Method for controlling a facility containing a plurality of electrolysers

Abstract

The invention relates to a method for controlling a facility containing a plurality of electrolysers that are fluidically in parallel, comprising the step of controlling the electrolysers in such a way as to seek to increase the uniformity of the individual loads on the electrolysers in operation, in order to minimize a specific electrical consumption of the facility for a predetermined total production load or for an electrical power available to power the facility.

Description

[0001] METHOD FOR CONTROLLING AN INSTALLATION CONTAINING SEVERAL ELECTROLYZERS

[0002] The present invention relates to the field of production of dihydrogen and dioxygen.

[0003] BACKGROUND OF THE INVENTION

[0004] The fight against global warming has forced authorities and industrialists to rethink the energy supply of our societies with a view to substituting fossil fuels with energies emitting less carbon dioxide, particularly in the field of transport for the motorization of vehicles but also for the manufacture of fertilizers and steel, without forgetting for energy storage and the general decarbonization of industrial processes using fossil fuels. The need to reduce the production of greenhouse gases and to use renewable energies is now well known. Dihydrogen is an alternative to hydrocarbons because it is an easily storable energy vector, unlike electricity, and its oxidation releases very significant energy (285 kJ / mole).

[0005] There are several methods for producing hydrogen. The most advantageous is electrolysis of the water molecule because it is a high-yield reaction that does not directly produce CO2, unlike the widely used processes of methane, coal, and hydrocarbon reforming.

[0006] Three main types of electrolyzers for water electrolysis are well known from the prior art:

[0007] - alkaline electrolysers (AWE), which are characterised by the use of a liquid electrolyte which allows the transfer of hydroxyl ions (0H-) from the cathode to the anode, high temperature electrolysers, the electrolyte of which is a ceramic; and

[0008] - membrane electrolysers (PEM), the electrolyte of which is a proton-conducting ion exchange membrane. In all three cases, the system must be supplied with very high purity water (supplying, in the case of alkaline electrolysers, an electrolytic solution of sodium hydroxide (NaOH) or potassium hydroxide (KOH)). In the remainder of the description, for reasons of brevity, reference will be made to an alkaline electrolyser, but it is understood that the present invention also applies to the membrane electrolyser (for example a proton exchange membrane).

[0009] According to the well-known method of the prior art, an electrolytic solution (commonly referred to by the English term lye) is brought into a set of electrolytic cells (known as an electrolyzer stack) through a specific inlet. The electrolytic solution passes through the electrolyzer stack. The water is decomposed into gaseous molecules of dihydrogen H2, at the cathode, and dioxygen O2, at the anode. A diaphragm generally separates the anode from the cathode so that, under normal conditions, dihydrogen and dioxygen do not mix. The installation comprises an outlet for dihydrogen and electrolyte flowing on the cathode (catholyte) side and an outlet for dioxygen and electrolyte flowing on the anode (anolyte) side.In other words, these are two separate streams so that there is a gas-liquid separator dedicated to the separation of dihydrogen from the catholyte, and a gas-liquid separator for the separation of dioxygen from the anolyte. The liquid outputs of the two gas-liquid separators are then mixed before feeding the electrolyzer stack again. In both streams, at the outlet of the electrolyzer stack, the liquid phase (lye) is loaded with gas bubbles. At the outlet of the gas-liquid separator, there are only a few gas bubbles left in the lye evacuated through the lower orifice of the gas-liquid separator dedicated to the liquid phase while the majority of the gas phase is extracted from the gas-liquid separator through the upper orifice of the gas-liquid separator. For various reasons, it is important to separate the gas from the lye.First of all, the more gas is separated from the electrolyte, the more gas is produced, which contributes to the good electrochemical efficiency of the process. Secondly, the H2 / O2 mixture is highly explosive. If the separation is not carried out correctly, a significant quantity of gas, commonly called "residual gas", is entrained at the liquid outlet of the gas-liquid separator. During the next circulation in the electrolyzer stack (the electrolyte rotates in a closed loop) some of this gas passes into the other compartment and therefore to the wrong side.

