MEMBRANE-BASED DESORPTION COOLING METHOD FOR PASSIVE THERMAL MANAGEMENT

Abstract

A membrane-based desorption cooling method for passive thermal management is presented. The module includes: (i) a covering layer for thermally conducting and transferring heat from a device to a solution; (ii) a solution layer for confining H.sub.2O/absorbent mixtures in a multi-compartment frame; (iii) a membrane layer configured to act as an interface between the solution and air; and (iv) a supporting layer configured to increase the mechanical strength and including apertures to permit mass transfer from the membrane through the supporting layer. The present membrane-based desorption cooling module is able to be used for thermal management of solar photovoltaic (PV) panels, electronics, batteries, or any other devices that require heat removal.

Claims

1. A membrane-based desorption cooling module, comprising: a covering layer for thermally conducting and transferring heat from a device to a solution; a solution layer for confining H.sub.2O/absorbent mixtures in a multi-compartment frame; a membrane layer configured to act as an interface between the solution and air; a supporting layer configured to increase the mechanical strength and including apertures to permit mass transfer from the membrane layer through the supporting layer.

2. The membrane-based desorption cooling module according to claim 1, wherein the solution layer is disposed between the covering layer and the membrane layer so as to connect the covering layer to the membrane layer.

3. The membrane-based desorption cooling module according to claim 2, wherein the multi-compartment frame includes an array of metal walls acting as fins to facilitate heat transfer.

4. The membrane-based desorption cooling module according to claim 3, wherein the metal walls extend from the covering layer to the membrane layer.

5. The membrane-based desorption cooling module according to claim 1, wherein the supporting layer is in contact with the membrane layer to abut against the membrane layer.

6. The membrane-based desorption cooling module according to claim 1, wherein the membrane layer is a microporous polymeric membrane.

7. The membrane-based desorption cooling module according to claim 6, wherein the microporous polymeric membrane is polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), combinations thereof, or their composites, and other porous materials.

8. The membrane-based desorption cooling module according to claim 1, wherein the membrane layer is impermeable to liquids.

9. The membrane-based desorption cooling module according to claim 1, wherein only vapor is allowed to pass through the membrane layer.

10. The membrane-based desorption cooling module according to claim 1, wherein the supporting layer is a hollow-plate supporting layer.

11. The membrane-based desorption cooling module according to claim 1, wherein the membrane layer is 50-200 μm thicknesses, 0.4-0.8 porosities, and 0.2-2.0 μm pore diameters.

12. The membrane-based desorption cooling module according to claim 1, wherein the H.sub.2O/absorbent mixture including H.sub.2O/salt solutions, H.sub.2O/ionic liquid solutions, other H.sub.2O/absorbent solutions, or their mixtures.

13. The membrane-based desorption cooling module according to claim 12, wherein the H.sub.2O/salt solutions further comprising LiBr, LiCl, CaCl.sub.2, KBr, NaOH, and KOH; and wherein the H.sub.2O/ionic liquid solutions further comprising [DMIM][DMP], [EMIM][Ac], [BMIM][BF.sub.4], [BMIM][Br], [DMIM][Cl], and [EMIM][EtSO.sub.4].

14. The membrane-based desorption cooling module according to claim 1, wherein the membrane-based desorption cooling module has a cuboid-shape channel therein, and the covering layer defines a boundary of the cuboid-shape channel.

15. The membrane-based desorption cooling module according to claim 14, wherein the supporting layer is farther from the cuboid-shape channel than the covering layer, the solution layer, and the membrane layer.

16. The membrane-based desorption cooling module according to claim 1, wherein the membrane-based desorption cooling module has a cylindrical-shape channel therein, and the covering layer defines a boundary of the cylindrical-shape channel.

17. The membrane-based desorption cooling module according to claim 14, wherein the supporting layer is farther from the cylindrical-shape channel than the covering layer, the solution layer, and the membrane layer.

18. The membrane-based desorption cooling module according to claim 1, further comprising: a condensation chamber integrated at a bottom of supporting layer for water harvesting during desorption.

