WO2016004907A1

WO2016004907A1 - A method for solar distillation of saltwater for acquiring fresh water and a device for carrying out this method

Info

Publication number: WO2016004907A1
Application number: PCT/CZ2015/000070
Authority: WO
Inventors: Zdeněk ZÁTOPEK
Original assignee: Zátopek Zdeněk
Priority date: 2014-07-08
Filing date: 2015-07-02
Publication date: 2016-01-14
Also published as: CZ305255B6; CZ2014469A3

Abstract

The method and device (1) for the distillation of saltwater (23) for acquiring fresh water (18) solves the problem of removing salt and minerals from saltwater (23) in areas with a shortage of fresh water (18) for drinking and utility use. The device (1) uses solar radiation (4) which supplies energy to the distillation process, wherein the gained thermal energy is managed so as to maximize the profitability of the fresh water (18).

Description

A method for solar distillation of saltwater for acquiring fresh water and a device for carrying out this method

Field of the invention

The invention relates to the solar distillation of saltwater for acquiring fresh water in areas beset by a shortage of potable and utility fresh water and with access to saltwater, and the invention also relates to a device for carrying out this method.

Background of the invention

The hitherto state of technology is primarily represented by a group of technologies known under the English name humidification-dehumidification technology, abbreviated in professional circles as HDH technology. This technology includes devices operating on the known physical principle of the water cycle in which, through the effect of supplied heat, water changes its state from liquid to gas, to water vapor. Upon the removal of heat from the water vapor, it changes back to its previous state. Given the fact that saltwater is a mixture of salt dissolved in water, the process of evaporation leads to the separation of impurities from the water itself, thus obtaining distilled or fresh water.

One of the known designs is described in patent application EP 2 690 069 A1 , which presents a device for the distillation of saltwater or contaminated water into clean and fresh water. The device includes a cover in the form of a pyramid tent inside which there is a dark area and which is transparent on the outside. The cover is built over a stable base which is secured to the ground, or is stably placed on a water surface. Below the apex of the pyramid cover there are means for capturing water vapor which are connected to a hollow central column. The water vapor is discharged through the central column to below the level of the base where there is a lower temperature, and water vapor condenses into a prepared reservoir. More saltwater is supplied to below the cover. The disadvantages of this design consist in the fact that for the distillation of fresh water the design uses incidental sunlight which heats the water and brings it to evaporation, whereupon the water vapor is condensed. The heat from the vapor is transferred during condensation to the surroundings as waste heat, thus being lost without use.

Another known design for desalinating water according to international patent application WO 85/04159 A describes a device for the desalination of water which comprises a hollow cylinder, horizontally oriented, into which saltwater is supplied. Above the surface of the saltwater stored in the cylinder there is supplied a current of air from captured wind which carries away the evaporating water vapor into a cooler. The air temperature corresponds to the temperature of the entire air flow, i.e. the ambient temperature. In the cooler the water vapor condenses and is collected in a reservoir. The air stream leaves the cooler and returns back into the atmosphere.

The disadvantages of this design consist in the fact that wind, which is a very unpredictable natural phenomenon, is needed for the air flow. Furthermore, the device suffers from a low desalination efficiency, since the water evaporates into cold air which it intercepts and removes a small amount of vapor.

The objective of the present invention is to create a method of solar distillation of saltwater for acquiring fresh water which would be more effective in terms of the cost- performance ratio than are the known embodiments of humidification- dehumidification (HDH) technology, a method which would not be complicated to implement and which would be easy to maintain in operation. A further objective of the invention is to create a device for the implementation of just such a method which would be financially accessible, nearly maintenance-free, easily repairable, and with a long life span.

Summary of the invention

This objective is solved by the method of solar distillation of saltwater for the acquisition of fresh water according to this invention. The method involves the well-known water cycle in which water vapor first evaporates from saltwater in an evaporative solar collector using solar radiation. Then, the water vapor condenses into fresh water through the removal of heat from the water vapor in a heat exchanger.

