WO1997034831A1

WO1997034831A1 - Saltwater distillation housing

Info

Publication number: WO1997034831A1
Application number: PCT/JP1997/000938
Authority: WO
Inventors: Hiroyuki Nakazato
Original assignee: Top Ecology Co., Ltd.
Priority date: 1996-03-18
Filing date: 1997-03-18
Publication date: 1997-09-25
Also published as: JPH11207318A; AU1944197A

Abstract

The object of the present invention is to provide a saltwater distillation housing that uses solar energy for efficiently evaporating, condensing, and desalinating saltwater. A housing wall (3) of the saltwater distillation housing opposite an incident wall (2) of solar light (1) comprises an inner vapor current separating plate (6) inside the housing along an outer wall (5) and an outer vapor current separating plate (7) outside the housing; and at the exterior surface of the outer wall (5) covered with the outer vapor current separating plate (7), a water retentive material (8) of non-woven fabric or cotton cloth is attached; and cooling water from the ocean is dispensed on this material (8) from a piping (9) to promote condensation by evaporation. The water basin (4) inside the housing is partitioned into a plurality of water tanks by partitions (19); and a saltwater of a very high salt concentration of a lower layer from an opening (2) at a lower section of the partition (19) is made to flow to the surface of the next section. The air that includes vapor evaporated from the water basin (4) is cooled by the outer wall and is condensed to produce water condensate as it descends through a space between the outer wall (5) and the inner vapor current separating plate (6). By this type of structure, a desalination rate ten times the prior rate is achieved.

Description

Saltwater Distillation Housing

Technical Field

The present invention is related to a saltwater distillation housing for extracting distilled freshwater from saltwater using natural renewable energy in desert, isolated islands, other areas where obtaining freshwater is difficult.

Background Art

Desalination of ocean water and underground saline water is one of the most important topics in desert and other areas where fresh, life— sustaining water is in short supply. Presently, desalination is achieved generally by burning oil or using reverse osmosis technology in a large facility where a tremendous amount of non-recyclable energy is required.

On the other hand, there are methods such as a basin evaporation method that involves a small self-sufficient facility utilizing natural energy such as thermal energy from the sun. The basin evaporation method requires placing a basin containing a certain amount of saltwater in a housing and collecting the resultant condensate cooled and condensed on the housing wall by the outside air. However, efficiency ^' i this method is very low; for instance, a basin with an open surface area of 400 m² would lead to extracting only 1 m³ of distilled freshwater per day.

The aforementioned method using solar heat has an extremely bad condensation rate because the vapor evaporated from the basin containing the saltwater can freely disperse away from the housing wall without being adequately cooled for condensation. Furthermore, there is a problem of a higher temperature saltwater of a very high salt concentration having an efficient evaporation rate being layered over by a lower temperature saltwater of a very low salt concentration having an inefficient evaporation rate, resulting in overall an inefficient evaporation of the saltwater.

The object of the present invention is to solve the problem as described above by using solar heat to efficiently evaporate saltwater as well as to present a saltwater distillation housing that can efficiently condense and desalinate saltwater.

Disclosure of Invention

In order to achieve the stated object above, a saltwater distillation housing of the present invention uses the following means. The invention provides a saltwater distillation housing for extracting freshwater from water vapor of saltwater evaporated within the housing, characterized in that an inner plate inside the housing is placed along the outer wall of the housing with a space between the outer wall and the inner plate, and freshwater is extracted by cooling a vapor current passing through the space within the housing. With this type of construction, the vapor current of the inner housing is cooled within the space between the inner plate and the outer wall by the outer wall; and since this cooled vapor current is prevented from dissipating by the inner plate, cooling and condensation processes are facilitated in the formation of water condensate for desalinating the saltwater.

The present invention further comprises means for adjusting the flow rate of the vapor current at a current outlet at which the vapor current flows through the space between the inner plate and the outer wall and out into the housing. In accordance with this, the speed of the vapor current passing through the space between the inner plate and the outer wall can be selectively set, and thereby, effectively executing cooling and condensation processes.

