FR2924952A1 - Autonomous system for potabilizing brackish and/or polluted water, comprises pipes for circulating water, a unit for capturing renewable energy, a unit for controlling electronic and/or informatic set, and an automatic control unit - Google Patents

Abstract

The autonomous system for the potabilization of brackish and/or polluted water, comprises pipes (7) for the circulation of water from an upstream inlet (8a) to two downstream outlets (8b, 8c), a unit for capturing renewable energy such as solar or wind to generate a Ub voltage fluctuating throughout the day and supplying electricity to the pumping unit, a unit for controlling electronic and/or informatic set that are connected to a sensor for measuring the generated voltage at the upstream pumping unit, an automatic control unit, and a voltage stabilizer. The autonomous system for the potabilization of brackish and/or polluted water, comprises pipes (7) for the circulation of water from an upstream inlet (8a) to two downstream outlets (8b, 8c), a unit for capturing renewable energy such as solar or wind to generate a Ub voltage fluctuating throughout the day and supplying electricity to the pumping unit, a unit for controlling electronic and/or informatic set that are connected to a sensor for measuring the generated voltage at the upstream pumping unit, an automatic control unit, and a voltage stabilizer such as a unit for electrochemical or electrostatic energy storage. The upstream inlet is arranged for suction of crude water. One of the outlets is used for treating water and another is used for the discharge of water. The pipes are associated with an upstream pumping unit for the suction and delivery of crude water at the upstream inlet, and a downstream unit for water filtration membrane connected to the downstream outlet for water treatment through an expansion valve. The value for generating the voltage increases for a same level of capturing, when the speed of the pumping unit is decreased and increased. The voltage stabilizer is located between the energy capturing unit and the pumping unit, and is permanently retained at full load or nearly full load. The control unit corresponds to the full load voltage of the stabilizer, or a nominal voltage for functioning the system. The pumping unit consists of a set of two pumps including a downstream lift pump and a downstream booster pump. The control unit is connected to the two pumps. A unit is arranged for measuring the pressure of the supplied water Peb within the pipe extending between the two pumps. The control unit is connected: to the downstream expansion valve; to a water flow sensor Qeb located on a first pipe extending between the pump unit and a filtration unit (3); to downstream of an inlet of a recycling loop; to a water pressure sensor either located on the first pipe for measuring a supplied pressure Pa or a second pipe extending between the filtration unit and the expansion valve for measuring a pressure Pc; to the recirculation pump; and to a sensor of recycling water flow Qrec mounted on recycling loop. The control unit is capable of automatically controlling: the speed of the pumping unit according to a value that allows the generated voltage Ub to achieve and to maintain a voltage set point Ubo; the speed of the upstream lift pump to achieve and to maintain a generated voltage set point Ubo; the speed of the downstream of the booster pump to achieve and to maintain the supplied water pressure set point Pebo corresponding to the optimal functioning value of the downstream pump; the opening of the expansion valve so that the pressure of discharge water Pc or supplied water Pa is maintained at a pressure reference value Pco or Pao; and the speed of the recycling pump so that the recycling rate Qrec achieves and maintains a recycling flow reference value Qreco. The reference value of pressure Pco or Pao varies according to the measured value of feed rate Qeb for obtaining and maintaining a minimum specific energy Wt. The pipes are arranged to form a recycling loop of which the inlet is located between the filtration unit and expansion valve and the outlet is located between the filtration unit and pumping unit. The recycling loop comprises a recirculation pump enhancing the flow of water from the inlet to the outlet. The reference value of flow Qreco varies according to the measured value of the feed rate Qeb for obtaining and maintaining a minimum specific energy Wt. The filtration is carried out by reverse osmosis or by nanofiltration. An independent claim is included for a process for the management of function of an autonomous system for the potabilization of water.

Description

The present invention relates to an autonomous water purification system of the type equipped with a water filtration unit membrane (s), particularly for brackish water and / or polluted. In many developing countries, access to safe drinking water for indigenous people is a major challenge. One of the interesting solutions is to equip the brackish and / or polluted water points with water purification systems operating by means of water filtration units on membrane (s). But in these countries, these systems of potabilization must in addition be able to operate autonomously on the energy plan, in particular because of the weak development of the electrical network. To overcome this problem, these water purification systems are preferably equipped in addition to means for capturing renewable energy, for example solar energy and / or wind.

These stand-alone water purification systems are usually structured to operate from a constant power supply; however, the electrical energy generated by these sensing means varies during the day. Energy storage means, very often of the electrochemical battery type, are then associated with these energy sensing means, in order to restore a constant electrical energy whatever the power available and delivered by said sensing means. These storage means must have a significant capacity for the accumulation of electrical energy, at least several tens of kilowatt hours; and they then operate continuously according to repeated charge and discharge sequences. The large capacity of the electrical storage means has the disadvantage of increasing the cost price and the weight of the drinking water system. These electrical storage means are in addition relatively polluting, and difficult to recycle. The present invention aims to remedy these drawbacks by proposing an autonomous water purification system that has the advantage of reducing the capacity of the electrical storage means, or to allow their removal. It also aims to obtain an optimum ratio of drinking water flow rate with respect to the electrical energy consumed, and this regardless of the instantaneous power generated at the means of energy capture.