The essence of the invention consists in that first, air is heated by soiar radiation in a hot-air solar collector and thereby acquires the ability to carry a larger amount of moisture in a given volume of air, with which it will continue to operate. Then the hot air is transported over the surface of the saltwater in an evaporative solar collector and is saturated with water vapor. After saturation with water vapor, the hot air, saturated with water vapor, is transported into a heat exchanger in which it passes the heat to a cooling medium and the water vapor condenses into fresh water. Simultaneously, the heated cooling medium is used during the heating of the air for solar distillation and/or during the heating of saltwater for solar distillation. This increases the efficiency of the device compared to a situation in which this heat would be purely lost as waste heat. The cooling of the vapor leads to the condensation of water vapor, meaning that it passes into liquid state, thus acquiring water for use, which is the target and desired state.

The advantage of this approach lies in the fact that hot vapor can carry a large amount of moisture, and that there exists a large difference in temperature between the hot vapor and the cooling medium. This creates great potential for the condensation of water vapor. Another advantage lies in the fact that the recovered heat is passed back to the evaporation process. n another preferred embodiment of the method of solar distillation of saltwater according to the present invention, the cooling medium of the heat exchanger is ambient air which, after the removal of heat from the hot-air-saturated water vapor, is transported into the hot-air solar collector and/or into the evaporative solar collector. Ambient air is an easily accessible cooling medium, is easily transported, and carries heat well from the heat exchanger. The heated air which carries the heat from the heat exchanger is heated rapidly to the desired temperature in the hot-air solar collector, since the temperature difference is smaller than in the case of heating the ambient air. It is also possible to preheat the saltwater in the evaporative solar collector with this air with a higher temperature so that the incidental solar radiation generates more vapor.

In another preferred embodiment of the method of solar distillation of saltwater according to the present invention, the cooling medium is saltwater which, after the removal of heat from the hot-air-saturated water vapor in the heat exchanger, is transported to the evaporative solar collector. The preheated saltwater is heated more easily in the evaporative solar collector to the optimum evaporation temperature because the substantial temperature difference between the fresh saltwater and the optimum temperature in the collector need not be overcome.

In another preferred embodiment of the method of solar distillation of saltwater according to the present invention, the non-condensed vapor from the heat exchanger is transported back to the hot-air solar collector. The water vapor which did not condense in the heat exchanger is returned to the distillation phase, where it once again obtains a high temperature and is supplemented with a new quantity of vapor. After repeated passage through the heat exchanger, all generated water vapor is condensed into fresh water and there is no loss of water vapor by its premature discharge into the environment as waste residue.

In another preferred embodiment of the method of solar distillation of saltwater according to the present invention, the hot non-evaporated saltwater is transported from the evaporative solar collector to the water heat exchanger in which it passes heat to the new saltwater transported to the evaporative solar collector. The saltwater increases its salinity in the evaporative solar collector. To prevent the evaporative solar collector from getting clogged with minerals, the saltwater is continuously exchanged for new water. At the same time, the new water has a lower temperature than the optimum temperature for evaporation, energy for heating must be supplied. To prevent the energy for heating saltwater from being wasted, the heat from the concentrated saltwater is collected and transmitted to the newly pumped saltwater, thus substantially reducing the temperature difference. The design includes also a device for the solar distillation of saltwater carried out by the method according to the present invention.

The device includes at least one evaporative solar collector for the formation of water vapor and at least one heat exchanger for the condensation of water vapor.

