Method for obtaining water from ambient air

Abstract

The invention relates to a method and a device for obtaining water from ambient air, wherein moisture-laden outside air is drawn in, isothermally compressed and then isothermally expanded in a closed, thermodynamic 4-stroke process, so that the pressure dew point that occurs during compression is below an unlimitedly available "cold sink", typically the ambient air, and the water vapour can be condensed out and collected.

Description

[0001] Process for extracting water from ambient air

[0002] The invention relates to a method and a device for extracting water from the ambient air.

[0003] Human-induced climate change leads to constantly rising global average air temperatures through the emission of greenhouse gases, and thus automatically to higher evaporation rates over oceans, waterways, forests and wetlands.

[0004] Since water vapor, as a “natural greenhouse gas,” occupies a dominant position in the mixture of atmospheric greenhouse gases, accounting for approximately 60%, this anthropogenically caused chain of effects is self-igniting, because with every unit of fossil fuel burned, the CO2 content in the atmosphere increases, along with the ambient temperature and, as a result, water evaporation.

[0005] If we also consider the fact that 0.63 kWh of energy is required to evaporate 1 liter of water, and that this "latent energy" is released in the same amount as heat when the invisible water vapor condenses in the form of rain, snow, or hail, we understand the fundamentals of rapidly and chaotically developing global weather patterns. To put this phenomenon into perspective, it is useful to realize that 20.6% of the total solar energy radiating onto our planet is used to evaporate water. The average solar energy radiated onto the surface of our planet is 1.5 x 10 to the power of 18 kWh.

[0006] This means that the evaporation work constantly performed by the sun is approximately 2000 times the total energy demand of humanity! Or, to put it another way: all earthly power plants and energy generation facilities would have to be increased by a factor of 2000 to replace this free service provided by the sun.

[0007] The 0.2% of solar radiation converted into wind, which disperses the water vapor produced by the sun in the atmosphere, is insignificant, yet corresponds to 20 times the output of all earth's power plants. They nevertheless play a crucial role, because the changing "transportation pathways" in the global climate—and thus in local weather systems—are the primary cause of the rapidly deregulating system, necessitating the adaptation of human habitats to ever more extreme contrasts in extremely short periods of time: arid drought and heat on the one hand, torrential rain on the other.

[0008] How could it be otherwise: Due to the described interactions, gigantic amounts of additional water vapor enter the atmosphere, and when it condenses, equally enormous amounts of energy are released, according to the laws of nature! These values ​​also demonstrate how inexorably life on our planet depends on its central star, the sun, because water is, quite literally, the basic prerequisite for our earthly life.

[0009] Even the greatest supporter and optimist of man-made technological progress as a solution to all current problems might be stumped if they tried to imagine how, even with the fusion reactor, which some consider "humanity's future energy source," the current earthly energy production potential could be multiplied by a factor of 2000, thus replacing the "sun as a freshwater machine." And with a little realism, especially considering the rare raw materials required for this and, as a direct consequence, the resulting price of the energy generated, they would inevitably come to the conclusion that they would be far better off trying to reclaim the water vapor produced by the great, celestial fusion reactor in the form of liquid fresh water.And this is precisely what the human inventive spirit offers itself when it seriously considers the future and the necessary correction of the anthropogenically created imbalance between technology and nature.

[0010] The rising water vapor content in the atmosphere, this frightening cause of climate change, therefore also has a positive side: It means that it is fundamentally easier to extract fresh water from the air. At first glance, the water content in the form of water vapor in the air appears disappointingly dilute when compared to the concentrated form of water from springs, lakes, and rivers. However, humans are increasingly and irresponsibly polluting these, primarily with industrial wastewater and nitrogen from agriculture; this necessitates, among other things, costly sewage treatment plants. This is one reason why seawater desalination is gaining increasing interest: the water reserves in the oceans are incomparably greater than those in freshwater reservoirs, but it suffers from the disadvantage that the salt must be removed from the water at great expense for human consumption.