The autonomous water purification system according to the invention is of the type comprising pipes for the circulation of water from an upstream intake intake of raw water to two downstream outlets, one for water treated and the other for the discharge water; these pipes are associated with an upstream pumping unit, ensuring the suction and discharge of the raw water at said upstream inlet and its flow under pressure in said pipes downstream, and a downstream filtration unit of water on membrane (s) (optionally composed of several membranes coupled in series and / or in parallel), connected to said outlet outlet of treated water and, via an expansion valve, to said outlet of reject water; this system also comprises means for capturing renewable energy, for example of the solar or wind energy type, which generate a fluctuating voltage Ub during the day and supplying electrical energy to at least said pumping unit, the value of said generated electrical voltage Ub increasing, for the same level of capture, when the speed of said pump unit decreases, and vice versa. The autonomous system according to the invention is characterized in that it comprises electronic and / or computer-like control means which are connected to a sensor for measuring said generated electrical voltage Ub and to the upstream pumping unit. These control means automatically control the speed of said pumping unit according to a value which allows said generated voltage Ub to reach and to maintain a given value of voltage known as voltage voltage Ubo. This particular structure allows a regulation of the operation of the pumping unit, and therefore of the entire system of potabilization, depending on the amount of energy collected by the sensing means. The means of storing energy (often heavy, expensive and polluting) thus become optional, or can at least be reduced in capacity and size, that with all the benefits that result. Thus, in the case of a water purification system devoid of energy accumulation means, the control means automatically control the speed of the pumping unit advantageously according to a value which allows the voltage generated Ub to reach and maintain at the level of the Ubo voltage setpoint corresponding to the nominal operating voltage of the potabilization system (often for example 96 V or 192 V).

Alternatively, the potabilization system may still include a device for damping electrical voltage fluctuations, for example of the type of electrochemical or electrostatic energy storage means interposed between the energy sensing means and the unit. pump, which is permanently maintained at full load or almost fully loaded. In this case, the control means automatically control the speed of the pumping unit advantageously according to a value which allows the generated voltage Ub to reach and to maintain the level of the voltage setpoint value Ubo corresponding to the voltage full load of said damping device. In general, this Ubo voltage setpoint value advantageously corresponds to the makeup voltage or floating voltage (that is to say, still the voltage value compensating the internal losses of the damping device).

According to a particular embodiment, the upstream pumping unit consists of a set of two pumps: an upstream lift pump and a downstream booster pump. In this case, the control means are connected to the two pumps, and means for measuring the supply water pressure Peb within the pipe extending between said two pumps.

The control means then advantageously and automatically control: on the one hand, the speed of one of said two pumps, and preferably that of the upstream lifting pump, so that the generated electrical voltage Ub reaches and is maintained at level of the Ubo voltage setpoint, - and secondly, the speed of the other of said two pumps, and preferably that of the downstream pump booster, so that the water supply pressure Peb reaches and is maintained at a given level of Pebo supply water pressure said supply pressure setpoint corresponding to the optimal operating value of said second pump. This particular regulation has the advantage of ensuring the optimal operation of the downstream booster pump, whatever the flow of raw water supplied to it by the upstream lifting pump. According to yet another characteristic, the control means are connected - to the downstream expansion valve - to a feed water flow sensor Qeb located on a first pipe extending between the pumping unit and the filtration unit, optionally upstream of an outlet of a recycling loop, and - a water pressure sensor located on said first pipe for measuring a supply pressure Pa, or on a second pipe extending between said filtration unit and said expansion valve for measuring a discharge pressure Pc.

In this case, the control means automatically control the opening of the expansion valve advantageously so that the discharge water pressure Pc or Pa supply reaches and is maintained at a given value of pressure called value pressure reference, respectively Pco or Pao; this pressure reference value Pco or Pao varies as a function of the measured value of the feed rate Qeb, for obtaining and maintaining a specific energy Wt minimum. This real-time control of the valve, as a function of the feed rate Qeb, contributes to obtaining a maximum yield of the entire system of potabilization, whatever the operating regime of the upstream unit of pumping.

According to another characteristic, pipes are arranged to form a recycling loop, the inlet of which is situated between the filtration unit and the expansion valve and the outlet of which is situated between said filtration unit and the pumping unit. , said recycling loop comprising a recirculation pump promoting the flow of water from the inlet to the outlet.