19. A membrane-based desorption cooling module, comprising: a covering layer for thermally conducting and transferring heat from a battery to a solution, wherein the covering layer is configured to define an outer boundary of a channel in the membrane-based desorption cooling module; a solution layer for confining H.sub.2O/absorbent mixtures in a multi-compartment frame; a membrane layer configured to act as an interface between the solution and air; a supporting layer configured to increase the mechanical strength and including apertures to permit mass transfer from the membrane layer through the supporting layer.

20. The membrane-based desorption cooling module according to claim 19, wherein the solution layer surrounds the covering layer, the membrane layer surrounds the solution layer, and the supporting layer surrounds the membrane layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a structure overview of the membrane-based desorption cooling module.

[0028] FIG. 2 depicts a membrane-based moisture desorption process in the daytime and may be used for PV thermal management.

[0029] FIG. 3 depicts a membrane-based moisture absorption process at night and may be used for PV thermal management.

[0030] FIG. 4 depicts a membrane-based desorption cooling module with water harvesting and may be used for PV thermal management.

[0031] FIG. 5 depicts a membrane-based desorption cooling module for electronics thermal management.

[0032] FIG. 6 depicts a membrane-based desorption cooling module for battery thermal management (cuboid battery).

[0033] FIG. 7 depicts a membrane-based desorption cooling module for battery thermal management (cylindrical battery).

[0034] FIG. 8 shows a comparison of different passive cooling methods.

[0035] FIG. 9 shows dynamic PV temperatures with and without desorption cooling module.

[0036] FIG. 10 depicts the dynamic temperatures of PV panels with direct dissipation, H.sub.2O/LiBr module, and H.sub.2O/IL module.

[0037] FIGS. 11A and 11B depict the simulation results of a membrane-based desorption cooling module for PV thermal management. FIG. 11A illustrates the evolution of temperature with time of the module with different solution layer thicknesses. FIG. 11B illustrates the concentration maps of the module with different solution layer thicknesses.

[0038] FIGS. 12A to 12E present the experimental studies of the membrane-based desorption cooling module for PV thermal management. FIG. 12A shows the setup for laboratory measurement. FIG. 12B presents the temperature test results obtained through laboratory measurement. FIG. 12C presents the temperature fields measured by an infrared camera. FIG. 12D shows the setup for field measurement. FIG. 12E presents the temperature test results as measured in outdoor environment.

[0039] FIG. 13A demonstrates the experimental prototype of a membrane-based desorption cooling module for battery thermal management module. FIG. 13B presents the temperature test results obtained with different hygroscopic solutions used in the module prototype.

[0040] FIGS. 14A and 14B illustrate the experimental studies for a membrane-based desorption cooling module prototype for electronics thermal management. FIG. 14A presents the surface temperatures of electronics with the module prototype with different solution thicknesses. FIG. 14B presents the respective solution layer mass changes in the module prototype with different solution thicknesses.

DETAILED DESCRIPTION

[0041] Common reference numerals are used throughout the drawings and the detailed description to indicate the same or similar components. Embodiments of the present disclosure will be readily understood from the following detailed description taken in conjunction with the accompanying drawings.

[0042] Spatial descriptions, such as “on,” “above,” “below,” “up,” “left,” “right,” “down,” “top,” “bottom,” “vertical,” “horizontal,” “side,” “higher,” “lower,” “upper,” “over,” “under,” and so forth, are specified with respect to a certain component or group of components, or a certain plane of a component or group of components, for the orientation of the component(s) as shown in the associated figure. It should be understood that the spatial descriptions used herein are for purposes of illustration only, and that practical implementations of the structures described herein can be spatially arranged in any orientation or manner, provided that the merits of embodiments of this disclosure are not deviated from by such arrangement.

[0043] Further, it is noted that the actual shapes of the various structures depicted as approximately rectangular may, in actual devices, be curved, have rounded edges, have somewhat uneven thicknesses, etc. due to device fabrication conditions. The straight lines and right angles are used solely for convenience of representation of layers and features.