[0011] This disadvantage does not apply to the water vapor content of the atmosphere, because the sun has already desalinated the atmosphere free of charge through the evaporation process. Although the water vapor content of the air in the dry regions of the Earth is on average approximately 5 grams / m 3 comparatively low, but per km 3 The volume of air contains a quantity of water that – assuming 25 liters of drinking water per person – is capable of supplying 2 million people with water. Considering how many cubic kilometers of air are above every area of ​​the Earth, one can see the water potential in the "transparent

[0012] It also becomes clear that, given this practically ubiquitous potential for almost all types of applications, it is much more sensible to use this freshwater source in a decentralized manner, rather than centralizing it in traditional large-scale facilities (reservoirs, desalination plants, sewage treatment plants, etc.) and transporting it to distant consumers at great expense. This is especially true for the Earth's large semi-arid and arid regions.

[0013] If we succeed in finding not only practical but also economically competitive systems, interesting possibilities will open up, especially for areas with a high specific water vapor content (typically coastal areas with high solar radiation), to replace the dominant seawater desalination plants with high external energy requirements and environmental damage (discharge of the remaining brine into the sea) with the direct freshwater extraction of water from the air.

[0014] The rapidly changing equilibrium states of global weather patterns, due to the anthropogenic contribution of greenhouse gases, are forcing humans and nature to adapt on ever shorter timescales. While "nature" will manage this regardless of time pressure through slow adaptation, without the threat of complete destruction as has often been the case, human civilization as a whole is potentially threatened.

[0015] As always, this threat also presents an opportunity. Just as it is (finally) becoming increasingly clear that only the use of solar energy can meet humanity's diverse needs in the long term, it makes sense to also consistently utilize an important component of solar energy: the water vapor in the atmosphere.

[0016] However, the described decentralized extraction of water from the atmosphere and its use for reforestation and in widespread permaculture systems creates the possibility that semi-arid and arid regions will gradually develop their own natural microclimate with local precipitation over time. In this respect, the described atmospheric water extraction techniques would primarily serve as temporary regulators for restoring desired weather conditions. Therefore, it is vital to find and develop suitable methods for extracting water from the air.

[0017] Two main methods, each with a variety of implementations, come into consideration:

[0018] 1 . Methods for local dew point undershoot.

[0019] 2. Methods of sorption-desorption of water vapor on hydrophilic materials.

[0020] The dew point method is based on the fact that air can only absorb a limited amount of water vapor (the absolute water content in grams per cubic meter of air) depending on its temperature. If this limit is exceeded, the water vapor spontaneously condenses into liquid water.

[0021] The conditions are shown in Fig. 1 as a dew point curve.

[0022] Fig. 2 shows the pressure dew points as a function of pressures from 1 bar to 50 bar.

[0023] From Fig. 1, for example, it can be seen that typically in an area such as the Iberian Peninsula, where in large parts during the summer “North African 1 ' Weather conditions (very hot days, significantly cooler nights) prevail, but also relative humidity of about 70%, and therefore absolute humidity of about 15 g / m 3 air and 25 g / m 3air, temperatures between 17 °C and 25 °C already fall below the dew point of the air; such temperatures already occur on some summer nights, which is manifested by the formation of dew.

[0024] The situation is quite different in dry deserts with relative humidity of approximately 2% to 5%. The resulting absolute humidity of a few grams / m 3 Air dew point temperatures range from approx. +2 °C to approx. -10 °C.

[0025] It can be seen that it is relatively easy to extract water from the air using the local dew point method in areas such as the Iberian Peninsula, but, although the principle is essentially the same, it is significantly more difficult to apply it in extremely dry desert areas.

[0026] Internationally, there are major efforts to reduce the temperature below the dew point, taking advantage of the fact that the atmosphere has a “second window” in the range between approximately 8 micrometers and 14 micrometers, through which, according to Boltzmann’s radiation laws and Wien’s displacement law, black bodies can exchange radiation with the cold of extraterrestrial space, thereby producing a theoretical maximum cooling capacity of approximately 100 W / m 2 cool to temperatures theoretically as low as -18 °C.

[0027] In Fig. 3b the relationships of the “T to the power of 4 radiation” through the second atmospheric window are shown schematically.

