DE102007055448A1 - Solar distillation plant for extracting clean fresh water from dirty primary water such as salt and brackish water, comprises housing closed with translucent cover, evaporation surface, medium circulation circuit and distillate container - Google Patents

Abstract

The solar distillation plant (1) for extracting clean fresh water from dirty primary water such as salt and brackish water, comprises a thermally insulated housing (2) closed upwardly with a translucent cover (8), an evaporation surface (12) present in the housing, a medium circulation circuit having lines for transporting a liquid medium to be distilled, where the lines have openings for guiding the medium on the evaporation surface, and a container (20) for collecting distillate of the medium in the housing. The evaporation surface is aligned on the cover. The solar distillation plant (1) for extracting clean fresh water from dirty primary water such as salt and brackish water, comprises a thermally insulated housing (2) closed upwardly with a translucent cover (8), an evaporation surface (12) present in the housing, a medium circulation circuit having lines for transporting a liquid medium to be distilled, where the lines have openings for guiding the medium on the evaporation surface, and a container (20) for collecting distillate of the medium in the housing. The evaporation surface is aligned on the cover so that solar energy passing through the cover arises on a top side of the evaporation surface. The evaporation surface is formed from a non-insulated, heat conducting material so that the energy is supplied back to the top side of the evaporation surface during the condensation of the medium at the lower surface of the evaporation surface. The difference of the air volumes above and below the evaporation surface is maximally 10%. A condenser arrangement (18), by which the circulation circuit is led, is arranged: in the upper area of the housing below the evaporation surface; in the lower area of the housing adjacent to the lower edge of the evaporation surface; in the housing above the evaporation surface; and in the lower area of the top side of the evaporation surface. The housing is formed from a fiber-reinforced plastic tub with integrally inserted insulant. The cover has an insulating glass pane. The top side of the insulating glass pane is roughened for reducing the reflection and is coated with silicon dioxide. The inner side of the lower windowpane lying in a vacuum area is coated with a silver-containing coating. The upper area of the evaporation surface adjacent to the condenser arrangement is thermally insulated. The evaporation surface is arranged in the form of steps and has step surfaces sequentially arranged in the distance from each other so that it partially overlaps the sequential step surfaces. The rear edges of the step surface are connected with the overlapping front edge of the step surface by a connecting plate. The evaporation surface is formed from a metal sheet. Condensate run-off grooves are arranged at the lower surface of the cover projecting into the housing and laterally conveys the distillate of the lower surface of the cover. A flow control valve is intended in the circulation circuit and is controllable as a function of the temperature in the housing so that a reduced flow of the medium takes place at less temperature and an increased flow of the medium takes place at higher temperature.

Description

The The invention relates to a solar distillation plant with a after closed at the top with a translucent lid Housing, an Evaporationsfläche in the housing, which is aligned on the lid so that passing through the lid Solar energy on top of the evaporation surface impinges, with a medium circulation circuit with lines for Transport of a liquid medium to be distilled, the towards the top of Evaporationsfläche aligned opening to direct medium to the evaporation surface, and with a device for collecting distillate of the medium in the housing arranged collecting container.

Solardestillen for obtaining clean fresh water from dirty primary water under direct use of solar energy, which heats a wetted with the primary water Evaporations- or evaporation surface are sufficiently for example from the DE 37 21 072 A1 and DE 38 29 725 A1 known. Without the use of electrical energy or failure-prone maintenance-intensive mechanical filter is done in the solar sterilization sterilization, cleaning and optionally desalting of primary water fact that the primary water evaporates on the evaporation surface and the distillate is collected as a product. Such solar quies are therefore advantageously used wherever there is no public water network with a central supply of consumers and consumers with clean fresh water. Rather, the clean fresh water from the primary water, especially salt and brackish water, can be generated individually on site.

In the DE 38 29 725 A1 a combination of condenser, heat exchanger and collector is proposed to control the mass flows and their proportioning. In this case, a self-regulating air mass circulation is to be achieved. The insulated evaporation surface is intended to ensure an optically improved temperature gradient between the upper side of the evaporation surface and the lower surface of the evaporation surface.

in the Over the course of the day, the thermal conditions change constantly. This leads to a not yet satisfied overall yield of the known solar stillilles.

task The present invention is therefore an improved solar distillation plant to create, which has an improved efficiency.