In this case, the control means are advantageously connected to the recirculation pump, to a water recycling flow sensor Qrec, mounted on the recycling loop, and to the feedwater flow sensor. Qeb, located on the pipe extending between the pumping unit and the filtration unit, upstream of the outlet of said recycling loop.

The control means then automatically control the speed of the recycling pump advantageously so that the Qrec recycling rate reaches and is maintained at a given value of recycle flow rate called Qreco recycle flow rate reference value, which reference value Qreco flow rate varies according to the measured value of the feed rate Qeb, for obtaining and maintaining a specific energy Wt minimum. Here again, this real-time servocontrol of the recycling pump, as a function of the feed rate Qeb, contributes to obtaining the maximum efficiency of the entire water purification system, whatever the operating regime of the system. upstream pumping unit.

The present invention also relates to a method for managing the operation of an autonomous water purification system as described above. This system is of the type comprising pipes for the circulation of water from an upstream intake inlet or discharge of raw water to two downstream outlets, one for the treated water and the other for the discharge water, which pipes are associated with: - a lifting pump, ensuring the suction and / or discharge of water at the upstream inlet, - a booster pump, ensuring the flow of water downstream and under pressure in the pipes, - a membrane water filtration unit, connected to said treated water outlet and, via an expansion valve, to said water outlet of rejection, and which system further comprises - possibly pipes arranged to form a recycling loop, whose inlet is located downstream of the filtration unit and whose outlet is located upstream of said filtration unit, said loop recirculation pump with recirculation pump water return, and - renewable energy harvesting means generating a fluctuating voltage Ub during the day, which supply electrical energy to the lift pump, the pump booster pump, and if necessary the pump recirculation.

The method according to the invention consists in: controlling the speed of the upstream lift pump according to a value which enables said generated voltage Ub to reach and to maintain a given voltage value, said voltage setpoint Ubo electric, said generated voltage Ub increasing, for the same level of capture, when the speed of said pump unit decreases, and conversely, - to control the speed of the booster pump so that the supply water pressure Peb, within the pipe extending between said lifting pump and said booster pump, reaches and is maintained at a given level of supply pressure Pebo said supply pressure setpoint corresponding to the optimum operating value of said booster pump, - controlling the opening of the expansion valve so that the measured water pressure is on a first pipe extending between the pump unit e and the filtration unit, said supply pressure Pa, or a second pipe extending between said filtration unit and said expansion valve, said reject water pressure Pc, reaches and is maintained at the level of a given pressure value referred to as the pressure reference value Pao or Pco, said pressure reference value Pao or Pco varying as a function of the supply flow rate value Qeb, measured in the pipe extending between the pumping unit and the filtration unit, if necessary upstream of the outlet of the recycling loop, and if necessary, to control the speed of said recycling pump so that the recycling flow Qrec reaches and is maintained at the level of a given recycling flow rate value referred to as the Qreco recycling flow rate reference value, said Qreco recycling reference value varying as a function of the measured value of said feed flow rate Qeb. The invention will be further illustrated, without being limited in any way, by the following description in relation to the accompanying drawings in which: - Figure 1 is a schematic representation of an autonomous water purification system according to the invention; FIG. 2 schematically represents, and by way of example, iterations obtained from the relationship of the specific energy of the installation Wt (in kilowatt hours per cubic meter), as a function of the recycle flow rate Qrec, from determined values of feed rates Qeb (here Qeb1, Qeb2 and Qeb3); FIG. 3 shows linearized relations between the Qeb feed rate and the Qreco and Pco reference values. The drinking water system 1 in question, shown in FIG. 1, consists of two main functional parts: a water or hydraulic part 2, involved in the treatment of water, arranged in particular around a filtration unit 3, membrane type (s), and - an electrical part 4, supplying energy to the water part 2 by the implementation in particular means 5 for the capture of renewable energy.

The hydric part 2 consists of a set of pipes 7: successive pipes 7a, 7b, and 7e in which the water travels from an upstream inlet 8a (where the raw water is sucked) to the unit filtration 3, and - downstream pipes 7d and 7e, which start from said filtration unit 3 and which are respectively connected to one of the two downstream outlets: one 8b for the treated water treated and the other 8th for discharge water. The filtration unit 3 here consists of a reverse osmosis filtration membrane. As an indication, this membrane could also for example consist of a nanofiltration membrane, electrodyalyse, piezo analysis or thermoosmosis. This filtration unit 3 may also consist of several membranes of the type mentioned above, suitably coupled in series and / or in parallel. Functional electromechanical means are provided to cause and regulate the flow of water from upstream (inlet 8a) downstream (outlets 8b and 8e).