[0010] It is understood that the economic and ecological benefits of using hydrogen in an energy process depend largely on the performance of the hydrogen production system. Ideally, it is necessary that:

[0011] - the manufacturing and operating costs of the production device are as low as possible;

[0012] - the impact on natural resources for the manufacture and operation of the production device is limited;

[0013] - the device produces little or no polluting emissions during its operation;

[0014] - the device is simple, efficient, reliable and relatively compact... Furthermore, the energy efficiency of the installation is not the only issue when considering operating costs. Indeed, objectives

[0015] - flexibility / responsiveness in adapting to rapid variation in demand for hydrogen production;

[0016] - and maintainability are also crucial for these installations often comprising several electrolysers operating on the same production site and / or controlled centrally. Finally, the ability to maximise electrical energy consumption for a given production of dihydrogen can paradoxically prove to be interesting in certain circumstances, particularly in terms of service to the regulation of the electricity network (local or not).

[0017] SUBJECT OF THE INVENTION

[0018] The invention aims in particular to improve all or part of the energy aspects of an installation containing several electrolysers.

[0019] SUMMARY OF THE INVENTION

[0020] To this end, the invention provides a method for optimizing the control of an installation containing several electrolysers in parallel (hereinafter referred to as “MIEL-S”).

[0021] The essential characteristic of the method of the invention is that the control is carried out to homogenize the individual loads of the electrolysers in operation while tending to minimize the specific consumption of the installation for a predetermined total production load of dihydrogen or for availability of an electrical supply power of the installation.

[0022] It is under these conditions that the installation can have optimal performance while promoting responsiveness and flexibility of the whole and also taking into account the constraints in terms of availability of the electrolysers (called "ELY" in the rest of the document) with respect to, for example, the maintenance program of the installation. The invention also makes it possible to exploit a strategy for maximizing the electrical power consumed by the "MIEL-S" for a given production of dihydrogen in order to maximize the range of regulation of electrical power absorbed within the framework of the regulation service of the electrical network (local or not). Other characteristics and advantages of the invention will emerge upon reading the following description of particular and non-limiting modes of implementation of the invention.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Let “MIEL-S” be a set of N electrolysers which are a priori identical (Multi Identical ELectolyzor System) and which can operate a number “n” of electrolysers, “n” ranging from 0 to N.

[0025] Let us consider a HOLOS (n) strategy, consisting of distributing the load homogeneously within the “n” electrolysers in operation (Homogenous Load Operation Strategy).

[0026] Reference will be made to the attached drawings, including:

[0027] [ Fig . 1 ] Figure 1 is a characteristic curve of the individual specific consumption of one of the multiple identical electrolysers of the MIEL-S;

[0028] [ Fig . 2 ] Figure 2 shows a network of N HOLOS curves. Each curve in the graph is associated with a number "n", where n can be equal to a value between 1 and N electrolysers in operation within the "MIEL-S" system, which includes N electrolysers in total. The n electrolysers in operation follow a "HOLOS" strategy and the other Nn electrolysers in the MIEL-S system are stopped (or on standby). The network of curves therefore shows the specific consumption ( kWh / Nm 3 ) of the MIEL-S as a function of the system load and the number "n" of electrolysers in operation, considering that the operating strategy is always of the HOLOS type regardless of the number "n". A HOLOS type strategy will always be based on this network of curves. An operating strategy not based on this network of curves is not of the HOLOS type;

[0029] [Fig. 3] Figure 3 is analogous to Figure 2 and shows the intersections of the curves with each other. These intersection points are called the “HOLOS points”. There are 2*N intersection points. These HOLOS points are numbered from 1 to 2*N in order of occurrence during a ramp-up of the MIEL-S system;

[0030] [Fig. 4] Figure 4 is analogous to Figure 2 and shows the best efficiency curve (BEL = Best Efficiency Line) of a MIEL-S;