The Task is with the solar distillation plant of the aforementioned Kind solved by the fact that the Evaporationsfläche formed from a non-insulated, thermally conductive material is so that when condensing medium at the bottom of the evaporation surface Energy returned to the top of Evaporationsfläche becomes.

It it was recognized that the efficiency of solar distillation plants significantly by exploiting the available in the housing Energy is determined and significant enthalpy in the condensation process plugged. It does not - as previously assumed - on it on, the bottom of Evaporationsfläche possible Keep cool to avoid condensation in the housing circulating vaporous medium at the bottom the Evaporationsfläche and on capacitors cause. Rather, it was realized that the heat flow from the bottom to the top of the Evaporationsfläche crucial for the efficiency of solar distillation equipment is. The thermal resistance The Evaporationsfläche is as low as possible, please include to stick to the at the bottom of the evaporation surface when Condensation of the vaporous medium released condensation energy back to the top of the Evaporationsfläche back to there to promote the evaporation process of the medium. Surprisingly performs this recycling of enthalpy the condensation on the back of the evaporation surface to the top of the Evaporationsfläche to a higher Yield, without that in comparison to the previously known Evaporationsflächen higher temperature of the underside of the Evaporationsfläche disproportionately affected the condensation process. This is due to the fact that the air masses above the Evaporationsfläche are much warmer than the air masses keeps the Evaporation surface, making it suitable for condensation not significantly on the temperature of the bottom of Evaporationsfläche arrives.

Around ensuring continuous air circulation is beneficial approximate the air volume above the evaporation surface equal to the volume of air below the Evaporationsfläche. This will ensure that the cooler air volume below the evaporation area in permanent Exchange with the warmer air volume above the evaporation surface stands.

Under An approximately equal volume of air is understood that the difference in air volumes below and above the evaporation surface maximum 10%.

Before applying the medium to the Evaporationsfläche it is advantageous to preheat this. This can be done with at least one capacitor arrangement through which the medium circulation circuit is guided and which is arranged in the housing. One of the capacitor arrangements can be arranged for example in the upper region of the housing below the Evaporationsfläche.

In A preferred embodiment is a further capacitor arrangement in the lower part of the housing adjacent to the lower edge of the housing Evaporation surface arranged. This allows the air exchange be improved, since the air au outside the capacitor array is cooled by the air masses in the area withdrawn Heat is at least partially passed into the medium.

Of the Efficiency can be achieved by heat insulation of the housing be further improved. A particularly robust, simple and inexpensive Variant is when the housing is made of a fiber reinforced plastic tub is formed with integrally incorporated insulating material. As fiber reinforced Plastic tub offers a glass fiber reinforced plastic (GRP) or a carbon fiber reinforced plastic. Of the Insulating material can in the vacuum process integral with the inner and outer plastic tub are made.

Of the Lid to the upper end of the housing preferably has at least one insulating glass pane. Such insulating glass or Thermopenscheiben are well known and consist of two or more about vacuum spaces separated from each other Slices. To improve the efficiency, it is advantageous if the surface of the insulating glass pane is roughened. Thus, the reflection of the insulating glass pane can be reduced so that the proportion of solar energy going into the housing is enlarged. The roughening of the surface The insulating glass pane can be covered by a coating of silicon dioxide respectively.

to Reduction of the escape of heat-carrying light radiation, in particular of UV light is the underside of the insulating glass pane preferably also treated by adding a silver-containing Coating is coated. The coating is preferably arranged on the inside of the lower glass pane, which is in the Vacuum space is located.

On This way it prevents the silver-containing coating is exposed to corrosion.

The Thermal in the case can be improved if one upper area of the evaporation surface adjacent to the capacitor arrangement is thermally insulated. In this way the temperature gradient becomes in the upper area of the housing between the air mass above the Evaporationsfläche and the air mass under half of Evaporation area increased, causing too An improved thermals leads without the energy recovery at the condensation from the bottom of the Evaporationsfläche is significantly impaired to the top.

to It is enlargement of the evaporation area advantageous to perform this staircase. A plurality of successive stair step surfaces is at a distance from each other so arranged that each successive Partially overlap staircase surfaces, this leads to a zig-zag staircase. The trailing edge of a respective step step surface is preferably with the overlapping leading edge of the above lying step step surface via a connecting plate connected with each other.

