ESfC), at which hydrogen is generated;

wherein

said Hydrogen separation chamber (HSC) is deployed with a level sensing device (LSD) to detect the level of electrolyte such that if the level sensing device (LSD) indicates low level of electrolyte then a water pump P is activated to inject water into the hydrogen separation chamber HSC at a pre-determined flow rate; said Oxygen separation chamber (OSC) Is provided with an oxygen connecting line CL(O) connecting the said chamber to the bottom of the said electrolyzer cell EC and a valve V for venting accumulated oxygen as a bye-product at a predetermined rate to prevent excessive flow of the electrolyte into the electrolyzer cell through said connecting line CL(O)

2. The electrolyzer cell EC as claimed in claim 1, wherein the said level sensing device (LSD) is selected from a group consisting of float level sensing device, a continuity probe sensing device, acoustic sensing device, capacitance probe or optical sensing device.

3. The electrolyzer cell EC as claimed in claim 2, wherein said float level sensing device comprises of polymer float PF deployed inside the hydrogen separation chamber (HSC) and a detector D deployed on the exterior of the hydrogen separation chamber (HSC(e)).

4. The electrolyzer cell EC as claimed in claim 3, wherein the polymer float PF is constructed from a polymer material having density lesser than the density of the electrolyte and is embedded with at least one magnet MG.

5. The electrolyzer cell as claimed in claim 3, wherein the detector D comprises of at least one magnetically sensitive reed switch RS.

6. The electrolyzer cell as claimed in claim 2, wherein said continuity probe sensing device comprises atleast a pair of electrically isolated probes PR1 and PR2 extending into the Hydrogen separation chamber HSC at lengths that define the minimum electrolyte level EL(H)1 and a maximum electrolyte level EL(H)h.

7. A method for controlling cell pressure balance and separator liquid level in an electrolyzer cell, said method comprising:

sensing the level of a electrolyte in a hydrogen separation chamber HSC of an electrolyzer cell EC by atleast one level sensing device LSD configured to Indicate a low level of the electrolyte EL(H)(1);

injecting water into the hydrogen separation chamber HSCat a predetermined flow rate when the level sensing device LSD indicates a low level of the electrolyte EL(H)(1) ; and

opening a valve V connected to the oxygen separation chamber (OSC) when the pressure of accumulated oxygen is greater than a predetermined pressure for venting oxygen at a rate that prevents excessive flow of the electrolyte from the oxygen separation chamber (OSC) to electrolyzer cell EC through the connecting line CL(O).

8. The method as claimed in claim 7, wherein the level sensing device LSD is selected from the group consisting of a float level sensing device, a continuity probe sensing device, acoustic sensing device, capacitance probe and optical sensing means.

9. The method as claimed in claim 8 , wherein float sensing device comprises of polymer float PF deployed inside the Hydrogen separation chamber (HSC) and a detector D deployed on the exterior of the hydrogen separation chamber (HSC(e)) which detects the rise and fall of the level of the liquid EL(H) inside the Hydrogen separation chamber HSC.

10. The method as claimed in claim 9, wherein said polymer float PF is constructed from a polymer material having density lesser than the density of the electrolyte and is embedded with at least one magnet MG.

11. The method as claimed in claim 9, wherein the detector D comprises of at least one magnetically sensitive reed switch RS .

12. The method as claimed in claim 11, wherein the detector D comprises a plurality of magnetically sensitive reed switches RS (1, 2, ...n) .

13. The method as claimed in claim 7, wherein said continuity probe sensing device comprises atleast a pair of electrically isolated probes PR1 and PR2 extending into the Hydrogen separation chamber HSC at lengths that define the minimum electrolyte level EL(H)1 and a maximum electrolyte level EL(H)h.

14. A passive circulation process in an electrolyzer cell EC, said process comprising:

15. An electrolyzer cell EC for direct production of ultra-high pressure hydrogen, by means of electrolysis_/ wherein the electrolyzer is adapted for controlling cell pressure balance and separator liquid level according to the method as claimed in claim 9.

16. An electrolyzer EC for direct production of ultra-high pressure hydrogen, by means of electrolysis, wherein the electrolyzer is adapted with a passive circulation loop for movement of electrolyte between the separation chamber and production chamber according to the method as claimed in claim 14.