The essence of the invention lies in the fact that the evaporative solar collector has, above the surface of the evaporated saltwater, a hermetically sealed space to which there is connected an output from at least one hot-air solar collector. The hermetically sealed space prevents the escape of water vapor and the reduction of temperature by the passing air in the space. The output from the hot-air solar collector delivers hot air, well saturated with water vapor, to the space. At the outlet from the hermetically sealed space there is connected at least one heat exchanger. The vapor-saturated hot air is led into the heat exchanger for the condensation of water vapor by the removal of heat. The conduit of the cooling medium of the heat exchanger has an inlet of cooling medium into the conduit adapted for the induction of air. The outlet of the heated cooling medium from the conduit of the heat exchanger is switchably connectable to the hot-air solar collector or to the evaporative solar collector. Through switching, one may decide into which phase of solar distillation it is required to supply heat and whether it is necessary to preheat the air or the new saltwater, and/or the conduit of the cooling medium of the heat exchanger has an inlet of cooling fluid into the conduit adapted for collecting saltwater and an outlet of heated saltwater connectable to the evaporative solar collector. If a combination of cooling medium such as air and saltwater is used, it is possible to split the return of the captured heat, or both conduits may work separately and alternately.

In another preferred embodiment of the method of solar distillation of saltwater according to the present invention, the heat exchanger is a counterflow heat exchanger. Due to the transfer of heat, the hot air with water vapor gradually cools and thus approaches the temperature of the air moving in the opposite direction of the heat exchanger as a cooling medium. This air, on the contrary, is heated to a temperature approaching the temperature of the vapor at the inlet into the counterflow heat exchanger. In another preferred embodiment of the method of solar distillation of saltwater according to the present invention, it is provided with at least one source of electrical energy from photovoltaic panels, a wind-powered generator, a battery, or a generator. The device is also provided with means, such as pumps, fans, sensors, and/or control devices which are driven by electrical energy and which are necessary for the correct operation of the device for the distillation of saltwater.

In another preferred embodiment of the method of solar distillation of saltwater according to the present invention, the solar collectors are provided with a positioning drive for tracking the sun in the sky. By rotating the solar panels according to the sun, more sunlight is absorbed, which means more energy is transferred to the distillation device.

In another preferred embodiment of the method of solar distillation of saltwater according to the present invention, the device is provided with floats for positioning it above the surface of the saltwater. Placing the device on the surface of the sea or on the surface of a salt lake will ease the process of desalination by eliminating the need to pump saltwater from the water source to the device on land. Also in the case of sea utilization, the device can be built on the docks and hauled to its destination by a tugboat.

In another preferred embodiment of the method of solar distillation of saltwater according to the present invention, there is arranged, around the circumference of the device, a shielding baffle wall to create a shaded and lee space beneath the device, while the inlet for drawing air into the conduit of the cooling medium of the heat exchanger is arranged in the shaded area. Shading and creating lee prevents the impact of sunlight and the flow of hot wind into the space which would heat the air in the space. The fact that the air is not heated means that a greater temperature difference is achieved between the hot air saturated with water vapor and the ambient air used in the heat exchanger as a cooling medium.

In another preferred embodiment of the method of solar distillation of saltwater according to the present invention, there is created, within the shaded space on the surface of the saltwater, a thermally insulated tank for retaining cold saltwater. Colder saltwater is pumped from the lower parts of the water column and is temporarily retained in the tank. The tank is insulated, so the colder water absorbs heat from the air located within the shaded space, thereby decreasing the air temperature. As the saltwater is heated, it is drained from the tank and new colder water is replenished into the tank.

The method of distilling saltwater and the device for carrying out this method allow for the acquisition of fresh water more efficiently in the cost/performance ratio as opposed to known distillation devices. The efficiency of the device created according to the invention for distilling saltwater corresponds to expensive known systems and devices which are however structurally more complex and prone to defect. The device can be universally used both on land and directly on the water surface.

Description of the drawings

The invention is more closely illustrated by drawings, in which Figure 1 shows a schematic illustration of the device for the distillation of saltwater.

Examples of the preferred embodiments of the invention

It is understood that the hereinafter described and illustrated specific examples of the realization of the invention are presented for illustrative purposes and not as a limitation of the examples of the realization of the invention to the cases shown herein. Experts who are familiar with the state of technology shall find, or using routine experimentation will be able to determine, a greater or lesser number of equivalents to the specific realizations of the invention which are specifically described here. These equivalents shall also be included into the scope of the patent claims.

