WO2018002456A1

WO2018002456A1 - Method and device for producing fresh water by solar distillation and renewable energy

Info

Publication number: WO2018002456A1
Application number: PCT/FR2017/000135
Authority: WO
Inventors: Thierry Gilles CARLIN
Original assignee: Marine Tech
Priority date: 2016-06-27
Filing date: 2017-06-29
Publication date: 2018-01-04
Also published as: FR3053036B1; FR3053036A1

Abstract

The invention relates to a method for distilling water from a body of water (11), comprising the following operations: - arranging an evaporation pan (12) near and above the body of water (11), in a first enclosure (16) that is airtight and comprises a solar radiation transparent wall (18) which extends above the pan and is inclined towards the outside of the pan; - connecting the evaporation pan (12) to the body of water (11) by means of a supply circuit comprising a pipe (22) and a water inlet (21); - connecting the first enclosure (16), by means of a second pipe (29), to a second airtight enclosure (31) which runs below the evaporation pan and the first enclosure, is used for collecting the distilled water (35), and is in thermal contact with the water or the ground; - keeping the first enclosure (16) in a constant vacuum, by the action of a vacuum pump (33) driven by a renewable energy source, so as to cause the conveying of water to be distilled to the evaporation pan (12) and to keep a constant water level (25) in the pan (12).

Description

Process and device for producing fresh water by solar distillation and renewable energies

TECHNICAL AREA

The present invention relates to a water treatment method and to a water treatment device by solar distillation.

The technical field of the invention is that of the manufacture of water desalination apparatus by solar distillation.

STATE OF THE ART

The use of solar energy to distil seawater seems known for several centuries.

US2424142 discloses a solar still for a lifeboat.

This distiller comprises an evaporator comprising two pieces assembled in a sealed manner which define an evaporation chamber whose annular portion contains the water vapor resulting from the evaporation of seawater introduced into the evaporation chamber.

The distiller comprises a condenser to be immersed which is connected to the evaporation chamber by a flexible conduit, and which opens into a collector receiving the water vapor condensed by the condenser, that is to say the seawater distilled.

A manually operated pump connected to the manifold provides a high vacuum - i.e. a high vacuum - in the collector, in the condenser, and in the evaporation chamber.

This depression, close to 29 inches of mercury, is measured by a gauge equipping the evaporator, and is maintained at a desired value by actuating the pump.

Means may be provided to draw a desired amount of seawater into the evaporation chamber.

This type of distiller is inefficient, expensive to produce, and difficult to use and maintain. In particular, the maintenance of a vacuum requires the permanent presence of an operator to operate the pump and control the (de) pressure in the distiller. The operation under a high vacuum generates mechanical stresses that limit the dimensions of the distiller. In addition, the suction of water in the evaporation chamber is likely to cause sudden pressure variations in the distiller, and to deteriorate the components thereof. Moreover, the contribution of solar energy to the water contained in the evaporator is effected by transfer through the opaque upper wall of the evaporator, which causes significant energy losses, especially when the face outer wall is swept by the wind or covered with water.

It has also been proposed to produce a multi-effect distiller using renewable energy, in particular solar, wind or geothermal energy, as described in patent FR2524335.

This distiller has several superimposed compartments containing seawater used to store renewable energy available, and allowing the recovery of the condensation heat.

This distiller is complex to make, use, and maintain.

STATEMENT OF THE INVENTION

An object of the invention is to provide an autonomous solar distiller, that is to say which operates only by supply of renewable energy (s), and which is simple to manufacture and implement.

An object of the invention is to provide a method and a device for water treatment by solar distillation, which is improved and / or which remedies, in part at least, the shortcomings or disadvantages of known methods and devices for treating water. water by solar distillation.

Unless explicitly stated or implied otherwise, in the present application, the term "pressure" refers to an absolute pressure, and the term "vacuum" refers to the absolute value of a difference between a pressure (absolute) and the atmospheric pressure.