The present invention is further characterized in that an outer plate is placed along the outer wall at an exterior side of the housing with a space between the outer wall and the outer plate, and outside air made light in weight by being warmed by a heat exchange process between the interior and exterior sides of the outer wall becomes a rising vapor current that passes through the space between the outer wall and the outer plate to further promote heat exchange between inside and outside of the housing through the outer wall.

The present invention further comprises water dispersing means for dispersing cooling water on an exterior surface of the outer wall to cool the outer wall effectively.

The present invention further comprises a water retentive material of non-woven fabric or cotton cloth for absorbing the cooling water at the exterior surface of the outer wall. By this, evaporation of the cooling water is facilitated and cooling processes of the outer wall are promoted.

The present invention is further characterized in that a basin having a plurality of water tanks connected together by water passage channels are placed inside the housing, have the water passage channels positioned at a lower part of the water tank, and let pass saltwater of a lower layer of the water tank. According to this construction, a heated reserved water of a high salt concentration at the lower layer is progressively brought to the surface as the water is transferred to the next tank.

The present invention is further characterized in that the basin is divided into the plurality of water tanks by partitions, each having an opening at a lower part of the basin, and these water tanks constituting the basin are integrally constructed. In this way, the water tanks are constructed with relative ease.

Another embodiment of the present invention is a housing wall panel of a saltwater distillation housing for extracting freshwater from water vapor of saltwater evaporated inside the housing, comprising a wall plate that separates inside and outside of the housing, an inner plate placed at a predetermined spacing along the wall plate and at an interior surface side of the housing, and an outer plate placed at a predetermined spacing along the wall plate and at an exterior surface side of the housing, and these components are integrally constructed. According to this construction, the housing wall panel of a vapor current separating construction leads to cooling the vapor current between the inner plate and the outer wall by utilizing effectively the outside air that rises between the outer plate and the outer wall; and by prefabricating these plates, they can be used to easily construct the saltwater distillation housings anywhere.

The present invention further comprises a piping for dispersing cooling water on an exterior surface of the wall plate. By the dispersion of the cooling water, the wall plate can be effectively cooled.

The present invention further comprises a water retentive material of non-woven fabric or cotton cloth placed on the exterior side of the wall plate. The process of evaporation is promoted by letting cooling water absorb into this water retentive material.

Still another embodiment of the present invention is a basin, including a plurality of water tanks for letting pass saltwater, for evaporating a water component of the saltwater in the water tanks by solar heat, characterized in that the basin has water passage outlets for progressively transporting between the water tanks, saltwater of a lower layer of the water tanks. In this way, water tanks can be presented that progressively transfer the heated water of a high salt concentration of the lower layer to the surface and evaporate the water component. The present invention is further characterized in that the water tanks constituting the basin are integrally constructed with partitions that divide the water tanks, and an opening for letting pass saltwater of the lower layer is provided at a lower part of each partition. In this way, a plurality of water tanks having a very simple structure that effectively evaporate saltwater can be easily constructed.

Brief Description of Drawings

The details of the present invention will be described in connection with the accompanying drawings, in which FIG. 1 is a cross-sectional view showing one structural embodiment of a saltwater distillation housing of the present invention; FIG. 2 is an enlarged cross-sectional view of part II of FIG. 1; FIG. 3 is a cross-sectional view of arrow III-III in FIG. 2. FIG. 4 is a planar view showing one structural embodiment of a water basin of the present invention; and FIG. 5 is a detailed view of arrow V-V in FIG. 4.

Best Mode for Carrying Out the Invention

Below, a structural embodiment of the present invention is described in conjunction with figures.

FIG. 1 is a cross-sectional view showing one structural embodiment of a saltwater distillation housing of the present invention. FIG. 2 shows detail of part II of FIG. 1 and is a detailed cross-sectional view showing a vapor current separating structure used in the present ructural embodiment. FIG. 3 is a cross-sectional view of arrow III-

III in FIG. 2.

As shown in these figures, the saltwater distillation housing according to the present structural embodiment uses the vapor current separating structure in a housing wall 3 opposite an incident wall 2 where solar light 1 irradiates on it. Furthermore, a basin 4 is provided r D in the housing for holding saltwater to be evaporated by solar heat.