Regarding the energy flow, the expected average annual solar input in the given area of the tropics is 250 W/m². Approximately 15% of this energy can be absorbed or reflected by a cover of polycarbonate film or other material on the solar collectors 2 and 6. This energy is thereby lost. Other energy loss occurs by the reflection of sunlight 4 from the absorber. The water layer converts approximately 80% of the supplied energy into latent heat of evaporation and 20% of the energy increases the apparent temperature of the saltwater 23 in the evaporative solar collector 6. With the rising temperature of the saltwater 23 in the evaporative solar collector 6, the intensity of the evaporation exponentially increases. The water vapor is carried by hot flowing air 5 with a temperature of about 90° C from the hot-air solar collector 2. The density of the water vapor at this temperature will be 0.4235 kg/m³ In the subsequent counterfiow heat exchanger 8 about 90% of the thermal energy of the vapor- saturated hot air 7 may be passed to the cooling medium - ambient air 9. If the average temperature of the ambient air 9 is 30° C, it cools the water vapor to 39° C. The density of the water vapor at this temperature is about 0.05115 kg/m³, and if this cooled vapor 11. would leave into the surroundings, the loss of precipitated moisture will be about 12%. About 87% of the moisture is precipitated into fresh water 18 in the heat exchanger 8.

It is understood that the cooled vapor 11_ can pass back into the hot-air solar collector 2. The residual heat and residual moisture thus are not lost. The heat of the saltwater 23 located in the evaporative solar collector 6 which increases its salinity by passing moisture to the air 5 can also be used. Upon its substitution for new saltwater 23, it can transmit its heat in the water heat exchanger 21 to this newly inflowing saltwater 23. The transfer efficiency of heat from the concentrated saltwater to the new saltwater 23 will be approximately 70-90%.

The hot-air solar collector 2 may be constructed from a transparent hermetically sealed outer cover, through which a pipe passes. The pipe contains two parts, a wire structure and aluminum film which is stretched around it. This pipe has a square profile, has a large area, and has a knurled or saw tooth profile of its top wall. Its upper side is blackened from above. The larger area allows it to better transmit energy of absorbed solar radiation 4 passing through the air 3, while the shape of its surface reduces the reflection of solar radiation 4 from the collector. None of its surfaces contact the outer surface of the transparent cover except for at fixed points. The hermetically sealed space between the cover and the pipe is filled with dry air or heavy gas for the worse transfer of heat outside the interior space of the pipe by means of convection. On the bottom side of the hot-air solar collector 2 there is placed an aluminum film which reflects the radiant heat from the pipe back to it. In the lower part of this hot-air solar collector 2 there may pass air 3 from heat recovery and there is an inlet of the hot-air solar collector 2. From the bottom and side, the cover connects with insulation material to limit heat loss.

An alternative design is a hot-air solar collector 2 composed of an upper transparent cover from two films, between which there is hermetically sealed an air pocket to reduce the transfer of heat. It may be filled with heavy gas that has better insulating properties than ordinary air. Under the upper cover there is a limiting space in which there is positioned a black absorber from a thin aluminum sheet. The transverse profile of the sheet has a saw tooth shape, thereby minimizing the reflection of light outside the collector. Air 3 flows around this sheet and is heated. In the bottom part there is a separating heat insulating film which separates the warming air from the thermally recovered supplied air 3.

The evaporating solar collector 6 of saltwater 23 with a space for evaporation from the free surface comprises a thermally insulated substrate surface, for example a polycarbonate plate with vacuolated profile and filled with thermally insulating foam. On it there is placed a black rubber film forming the base as well as the collector absorber. The ceiling of the collector is horizontal, about 0 cm above the base and consisting of two polycarbonate films whose hermetically sealed intermediate space forms an air pocket limiting the heat loss from the collector.