Unless explicitly stated or implied otherwise, in this application, the terms "below" and "above" are used to mean "at a level (or altitude) less than" and "at a level (or altitude) greater than that ", without this does not imply that two elements concerned by these expressions are vertically one of the other.

According to one aspect of the invention, for distilling water from a body of water:

an evaporation pan is disposed above the body of water, in a first chamber (also known as an evaporation chamber) which is (substantially) airtight and comprises at least one wall that is transparent to solar radiation which extends above the evaporation pan and is inclined towards the outside of the evaporation pan;

- The evaporation tank is connected by a first conduit to a distilling water intake which extends below the evaporation pan;

the first enclosure is connected by a second duct to a second (substantially) airtight enclosure, which extends below the evaporation pan and below the first enclosure, which is in thermal contact with the first enclosure; the body of water or with the soil (used as a cold source), and serves to condense water vapor produced in the first enclosure, and to collect and store (temporarily) the distilled water (the condensates obtained);

the first enclosure is maintained in a substantially constant vacuum by the action of at least one vacuum pump driven (or fed) by at least one renewable energy source, so as to cause the transport of water to be distilled, from the water intake to the evaporation pan, and to maintain a substantially constant water level in the evaporation pan.

In other words and according to one aspect of the invention, there is provided a water treatment device taken from a body of water, which comprises;

- an evaporation pan located above the body of water

- an evaporation chamber (substantially) airtight, containing the evaporation pan, and comprising (at least) a transparent wall to solar radiation which extends above of the evaporation pan and is inclined towards the outside of the evaporation pan;

- A water transport conduit to be treated, which connects the evaporation pan to a water intake to be treated which extends below the evaporation pan;

means for condensing the water vapor produced in the evaporation chamber and means for collecting treated water (condensed / distilled), in particular a chamber for condensing and collecting treated water (distilled) , which is (are) airtight, which is arranged (are arranged), at least in part, below the evaporation chamber, and which is (are) in thermal contact with the body of water or with the ground;

a condensate and gas transport duct connecting the evaporation chamber to the condensation and collection means, in particular to the condensation and collection chamber;

a vacuum pump driven by (at least) a renewable energy source and arranged to cause a depression in the evaporation chamber; and

means for maintaining the pressure prevailing in the evaporation chamber at a (substantially) constant value which is less than that of the atmospheric pressure - i.e. to maintain a constant depression in the evaporation chamber - so as to cause the transport of water to be treated, from the water intake to the evaporation pan, and to maintain a water level (substantially ) constant in the evaporation pan.

Preferably, to maintain a constant depression in the first chamber, a constant negative pressure is maintained in the second chamber and / or in the condensation and collection means.

For this purpose, the means for maintaining the pressure prevailing in the evaporation chamber at a (substantially) constant value can then essentially be constituted by means for maintaining the pressure prevailing in the condensing chamber and collection, at a value (substantially) constant.

The invention makes it possible to feed the evaporation tank with water taken from the water intake, if necessary substantially continuously, as the water contained in the tank is evaporated under the effect of the solar radiation, if necessary without using a water pump.

The invention also makes it possible to avoid an overflow of the evaporation pan in the first enclosure.

The vapor of the water contained in the evaporation tank, which is formed in the first chamber under the effect of solar radiation, can condense on walls of the first chamber, also on walls of the second chamber, and where appropriate on walls of the duct connecting these two enclosures, these walls forming the means of condensation - or part of these means -.

At least a portion of a concentrate (especially brine or brine) produced in the evaporation pan (due to evaporation of water) can be removed from the evaporation pan. if necessary substantially continuously, by gravitational transport in the first conduit, against the current of the water transport to be treated, the rate of upward flow in the first conduit is very low.

For this purpose, the first conduit may have a large cross section.

Alternatively or in addition, the concentrate accumulating in the evaporation tank can be evacuated "manually" from the tank when the enclosures are vented, in particular during the maintenance operations of the water treatment device, or when recovering the distilled water accumulated in the condensation and collection chamber.