[0044] In the following description, semiconductor devices/dies/packages, methods for manufacturing the same, and the likes are set forth as preferred examples. It will be apparent to those skilled in the art that modifications, including additions and/or substitutions may be made without departing from the scope and spirit of the present disclosure. Specific details may be omitted so as not to obscure the present disclosure; however, the disclosure is written to enable one skilled in the art to practice the teachings herein without undue experimentation.

[0045] Turning to the drawings in detail, a membrane-based desorption cooling module is provided. FIG. 1 depicts the module 100 attached to the PV panel 20 back portion and includes a covering layer 30, a solution layer 40, a membrane layer 50, and a supporting layer 60. The covering layer 30 is thermally conductive and transfers heat from the PV panel 20 to the solution.

[0046] The covering layer 30, the solution layer 40, the membrane layer 50, and the supporting layer 60 are connected to each other in a module 100. Specifically, the solution layer 40 is disposed between the covering layer 30 and the membrane layer 50 so as to connect the covering layer 30 to the membrane layer 50. The membrane layer 50 is disposed between the solution layer 40 and the supporting layer 60.

[0047] The solution layer 40 confines H.sub.2O/absorbent mixtures in a multi-compartment frame with metal walls as fins to facilitate heat transfer. The metal walls can vertically extend from the covering layer 30 to the membrane layer 50. The membrane layer 50 is a microporous polymeric membrane that functions as an interface between the solution and the air. This membrane layer 50 features selectivity characteristics: it is impermeable to liquids and only allows vapor to pass through. Vapor can be separated by the direct diffusion of water molecules through the membrane, which lowers the desorption temperature. In some embodiments, only vapor is allowed to pass through the membrane layer 50. The hollow-plate supporting layer 60 is adopted to increase the mechanical strength for high durability without affecting the mass transfer through the membrane. In some embodiments, the supporting layer 60 is in contact with the membrane layer 50 to abut against the membrane layer 50, so as to achieve the increase in the mechanical strength.

[0048] In one aspect, the membrane-based moisture desorption process during the daytime is depicted in FIG. 2. The waste heat generated by the PV panel 20 is transferred to the solution layer 40 via the covering layer 30 and the multi-compartment frame in the daytime. The temperature of the solution increases and the vapor pressure of the solution is enhanced. When the vapor pressure of the solution is higher than that of the ambient air, water vapor is driven by the pressure difference to pass through the membrane and enter the air. This moisture desorption process provides high-flux cooling due to the large heat of vaporization. As desorption continues, the PV panel 20 cools down and the solution gets concentrated.

[0049] In another aspect, the membrane-based moisture absorption process at night is depicted in FIG. 3. There is no solar radiation and the PV panel 20 maintains a low temperature at night. The concentrated solution (after the daytime desorption) holds a lower vapor pressure than the ambient air, which enables the water vapor to pass through the membrane from the air to the solution. The moisture absorption process recovers the solution (which becomes a diluted solution) for the next-cycle desorption cooling.

[0050] The porous membrane materials include polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), combinations thereof, or their composites; however other porous materials may also be used.

[0051] Typical membrane geometries include membrane thicknesses of 50-200 μm, porosities of 0.4-0.8, and pore diameters of 0.2-2.0 μm. Typical solution layer geometries design include a layer thickness of 2-20 mm and compartment size of 20-100 mm. Note that the geometries are not limited to these typical values.

[0052] Various working fluids (aqueous solution) may be used in the desorption cooling module 100, including H.sub.2O/salt solutions, where the salt solutions are LiBr, LiCl, CaCl.sub.2, KBr, NaOH, and KOH; H.sub.2O/ionic liquid solutions, where the ionic liquid solutions are [DMIM][DMP](1,3-dimethylimidazolium dimethylphosphate), [EMIM][Ac](1-ethyl-3-methylimidazolium acetate), [BMIM][BF.sub.4](1-butyl-3-methylimidazolium tetrafluoroborate), [BMIM][Br](1-butyl-3-methylimidazolium bromide), [DMIM][Cl](1,3-dimethylimidazolium chloride), and [EMIM][EtSO.sub.4](1-ethyl-3-methylimidazolium ethyl sulfate), other H.sub.2O/absorbent solutions, or their mixtures.