An alternative embodiment of the evaporating solar collector 6 consists in the fact that the base - the black rubber sheet and the substrate plate are not adjacent to each other, but the support structure between them defines a space through which there flows heated air from the heat recuperation, it thus transfers some of its heat through the bottom to the saltwater 23 in the evaporative solar collector 6.

The counterflow heat exchanger 8 is formed by cavities through which the hot water vapor with air 7 is led in one direction, and by other cavities created between them in which the ambient air 9 flows in the opposite direction. These cavities are defined by a large area, through which there is a transfer of heat energy from the vapor and a heating by the opposite side of the flow of air 9, and this heat transfer surface defining individual cavities may be made out of aluminum film stretched over a wire construction. The cover of the counterflow heat exchanger is thermally insulated from the surroundings.

In one possible embodiment, the heated air 3 from the counterflow of the heat exchanger heats the bottom side of the rubber sheet and thus heats the layer of water in the evaporative solar collector 6 from below. For this purpose, the rubber film is placed on a wire mesh providing mechanical strength of the base which is fixed to the substrate plate by point columns, while the interspace is designed for moving the hot air 3 and for transferring the heat of the saltwater 23. At the bottom of the substrate plate there may be positioned an aluminum film to reflect radiant heat from the wire structure and rubber sheet back to them.

These examples of recuperation or accumulation of heat can be represented in the device simultaneously.

The transfer of heat from saltwater 24 with increased salinity, from the evaporative solar collector 6 to the newly inflowing saltwater 23, can take place through a recuperative water heat exchanger 21. with a heat exchange corrugated surface tube worm. The waste concentrated saltwater flows from the heat exchanger 21 on the basis of the siphon effect. Saltwater 23 comes to the surface from lower depths after being drawn in.

It is understood that in the device 1 there are connected electronic components such as fans or pumps. The energy for their propulsion may be supplied by photovoltaic panels, a windmill electricity generator, or otherwise.

The entire device i can be located close to the sea on dry land, or directly on the water. In this case, the construction includes floats 17 which carry it. They are narrow, so they have a small area against which the mechanical resistance of the waves would act. For greater mechanical resistance against the pressure of waves, they may be interconnected by a connector 19 in the immersed part.

In order for a greater amount of moisture to precipitate from the hot vapor in the air 7 in the counterflow heat exchanger 8, it is preferable that the air 9 in the opposite direction has a low initial temperature. For this purpose, a shielding baffle wail 12 may be led from the supporting structure of the device along the sides. This creates an area below the device 1 , between it and the sea, where no sunlight shines, where no wind blows heat from the surroundings, and where the basic conditions are thus formed for cooling the air 9. This may be supplemented by an inlet of saltwater inlet 23 from a greater depth into the tank 14 in the form of a shallow pool. This pool is thermally insulated. The material which could be used for the preparation of such a pool is bubble wrap. Saltwater 23 from the lower depths thus reaches the surface. The transfer of heat to the surrounding mass of water is reduced and the heat is transferred between this water and the air 9 in the space defined by the baffle shielding wall 12 from the sides and the actual desalination device from the top. The baffle shielding walls 12 contain vents through which air is drawn in from the surroundings, is cooled on the surface of cold water, then enters into the counterflow heat exchanger 8 as a cooling medium. This is therefore a heat exchanger: air/water without a separating heat exchange surface.

Part of the desalination device may further be a thermally insulated tank having an inner heat transfer surface in which there is a transfer of thermal energy of the vapor and hot air 7 or the thermally recovered air 3 into the saltwater. This water can then be pumped into the vapor space of the evaporative solar collector 6 for the purpose of re-evaporation from the water surface. The hot-air solar collector 2 may be tilted towards the sun.