The Evaporation surface is preferably made of a metal sheet formed that low thermal resistance between Has bottom and top of metal sheet.

To the Collecting not only at the bottom of the Evaporationsfläche, but also on the inside of the lid accumulating distillate It is advantageous if on the inside surfaces the glass covers closing the case Condensate drainage channels are arranged, which the distillate laterally divert so that this flow into the collecting container can.

In corresponding way can also gutters at the bottom the Evaporationsfläche be provided.

Farther It is advantageous if at least one flow control valve is provided in the medium circulation circuit, depending on of the temperature in the housing is so controllable that at lower temperature a reduced flow of the medium and at elevated temperature an increased flow the medium takes place. This flow control valve can be over be connected to an electronic control. Is particularly advantageous However, if the flow control valve automatically, for example with the help of a bimetal or a hydraulic expansion body adjusts the flow to the temperature in the housing. In order to is a nearly optimal operation of the solar distillation plant without consuming Control electronics possible. In particular, by the Reduction of the medium inflow at a lower temperature on the Evaporation area ensures that with the available Energy the medium in as large a quantity as possible the vapor phase can pass.

The The invention will be described below with reference to the accompanying drawings explained in more detail. It shows:

1 - Cross-sectional view of a Solardes tilling plant for carrying out the operation control procedure;

2 - Sketch of a zigzag-shaped evaporation surface.

The 1 lets a sectional view of a solar distillation plant 1 with a housing 2 recognize that is preferably formed from a plastic tub or is coated inside with plastic. Such a plastic tub can be made for example of glass fiber reinforced plastic GRP.

The housing 2 has a front and back wall 3a . 3b , unrecognizable side walls and a floor 4 who may be on a foundation 5a . 5b rests. The plastic tub can also be stored on height-adjustable feet. Below the ground 4 may be used to collect distillate as purified fresh water a cistern 6 be provided. For installation and control of inside the case 2 arranged components can be an entry 7 For example, in the back wall 3b be installed.

The top of the case 2 is with a translucent lid 8th locked. The lid 8th is in relation to the ground 4 of the housing inclined, wherein the inclination angle is preferably about 10 ° to 75 °. In the lid, several preferably hinged (insulating) glass windows 9a -E be installed, the lower side via gutters 10 for distillate.

In the case 2 is also a tilted plastic tub 11 for receiving a good thermal conductive Evaporationsfläche 12 installed, which the Evaporationsraum (evaporation space) 13 and the condensation room 14 separates and thermally isolated from each other. The evaporation surface 12 has a fringing edge and a terraced structure, which also has a fleece 15 can be covered. The Evaporationsfläche 12 For example, not shown nozzles via the inner medium circulation circuit primary medium from a pump 16 from a brine tank 17 over capacitors 18 and possibly an inlet channel 19 fed. The terraced structure of the evaporation area 12 as well as the fleece 15 allow almost complete and safe wetting and maximum evaporation of the primary medium in the evaporation room 13 ,

Below the plastic tub 11 in the front of the solar stillness 1 is a distillate collection container 20 intended. The distillate collection container 20 and the distillate drain opening in the plastic tub 11 are not in the area of the lower edge of the plastic container to avoid contamination 11 but are slightly shifted to the right. The in the distillate collection container 20 Collected distillate is then transferred via a pipe to the cistern 6 guided.

For collecting non-distilled medium is in the lower part of the Evaporationsfläche 12 a gutter 21 provided, via a pipeline to the brine tank 17 is guided. The brine tank 17 has an overflow for the discharge of excess primary medium from the brine tank 17 ,

With a float 23 is the feed from the primary medium 24 controlled from the outside of an outer medium circulation circuit in the inner medium circulation circuit (bypass). The fresh medium 25 in the outer medium circulation circuit is via a capacitor 26 and a control unit 27 , z. As a pump, in required subsets in the brine tank 17 guided.