[0028] In reality, however, we are still far from reaching these potential limits. Therefore, there is a wide field for the use of active chillers, such as refrigeration compressors, absorption chillers, Peltier coolers, and other active cooling methods. These naturally complicate the corresponding systems, and consequently, the price of the extracted freshwater increases.

[0029] The second technology, developed in a variety of forms, is the sorption and desorption method. This method utilizes the fact that certain substances have the ability to adsorb water vapor (sorption) and release it again with the appropriate supply of heat (desorption). Because the escaping water vapor is at an elevated temperature, its condensation is not subject to the restrictions that apply to the local dew point method. Silica gels, zeolites, and certain metal-organic solid materials (MOF), as well as liquid sorbers such as salt solutions (LiCl) or acids, are used.All of these methods are relatively complex in their overall configuration, depending on their performance, since they combine chemical and thermodynamic principles and the individual efficiencies of the various components, due to their multiplication to the overall efficiency, make it relatively difficult to achieve high efficiency and correspondingly low production costs for the water extracted from the atmosphere.

[0030] The invention is based on the object of proposing a method and a device with which the extraction of water from the ambient air can be carried out in a simple manner.

[0031] With regard to the method, the object is achieved by the features of claim 1. Embodiments of the method are described in claims 2, 3 and 4.

[0032] With regard to the device, the problem is solved by the features of claim 5 or—in a reversal of the movable components—by the features of claim 6. Embodiments of the two equivalent solutions can be found in claims 7 to 14.

[0033] The present invention of the "sky milker" and the corresponding process is based on a purely thermodynamic machine, or in other words: It uses a purely thermodynamic process to circumvent the dew point temperature problem of classical methods for lowering the dew point. According to the invention, the dew point temperature is increased by isothermal compression of the water vapor-containing air in such a way that the resulting "pressure dew point" lies above the prevailing air temperature or another easily accessible "cold sink." Examples of this are mentioned in the claims.

[0034] The physical basis for this process is given by the Boyle-Mariotte law:

[0035] P • V = const. At a given temperature

[0036] Boyle's law, which is formulated for ideal gases but also applies to air and water vapor to a good approximation, states that the pressure of an air-water vapor mixture enclosed in a cylinder with a moving piston is inversely proportional to the volume, assuming a constant amount of substance and an isothermal change of state. For a space sealed by the piston, the "constant amount of substance" condition is easily met.

[0037] However, even experience with simple air-piston systems (bicycle pumps) shows that the process is by no means "isothermal," meaning it occurs at a constant temperature, but rather that considerable heat is generated during the compression of the air, and a significant cooling is observed during the subsequent expansion of the same air. Therefore, the first inventive technical development step must be to realize a piston-air-steam arrangement in such a way that the gas mixture, constantly alternating between compression and expansion, passes through these states isothermally (isothermalization of the real process).

[0038] The invention is explained in more detail with reference to the following figures. They show:

[0039] Fig. 1: a representation of the dew point curve,

[0040] Fig. 2: a representation of the pressure dew point curve family,

[0041] Fig. 3a: a sketched representation of the permeability of the atmosphere to radiation as a function of wavelength,

[0042] Fig. 3b: the formulas for Wien’s law and Boltzmann’s law,

[0043] Fig. 4: a cross-section through a first embodiment of the device according to the invention when sucking in moisture-laden ambient air,

[0044] Fig. 5: a cross-section through the embodiment of the device according to the invention shown in Fig. 1 during the isothermal compression of the sucked air and the condensation of the air water vapor,

[0045] Fig. 6: a cross-section through the embodiment of the device according to the invention shown in Fig. 1 during isothermal expansion, Fig. 7: a cross-section through the embodiment of the device according to the invention shown in Fig. 1 during the expulsion of the dried air and the water separation,

[0046] Fig. 8: a cross-section through a second embodiment of the device according to the invention when sucking in moisture-laden ambient air,

[0047] Fig. 9: a cross-section through the embodiment of the device according to the invention shown in Fig. 8 during the isothermal compression of the sucked air and the condensation of the air water vapor,

[0048] Fig. 10: a cross-section through the embodiment of the device according to the invention shown in Fig. 8 during isothermal expansion,

[0049] Fig. 11: a cross-section through the embodiment of the device according to the invention shown in Fig. 8 during the expulsion of the dried air and the water separation, and

[0050] Fig. 12: a representation of a normalized stroke-pressure diagram.