First, on the side of the upstream inlet 8a, these electromechanical means are in the form of an upstream pumping unit 9. The latter ensures the suction and / or the discharge of the raw water at the level of the Upstream inlet 8a, then its flow and its pressure discharge, downstream, in the pipes 7 and through the filtration unit 3. This upstream pumping unit 9 here consists of a pair of pumps: an upstream lifting pump 10, for example of the surface type or submerged, providing the suction and / or discharge function, and a downstream booster pump 11, for example of the piston or multicellular type, involved in the function of backflow of water downstream, under pressure. Alternatively, these two pumps could be replaced by a single pump type multicellular surface or immersed. Similarly, electromechanical means in the form of a motorized expansion valve 12 are provided on the pipe 7e extending between the filtration unit 3 and the discharge water outlet 8c. This expansion valve 12 is for example of the seat type. This water part 2 also comprises an optional conduit 7f, arranged to form a recycling loop, the inlet of which is located on the rejection duct 7e (between the filtration unit 3 and the valve 12) and whose output is located on the feed pipe 7c of the filtration unit 3 (between said filtration unit 3 and the booster pump 11). A recirculation pump 13, for example of the centrifugal magnetic drive type, is mounted on this recycle line 7f to cause and control the flow of water from the inlet to the outlet.

As developed subsequently, this recycling loop 7f serves to optimize the energy efficiency of the installation 1; the recycling of the water at the outlet of the membrane (s) 3, reinjected directly at the inlet of the filtration unit 3 and downstream of the pumping unit 9, consumes less energy than a recycling reinjecting the water between the lift pumps 10 and overpressure pumps 11 or a total absence of recycling; it also makes it possible to optimize the purification of water and to limit the volumes of water discharged at exit 8e. Regarding the electrical part 4, the renewable energy capture means 5 consist of photovoltaic solar panels, or a wind turbine type device (s) or hydraulic type. The power captured by these sensing means 5 is converted into voltage electrical energy Ub, for example a value of 96 or 192 volts.

An electrical circuit 15, suitably structured, connects the sensing means 5 with the various electromechanical means of the water part 2, namely in particular the aforementioned pumps 10, 11 and 13 and also the motorization of the valve 12 (this electrical circuit 15 is shown schematically and only partially to simplify the figure).

An optional voltage limiter device 16 is provided between the sensing means 5 and the remainder of the electrical circuit 15 to act as a safety element to avoid power surge problems. This electric circuit 15 is also equipped with electrical energy storage means 17, whose function is, according to the invention, to serve as buffer damping energy fluctuations provided by the sensing means 5, and as a corollary to damping buffer of power supply voltage fluctuations. Thus, in the event of rapid variations (in growth or decay) of the energy input by the sensing means (and therefore of rapid variations in the supply voltage), the buffer means instantaneously absorb these variations in order to reduce them. amplitude (for example, a voltage variation Ub of 100% in a few seconds can be reduced to a variation of less than 5%). These accumulation means 17 are here of electrochemical battery type, conventional in themselves, connected to the general electrical line 15 under voltage Ub; this electrochemical battery could also be replaced by a capacitor bank, or by a kinetic accumulator of the flywheel type. For example, these accumulation means 17 may have an accumulation capacity of a few kilowatt hours, for an installation intended to produce about one cubic meter of drinking water per hour; this still corresponds to a few tens of ampere hours in the case of a 100 volt electrochemical battery. According to the invention, the potabilization system 1 further comprises control means 18 of the electronic and / or computer type which are connected to the various electromechanical means 10, 11, 12 and 13 of the water part 2, so as to enslave or to regulate their respective operations.

These control means 18 may for example consist of one or more PID controllers (Proportional - Integral - Derivative) or programmable controllers, equipped in particular with inputs of physical magnitude sensor type and control outputs connected to the electromechanical means 10, 11, 12 and 13 above.

As detailed below and shown in Figure 1, these control means 18 may consist of several control devices, each dedicated to act on one of the electromechanical means 10, 11, 12 or 13. Alternatively, the The installation can integrate a single control means 18 for the central control of these electromechanical means 10, 11, 12 and 13.

In this case, the upstream pump lifting 10 is connected to control means 18a provided with an input connected to a sensor 19a for measuring the voltage Ub within the electrical circuit 15. This sensor 19a is located on the general power supply line 15. It measures the voltage Ub which corresponds to the voltage directly generated by the energy sensing means 5; this voltage Ub increases, for the same level of capture, especially when the speed of this upstream pump 10 decreases, and vice versa.

It should be noted that, in practice, the speed of the other pumps 11 and 13 also affect this voltage Ub, but this generally in the same direction of variation as that caused by this lifting pump 10; these other pumps 11 and 13 are said follower, and the control means 18a of the lift pump thus takes them into account.