Figure 1 shows the schematic interconnection of the device 1 for the solar distillation of saltwater 23. To the hot-air solar collector 2 there enters air 3 which is heated by sunlight 4. The air 3 may be directly ambient air 9 from around the device 1 corresponding to its ambient temperature, or may be preheated air 3 exiting from the heat exchanger 8. Hot air 5 continues to flow through the evaporative soiar collector 6. In the evaporative soiar collector 6, saltwater 23 is poured in a thin layer and above the saltwater 23 there is formed a hermetically sealed space 25, through which the solar radiation 4 penetrates into the saltwater 23. Over its surface there collects hot air 5 evaporating the moisture and becoming saturated with nearly 100% relative humidity.

From the evaporative solar collector 6 there exits hot humid air 7 which passes into the counterflow heat exchanger 8, in which there occurs heat recovery and condensation of water vapor to fresh water 18. In the opposite direction, air 9 flows driven by a fan 10. By taking the heat from the hot moist air 7, it becomes a carrier for thermal energy and as such heats the cavity of the evaporative solar collector 6, hot- air solar collector 2, and subsequently forms a hot air current entering the hot-air solar collector 2. The flow of air 3 is therefore the carrier of the residual heat and forms on the basis of heat recovery.

Moist warm air 7, cooled by the air 9 in the heat exchanger 8 loses most of its moisture and heat and goes into free space as air 11 In this embodiment of the device 1_, the residual moisture in the air is not recycled. The air 9 designed for cooling the vapors begins in the space between the sea level and the lower part of the device 1. This is a shielded space 26 hidden from the sun and surrounded on the sides by a flexible shielding baffle wall 12 which does not present mechanical resistance to the surrounding waves and thus does not burden the supporting structure of the device 1. Ambient air enters into this space 26 from the surroundings through the vent holes in the wall of the baffle wall 12 and is actively cooled by the sea surface, where saltwater 23 was drawn from a greater depth by a pump 13, so it is cooler than the surface layer of saltwater 23 and thus better cools the air 9. This cold saltwater 23 is surrounded by the surrounding mass of saltwater 23 by a shallow tank 14 which reduces the transmission of heat downwards. If excessive heating occurs of this saltwater 23 on the surface, the outlet 15 is activated. The tank 14, which is lighter than the saltwater 23, thus comes above the surface, thereby emptying and new cold saltwater 23 can subsequently be pumped. The tank 14 is flexibly attached to the construction of the device by a connector 16 to a float 17 which forms the supporting pillar. The water vapor, after condensation in the counterflow heat exchanger 8, flows as fresh water 18 into the reservoir. The floats 17 which provide buoyancy to the device 1_ so that it is above the surface of the water are, in their lower parts, connected by a connector 19, thereby increasing the mechanical strength of the construction and thus can more easily withstand the dynamic environment of the sea surface.

The saltwater 24 located in the evaporative solar collector 6 salinizes through intense evaporation, which could lead to crystallization of the evaporate on the bottom of the evaporative solar collector 6. This is why after a certain time it is replaced with new saltwater 23. This is carried out by a pump 20, and to avoid the unnecessary loss of heat during the exchange of saltwater 24, the concentrated saltwater 24 from the evaporative solar collector 6 transfers heat to the newly inflowing saltwater 23 in a recuperative heat water heat exchanger 21.

Stabilization of the device \ in the sea is done by multiple anchoring 22 consisting of a pulley, into which there is a rope at one end which is anchored to the sea floor on the other end. The device 1 is stabilized on the water surface while at the same time reacts to changes in the height of the water column.

Industrial applicability

A method of solar distillation of saltwater for acquiring fresh water, and a device for implementing this method according to the invention, are useful in areas with a shortage of fresh drinking and utility water but which have access to salt water either as saltwater or salt lake water. Overview of the positions used in the drawings

1 device for solar distillation of saltwater

2 hot-air solar collector

3 air entering the hot-air solar collector

4 solar radiation (sunlight)