[0031] [Fig. 5] Figure 5 is a graph showing the position of the 2*N “HOLOS points” on the individual specific consumption characteristic of the multiple identical electrolysers of the MIEL-S;

[0032] [Fig. 6] Figure 6 is a graph showing the evolution of the charge of the electrolysers within the MIEL-S during the occurrences of the 2*N HOLOS points;

[0033] [Fig. 7] Figure 7 is a graph showing the relative load ratio at consecutive HOLOS points during a monotonic ramp-up of the MIEL-S;

[0034] [Fig. 8] Figure 8 is analogous to Figure 2 and shows the best efficiency curve (BEL) for electrolysers considered “invisible” in groups of four in terms of load;

[0035] [Fig. 9] Figure 9 is analogous to Figure 4 and shows the worst efficiency curve (WEL = Worst Efficiency Line) which does not follow a HOLOS type strategy. Its interest, in a context of electrical network regulation service (local or not), is to identify the upper limit of electrical energy that the MIEL-S can consume for a given production of dihydrogen;

[0036] [ Fig . 10 ] Figure 10 is analogous to Figure 9 and shows the worst efficiency curve (HOLOS-type WEL) under the HOLOS strategy;

[0037] [ Fig . 11 ] Figure 11 is analogous to Figure 9 and shows the curve minimizing the number of electrolysers in operation (T LEO L = The Less Electrolyser in Operation Line) for a given load of the MIEL-S and aiming to maintain a HOLOS type strategy;

[0038] [ Fig . 12 ] Figure 12 is analogous to Figure 9 and shows the curve maximizing the number of electrolysers in operation (T MEO L) for a given load of the MIEL-S and aiming to maintain a HOLOS type strategy;

[0039] [ Fig . 13 ] Figure 13 shows the number of electrolysers in operation as a function of the MIEL-S load and this for the different HOLOS strategies mentioned above;

[0040] [ Fig . 14 ] Figure 14 shows an example of the desired hydrogen production curve of the plant as a function of time and plant load;

[0041] [ Fig . 15 ] Figure 15 is analogous to Figure 14 and additionally shows the response curve in terms of the number of electrolysers in operation when the strategy followed is of the “BEL” type;

[0042] [ Fig . 16 ] Figure 16 is analogous to Figure 14 and also shows the response curve in terms of specific consumption when the strategy followed is of the “BEL” type;

[0043] [ Fig . 17 ] Figure 17 is similar to Figure 14 and also shows the response curve in terms of power consumed by the installation when the strategy followed is of the “BEL” type.

[0044] It should be noted that the values ​​are given for information purposes only in order to give orders of magnitude and also depend on the configurations of the equipment constituting the electrolysers.

[0045] The same applies to the time scales, which are also mentioned for information purposes.

[0046] DETAILED DESCRIPTION OF THE INVENTION

[0047] For example, the multi-electrolyzer installation or system (MIEL-S or “Multi Identical ELectrolyzer System”) is here composed of N=24 identical electrolyzers (ELY) of 1000Nm 3 / hf fluidically connected in parallel, each is assumed to be totally independent in terms of production load. The invention is obviously applicable to any other nominal capacity of electrolysers (typically 1 Nm 3 / h at 4000 Nm 3 / h, especially between 100 Nm 3 / h and 2000 Nm 3 / h, in particular 500 Nm 3 / h at 1500 Nm 3 / h) .

[0048] Optimizing the control of a multi-electrolyzer installation is not trivial and needs to be conceptually constructed step by step.

[0049] The first part of this description sets out a methodology for establishing different operating strategies for a MIEL-S, answering, for example, the following questions:

[0050] • how to distribute the production load within a MIEL-S?

[0051] • at what production load should an ELY be stopped or started within a MIEL-S?