The control unit 27 also serves concentrated brine 28 from the brine tank 17 depending on the inlet of the primary medium 24 derive.

The use of an external medium circulation circuit is optional, but preferred. The derivation of brine concentrate 28 should be done in a ratio that the solubility product of the brine tank 17 dissolved substances is not fallen below. In this way, the crystallization z. B. of salts prevented.

Sunlight is generated in the plastic tub 11 an internal circulation of the air masses around the evaporation area 12 that builds up self-sufficient. This circulation represents a thermodynamic cyclic process, which independently forms between evaporation and condensation and sets itself autonomously. This is the basis for an internal recovery of Evaporationsenergie by the condensation of the primary medium 24 and the consequent heating of the primary medium 24 created. The operation of the solar stillness 1 should be regulated so that the air masses and the brine are circulated in such a way that the evaporation energy on the condensation on the primary medium 24 in the ratio 1: 1 again for evaporation in repeated cycles is provided. In addition, it is advantageous to operate the solar still 1 to move up in three phases.

In a preheating phase, no primary medium is applied to the evaporation surface 12 applied. Instead, the incoming solar energy is used to the interior of the plastic tub 11 heat.

The operating phase is only started when in the upper area of the Evaporationsraums 13 or the Evaporationsfläche 12 a temperature of at least 80 ° C and in the lower part of Evaporationsraums 13 or the Evaporationsfläche 12 a temperature of at least 50 ° C prevails. These are approximate temperatures with a tolerance of about 10 ° C.

In the operating phase then becomes dependent on the temperature on the Evaporationsfläche 12 an optimal amount of the primary medium 24 on the Evaporationsfläche 12 guided so that the largest possible amount of liquid passes into the vapor phase. The water vapor-saturated air masses flow in the upper air volume above the Evaporationsfläche 12 upwards and are led from there due to the resulting air circulation in the air volume below the Evaporationsfläche, where this at the bottom of Evaporationsfläche 12 can condense. In the process, the different specific gravity of the air masses above and below the Evaporationsfläche is exploited.

Furthermore, air circulation is preferably achieved by targeted cooling of the space in the upper region of the evaporation surface 12 Set up to cool air masses from the bottom of the evaporation surface 12 through the evaporation room 13 as a space between Evaporationsfläche 12 and lid 8th to the upper area of the Evaporationsfläche 12 stream. For cooling, preferably fresh primary medium 27 over the capacitor 26 the outer medium circulation circuit is thereby heated and heat energy from the upper region of Evaporationsraums 13 extracts.

This heated fresh medium can either be removed again or in partial quantities or completely via the control unit 27 the brine tank 17 and thus supplied to the inner medium circulation circuit.

The change between the preheating phase and the operating phase and possibly the change between the operating phase and a decay phase can be determined by evaluating a day temperature profile of the temperature in a region within the solar still 1 or the outside temperature. From this daily temperature profile, the expected maximum daily temperature is estimated. An indication of the expected maximum daily temperature value with reasonable accuracy is given by the slope of the rising edge of the temperature history when the temperature rises high in the morning until noon. The operating phase is then started as a function of the instantaneous temperature and the expected maximum daily temperature value. For example, the average daily efficiency of the solar stillness 1 can be increased if at low daily temperature value, the operating phase is already started when reaching a sufficient temperature for distillation, while, for example, a higher limit temperature is provided for starting the operating phase in midsummer at an expected higher maximum daily temperature value and instead the preheating is optimized.

2 leaves a sketch of a zigzag-shaped evaporation surface 12 detect. The surface of the evaporation surface 12 is significantly increased by the fact that the step surfaces 29 the evaporation area 12 are arranged at a distance from each other in parallel so that the adjoining step surfaces 29 partially overlap. The obliquely opposite front and rear edges of the step step surface 29 are about a connection plate 30 closed together so that a substantially closed Evaporationsfläche 12 is created.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3721072 A1 [0002]
• - DE 3829725 A1 [0002, 0003]

Claims (19)