According to one embodiment, the water intake can be immersed in the body of water.

When the evaporation pan is disposed at a height - measured by reference to the water level of the body of water - which is greater than about ten meters, the device further comprises a buffer tank receiving the water intake, and optionally a pump (water) for transporting water taken from the body of water, into the buffer tank, this pump being driven (or powered) by a renewable energy source.

This can also be the case when the evaporation pan is placed at a lower height.

The buffer tank is preferably open in its upper part, or otherwise placed in communication with the ambient atmosphere, so that the vacuum to be maintained in the evaporation chamber (and if necessary in the second chamber) corresponds substantially to the pressure exerted by a water column (to be treated) whose height is equal to the difference in dimension between the level of the free surface of the water in the evaporation pan and the level of the free surface of the water in the buffer tank, and corresponds substantially to the pressure exerted by a water column whose height is equal to the difference in size between the level of the free surface of the water in the evaporation pan and the intake of water. 'water.

When the device is devoid of buffer tank, the vacuum to be maintained in the evaporation chamber (and if necessary in the second chamber) substantially corresponds to the pressure exerted by a water column (to be treated) whose height is substantially equal to the difference in dimension between the level of the free surface of the water in the evaporation pan and the level of the free surface of the body of water.

The water level in the evaporation pan is thus kept constant by the application of a constant depression in the evaporation chamber.

The device may comprise means for keeping the level of the water collected in the buffer tank substantially constant.

The buffer tank is generally installed in a fixed manner, on land or in the body of water, for example above the body of water. When the level of water to be maintained in the buffer tank is lower than that of the water body, for example when the device is installed in a polder or on a platform floating on the body of water, the transfer of water the water taken from the body of water, up to the buffer tank, can be carried out by gravity. If this is not the case, the device comprises a lifting pump (water pump) ensuring the transport of the water taken from the body of water, into the buffer tank, this pump being driven (or fed) ) by a renewable energy source.

The level of the water in the buffer tank can be kept constant by ensuring a feed rate of the reservoir which is greater than the flow rate of water taken from this reservoir to feed the evaporation pan, the surplus water then being able to overflow by a planned overflow in the buffer tank.

This overflow can allow to evacuate at least a portion of the concentrate collected in the buffer tank, by hydraulic drive of the concentrate by the water overflowing the reservoir.

The evaporator pan is also usually installed in a fixed manner, on or off the body of water, at a height measured above the free surface of the water in the buffer tank - if applicable above of the stretch of water - which is less than ten meters or so.

Preferably, this height is in a range of about two to three meters to about eight or nine meters, especially in a range of about three or four meters to about six or seven meters.

For example, when this height is five meters, the absolute pressure to be maintained in the evaporation chamber (where applicable in the enclosures) is approximately 0.5 bar (ie about 50000 Pascal), this value being able to vary in depending on the density of the water drawn. The vacuum pump, as the case may be the water pump, can be driven by the effect of movements of water from the body of water, or by solar or wind energy.

In particular, a pump may be a piston pump (s) driven in motion by waves or waves, for example a liquid piston pump as described in the patent FR385045.

A pump may be a piston pump (s) driven in motion by a wind turbine.

A pump may be a pump driven in rotation by an electric motor powered by a photovoltaic solar panel.

The walls of the evaporation chamber may define with the tank at least one passage for condensates dripping on an inner face of an inclined wall of the evaporation chamber.

The means for maintaining the vacuum at a constant value in the evaporation chamber - or in the enclosures - may comprise - and where appropriate consist essentially of - a pressure reducer or pressure regulator, which serves to attenuate ( filter) variations in vacuum produced by the vacuum pump.

This regulator or regulator may be arranged between the vacuum pump and the condensation and collection chamber.

The condensation and collection means are preferably sheltered from solar radiation and other sources of heat.