[0051] Before the technical implementation is described in more detail using Figs. 4, 5, 6 and 7, the rationale behind the function of the "sky milker" is illustrated here using Fig. 1 and Fig. 2. The idea is to achieve a pressure dew point for every conceivable climatic situation through isothermal compression, which allows the use of high ambient air temperatures as a "cold sink" to condense the water vapor from the ambient air.

[0052] A typical extreme example: The dew point curve (Fig. 1) shows that in a desert with only 2.3 g water / m 3 The air temperature must fall below -7.5 °C for atmospheric water to condense. However, air temperatures of only 40 °C would be available during the day, and 20 °C at night (significant cooling due to the clear night skies in deserts).

[0053] The dashed vertical line in Fig. 2, which runs vertically upwards from the abscissa at -7.5 °C, intersects a set of straight lines, where each individual line represents a defined pressure at which the air-water vapor mixture is isothermally compressed. If one now moves horizontally to the left from the respective intersection point of the vertical line with any line, the intersection point of this horizontal line with the ordinate marks the respective valid "pressure dew point" temperature, below which water vapor condensation occurs.

[0054] So in the present case, during the day, at an air temperature of 40 °C, the isothermal compression of the initial volume under 1 bar pressure to 20 bar and 1 / 20 volume would lead to the dew point being undercut below 42 °C, whereby "hot" ambient air of 40 °C already allowed the "milking of the sky".

[0055] However, if one wanted to extract water during the night when air temperatures were only 25 °C and the same absolute humidity, a compression to 10 bar would be sufficient so that the outside air temperature below the pressure dew point temperature of 28 °C could be used to condense the water.

[0056] Another extreme example is found in the coastal areas of hot arid or tropical zones. Here, with day and night air temperatures of around 30 °C remaining almost constant, absolute humidity levels of 25 grams of water / m 3 air and more, occur.

[0057] Fig. 1 shows that in this case – under atmospheric pressure – the dew point temperature is 26.3 °C, and that the ambient air temperature of 30 °C would therefore be too high for water vapor to condense. If, for this case, a vertical line is drawn upwards in Fig. 2 (a dashed line), starting at the temperature of 26.3 °C on the abscissa, it can be seen that even an isothermal compression to 2 bar is sufficient for the dew point temperature to rise to 38 °C, thus causing the available ambient air temperature of 30 °C to condense.

[0058] Since weather parameters such as humidity and air temperatures vary greatly both in terms of time at a given location and in terms of location, it is important for the present invention that the best compression factor adapts adaptively to the external conditions.

[0059] How this happens is explained in the following figures. Figures 4, 5, 6, and 7 represent a schematic cross-sectional view of the 4-stroke operating sequence of a "sky milker" machine according to the invention.

[0060] The four bars are:

[0061] 1 . Intake of moisture-laden outside air, Fig. 4

[0062] 2. Isothermal compression of the sucked air, condensation of the air-water vapor, Fig. 5

[0063] 3. Isothermal expansion, recovery of compression energy, Fig. 6

[0064] 4. Expulsion of the dried air, water separation, Fig. 7.

[0065] In Fig. 4 (as well as in the following figures), the main components of the "sky-milker" system are schematically illustrated. (1) is the "water reactor cylinder," 2 the associated working piston, which is connected to the flywheel (3) via the connecting rod (3a). Reference numeral 4 denotes the drive motor of the piston-cylinder unit. As will be explained in more detail in the description of Fig. 6, this only has to compensate for minor friction losses and a similarly small reduction in the recovery of compression energy, since the flywheel fully smooths out the inversely equivalent compression and expansion energies.