[0052] • does the answer to these first two questions change depending on the objective pursued such as: o minimizing the energy consumption necessary for the production of dihydrogen; o maximizing the reactivity in terms of variation in production load; o increasing the maintainability of the system; or o minimizing the degradation of the energy performance of the system? This methodology also allows the operator of a MIEL-S (or its designer) knowing the properties of the installations (specific consumption as a function of the load, shutdown / start-up time, degradation rate as a function of operational demands, etc.) to arbitrate between the different operating strategies and to identify the one which will be best suited to its operating context.

[0053] This first part is based on an idealized approach to reality, taking into account only the theoretical behavior of the installation at the start of its life (BOL) to define a strategy for optimizing its management.

[0054] The second part of this description aims to complete this approach with “non-ideal” phenomena such as, for example, the impact of performance degradation over time on piloting optimization.

[0055] The initial hypothesis is that the demand in terms of hydrogen production load is perfectly known over a time horizon T and that the problem to be solved is to minimize the specific electrical consumption of the installation (specific consumption Cs [kwh / Nm 3 ] ) taking into account this production load over this time horizon T .

[0056] 1. Idealized approach a. Critical points of an electrolyzer efficiency curve (see Figure 1) Three characteristic points are to be noted on the specific consumption curve, Cs, of the ELY:

[0057] - MCR or maximum continuous rate. In the example in Figure 1, 100% load (equivalent to a nominal production of, for example, 1000 Nm 3 / h) for a Cs of 4.66 kwh / Nm 3 ;

[0058] - BEP or best efficiency point. That is 52% load for a Cs of 4.56 kwh / Nm 3 in the example of figure 1. The specific consumption curve actually passes through a minimum (BEP) which results from the antagonistic phenomena internal to the electrolyser stack when its current density varies;

[0059] - MSOL or "minimum stable operating point". In Figure 1, the minimum stable operating point is located at 27% of the hydrogen production load. b. Best Efficiency Line (BEL) - Optimizing the operation of a MIEL-S installation

[0060] Given the concavity of the curvature (positive second derivative) of the Cs curve in Figure 1 mentioned above, a system operating with several ELYs and having to meet a given load will always minimize its specific consumption by homogenizing as much as possible the individual production load of each ELY within the system. In the installation example described here, let us consider that the twenty-four ELYs each operate at 70% of their load, the installation will then be at 70% of its total capacity (or load). The specific consumption of the installation would then be (see Figure 2, left scale) approximately 4.59 kWh / Nm 3We could imagine varying the individual load of one of the twenty-four ELYs downwards and keeping the total load of the installation unchanged by varying another of the twenty-four ELYs in the same proportions. The result would be less good in terms of the specific consumption of the installation.

[0061] This defines a first optimization strategy by homogenization of operating load, named HOLOS for “Homogeneous Load Operation Strategy”, considering for simplicity that all the electrolysers have at all times the same specific consumption curve.

[0062] This strategy is based on the principle that for a given number of ELYs in operation out of the twenty-four in the installation (MIEL-S), they will minimize the electrical consumption of the installation for a given total production load by all being at the same individual production load. Furthermore, in Figure 2, twenty-four specific consumption curves are considered. They are all of the HOLOS type. The first one mentioned above relates to the case where the twenty-four ELYs are in operation. The other twenty-three curves correspond to 23, 22, 21, ..., 3, 2, 1 ELY in operation, therefore following a HOLOS strategy (i.e. the individual loads of the electrolysers in operation are identical to each other).

[0063] The next step is to define when to stop or start an ELY when the load of the MIEL-S installation varies. This is the subject of Figure 3 which shows the intersections of the curves HOLOS (24) with HOLOS (23); HOLOS (23) with HOLOS (22); ...; HOLOS (2) with HOLOS (1). The production loads at the said intersections (HOLOS points) are in reality the percentages of production load of the installation (MIEL-S) at which it is theoretically appropriate to vary the number of ELYs in operation in order to minimize the specific consumption of the system.

[0064] This optimization does not take into account, at this stage, the penalty that the MIEL-S installation suffers in terms of performance degradation for the future, or the variations in performance within the same batch due to manufacturing tolerances. This "non-ideal" aspect will be addressed in the dedicated section of this description.