5 hot air

6 evaporative solar collector

7 vapor-saturated hot air

8 heat exchanger

9 ambient air

10 fan

11 uncondensed water vapor

12 shielding baffle wall

13 pump

14 tank for cold saltwater

5 outlet

6 connector

17 float pillar

18 fresh water

19 connector

20 pump

21 water heat exchanger

22 anchoring

23 saltwater

24 non-evaporated hot saltwater

25 hermetically sealed space

26 shaded area

Claims

1. A method for the solar distillation of saltwater (23) to acquire fresh water (18), consisting first of the evaporation of saltwater (23) in an evaporative solar collector (6) by means of solar radiation (4) and the subsequent condensation of water vapor using the removal of heat from the water vapor in a heat exchanger (8), c ha racte ri zed i n th at first, air (3) is heated by means of solar radiation (4) in a hot-air solar collector (2), then the hot air (5) is transported above the surface of the saltwater (23) in an evaporative solar collector (6) and saturated with water vapor, then the vapor-saturated hot air (7) is transported to a heat exchanger (8) in which it passes the heat to a cooling medium and the water vapor condenses to fresh water (18), wherein the heated cooling medium is used for heating the air (3) for solar distillation and/or for heating the saltwater (23) for solar distillation.

2. A method of solar distillation according to claim 1 , c h a racte rized i n th at the cooling medium of the heat exchanger (8) is the ambient air (9) which, after the removal of heat from the vapor-saturated hot air (7), is transported into the hot-air solar collector (2) and/or to the evaporative solar collector (6).

3. A method of solar distillation according to claim ^ c h a ra cte rize d i n that the cooling medium is saltwater (23) which, after the removal of heat from the vapor-saturated hot air (7) in the heat exchanger (8), is transported to the evaporative solar collector (6).

4. A method of solar distillation according to at least one of claims 1 to 3, c h a ra cte rized i n th at the non-condensed water vapor (11) from the heat exchanger (8) is transported back to the hot-air solar collector (2).

5. A method of solar distillation according to at least one of claims 1 to 4, c h a ra c te rize d i n th at the hot non-evaporated saltwater (24) is transported from the evaporative solar collector (6) to the water heat exchanger (21) in which it transfers heat to the new saltwater (23) transported to the evaporative solar collector (6).

6. A device (1) for the solar distillation of saltwater (23) according to at least one of claims 1 to 4, comprising at least one evaporative solar collector (6) and at least one heat exchanger (8), characterized in that the evaporative solar collector (6) has, above the surface of the evaporated saltwater (23), a hermetically sealed space (25) to which there is connected an outlet from at least one hot-air solar collector (2) and to the outlet from the hermetically sealed space (25) there is connected at least one heat exchanger (8), wherein the conduit of the cooling medium of the heat exchanger (8) has an inlet adapted for the intake of air (9) and an outlet switchably connectable to the hot-air solar collector (2) or to the evaporative solar collector (6), and/or the conduit of the cooling medium of the heat exchanger (8) has an inlet adapted for drawing saltwater (23) and an outlet connectable to the evaporative solar collector (6).

7. A device for solar distillation according to claim 6, characterized in that the heat exchanger (8) is a counterflow heat exchanger (8).

8. A device for soiar distillation according to claim 6 or 7, characterized in that it is equipped with at least one source of electrical energy from photovoltaic panels, a wind-powered generator, battery, or generator.

9. A device for solar distillation according to at least one of claims 6 to 8, characterized in that the solar collectors (2, 6) are equipped with a positioning drive for tracking the sun in the sky.

10. A device for solar distillation according to at least one of claims 6 to 9, characterized in that it is equipped with floats (17) for placement above the surface of the saltwater (23).

11. A device for solar distillation according to claim 10,characterized in that around the periphery of the device (1) there is arranged a shielding baffle wall (12) to create a shaded space (26) below the device (1), wherein the inlet for taking the air (9) into the conduit of the cooling medium of the heat exchanger (8) is arranged in the shaded space (26).

12. A device for solar distillation according to claim 11, characterized in that inside the shaded space (26), on the surface of the saltwater (23), there is a thermally insulated tank (14) for retaining the cold saltwater (23).