The control means 18a are configured and programmed to automatically control the speed of this lifting pump 10 according to a value which allows the generated voltage Ub above to reach and to maintain a predetermined value of electrical voltage called setpoint. Ubo voltage, corresponding here to the full load voltage buffer storage means 17 (also known as booster or floating voltage, which corresponds to the compensation voltage of the internal loss of these accumulation means ). This regulation of the speed of the lifting pump 10 as a function of the voltage Ub is aimed in particular at obtaining a flow of drinking water which is a direct function of the energy captured. The downstream booster pump 11 is in turn connected to control means 18b whose input is associated with a sensor 19b for measuring the supply water pressure Peb within the pipe 7b extending between the pump lift 10 and this booster pump 11.

These control means 18b are configured and programmed to automatically control the speed of this booster pump 11 so that the supply water pressure Peb reaches and is maintained according to a predetermined value of supply water pressure Pebo said setpoint supply pressure corresponding to the optimum operating value of this booster pump 11.

In general, in operation, an increase in the speed of this pump 11 ensures a reduction of the supply pressure Peb, and vice versa.

This regulation of the speed of the booster pump 11 as a function of the pressure set point Pebo, aims in particular to maintain optimal operation of this pump 11.

The control means 18c connected to the expansion valve 12 are in turn connected to two measurement sensors 19c: a first water supply flow sensor 19c, Qeb, situated at the level of the pipe 7e extending between the pumping unit 9 and the filtration unit 3, upstream of the recycling circuit 7f, and a second outlet water pressure sensor 19c2 Pc located on the pipe 7e extending between the unit of filtration filtration 3 and the expansion valve 12 (here downstream of the recirculation circuit 7f).

The control means 18c in question are here configured and programmed to automatically control the opening of the expansion valve 12 so that the discharge water pressure Pc, measured by the dedicated sensor 19c2, reaches and is maintained at the level of a given value of pressure known as the reference value of the supply pressure Pco.

In practice, as developed subsequently, this reference value Pco varies with the feed rate value Qeb (measured by the dedicated sensor 19c1). The control means 18d associated with the recycling pump 13 are in turn connected to a water recycling flow sensor 19d, mounted on the recycling loop 7f and upstream of said recirculation pump 13, and to the above-mentioned Qc feed rate sensor 19c1. These control means 18d are configured and programmed to automatically control the speed of the recycling pump 13 so that the recycling rate Qrec (measured by the dedicated sensor 19d) reaches and is maintained at a given value of recycling said Qreco Recycling Flow Reference Value. In operation, as detailed hereinafter, this reference value Qreco also varies according to the value of the feed rate Qeb (measured by the dedicated sensor 19c1). This servocontrol of the valve 12 and the recirculation pump 13 as a function of the two reference values Pco and Qreco mentioned above makes it possible in particular to obtain an optimum flow of drinking water at the outlet 8b, for an energy output. given, and produced by the energy sensing means 5.

In this case, the reference value of the Qreco recycling rate (function of the Qeb feed rate) is obtained from the equation defining the value of the specific energy of the installation (in kilowatt hours per m3). that is to say the specific energy consumed by the electromechanical means 10, 11, 12 and 13 of the water part 2, and per unit of volume of drinking water.

This equation defining the value of the specific energy Wt of the installation is in particular a function of the pressures, flow rates, salt levels in the different ducts, but also the characteristics of the filtration unit and the pumps. This equation defining Wt can be established by a person skilled in the art, this according to and taking into account the structure of the installation.

More precisely, the Qreco relation, as a function of the feed rate Qeb, can be established by solving the equation defining the value of the specific energy Wt; this equation is, for this purpose, derived and equal to zero.

This relation Qreco function of Qeb can also be established by iteration on the relation of the value of the specific energy Wt as a function of the recycle flow Qrec. More precisely, for a given power flow rate value Qeb (for example Qeb1, Qeb2 or Qeb3 in FIG. 2), the curve of the specific energy Wt as a function of the recycle flow rate Qrec (FIG. 2) makes it possible to identify the recycling flow rate value Qrec corresponding to the value of the specific energy minimum Wt; this determined minimum flow rate Qrec value corresponds to the Qreco recycling flow rate reference value for the Qeb feed rate studied. In all cases, it is advantageous to define, for a given feed rate Qeb, the value of the Qreco recycling flow rate for obtaining the specific energy Wt minimum. The relation between the reference value Pco and the feed rate Qeb is deduced from the aforementioned relationship between the reference value Qreco and the feed rate Qeb.

The relations between the reference values Qreco and Pco, as a function of the measured value of the feed rate Qeb, can be linearized as represented for example in FIG. 3, in the forms Qreco = a.Qeb + b and Pco = c.Qeb + d; the parameters a, b, c and d are measured on the graphs of the linearization lines.