Solar distillation plant ( 1 ) with an upward with a translucent lid ( 8th ) enclosed housing ( 2 ), an evaporation surface ( 12 ) in the housing ( 2 ) on the lid ( 8th ) is aligned so that through the lid ( 8th ) passing through solar energy on an upper surface of the Evaporationsfläche ( 12 ) occurs, with a medium circulation circuit with lines for transporting a liquid medium to be distilled, which in the direction of the top of Evaporationsfläche ( 12 ) aligned openings for conducting medium on the Evaporationsfläche ( 12 ) and with a device for collecting distillate of the medium in the housing ( 2 ) arranged collecting container, characterized in that the Evaporationsfläche ( 12 ) is formed from a non-insulated, heat-conducting material, so that in the condensation of medium at the bottom of Evaporationsfläche ( 12 ) Energy to the top of the Evaporationsfläche ( 12 ) is returned. Solar distillation plant ( 1 ) according to claim 1, characterized in that the volume of air above the Evaporationsfläche ( 12 ) and the volume of air below the Evaporationsfläche ( 12 ) are approximately equal. Solar distillation plant ( 1 ) according to claim 2, characterized in that the difference of the air volume above and below the Evaporationsfläche ( 12 ) is a maximum of 10%. Solar distillation plant ( 1 ) according to one of the preceding claims, characterized in that at least one capacitor arrangement ( 18 ), through which the medium circulation circuit is guided, in the housing ( 2 ) is arranged. Solar distillation plant ( 1 ) according to claim 4, characterized in that a capacitor arrangement ( 18 ) in the upper area of the housing ( 2 ) below the evaporation surface ( 12 ) is arranged. Solar distillation plant ( 1 ) according to claim 4 or 5, characterized in that a capacitor arrangement ( 18 ) in the lower part of the housing ( 2 ) adjacent to the lower edge of the Evaporationsfläche ( 12 ) is arranged. Solar distillation plant ( 1 ) according to claim 4, characterized in that capacitor arrangements ( 18 ) in the housing ( 2 ) above the evaporation surface ( 12 ) and in the lower part of the upper side of the Evaporationsfläche ( 12 ) are arranged. Solar distillation plant ( 1 ) according to one of the preceding claims, characterized in that the housing ( 2 ) is thermally insulated. Solar distillation plant ( 1 ) according to one of the preceding claims, characterized in that the housing ( 2 ) is formed of a fiber-reinforced plastic tub with integrally incorporated insulating material. Solar distillation plant ( 1 ) according to one of the preceding claims, characterized in that the lid ( 8th ) has at least one insulating glass pane. Solar distillation plant ( 1 ) according to claim 10, characterized in that the upper side of the insulating glass pane is roughened to reduce the reflection. Solar distillation plant ( 1 ) according to claim 10, characterized in that the upper side of the insulating glass pane is coated with silicon dioxide. Solar distillation plant ( 1 ) according to any one of claims 10 to 12, characterized in that the underside of the insulating glass pane, preferably the inside of the lower glass pane located in a vacuum space, is coated with a silver-containing coating. Solar distillation plant ( 1 ) according to one of the preceding claims, characterized in that an upper, to a capacitor arrangement ( 18 ) adjacent area of Evaporationsfläche ( 12 ) is thermally insulated. Solar distillation plant ( 1 ) according to one of the preceding claims, characterized in that the Evaporationsfläche ( 12 ) is stair-shaped and has a plurality of successive, spaced apart so arranged stair step surfaces that the successive stair step surfaces partially project beyond. Solar distillation plant ( 1 ) according to claim 15, characterized in that the trailing edge of a respective step step surface with the overlapping leading edge of the overlying stepped step surface are interconnected via a connecting plate. Solar distillation plant ( 1 ) according to one of the preceding claims, characterized in that the Evaporationsfläche ( 12 ) is formed of a metal sheet. Solar distillation plant ( 1 ) according to one of the preceding claims, characterized in that on the in the housing ( 2 ) protruding underside of the lid ( 8th ) Condensate drainage channels ( 10 ), which distillate from the sub side of the lid ( 8th ) derive laterally. Solar distillation plant ( 1 ) according to one of the preceding claims, characterized by at least one flow control valve in the medium circulation circuit, which is dependent on the temperature in the housing ( 2 ) is controlled so that at a lower temperature, a reduced flow of the medium and at higher temperature, an increased flow of the medium takes place.