In particular, the condensation and collection chamber can be buried or immersed so that the chamber is kept at a temperature lower than that of the evaporation zone, and thus promote the condensation of water vapor in the enclosure condensation and collection.

Condensation is carried out by cooling the condensing means - in particular by cooling the walls of the condensation chamber - by the soil or water of the body of water in which - the - the means are placed. condensation, the soil or water then serving as a cold source. For this purpose, the walls of the condensation means - in particular the walls of the condensation chamber - are made of a material that promotes heat transfer through these walls, for example in a metallic material.

The device may comprise a reflector arranged to reflect solar radiation to the tank, in particular to a lower face or wall of the tank, so as to increase the flow of solar radiation reaching the tank.

In particular, the device may comprise a reflector extending under the tray, in particular under the evaporation chamber, for example a horizontal plane reflector.

The tray may include a main / central wall, which may be substantially flat and horizontal, forming the bottom of the tray, and a peripheral wall extending upwardly from the bottom, and may have a low height.

The bottom of the tray may be pierced with an opening through which the water transport conduit to be treated opens into the tray. The bottom of the tray may be at least partially (slightly) inclined towards this opening.

The tray may consist essentially of a heat-absorbing solar radiation-absorbing material, in particular a metal coated with a radiation absorbing material, for example a metal alloy such as aluminum coated with an absorbent coating such as than a black painting.

The inner face of the tank walls can be subject to a surface treatment, in particular a mechanical or chemical treatment, limiting the adhesion of particles on this face.

In particular, the upper face of the bottom of the tray may be coated with an anti-adhesive material limiting the adhesion of solid particles of the concentrate, in particular the salt adhesion, on this face.

Other aspects, features, and advantages of the invention appear in the following description which refers to the figures and illustrates, without any limiting character, preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 schematically illustrates a water treatment device taken from a body of water, according to one embodiment.

Figure 2 schematically illustrates a water treatment device taken from a body of water, according to another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise explicitly or implicitly stated, elements or members - structurally or functionally - identical or similar are designated by identical reference numerals in the different figures.

With reference to FIG. 1 in particular, the water treatment device 10 makes it possible to distil water taken from a body of water 11, for example seawater taken off at the seaside.

The device 10 comprises a buffer tank 54 for temporarily storing water to be treated which has been taken from the body of water 11.

The reservoir 54 is fixed on a support 52 and is open in its upper part 56 forming an overflow, so that the excess water introduced into this reservoir can overflow (according to the arrows 53) and the water level 26 in this tank can be kept constant.

When, as illustrated in FIG. 1, the level 26 of water in the reservoir 54 is greater than the (minimal) level of the free surface of the body of water, the device 10 comprises a pump 55 with water disposed on a conduit 57 opening into the reservoir 54.

The device 10 comprises an evaporation tank 12 which is disposed near and above the level 26 of water maintained in the buffer tank, and a conduit 22 connecting the tank 54 to the tank 12 and whose lower mouth 21 forming a intake, extends below the level 26 of the water in the reservoir 54. The bottom 13 of the tray 12 has a frustoconical shape, slightly flared upwards. In another embodiment (not shown), the bottom of the tray may be substantially planar.

The bottom 13 extends along a horizontal plane, and is surrounded by a peripheral wall 14, substantially vertical, which extends above - and from - the bottom 13, on a low height.

The tank 12 is disposed in an evaporation chamber 16 which is airtight, so that the space 17 delimited by the walls of the enclosure 16 can be maintained at a pressure lower than the ambient atmospheric pressure. which in particular makes it possible to lower the evaporation temperature of the water contained in the tank.

The upper wall 18 of the enclosure 16, which extends above the tank, is transparent to the solar radiation, in particular in the wavelength range corresponding to the infra-red radiation, so that the solar radiation 19 can pass through. this wall and can heat the tank and the water contained in the tank (see Figure 2).