[0065] From this point on, it is possible to plot the BEL envelope curve of the MIEL-S. This is shown in Figure 4 and constitutes a lower bound of the specific consumption of the installation (MIEL-S). In other words, the BEL envelope curve defines the lower limit of the set of specific consumption curves. Although this line appears to describe a plateau (in particular between 25% and 50% load in the example considered here), it actually passes over twenty-four minima, all equal and corresponding to the BEP defined above.

[0066] The individual loads of the ELYs of the installation when the number of ELYs in operation changes at the installation level are represented in Figure 5. The chronology of the numbers shown on the graph corresponds to a ramp-up of the MIEL-S installation starting with an ELY operating at MSOL (point 1). This ELY ramps up, following the Cs curve until point 2, when a second ELY must be started to minimize the specific consumption Cs while continuing to increase the load of the installation (MIEL-S). In doing so, the individual load of the two ELYs is positioned "instantaneously" at point 3. The individual loads thus continue to evolve towards points 4, 5, 6, 7, ..., 46, 47. These points are called "HOLOS points" in the following. For simplicity, the start-up / ramp-up times of each additional electrolyser are neglected here: this is a static optimization in steady state.

[0067] The graph in Figure 6 shows the evolution of the “HOLOS points” located “to the left and right” of the BEP.

[0068] The individual load ratio of consecutive HOLOS points (just before and just after the change in the number of operating ELYs) follows a logical sequence illustrated in the graph of Figure 7.

[0069] If the MIEL-S installation were to include ELYs arranged four by four in terms of load (for example considering six ELY4000s instead of twenty-four ELY1000s), the BEL would evolve as shown in the graph in Figure 8 (consider the red line and not the black line). c. Worst Efficiency Line (WEL) of a MIEL-S installation

[0070] In Figure 9, the worst efficiency line WEL (in red) is plotted in addition to the best efficiency line BEL (in black) to show the maximum improvement potential allowed by trying to get closer to the best efficiency line BEL. Also, the difference between these two curves, for a given dihydrogen production, is the image of the lever of variation of electrical power consumed by the MIEL-S. This notion is useful in the context of an electrical network regulation service, whether it is local or not.

[0071] The WEL corresponds to a two-phase implementation. Considering a monotonic load decrease and starting from an initial situation where the MIEL_S is at full load (all ELYs being at 100% load), during phase 1, the load decrease is organized as follows: a number i (i ranging from Nl to 0) of ELYs at 100%, a number equal to Ni-1 of ELYs at MSOL and an ELY adjusting the load of the installation with its own load. When this ELY reaches MSOL, i becomes i-1 and one of the ELYs operating at 100% load starts to regulate, alone in turn, the load of the MIEL-S. Phase 1 leads to a final situation where the N ELYs are all at MSOL.

[0072] Phase 2 therefore begins with an initial situation which is the final situation of phase 1, namely all N ELYs at MSOL. During phase 2, the continuation of the load reduction is managed as follows: a number j (j ranging from N-2 to 0) of ELYs at MSOL, a number equal to Nj-1 of ELYs are stopped (or on standby) and an ELY adjusts the load of the installation with its own load. When this ELY reaches MSOL, it is stopped (or on standby), and j becomes j-1. Phase 2 results in a final situation where the N ELYs are all stopped (or on standby).

[0073] The graph in Figure 10 shows a deliberately downgraded alternative to the Best efficiency line: the "Worst Efficiency Line - HOLOS". Although this alternative still considers a HOLOS approach, it ignores the "HOLOS points" defined above. Indeed, considering for example the case of a monotonic load decrease and starting from the case of twenty-four ELYs at 100% load, the strategy followed consists of stopping the ELYs as early as possible, one by one, thus leaving the other ELYs to operate at a relatively high individual load and this permanently.After stopping a certain number K of ELYs (K being fifteen in the defined numerical example) and lowering the load of the other NK (NK being nine in the described numerical example) ELYs remaining in operation, a second phase of this strategy consists, when the installation load is low enough to cross the HOLOS curve (N), in restarting all N (N being twenty-four) ELYs to make them all operate at a very low individual load, where the individual specific consumptions are less good. The rest of the illustration also considers stopping the ELYs one by one until the situation where only one ELY is in operation and goes down to its MSOL.