[0066] Reference numeral 5 designates plates (or tubes) rigidly connected to the oscillating piston 2. Through their reciprocating movement within the water volume 6, which fills part of the cylinder 1, they are capable of very efficiently transferring heat generated during the compression of the air-water vapor volume and the condensation of the contained vapor, as well as cold generated during the expansion of the air, into the water volume and extracting it from the water volume.

[0067] With correct dimensioning of the total area of ​​the thin plates 5 and the water volume 6 with a much larger heat capacity compared to the air-water vapor volume, the described 4-stroke thermodynamic cycle can be practically isothermal.

[0068] Reference numeral 7 represents the hose for the temporary connection to the outside air. Reference numeral 7a denotes the check valve that opens automatically upon air intake, while reference numeral 7b denotes the check valve that opens automatically upon air exhaust. Reference numeral 7c represents the process-controlled valve built into piston 2. It ensures that the air-water vapor mixture is hermetically sealed within the cylinder during the compression and expansion phases.

[0069] Reference numeral 8 denotes an external cooler. This serves to transfer the condensation heat transferred into the water volume 6 to the outside air.

[0070] If - in special cases - a free temperature sink with a significantly lower temperature than that of the ambient air is available (examples: seawater, when water is to be extracted from the very humid air in the immediate vicinity of the sea; or in very hot, dry areas, when cool air is taken from underground air ducts, for example), the temperature in the "water reactor" can be reduced via the cooler 8 so that water precipitates even at a lower degree of compression.

[0071] The water extracted from the air precipitates on the surface of the plates 5 and trickles from there into the water volume 6. A level switch 9 ensures that during phase 4 of the process (Fig. 7 or Fig. 9 - expulsion of the dried air) the valve 9a opens and the extracted water flows into the water collection container 10.

[0072] The compression ratio can be continuously adjusted to the locally changing temperature and humidity conditions of the ambient air via the water level in the cylinder. For this purpose, the corresponding digital signals from sensor unit 11a are exchanged with processor 11b.

[0073] Processor 11b calculates the lowest possible compression ratio to reach the pressure dew point under the prevailing conditions such that condensation already occurs at a temperature slightly above the prevailing outside air temperature. In an automated process, this occurs adaptively, with the signals from sensor unit 11a or processor 11b being fed to the movable level monitor 9b, valve 9a, and charge pump 11, which then perform the automatic adjustment control in conjunction with the components. The air mass flow and the frequency of the process are then practically constant throughout the changes.

[0074] Air temperatures and humidity levels change very slowly, especially in semi-arid and arid target countries. Therefore, in these cases, a manual adjustment based on measured temperature and humidity values ​​over a longer period of time is usually sufficient. This particularly simplifies small, decentralized "sky milking" systems in rural (village) regions.

[0075] The following is a description of the 4 working cycles of the “Sky Milker” machine with additional explanations.

[0076] The first power stroke 1 is shown in Fig. 4 (analogous to Fig. 8): Moisture-laden outside air is drawn in. The flywheel-motor arrangement 3, 4 moves the working piston 2 via its connecting rod 3 to its top dead center. Moist outside air is drawn via the air hose 7 and the open valve 7c into the volume above the water volume 6 in the working cylinder 1. During this process, the air flap 7a opens automatically, and the air flap 7b closes automatically. The line cross-sections and their shapes are dimensioned in function of the air mass flow to minimize friction losses. The same applies to the opening cross-section of valve 7c.

[0077] The second power stroke can be seen in Fig. 5 (or Fig. 9): isothermal compression of the intake air and condensation of the air-water vapor. The working piston 2 is moved downward by the flywheel-motor arrangement 3, 4 until it reaches bottom dead center. This compresses the trapped, moist air volume. Valve 7c is closed.

[0078] The compression process is, to a good approximation, isothermal, since the large surface areas of the plates 5 immersed in the water bath below efficiently transfer the resulting compression heat into the cool water. Two properties of the plates are crucial here:

[0079] 1. Their good thermal conductivity due to their materials and thickness (preferably copper or aluminum). 2. The excellent heat exchange that occurs between the surface of the dynamically oscillating plates immersed in the water and the water volume.