The transparency of the wall 18, the depression in the enclosure 16, the shallow depth of water 15 contained in the tank, and the choice of a material that absorbs solar radiation, for example an aluminum alloy provided with a black coating, to build the tray 12, help to effectively provide heating and evaporation (illustrated schematically by the arrows 20 Figure 2) of the water 15 in the tray 12, inside the enclosure 16.

The water to be distilled is taken from the body of water 11 through a mouth 58 of the water transport conduit 57 which also opens into the buffer tank 54 and is equipped with the water pump 55 so that is collected in the reservoir 54.

The conduits 22, 57, the pump 55, and the tank 54 thus form a water supply circuit of the evaporation tank - and the device 10-.

The pump 55 is driven by the movements of the water body, for example as described in detail below with respect to the vacuum pump. The transport of the water taken from the buffer tank 54, through the lower mouth 21 of the conduit 22, results from the depression maintained in the enclosure 16, the speed of displacement of the water in this conduit 22, according to a flow ascending illustrated by the arrow 59, being very weak.

The pressure P16 that it is necessary to maintain in the chamber 16 to ensure this transport substantially corresponds to the difference between the atmospheric pressure Patm and the pressure exerted by the water column present in the duct 22.

To ensure a level of water 15 in the substantially constant and adequate tray 12, it suffices to keep the level 26 of the water contained in the buffer tank substantially constant and adequate - which is obtained by the overflow 56 -, and maintain a suitable (and constant) depression in the enclosure 16.

The wall 18 of the enclosure 16 forms a dome covering the tank 12, and the enclosure 16 further comprises an inclined lower wall 27 which extends under the tank 12, in the extension of the wall 18.

The lower wall 27, which may be in the form of an inverted cup or dome, is pierced at its lowest point of an orifice 28 through which the enclosure 16 communicates with a conduit 29 for conveying - and discharging - condensates 30 and gases and vapors present in the chamber 16, the duct 29 being also airtight.

The walls 18, 27 of the enclosure 16 may confer on this enclosure a spherical shape substantially centered on the center of the tank 12 and / or on the orifice 23.

Since the temperature of the walls 18, 27 of the enclosure 16 is generally lower than that of the water vapors resulting from the evaporation of the water 15 contained in the tank 12, these vapors condense on these walls forming drops. 30 that can run off these walls because of the inclination of these walls.

The walls 18, 27 of the enclosure 16 may delimit with the peripheral wall 14 of the tray 12, an annular space surrounding the tray and that The condensates may flow through the inner face of the wall 18, so that the condensates can then flow on the inner face of the wall 27, to the orifice 28 through which the condensates enter the conduit 29.

The device 10 further comprises an enclosure 31 for condensing and collecting treated water (distilled), which is airtight and disposed beneath the evaporation chamber 16.

This chamber 31 is connected to the evaporation chamber 16 via the duct 29 which opens into the chamber 31 through an opening 32.

The chamber 31 may be immersed in the body of water 11, or it may be buried beneath the enclosure 16, preferably close to the enclosure 16, so as to be protected from heat source (s) (solar in particular), and to be maintained at a temperature lower than that of the vapors 20, preferably at a temperature lower than that of the walls 18, 27 and that of the duct 29, so as to promote condensation of water vapors carried by the conduit 29, in the enclosure 31.

The chamber 31 thus serves to collect the condensates 30 formed in the chamber 16 and transported by the conduit 29, as well as those formed in the conduit 29 and in the enclosure 31, ie. the distilled water produced by the device 10.

The device 10 further comprises a vacuum pump 33 connected to the enclosure 31 by a gas transport duct 34 which is airtight and opens into the upper part of the enclosure 31.

The pump 33 comprises an inlet valve 36 and an outlet valve 37 which are respectively arranged to allow the inlet 38 of gas coming from the duct 34, into the body of the pump 33, and to allow the discharge 39 of these gases. in the air.