The vapor current separating structure of the housing wall 3 according to the present structural embodiment includes an inner vapor current separating plate 6 along an outer wall 5 and inside the housing. The saltwater vapor current that passes through an inner space 26 provided between the inner vapor current separating plate 6 and the outer wall 5 is cooled and condensed while descending the space and turns into liquid to produce freshwater. Moreover, in order to promote efficient condensation, descending speed of the saltwater vapor current is made to be adjustable by providing current rate adjustment means 28 comprising a structure such as an adjustment valve for constricting an opening for adjusting the current rate at an exit mouth in the lower section where the vapor current of the inner space 26 circulates out into the interior of the housing.

Furthermore, an outer vapor current separating plate 7 is provided along the exterior side of the outer wall 5. Still further, a water retentive material 8 of non-woven fabric or cotton cloth is placed on an exterior surface of the outer wall 5 which is further covered by the outer vapor current separating plate 7; and by dispersing cooling water such as saltwater from a piping 9, this water retentive material 8 is made to absorb the cooling saltwater. As this cooling saltwater evaporates, the outer wall is cooled and the cooling of the vapor current in the inner space 26 is promoted to achieve efficient condensation. On the other hand, outside air, warmed and made light in weight by heat exchanging with the inner housing through the outer wall 5. rises through an outer space 27 provided between the outer vapor current separating plate 7 and the outer wall 5 to promote evaporation of the cooling water and to exchange heat efficiently with the inner housine;. At the lower section of the housing wall 3, a freshwater collecting channel 10 is provided on the floor of the inner housing for collecting the water condensate produced within the inner space 26. On the ground outside the housing, a water drainage channel 11 for the cooling water dispersed within the outer space 27 is provided.

The vapor current separating structure of the housing wall 3 is, as shown in FIGS. 2 and 3, provided with the inner and outer vapor current separating plates 6 and 7 held in place by, for example, an acrylic plate fixing support material 15. Predetermined spaces set by interval adjustment materials 13 and 14 are provided between the plates 6 and 7 respectively with respect to the outer wall 5, which is placed on rafters or hanging wood 12 with a packing material 16 therebetween. In the present structural embodiment, the outer wall 5 and the inner and outer vapor current separating plates 6 and 7 are acrylic plates, but the present invention does not need to be limited to acrylic material. Glass, plastic or other transparent material may also be used. That is, a preference is made to a material that is easily handled, does not break easily, and has excellent durability.

The inner and outer spaces 26 and 27 of the outer wall do not need to be equally spaced apart, and although in the present structural embodiment, for example, theses spaces appear to have equal spacing above and below the wall but this is not always necessary to conduct desalination.

Furthermore, the solar light incident wall 2 of the housing has an acrylic plate 17 on the hanging wood 12 with the packing material 16 therebetween and is held in place by screws 18. A known structure may be used so long as solar heat irradiates on the wall adequately.

Next, the basin 4, which is put into place for evaporating saltwater, is explained by using FIGS. 1, 4, and 5. FIG. 4 is a planar view of one structural embodiment of the basin 4 of the present invention. FIG. 5 is a detailed view of arrow V-V in FIG. 4.

As shown in these drawings, the basin 4 placed on the ground inside the housing is divided into a plurality of water tanks having oblong and large length to breath ratio (figure shows 9 tanks); and an opening 20 for transporting a saltwater of a very high salt concentration from one tank to the next is provided at the lower part of each partition 19. Two openings for every one tank are placed at the farthest ends. The basin 4 in the present structural embodiment has a waterproof sheet 22 overlaid on a bottom plate 21 and is divided by the partitions 19 and processed to prevent water leakage by a caulking 23. It is a structure that can be easily manufactured.

Below, the operation of the saltwater distillation housing of the present invention is explained.