[0074] The use of WEL and WEL HOLOS strategies results in an increasing relative lack of optimization as the plant load decreases. d. HOLOS line of the minimum number of electrolyzers in operation (T LEO L = The Less Electrolyzer in Operation Line) of a MIEL-S plant

[0075] This strategy, illustrated in Figure 11, consists of stopping an ELY as soon as possible once the total production load of the MIEL-S installation allows it, while being part of a HOLOS strategy. The number of electrolysers simultaneously in operation is therefore reduced to the minimum number necessary to provide the total production load of dihydrogen: the result is that the individual load of the electrolysers in operation is rather relatively high even when the total production load is relatively low. The primary optimization objective concerns the number of electrolysers and the specific consumption is a secondary objective.

[0076] This strategy is preferably used during plant maintenance operations that require stopping as many ELYs as possible or in the case where a rapid drop in a total production load is required. e. HOLOS line of the maximum number of electrolyzers in operation (T MEO L = The Most Electrolyzer in Operation Line) of a MIEL-S plant

[0077] This strategy, illustrated in Figure 12, consists of maintaining a maximum possible ELY in operation during a monotonic decrease in the MIEL-S load, while following a HOLOS strategy. When the load drops below the load threshold corresponding to N ELY at MSOL, an ELY is switched off (or on standby) and the MIEL-S then moves to HOLOS (Nl). The continuation of the load decrease is managed in an identical manner by successively moving from HOLOS (Nl) to HOLOS (N- (1+1) ) (1 going from 0 to N-2). When the load leads to MSOL on HOLOS-1, the last ELY is switched off (or on standby) in turn. As a result of this strategy, the individual load of the electrolysers in operation is relatively low when the total production load is low.

[0078] This strategy can be used throughout the lifetime of the installation, for example, to mitigate performance degradation related to the individual charge rate of the electrolysers. Furthermore, this strategy offers the widest range of operation without stopping and starting (between 27% and 100%). This range without stopping / starting can be called "SSL" (Start & Stop Less). This SSL range offers, on the one hand, a minimization of performance degradation due to start / stop occurrences and, on the other hand, a maximization of the system's responsiveness (thanks to the absence of an ELY stopping / starting procedure within the MIEL-S, which is costly in terms of operating time) in the face of load variations which would have led, through other operating strategies, to ELY stopping / starting, increasing performance degradation and reducing the responsiveness of the entire MIEL-S.Furthermore, this strategy simplifies the control of the installation and its operation. Note that it is possible to generalize the notion of T MEO L as follows. The case just described considers the initial situation "HOLOS (N)" (here "HOLOS (24)"). The resulting SSL range can be precisely named SSL (N) (here "SSL (24)"). And we then note that this strategy can be specifically noted T_MEO_L (N). For a given MIEL-S, it is quite possible to observe that during a given period the load will often vary, mainly, in a range "P" not included in the SSL (N) range. It will then be entirely possible to optimize the choice of another T MEO L (m) (with m < N) which would lead to better including the P range in the SSL (m) thus generated by this choice of operating strategy.In other words, the electrolysers are controlled to operate at their optimal operating point a maximum number m of electrolysers less than the total number N of electrolysers, the maximum number m corresponding to a load of the installation varying in an operating range less than a maximum operating range of the installation involving the total number of electrolysers. f. Management of the load of a MIEL-S installation.

[0079] The plant load can be managed using a first approach based on the production of hydrogen or a second approach based on the availability of the electrical power supplying the plant. The description in this document assumes the first approach. Indeed, from the graph in Figure 1, the ordinate is expressed as a function of the hydrogen production load. All the graphs and operating strategies described below are therefore expressed as a function of the hydrogen production load. To consider the second approach, it is sufficient to reproduce the same reasoning as that used for the first approach, starting from an alternative to the graph in Figure 1 by expressing "the evolution of specific consumption as a function of the electrical load" instead of "the evolution of specific consumption as a function of the hydrogen production load".The graphs are substantially similar in appearance and lead to the same types of reasoning and analysis.