For this purpose, the pump 33 comprises a piston 40 slidably mounted in the pump body 42, along an axis 41 which may be substantially vertical. The piston 40 is connected to a motor member 43, for example a float, by a rod 44. The member 43 is driven in movement, in particular in reciprocating translation movement, by the waves or the wave 110 formed (s) on the expanse of water 11, and thus causes the piston 40 in alternative translational movement according to the invention. 41 axis, causing the suction of gas transported through the conduit 34 in the chamber 42 of the pump 33, and their discharge into the atmosphere.

Several other vacuum pumps 33 can be connected to the duct 34 to put the ducts 29, 34 and the enclosures 16, 31 in a vacuum, in particular at least one pump driven by a wind turbine (not shown), and / or at least one pump driven by an electric motor powered by a photovoltaic solar panel (not shown).

To regulate the pressure P16 prevailing in the evaporation chamber 16 to a value adapted to ensure a level of water 15 in the substantially constant tank 12, the device 10 comprises a pressure regulator 50, which can essentially consist of an expansion valve disposed on the duct 34 connecting the pump 33 to the chamber 31 of condensation and collection.

The regulator / regulator 50 comprises an upstream pressure tap 51 which is sensitive to the pressure prevailing in the duct 34, and consequently to that prevailing in the enclosure 31 and in the enclosure 16.

The expander further comprises means for adjusting a setpoint of the depression it must provide in the duct 34, as a function of the height H separating the tank 12 from the water level in the buffer tank. In particular, the regulator may comprise an adjustment mechanism, for example a weighed diaphragm and spring mechanism, which is arranged to adjust this vacuum setpoint.

Thus, the pump 33 and the expander / regulator 50 can cause a constant depression whose value is equal to Patm - p * g * H, where H is the height between the level of the buffer tank and the tray level. In steady state operation of the device, this depression prevails in the duct 34, in the enclosure 31 of condensation and collection, in the conduit 29, and in the chamber 16 of evaporation.

The device 10 comprises a reflector 60 arranged to reflect an incident solar radiation 61 incident on the upper face of the reflector, forming a reflected solar radiation 62 propagating towards the face or lower wall of the tank 12, so as to increase the flow of solar radiation reaching the tank (see Figure 2).

For this purpose, the lower wall 27 of the enclosure 16 is partly at least transparent to solar radiation.

The reflector 60 may be a horizontal plane reflector which extends under the tank and under the evaporation chamber 16.

The enclosure 16 may be formed of two substantially identical transparent domes 18, 27 of hemispherical shape, arranged facing each other, each dome having a flange. For the sealed assembly of the domes, an annular-shaped seal may be disposed between the flanges. Feet may be provided to support the enclosure 16 and the reflector 60, to adjust the height of the tray 12 above the buffer tank, and to ensure the horizontality of the bottom of the tray.

Alternatively, the enclosure 16 may have other shapes, in particular a cylindrical shape whose section may be circular, and whose axis may be substantially horizontal or vertical

Part of the water inlet pipe 22 extends inside the vapor and condensate outlet pipe 29, which makes it possible to heat the water to be distilled by these condensates and vapors, and to improve the effectiveness of the device.

After having installed and interconnected the components of the device 10, the water 11 is sucked by the pump 55, through the mouth 58, circulates in the conduit 57, and accumulates in the reservoir 54.

At the same time, the pump 33 sucks the gases (air) present in the enclosures 16, 31 and the ducts 22, 29, and 34.

When the level 26 of water in the tank 54 reaches the mouth 21 of the duct 22, the ambient air is no longer allowed in this chamber. duct and the suction produced by the pump 33 causes a lowering of the pressure in the enclosures 16, 31 and the ducts 22, 29, 34.

The depression thus created in the chamber 16 causes the rise 59 of the water taken from the reservoir 54, in the conduit 22.

When the water level 26 in the reservoir 54 reaches the overflow 56, this level then remains constant, as long as the flow rate of water taken from the body of water by the pump 55 remains higher than the flow rate of water withdrawn in the tank 54 through the mouth 21 under the effect of the depression in the chamber 16.