[0080] This can be further improved by appropriate structuring of the plate surfaces.

[0081] The compression ratio required to reach the pressure dew point and thus cause the condensation of the water vapor contained in the air is determined by correlating the current real values ​​of air temperature and humidity measured by sensor unit 11a via processor 11b. The physical relationships were described at the beginning.

[0082] The determined compression ratio is actually realized by varying the water volume 6 in the manner described.

[0083] Since the plate surfaces immersed in the air have temperatures 5 below the pressure dew point, the water vapor in the air condenses on them.

[0084] The process is strongly supported by the following conditions:

[0085] - The relative movement between air and plates

[0086] - The large-sized contact area between air and plates

[0087] To ensure that the water condensing on the plate surface can flow smoothly down along the plates into the water volume, two further measures are useful:

[0088] - Coating the plate surfaces with a very thin, hydrophobic layer. Fluoropolymer layers in the micrometer thickness range are particularly suitable for this purpose; these can be produced, for example, by dipping them into liquid fluoropolymer solutions.

[0089] Structuring of the surfaces with microstructures ("lotus effect"); these also ensure easy, even water drainage and also improve (see above) the heat exchange between air, plates, and water. The water condensed from the air flows, as described, into the water volume 6. Here, it leads to an increase in volume, which is detected by the level monitor 9 and periodically fills the water collector 10 via the valve 9a. To compress the compressible air-water vapor mixture as desired, volume work must be performed.

[0090] In the case of isothermal compression, the process is in principle reversible, i.e. the compression energy stored in the “spring” of the gas (Fig. 5, Fig. 9) is released again when the gas expands to its initial state (Fig. 6, Fig. 10).

[0091] In the present real case, this ideal state is achieved to a good approximation. This is primarily due to the described "isothermalization" of the process through the inventive heat conduction and distribution of the air heat generated during the compression and expansion phases through the described plates (5) into the high heat capacity water volume (6), which is maintained at a nearly constant low temperature.

[0092] The reduction due to the fact that the air-water vapor mixture is not an "ideal gas" is negligible. The other significant, irreversible losses in the described system arise from dynamic air friction and the friction of the piston seal. In the first case, this loss can be minimized, as already described, by appropriate cross-sections and shapes of the air-conducting structures, including the valves. For the piston seal, a diaphragm seal can be used instead of traditional piston ring seals – advantageously and with significantly lower friction forces. A very small component of the irreversibility of the compression energy is that the extraction of the (relatively small) water vapor content in the air-water vapor mixture results in slightly less restoring force.

[0093] The recovery of as much of the compression energy as possible in the 4-stroke process of the "Himmels Melker" represents an essential component of the present invention. Without it, the full compression energy would have to be realized by external energy via the engine 4; this would work, but would have a severely negative impact on the economics of the process.

[0094] The fundamentally simple method of recovering compression energy (power stroke 2, Fig. 5 or Fig. 9) is to use a flywheel that stores the expansion energy and returns the necessary compression energy (both energies are identical in the isothermal case). The flywheel should be designed so that the torque is sufficiently uniform throughout the entire 4-stroke cycle; this protects the drive motor 4 and all components subject to force and alternating pressure.

[0095] The standardized “pressure and stroke diagram” in Fig. 12 of the “sky milker” shows the alternating loads occurring during the entire cycle.

[0096] The 4 beats of the cycle unfold over the course of two rotations in function of the angle of rotation and the 4 phases as follows:

[0097] 1 . From 0° to 180° air intake

[0098] 2. From 180° to 360° isothermal compression and moisture condensation

[0099] 3. From 360° to 540° isothermal expansion

[0100] 4. From 540° to 720° (4*Pi) air expulsion and water expulsion

[0101] The essential additional energy to compensate for the described irreversible losses of the cycle is coupled into the flywheel via motor 4.