[0080] Figure 13 therefore illustrates the first approach and represents the production of dihydrogen by the MIEL-S installation as a function of the number of ELYs in operation and according to different usable strategies, namely BEL, T LEO L, TMEO L (N), HOLOS WEL.

[0081] Figure 14 shows the required production load of dihydrogen (thin continuous line) according to the first approach (profiles of different shapes were chosen to illustrate the adaptation of the production of the installation to these different profiles).

[0082] Figure 15 shows this same required production load of dihydrogen (thin dotted line) on which the load produced in response by implementing the BEL strategy (thick red solid line) and the number of ELYs in operation (thick blue broken line) are superimposed.

[0083] Figure 16 shows this same required production load of dihydrogen (thin dotted line) on which the load produced in response by implementing the BEL strategy (thick solid line) and the specific consumption Cs of this strategy (thin blue solid line) are superimposed.

[0084] Figure 17 shows the required production load of dihydrogen (thin dotted line) on which the load produced in response by implementing the BEL strategy (thick solid line) and the power of the MIEL-S installation (thin blue solid line) are superimposed.

[0085] 2. Taking into account non-ideal phenomena a. List of “non-ideal” phenomena influencing the optimization of the load management of the MIEL-S installation:

[0086] - Limitation of the operating range (% of dihydrogen production load) linked to certain components of the installation (including internal to the ELYs in the event of pooling of several ELYs);

[0087] - Degradation of performance linked to stops and starts of ELYs;

[0088] - Degradation of performance linked to the operating hours of the ELYs;

[0089] - ELY shutdown and startup times as well as energy losses during transients;

[0090] - Performance imbalance between the ELYs of the electrolyser stack (the electrolysers are theoretically all identical but in reality their performances are different); - Dynamic need for absorption or reduction of load of the MIEL-S installation according to the prediction of the production demand;

[0091] - The total or partial unavailability of one or more ELYs;

[0092] - Occurrence of emergency shutdown. b. Consideration of “non-ideal” phenomena influencing the optimization of the load management of the MIEL-S installation

[0093] Generally speaking, the answer to the question "at what plant load should the ELYs be stopped or started within a multi-ELY system (MIEL-S)?", taking into account these "non-ideal" phenomena, will be a function of the prediction of the future load and the remaining life of the plant...

[0094] Indeed, bearing in mind, for example, that each shutdown of an ELY implies a deterioration in its future performance, is it necessary, during operation and facing an increase in demand for hydrogen production:

[0095] - start an additional ELY to reduce the average load of the ELYs and thus reduce the energy consumption of the installation in the short term while we are at the same time informed that this load, which has been increasing until now, is about to decrease and that the ELY which has just been started will have to be stopped soon? or

[0096] - on the contrary, tolerate a lack of optimization in the short term to preserve the performance of the installation in the longer term?

[0097] The answer to this question will not necessarily be the same depending on when we ask it in the life of the installation. This involves the concept of LCOH and its continuous recalculation based on short- and long-term load predictions.

[0098] Thus, the optimization of the performance of an installation can be obtained by, separately or in whole or in part in combination:

[0099] - individual homogenization of ELYs;

[0100] - the operation of a maximum of ELY at its optimal operating point;

[0101] - the dynamic determination of the load of each ELY individually according to its particular specific efficiency (linked to its own aging, its own capacity, etc.);

[0102] - adaptation of individual installation capacities in order to refine the load or production capacity and optimize the installation's efficiency.

[0103] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0104] In particular, numerical values ​​are given for example purposes only.