A computer program is advantageously used to perform these iterations and calculations. For example, for an installation whose filtration unit comprises a single reverse osmosis membrane, the system of equations governing the hydraulic operation would advantageously be as follows:

(1) Qa = Qeb + Qrec (2) Qp = Qa - Qc (3) Ca. Qa = Ceb. Qeb + Cc. Qrec (4) Ca. Qa = Cc. Qc

(5) Qp = A. [Pc + AP / 2 - B. (Ca + Cc) / 2]

(6) Wt = Pc. Qeb / na. Qp + AP. Qrec / nrec. Qp

in which: Qa, Ca, and Pc respectively correspond to the water flow, to the salt concentration and to the pressure in the part of the pipe 7c situated downstream of the injection of the water recycling and to the entrance of the membrane 3; Qeb and Ceb are respectively the flow rate and the salt concentration in the portion of the pipe 7e situated between the outlet of the booster pump 11 and the injection of the water recycling; Ceb is a data of the user; - Qc and Cc respectively correspond to the water flow and the salt concentration in the portion of the pipe 7e located between the outlet (concentrate) of the membrane 3 and the bypass to the water recycling loop 7f; Qc is a given, either from the manufacturer of the membrane, or from a choice justified by the more or less rapid clogging of the membrane (choice of Fouling Index or clogging power); Qrec is the flow of recycle water in line 7f; Qp is the flow of drinking water at the outlet 8b of drinking water of the membrane 3;

LP is the pressure loss in pressure in the membrane 3 between the water inlet at 7c and the rejection outlet at 7e; AP is a data from the manufacturer of the membrane; - A is a data from the manufacturer of the membrane, it depends on its permeability, its surface and the temperature of the introduced water; B is a datum of the classical physico-chemical theory of the osmosis phenomenon; it is established by the nature of the salts present in the water to be treated, their molar mass and their number of dissociated ions in the water as well as the temperature of this treated water; the term B. (Ca + Cc) / 2 represents the average osmotic pressure on the membrane; the term Pc + API2 represents the transmembrane pressure; and qa and nrec are respectively the pump yields of the pumping unit 9 and the recycle pump 13. In this case, in the case of this installation, the filtration unit comprises a reverse osmosis membrane. and as shown in FIG. 3, the reference values of the discharge pressure Pco and of the recycling flow rate Qreco change inversely with respect to one another as a function of the measured value of the feed rate Qeb.

More specifically, the Qreco recycling flow rate reference value decreases when the measured value of the feed rate Qeb increases, and vice versa. On the other hand, the reference value of pressure Pco increases when the measured value of feed rate Qeb increases, and vice versa.

For example, in operation, when the power produced by the sensing means 5 decreases (for example due to a decrease in solar radiation or wind speed), the voltage Ub decreases at the electrical circuit 15. Buffer accumulator means 17 may only intervene to dampen this decrease.

The control means 18a associated with the lifting pump 10 detect this voltage variation via its sensor 19a. These control means 18a then implement the control loop consisting in reducing the speed of the associated lift pump 10 until the measured voltage Ub returns to the level of the voltage setpoint Ubo. By way of example, this Ubo voltage set point is of the order of 100 V for a 96 V electrochemical battery. This reduction in the speed of the lifting pump 10 results in a reduction in the flow rate and the pressure downstream, especially within driving 7b.

The control means 18b associated with the booster pump 11 then come into action by the implementation of the control loop aimed at restoring a desired and predefined Pebo supply pressure. For this, the control means 18b cause a decrease in the speed of the booster pump 11, until the pressure Peb measured by the sensor 19b returns to the level of the pressure set Pebo (for example of the order of 1 bar). This reduction in the speed of the booster pump 11 then leads to a decrease in the flow rate and the downstream pressure, and in particular the feed rate Qeb and the discharge pressure Pc (but not according to the reference value Pco desired for the optimal operation of the system), with the resulting decrease in the efficiency of the filtration unit 3. To restore the optimal operation of this filtration unit 3, the control means 18p, associated with the valve 12, intervene by the implementation of the control loop described above; these control means 18c calculate, in real time, the reference value Pco (according to the relationship cited above).

The flow Qeb varies, the reference value Pco also varies; the control means 18c then intervene by suitably modifying the opening of the expansion valve 12 until the pressure Pc returns to the reference value Pco. Similarly, the evolution of the feed rate Qeb causes the servo loop to be actuated at the level of the recycling pump 13. These control means 18d calculate, in real time, the reference value Qreco on the basis of the aforementioned relationship. In practice, because of the reduction of the feed rate Qeb, the Qreco reference value varies, which corresponds to a variation of the speed of this recycling pump 13, in order to maintain an optimum flow of water at the level of the unit. filtration 3.

Of course, in the case where the power generated by the sensing means 5 was to increase, the different pumps and the valve will be driven in the opposite direction to that described above to maintain optimal operation of the installation. Similarly, in the case where the sensing means generate a voltage Ub below a minimum threshold determined, the installation is automatically shut down (in particular by stopping the upstream pumping unit 9). In general and as an alternative, the pressure sensor 19c2 associated with the control means 18p (driving the valve 12) can be placed on the pipe 7c extending between the booster pump 11 and the filtration unit 3, this if necessary upstream of the recirculation loop 7f.