(1) Operation of the inner vapor current separating plate 6. It is often observed that during winter, water condensate appears on glass windows of a heated room where a curtain is drawn across, and consequently a large amount of water condensate drips off down below the curtain. In contrast, the windows that are left exposed without the curtain drawn across them only become slightly cloudy. The reason for this is that, between the windows and the curtain, air becomes sufficiently cooled for condensation to occur, but when the glass windows are exposed without the curtain drawn across them, the room air disperses quickly without being sufficiently cooled by the outside air through the glass windows so that no condensation takes place. Based on this kind of observation, the inventor placed the inner vapor current separating plate 6 inside the housing with appropriate spacing from the outer wall 5. The air current, containing water vapor warmed in the housing, as shown as arrow 24 in FIGS. 1 and 2, is cooled while descending through the inner space 26 provided between the inner vapor current separating plate 6 and the outer wall 5, and then the vapor phase and the liquid phase are separated by condensation because of cooling. The liquid phase results into water condensate which drips into the water collecting channel 10 used for collecting freshwater, and the vapor phase travels down as it loses moisture and circulates into the interior of the housing from the outlet at the lower section. In this way, evaporation of saltwater within the basin 4 is promoted. By providing vapor current adjustment means at the vapor current outlet, the descending speed of the vapor current within the inner space 26 can be selectively set to execute the condensation process effectively.

(2) Operation of the outer vapor current separating plate 7.

By the heat exchange that occurs between inside and outside of the housing through the outer wall 5, the outside air is warmed and made light in weight as the weight of the vapor evaporated at the outer wall 5 is less than half that of the air (air to vapor ratio is approximately 0.45).

This air. as is contained within the outer space 27 formed by the outer vapor current separating plate 7 and as shown as arrow 25 in FIGS. 1 and 2, becomes a strong rising current, and the air sucked from the bottom of the outer vapor current separating plate 7 promotes evaporation as it passes over the exterior surface of the outer wall 5.

(3) Water dispersion process on the water retentive material 8. For instance, when a clear plastic bag is washed, wrung off of water, and then has its mouth closed after being inflated, after a while water condensate starts to form at various places inside the bag as it becomes cloudy. If closely observed, it will be noticed that the formation of water condensate occurs precisely at those places where some water still remains on the outside of the bag. The reason for this is that as the water outside evaporates, the cooling effect makes the vapor inside the bag condense onto the interior side of the bag. The inventor aims to reproduce this phenomenon on a much larger scale by using the water retentive material 8 of the present invention. The water retentive material 8 of non-woven fabric or cotton cloth — materials that can absorb water easily — is attached on the exterior side of the outer wall 5 and saltwater is dispensed to moisturize the material 8. In this way, as the saltwater outside evaporates, the outer wall 5 is cooled and consequently the interior side of the outer wall 5 is also cooled, promoting the condensation of the vapor current inside the housing to produce a large amount of freshwater. The saltwater for cooling purposes dispersed on the exterior surface of the outer wall 5 is drained through a water drainage channel 11 before any salt crystals can form. It is also possible to extract salt from the saltwater to be drained.

(4) Operation of the basin partition 19. When saltwater is warmed by solar heat, the heavy water of an increased salt concentration due to evaporation resides below the layer of light water of a low salt content, and through this, heat from the solar light is stored. In this type of situation, a phenomenon called "heat pond" occurs where no convection occurs between the upper layer and the lower layer. Reserved heat of this phenomenon is even used in power generators, but in order to tie solar energy with evaporation in the instant case, this phenomenon must be prevented to occur.

The inventor, therefore, used a plurality of long water channels in the water tanks 4, where each tank is made to have an opening 20 to let flow the saltwater in or out of the lower layer. In order to position the inlet and the outlet as far apart as possible, the openings 20 at the lower sections of the partitions 19 were positioned alternately and diagonally with each other.

In this way, a heat reserved water of a high salt concentration of the lower layer in one tank flows into the adjacent tank through the opening 20 to form an upper layer. The supplied saltwater passes through the oblong tank while evaporating; the saltwater of the lower layer flows through progressively through the openings such that the heated water of a very high salt concentration of the previous tank comes up progressively to the surface of the next tank to have the water component evaporated. The water of the lower layer from the previous tank rises to the surface of the next tank because it is assumed that the salt concentration is higher in the next tank owning to continuing evaporation. As a result of the above, not only evaporation is promoted but also heat energy of the saltwater of a very high salt concentration is used efficaciously for evaporation. According to the present structural embodiment, in comparison with the prior basin evaporation method, approximately 10 m³ of freshwater per day can be extracted for an open basin area of 400 m². For this reason, over ten times the desalination rate is achieved, and furthermore, natural salt can also be extracted if desired.