[0105] The values ​​of specific consumption Cs and production of dihydrogen are valid for electrolysers at the maximum limit of their operation, taking into account energy losses (electrolyser stack, rectifier, transformer, gas-liquid separator, purifier, pump, etc.) and dihydrogen losses in the gas-liquid separation and purification units.

[0106] The cubic normometer is considered at 0°C and 1 atm.

[0107] The number of electrolysers can be less or more than twenty-four.

[0108] Actual operating parameters are determined by monitoring the installation or by statistical analysis of existing installations.

[0109] Each electrolyser can be equipped with its own power conversion device (rectifier). In another case, at least two stacks can be electrically connected in series (voltage addition).

[0110] The method may comprise the step of defining a worst efficiency mode in which the load of the installation is adjusted by adjusting the load of only one of the electrolysers, the other electrolysers being either at their maximum load, or at their minimum operating point, or at a standstill; and the step of controlling the installation between an optimal mode corresponding to the homogenisation of the individual loads of the electrolysers in operation and the worst efficiency mode.

[0111] It should be noted that the Cs versus load curve is preferably representative of the complete installation (therefore including the 'Balance Of Plant') rather than that representative only of the electrolyser stack (and some of its loss mechanisms) since the end user is interested in the overall consumption (i.e. including the BOP).

Claims

CLAIMS 1. Method for controlling an installation containing several electrolysers fluidically in parallel, comprising the step of controlling the electrolysers by seeking to homogenize individual loads of the electrolysers in operation to minimize a specific electrical consumption of the installation for a predetermined total production load or for an electrical power available to supply the installation.

2. Method according to claim 1, comprising the step of determining specific consumption curves each corresponding to a number nd' of electrolysers in operation, the number n varying from 1 to N which is the total number of electrolysers in the installation.

3. A method according to claim 2, comprising the step of determining an envelope curve representing a lower limit of the set of specific consumption curves.

4. Method according to claim 3, in which the number of electrolysers to be kept in operation simultaneously is determined as a function of the envelope curve.

5. A method according to claim 4, comprising the step of reducing the number of electrolysers simultaneously in operation to a minimum number necessary to provide the total production load.

6. A method according to claim 4, comprising the step of increasing the number of electrolysers simultaneously in operation to a maximum number necessary to supply the total production load.

7. Method according to claim 1, in which a theoretical mode of control of the installation is first determined on the basis of the state of the installation at the start of its life then we modify the theoretical control mode according to at least one real operating parameter of the installation.

8. Method according to claim 7, in which the actual operating parameter belongs to the following group of parameters: - limitation of an operating range of at least one component of the installation; - performance degradation linked to the stopping and starting cycle of the electrolysers; - performance degradation linked to the operating time of the electrolysers; - stopping and starting times of electrolysers and energy losses during the transient phase between stopping and starting the electrolysers; - performance imbalance between electrolysers; - dynamic need for absorption or reduction of the installation load based on a prediction of production demand; - total or partial unavailability of at least one electrolyser; - occurrence of emergency shutdown of all or part of the installation.

9. Method according to claim 7 or 8, wherein the actual operating parameter is determined by monitoring the installation or by statistical analysis of existing installations.

10. The method of claim 1, comprising the step of controlling the electrolysers to operate a maximum of electrolysers at their optimal operating point.

11. The method of claim 1, comprising the step of controlling the electrolysers to operate at their optimum operating point a maximum number of electrolysers less than the total number of electrolysers, the maximum number corresponding to a load of the installation varying in an operating range less than a maximum operating range of the installation involving the total number of electrolysers.

12. The method of claim 1, comprising the step of dynamically determining the individual load of each electrolyzer based on its particular specific efficiency.

13. Method according to any one of the preceding claims, comprising the step of defining a worst efficiency mode in which the load of the installation is adjusted by adjusting the load of only one of the electrolysers, the other electrolysers being either at their maximum load, or at their minimum operating point, or at a standstill.

14. Method according to claim 13, comprising the step of controlling the installation between an optimal mode corresponding to the homogenization of the individual charges of the electrolysers in operation and the worst efficiency mode.

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