The control means 18c are then programmed and configured with a reference value of supply pressure Pao (supply pressure of the filtration unit 3), always a function of Qeb and calculated on the basis of equations similar to those used to determine the Pco reference value. It is noted that the pressures Pc and Pa are normally of similar values.

According to yet another alternative form of embodiment, the control means 18a and 18b, associated respectively with the lifting pump 10 and with the booster pump 11, can be configured and programmed so that: - on the one hand, the the booster pump 11 ensures the achievement and maintenance of the voltage setpoint Ubo generated, and - the speed of the upstream pump ensures the achievement and maintenance of the Pebo supply water pressure setpoint then corresponding to the optimum operating value of said lift pump. In general, the flow of drinking water, discharged at the outlet

8b, varies according to the power generated by the sensing means 5 (depending on the intensity of the solar radiation or the wind speed, as the case may be). Ways

energy accumulation devices 17 serve only to dampen voltage fluctuations; the capacity of electrical energy storage within the potabilization system can thus be significantly reduced compared to prior systems operating at constant electrical voltage. For some applications, these accumulation means can even be deleted; the Ubo voltage setpoint then corresponds to the nominal electrical operating voltage of the water purification system; moreover, in practice, the electrical system 4 is advantageously equipped with a contactor relay with maximum / minimum voltage, to avoid the problems of extreme variations in electrical voltage. For example for solar panels, only available solar energy is used; the accumulation means do not discharge. This gives a concept of production of water powered by the sun (also called Max Solar Power Tracking - MSPT) or wind (also called Max Wind Power Tracking - MWPT). Similarly, the valve 12 and the recycling pump 13 are controlled to obtain a minimum energy consumption, regardless of the level of water production (also called ROME concept - Optimized Energy Minima). The combination of the two concepts can be called ROSME - Optimized Diets Followers to Minima d'Energie.

Claims (10)