[0102] Sky-milking systems are primarily needed in sunny regions. Therefore, it makes sense to provide the required additional energy from the abundant, free solar energy. A pragmatic solution is the use of photovoltaic panels to operate engine 4, which in this case is designed as an electric motor. If the system is to extract water from the air at night, as described, the photovoltaic panels must also be supplemented by an electrical battery storage system. A fundamentally more effective solar drive unit consists of a solar low-temperature Stirling engine with a thermal night storage unit; in this case, the flywheel of the Stirling engine can be coupled directly to the flywheel of the sky-milking machine, making sensitive and costly electronic components obsolete.

[0103] The third power stroke (Fig. 6, Fig. 10) is the isothermal expansion. During this power stroke, all valves are closed; the "spring energy" stored in the compressed air volume propels piston 2 upward. The expansion energy is stored in the flywheel 3. The gas, which cools during expansion, undergoes this process isothermally thanks to the plates 5; this corresponds in function to the reverse process described for compression (power stroke 2, Fig. 5 and Fig. 9).

[0104] The fourth working stroke (Fig. 7 or Fig. 11) consists of expelling the dried air and separating the water. With valve 7c, check valve 7b, and valve 9a open, piston 2 moves downward, driven by flywheel 3, forcing the dried air through hose 7 into the outside space. The extracted water, whose level is detected by level switch 9, flows through valve 9a into the collection tank 10.

[0105] The expelled dry air, after appropriate solar reheating, can be used for solar drying of agricultural products. This is particularly useful when the "sky milker" supplies water for "desert greenhouses" in arid regions and medicinal plants grown there are to be dried for preservation.

[0106] The system according to the invention for the thermodynamic extraction of water from the atmosphere thus described is shown in a preferred configuration in Figures 4 to 7. Taking into account the essential system parameters described, variants such as those shown in Figures 8 to 11 can also be implemented. In this variant, the water is moved relative to the stationary plates. This provides more freedom in the dimensioning (length) of these plates. However, in this case, the greater inertia of the entrained water column must be taken into account. Thus, for the technically knowledgeable, various embodiments are possible, both in terms of geometries, the selected materials, and the type of additional drive. However, they are all subject to the points formulated below in the claims of the invention.

[0107] Finally, an estimate of possible dimensions and applications of the “sky milker”.

[0108] As an example unit, a device with the following system parameters is selected:

[0109] • Volume of the air part: 10 liters

[0110] • Volume of the water part: 10 liters

[0111] • Operating frequency: 1 Hz

[0112] The aim is to determine the amount of freshwater generated per day (24 hours) for three typical cases. Three climate zones are considered:

[0113] 1. Arid (desert) climate with 5 g water / m 3 Air.

[0114] 2. Mediterranean climate with 10 g water / m 3 Air.

[0115] 3. Humid-hot coastal climate with 30 g water / m 3 Air.

[0116] The system processes 432 m in 24 h 3Ambient air. This yields 2.16 liters of fresh water in a desert climate, 4.32 liters in a Mediterranean climate, and 13.0 liters in a hot, humid coastal climate.

[0117] The example was deliberately chosen to show that even very small systems, typically as “survival systems” for (desert) expeditions and similar extreme situations, seem to make sense.

[0118] However, it can also be seen that the system can be scaled up to medium-sized systems (e.g., supplying residential units, medical facilities, hospitals) and large-scale systems (e.g., farms, oases, replacing seawater desalination plants) in a compact and modular design (combining "N" basic modules, whereby the basic modules can have significantly larger "air intake volumes" than the 10-liter system mentioned in the example). The operating frequency used in the example can also generally be higher than 1 Hz. This makes it possible to increase the water yield linearly with the frequency. Another important feature of the "sky milker" not yet mentioned is that, due to its design, it does not require fans, unlike many other types of air-based water extraction systems, to introduce the air to be dehydrated into the system. "Sky milker" systems are "self-breathing."Finally, it should be noted that by removing water vapor from the atmosphere, the “natural greenhouse effect” produced by water vapor is reduced.

Claims

Patent claims 1 . A process for extracting water from ambient air, wherein, in a closed, thermodynamic 4-stroke process, moisture-laden outside air is sucked in, isothermally compressed and then isothermally expanded, so that the pressure dew point resulting from compression is below an unlimitedly available "cold sink", typically the ambient air, and the water vapor is condensed and collected.