According to the present invention as shown above, by suitably using the means listed below, excellent results are achieved as delineated below.

(1) An air current that includes water vapor inside the housing turns to liquid according to the condensation process while descending through the space between the inner vapor current separating plate and the outer wall and forms water condensate which drips off below. (2) Outside air, warmed by the heat exchange between inside and outside of the outer wall, becomes light in weight and turns into a rising air current, rising from the lower section of the outer vapor current separating plate, and promotes evaporation by passing over the exterior surface of the outer wall. This evaporation causes the housing inside to be cooled as heat exchange occurs. (3) The outer wall is cooled by having water evaporate from the water retentive material, which is attached onto the exterior side of the outer wall, previously soaked with cooling water. Concomitantly, the inner housing side of the outer wall is cooled to promote condensation. (4) Since the water basin is partitioned into several tanks by the partitions that have openings at the lower part, the heat reserved water of a very high salt concentration of the lower section progressively passes through each of the tanks through the openings to come up to the surface to have the water component evaporated. By utilizing these means individually or by suitably combining them in a self-sufficient facility that utilizes natural energy such as solar heat, saltwater can be efficiently evaporated and condensed for desalination. For this reason, a saltwater distillation housing especially adapted for extracting a large quantity of freshwater is presented for arid land areas such as desert and isolated islands where obtaining freshwater is difficult.

Claims

1. A saltwater distillation housing for extracting freshwater from water vapor of saltwater evaporated within the housing, characterized in that an inner plate inside the housing is placed along the outer wall of the housing with a space between the outer wall and the inner plate, and freshwater is extracted by cooling a vapor current passing through the space within the housing.

2. The saltwater distillation housing of claim 1, further comprising means for adjusting the flow rate of the vapor current at a current outlet at which the vapor current flows through the space between the inner plate and the outer wall and out into the interior of the housing.

3. The saltwater distillation housing of claim 1, further characterized in that an outer plate is placed along the outer wall at an exterior side of the housing with a space between the outer wall and the outer plate, and heat exchange between outside and inside of the housing at the outer wall is promoted by a rising vapor current that passes through the space between the outer wall and the inner plate.

4. The saltwater distillation housing of claim 1 or 3, further comprising water dispersing means for dispersing cooling water on an exterior surface of the outer wall.

5. The saltwater distillation housing of claim 4, further comprising a water retentive material of non-woven fabric or cotton cloth for absorbing the cooling water at the exterior surface of the outer wall.

6. The saltwater distillation housing of claim 1, further characterized in that a basin having a plurality of water tanks connected together by water passage channels is placed inside the housing, has the water passage channels positioned at a lower part of the water tanks, and lets pass saltwater of a lower layer of the water tanks.

7. The saltwater distillation housing of claim 6, further characterized in that the plurality of water tanks constituting the basin is divided by partitions, each having an opening at a lower part of the basin, and the water tanks are integrally constructed.

8. A housing wall panel of a saltwater distillation housing for extracting freshwater from water vapor of saltwater evaporated inside the housing, comprising a wall plate that separates inside and outside of the housing, an inner plate placed at a predetermined spacing along the wall plate and at an interior surface side of the housing, and an outer plate placed at a predetermined spacing along the wall plate and at an exterior surface side of the housing, wherein the wall plate, the inner plate, and the outer plate are integrally constructed.

9. The housing wall panel of claim 8, further comprising a piping for dispersing cooling water on an exterior surface of the wall plate.

10. The housing wall panel of claim 9, further comprising a water retentive material of non-woven fabric or cotton cloth placed on the exterior side of the wall plate.

11. A basin, including a plurality of water tanks for letting pass saltwater, for evaporating a water component of the saltwater in the water tanks by solar heat, characterized in that the basin has water passage outlets for progressively transporting between the water tanks, saltwater of a lower layer of the water tanks.

12. The basin of claim 11, further characterized in that the water tanks are integrally constructed in accordance with partitions that divide the water tanks, and an opening for letting pass saltwater of the lower layer is provided at a lower part of the partition.