Continued operation of the pump 33 causes an increase in the vacuum in the enclosure 16 until the expander 50 limits this vacuum to the preset setpoint which corresponds to the above-mentioned height H of the water column in the chamber. conduit 22, by closing the conduit 34 (or by limiting the flow of gas sucked into this conduit by the pump 33).

The level of the water in the tank 12 has then reached the desired value which corresponds to the maintenance of a thin layer of water in the tank.

Therefore, in theory and "ideally", ie provided that the water level 26 does not lower below the level of the mouth 21 of the duct 22 (which would cause a "defusing" of this duct), that the components of the device maintained in depression are perfectly sealed to air, and that the capacity of the condensation means remains greater than that of the evaporation means of the water contained in the tank, the expander 50 remains closed, the condensed water accumulating in the chamber 31.

In practice, an introduction of air into the circuit 16, 22, 29, 31, 34 put under vacuum (due to a leakage of this circuit) and / or "overproduction" of water vapor may cause a depression of the depression prevailing in this circuit, causing the opening the regulator 50 to maintain this depression at the set point.

To compensate for the unavailability of a renewable energy source driving the pumps 33, 55, other buffer tanks may be provided between the pump 33 and the expander 50 on the one hand and / or between the pump 55 and the reservoir 54 on the other hand, for example.

In the variant embodiment illustrated in FIG. 2, the water supply circuit of the evaporation tank 12 does not comprise a buffer tank or a pump, consisting essentially of the conduit 22 terminated by the water intake 21 and opening into the tray 12.

The water to be distilled is thus taken from the expanse of water 11 through the mouth 21 of the conduit 22 which is immersed in the body of water.

The invention allows in particular to distil water with increased efficiency, without using fossil energy or human or animal traction, using a simple device to manufacture and use.

Claims

claims

1 - Process for distilling water from a body of water (11), characterized in that it comprises the following operations:

placing an evaporation tank (12) near and above the body of water (11) in a first chamber (16) substantially airtight and comprising at least one wall (18) transparent to the solar radiation that extends above the tank and is inclined towards the outside of the tank;

- connect the evaporation tank (12) to the water body (11) by a tank feed circuit comprising a first conduit

(22) opening into the tank and a water intake (21);

connecting the first enclosure (16), via a second conduit (29), to a second enclosure (31) substantially airtight, which extends below the tray and the first enclosure, which serves to collect the distilled water (35), and is in thermal contact with the cold water or soil;

- maintain the first chamber (16) substantially constant vacuum, by the action of at least one vacuum pump (33) driven by at least one source (110) of renewable energy, so as to cause the transport of water to be distilled to the tank, and to maintain in the tank (12) a level (25) of water (15) substantially constant.

2 - Process according to claim 1, wherein the depression maintained in the first chamber (16) substantially corresponds to the pressure exerted by the water column present in the first conduit (22).

3 - Process according to any one of claims 1 or 2 wherein the supply circuit comprises a buffer tank (54) in which is immersed the water intake (21) formed by the lower end of the first conduit (22). ), and in which the transport of the water taken from the body of water, into the buffer tank, is provided by a pump (55) driven by a source (110) of renewable energy.

4 - Process according to claim 3 wherein is maintained substantially constant level (26) of the water in the buffer tank.

5 - Process according to any one of claims 1 to 4 wherein at least a portion of a concentrate produced in the evaporation pan is removed from the tank by gravitational transport in the first conduit, against the current of an upward flow of water to be treated.

6 - Process according to claims 3 to 5 wherein ensures a buffer tank supply flow (54) which is greater than the flow rate of water taken from the reservoir, the excess water may overflow (53) by an overflow (56) provided in the buffer tank, so that the level (26) of water in the buffer tank (54) is kept constant and at least a portion of the concentrate collected in the tank (54) is removed.

7 - Process according to any one of claims 1 to 6 wherein the tray is installed at a height (H) measured above the level of the body of water or measured above the level (26) of the water in the buffer tank (54), which is less than ten meters, preferably in a range of from two or three meters to approximately eight or nine meters, in particular in a range of from three to four meters to six or about seven meters.