2. A method according to claim 1, wherein the energy to be supplied to a system during the isothermal compression phase is almost completely recovered in a system during the isothermal expansion phase, so that for continuous operation a small amount of external energy is required to compensate for irreversible losses such as friction and volume change due to water vapor removal.

3. Method according to claim 1 or 2, wherein the isothermalization of compression and expansion phases is achieved by an arrangement of plates (5) and / or tubes in good thermal contact with both the air and a defined volume of water (6) in a working cylinder (1) in that the plates (5) release the heat generated during the compression phase or the cold generated during the expansion phase to a water bath (6) kept at a low temperature level and thus the air is also kept isothermally at approximately this level.

4. Method according to one or more of claims 1-3, wherein the four working strokes are the following: - Suction of moisture-laden ambient air Isoterm compression of the sucked air and condensation of the air-water vapor - Isothermal expansion and recovery of compression energy - Expulsion of dried air and water separation.

5. Apparatus for carrying out the method described in claims 1-4, wherein a closed system is provided with a working cylinder (1) in which a water bath (6) is located, and with a plurality of plates (5) made of a thermally conductive material, wherein the plates (5) are arranged such that they form a closely spaced arrangement of large-area heat exchangers arranged essentially parallel to one another, which are rigidly connected to a working piston (2), and wherein a mechanism acting on the working piston (2) is provided, via which mechanism the plates (5) cyclically dip into and out of the water bath (6), so that the heat exchange takes place through the resulting relative movement between the plates (5) and the water bath (6).

6. Device for carrying out the method described in claims 1-4, a closed system with a working cylinder (1) in which the water bath (6) is located, and with a plurality of plates (5) made of a thermally conductive material, wherein the plates (5) are arranged such that they form a closely spaced arrangement of large-area heat exchangers arranged essentially parallel to one another, wherein the plates (5) are arranged stationary in the working cylinder, and wherein a mechanism acting on the working piston (2) is provided so that the working piston moves the water bath up and down in an oscillating manner.

7. Device according to claim 5 or 6, wherein the plates (5) are coated with a thin hydrophilic layer and / or have a micro-structure so that the condensing water vapor can flow over the entire surface into the water bath (6).

8. Device according to one or more of the preceding claims 5-7, wherein the working piston (1) is connected to a flywheel (3) via a connecting rod (3a) and wherein the flywheel (3) has a sufficiently large mass inertia to generate a sufficiently uniform torque over the four working strokes.

9. Device according to one or more of claims 5-8, wherein a controllable mechanism is provided which makes it possible to continuously change the compression factor of the air to be dewatered by varying the volume of the water bath (6) in the working cylinder (1).

10. Device according to one or more of claims 5-9, characterized in that a processor (11b) is provided which determines the optimal compression factor at a given time by correlating the outside air humidity and temperature measured by sensors (11a), wherein the processor (11b) calculates the pressure dew point such that the ambient air temperature serves as a "cold sink" for the water vapor condensation.

11. Device according to one or more of claims 5-10, wherein a mechanism, preferably consisting of a charging pump (11), an outlet valve, an external water reservoir (12) and a level monitor (9), is provided, which automatically adjusts the compression factor predetermined by the processor (11b) by targeted inflow or outflow of water.

12. Device according to one or more of claims 5-11, wherein an electric motor operated by a photovoltaic module is provided, which provides the required additional energy to a flywheel, and wherein, if necessary, a battery is additionally provided, so that continuous operation is possible even in the absence of solar energy.

13. Device according to one or more of claims 5-11, wherein a (low-temperature) Stirling engine is provided which transfers the required additional energy of the flywheel (3) directly mechanically to the flywheel (3), and wherein, if necessary, a thermal storage device is provided for the purpose of supplementation, so that continuous operation is possible even in the absence of solar energy.

14. Device according to one or more of claims 5-13, wherein instead of the ambient air, another cold sink of more favorable temperature, such as sea water or cool air from caves or underground channels, represents the reference temperature for the pressure dew point, which leads to the necessary compression factor being lower than in the case of using the ambient air.

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