- 1.- Autonomous water purification system, in particular for brackish and / or polluted water, which system comprises pipes (7) for the circulation of water from a suction inlet (8a) raw water up to two downstream outlets, one (8b) for treated water and the other (8c) for discharge water, which lines (7) are associated with: - an upstream pumping unit ( 9), ensuring the suction and discharge of raw water at said upstream inlet (8a) and its flow under pressure in said pipes (7) downstream, - a downstream unit (3) of filtration water on membrane (s), connected to said treated water outlet (8b) and, via an expansion valve (12), to said discharge water outlet (8c), which system further comprises means (5) for capturing renewable energy, for example of solar or wind energy type, to generate a fluctuating voltage Ub during the day and supply introducing into electrical energy at least said pumping unit (9), the value of said generated electrical voltage Ub increasing, for the same level of capture, when the speed of said pumping unit (9) decreases and vice versa, characterized in that said system (1) comprises control means (18a) of the electronic and / or computer type which are connected to a sensor (192) for measuring said generated electrical voltage Ub and to said upstream pumping unit (9), which means control device (18a) automatically control the speed of said pump unit (9) according to a value which allows said generated voltage Ub to reach and to maintain a given value of electrical voltage Ubo voltage setpoint voltage . 2.- water purification system according to claim 1, characterized in that it comprises a damping device voltage fluctuations (17), for example of energy storage type electrochemical or electrostatic type, located between the energy collecting means (5) and the pumping unit (9), permanently maintained at full load or almost at full load, and in that the control means (18a) automatically drive the speed of the pumping unit (9) according to a value which allows the generated voltage Ub to reach and maintain the voltage setpoint value Ubo corresponding to the full load voltage of said damping device. 3.- water potabilisation system according to claim 1, characterized in that the control means (18a) automatically control the speed of the pumping unit (9) to a value that allows the voltage generated Ub to reach and to maintain the level of the Ubo voltage setpoint corresponding to the nominal electrical operating voltage of the water purification system. 4.- water purification system according to any one of claims 1 to 3, characterized in that the pumping unit (9) consists of a set of two pumps: - an upstream pump lift (10 ) and - a downstream booster pump (II), in that the control means (18a, 18b) are connected to said two pumps (10, 11), and means (19b) for measuring the water pressure d supply Peb within the pipe (7b) extending between said two pumps (10, 11), which control means (18a, 18b) automatically control: - on the one hand, the regime of one of said two pumps (10) so that the generated electrical voltage Ub reaches and is maintained at the voltage set point Ubo, - and secondly, the speed of the other of said two pumps (11) so that the pressure supply water Peb reaches and is maintained at a given level of water supply pressure Pebo said supply pressure setpoint correspon to the optimum operating value of said second pump (11). 5.- water potabilization system according to claim 4, characterized in that the control means (18a, 18b) automatically control: -the one hand, the speed of the upstream pump lift (10) to ensure the l reaching and maintaining the voltage setpoint generated Ubo, - and secondly, the speed of the downstream pump booster (11) to ensure the achievement and maintenance of the Pebo supply water pressure setpoint corresponding to the optimum operating value of said downstream pump (11). 6. A water treatment system according to any one of claims 1 to 5, characterized in that the control means (18p) are connected - to the downstream expansion valve (12) - to a sensor (19c1 ) of the feed water flow Qeb located on a first pipe (7c) extending between the pumping unit (9) and the filtration unit (3), optionally upstream of an outlet of a recycling loop 7f, and - a water pressure sensor (19c2) situated either on said first pipe (7c) for measuring a supply pressure Pa, or on a second pipe (7e) extending between said filtration unit (3) and said expansion valve (12) for measuring a discharge pressure Pc, which control means (18p) automatically drive the opening of said expansion valve (12) so that the pressure of discharge water Pc or Paatteigne supply and is maintained at a given value of pressure called pressure reference value Pco or Pao, which pressure reference value Pco or Pao varies according to the measured value of feed rate Qeb, for obtaining and maintaining a specific energy Wt minimum. 7.- water potabilisation system according to any one of claims 1 to 6, characterized in that it comprises conduits (7f) arranged to form a recycling loop, whose input is between the unit filter (3) and the expansion valve (12) and whose outlet is located between said filtration unit (3) and the pumping unit (9), said recycling loop comprising a recirculation pump (13) favoring the flow of water from the entrance to the exit. 8.- water purification system according to claim 7, characterized in that the control means (18d) are connected - to the recirculation pump (13) - to a recycling flow sensor (19d) of water Qrec, mounted on the recycle loop (7f), and - the feed water flow sensor (19c1) Qeb, located on the pipe (7c) extending between the pumping unit (9) and the filtration unit (3), upstream of the outlet of said recycling loop (7f), which control means (18d) automatically control the speed of said recycling pump (13) so that the recycle flow Qrec reaches and is maintained at a given recycling flow rate value called Qreco recycling flow rate reference value, which Qreco flow rate reference value varies according to the measured value of the feed flow rate Qeb, for obtaining and maintaining a specific energy Wt minimum. 9. A water purification system according to any one of claims 1 to 8, characterized in that the filtration unit (3) consists of at least one reverse osmosis filtration membrane or nanofiltration. 10. A method for managing the operation of an autonomous water purification system according to any one of claims 1 to 9, which system comprises pipes (7) for the circulation of water from an upstream inlet (8a). ) sucking raw water up to two downstream outlets, one (8b) for treated water and the other (8c) for reject water, which lines (7) are associated with: - a lifting pump (10), ensuring the suction of water at the upstream inlet (8a), - a booster pump (11), ensuring the flow of water downstream and under pressure in the pipes (7), - a water filtration unit on membrane (s) (3), connected to said downstream outlet (8b) of treated water and, via an expansion valve (12) at said outlet (8c) of reject water, and which system further comprises - optionally pipes (7f) arranged to form a recycling loop, whose inlet is located downstream of the filtration unit (3) and whose outlet is located upstream of said filtration unit (3), said recycling loop comprising a recirculation pump (13) promoting the return flow of water, - means (5) for collecting water. renewable energy generating a fluctuating voltage Ub during the day, which supply electrical energy to the lifting pump (10), the booster pump (11) and, where appropriate, the recirculation pump (13), which process consists in: - controlling the speed of said upstream lifting pump (10) according to a value which enables said generated voltage Ub to reach and to maintain a given value of electrical voltage called Ubo voltage set point, said generated electrical voltage Ub increasing, for the same level of capture, especially when the speed of said pump unit (10) decreases, and vice versa, - to control the speed of said booster pump (11) so that the pressure of supply water Peb, within the pipe (7b) extending between said lifting pump (10) and said booster pump (11), reaches and is maintained at a given level of supply pressure Pebo said setpoint supply pressure corresponding to the optimum operating value of said booster pump (11), - controlling the opening of said expansion valve (12) so that the measured water pressure is on a first pipe (7c ) extending between the pumping unit (9) and the filtration unit (3), said supply pressure Pa, or on a second pipe (7e) extending between said filtration unit (3) and said expansion valve (12), referred to as the discharge water pressure Pc, reaches and remains at a given pressure value, referred to as the pressure reference value Pao or Pco, said pressure reference value Pao or Pco varying according to of the feed rate value Qeb, measured in the pipe is extending between the pumping unit (9) and the filtration unit (3), for obtaining and maintaining a specific minimum energy Wt, and, if necessary, controlling the speed of said recycling pump (13) for the recycle flow rate Qrec to reach and maintain at a given recycle flow rate value Qreco recycle flow rate reference value, said Qreco recycling reference value varying as a function of the measured value of said recycle flow rate. Qeb power supply, for obtaining and maintaining a specific energy Wt minimum.