8 - Process according to any one of claims 1 to 7 wherein at least one pump (33, 55) is driven by the effect of movements (110) of the body of water, or by solar or wind energy .

9 - Process according to any one of claims 1 to 8 wherein, to maintain a constant vacuum in the first chamber (16), maintains a constant vacuum in the second chamber (31). 10 - Device (10) for treating water taken from a body of water (11), characterized in that it comprises:

- an evaporation tank (12) disposed near and above the body of water (11);

an airtight evaporation chamber (16) containing the evaporation pan and comprising at least one wall (18) transparent to solar radiation which extends above the evaporation pan and is inclined towards the outside of the tray (12);

- A tank supply circuit comprising a conduit (22) for transporting water to be treated and a water intake (21);

means (18, 27, 29, 31) for condensing the water vapor produced in the evaporation chamber and means (31) for collecting treated water (35), which are impervious to air, at least partly disposed below the evaporation chamber, and in thermal contact with the soil or body of water;

- A conduit (29) for transporting condensates (30) and gas connecting the evaporation chamber (16) to the means (31) of condensation and collection;

- A vacuum pump (33) driven by at least one source (110) of renewable energy and arranged to cause a vacuum in the evaporation chamber; and

- Means for maintaining substantially constant depression in the evaporation chamber (16).

11 - Device according to claim 10 which comprises a buffer tank (54) into which opens (21) the conduit (22) for transporting water, the buffer tank (54) being open in its upper part (56) or otherwise put in communication with the ambient atmosphere.

12 - Device according to claim 11 wherein the buffer tank (54) comprises an overflow (56) or other means (53, 56) for maintaining substantially constant level (26) of the water in the buffer tank. 13 - Device according to any one of claims 11 or 12 which comprises a pump (55) for transporting water taken from the body of water, into the buffer tank, this pump being driven or fed by a source (110) of renewable energy.

14 - Device according to any one of claims 10 to 13 wherein the vacuum pump (33) - and / or if appropriate the lifting pump (55) - is driven by the effect of movements (110) of the water body (11), the (or each) pump being a piston pump driven by waves or waves.

15 - Device according to claim any one of claims 10 to 14 wherein the walls (18, 27) of the evaporation chamber (16) define with the tray (12) at least one passage (63) for condensate (30) dripping on an inner face of the evaporation chamber which is inclined outwardly of the tray (12).

16 - Device according to claim any one of claims 10 to 15 wherein the means for maintaining a constant vacuum in the evaporation chamber, comprise - and essentially consist of - a pressure reducer or pressure regulator (50 ), in particular an expander or regulator disposed on a duct (34) connecting the vacuum pump (33) to a condensation and collecting chamber (31).

17 - Device according to any one of claims 10 to 16 wherein the condensing means and collection (29, 31) are sheltered from solar radiation and other heat sources, in particular buried or immersed.

18 - Device according to any one of claims 10 to 17 which comprises a reflector (60) arranged to reflect solar radiation to the tray (12), in particular a substantially horizontal reflector extending under the evaporation chamber for reflect the solar radiation towards a lower face or wall (13) of the tank evaporation, so as to increase the flow of solar radiation reaching the tray.

19 - Device according to any one of claims 10 to 18 wherein the bottom of the evaporation pan is pierced with an opening (23) through which the conduit (22) for transporting water to be treated opens into the tray, and the bottom of the tray is, at least in part, slightly inclined towards the opening (23).

20 - Device according to any one of claims 10 to 19 wherein the inner face of the walls of the evaporation pan, in particular the upper face of the bottom (13) of the tray, is coated with an anti-adhesive material limiting the adhesion of solid particles of the concentrate, in particular salt adhesion, on this face.

21 - Process according to any one of claims 1 to 9 wherein using a device according to any one of claims 10 to 20.