[0053] Optionally, quantum dots may be included in the working fluid solution. For example, carbon quantum dots into H.sub.2O/ionic liquids may increase heat/mass transfer whilst avoiding deposition risk (increasing reliability).

[0054] The desorption-absorption mechanism of the desorption cooling module 100 is represented by the equation below:

[00001]$\mathrm{Diluted}{H}_{2}O/\mathrm{Absorbent}+\mathrm{heat}\begin{array}{c}\stackrel{\mathrm{desorption}}{⟵}\\ \underset{\mathrm{absorption}}{.Math.}\end{array}\mathrm{Concentrated}{H}_{2}O/\mathrm{Absorbent}+H_{2}O$

[0055] FIG. 4 depicts a membrane-based desorption cooling process for PV thermal management and water harvesting. In addition to passive thermal management, the present invention can also offer the unique ability to harvest water from the atmosphere. As shown in FIG. 4, a condensation chamber 70 can be further integrated at the bottom of the membrane-based desorption cooling module 100 for water harvesting during desorption. The harvested water can be used for PV dust cleaning, agriculture irrigation, daily living, etc. Therefore, the present invention is significant for developing novel versatile solar power technologies.

[0056] Apart from PV thermal management, the proposed membrane-based desorption cooling method can also be used for the passive thermal management of electronics (e.g., chips), batteries, or any other devices that require heat removal. The membrane-based desorption cooling module 100 in FIG. 1 may be fabricated into different shapes and dimensions to accommodate different devices.

[0057] For example, FIG. 5, depicts a membrane-based desorption cooling module 100 attached to an electronic 110 for electronics thermal management. In this regard, the covering layer of the membrane-based desorption cooling module 100 as afore mentioned can make contact with the electronic 110.

[0058] FIG. 6 depicts a membrane-based desorption cooling module 100 for thermal management of cuboid-shape batteries. As illustration, a membrane-based desorption cooling module 100 is attached to a cuboid-shape battery 120 for battery thermal management. Specifically, the membrane-based desorption cooling module 100 may have a cuboid-shape channel therein. The covering layer can serve as the most inside one among the layers of the membrane-based desorption cooling module 100. As such, the covering layer can define a boundary of the cuboid-shape channel, which is the outer boundary/border of the cuboid-shape channel. The covering layer of the membrane-based desorption cooling module 100 can make contact with the cuboid-shape battery 120. Furthermore, from the cuboid-shape channel to the outer border of the membrane-based desorption cooling module 100, the solution layer surrounds the covering layer; the membrane layer surrounds the solution layer; and the supporting layer surrounds the membrane layer, so that the supporting layer can be farther from the cuboid-shape channel than the covering layer, the solution layer, and the membrane layer.

[0059] FIG. 7 depicts a membrane-based desorption cooling module 100 for thermal management of cylindrical-shape batteries. As illustration, a membrane-based desorption cooling module 100 is attached to a cylindrical-shape battery 130 for battery thermal management. Similarly, the membrane-based desorption cooling module 100 may have cylindrical-shape channel therein. The covering layer can define a boundary of the cuboid-shape channel as well. The covering layer of the membrane-based desorption cooling module 100 can make contact with the cylindrical-shape battery 130. Note that other shapes are also applicable.

[0060] FIG. 8 shows the comparison of the temperature drops and cooling capacity of different passive cooling methods. The proposed membrane-based desorption cooling module is compared with conventional and emerging passive thermal management technologies, including finned structures, floating PV, spectrum splitting, radiative cooling, phase change material, and adsorptive hydrogel. The present invention of membrane-based desorption cooling method significantly outperforms the others, yielding a much higher cooling power and greater temperature drop.

Example 1

[0061] FIG. 9 depicts dynamic PV temperatures with and without desorption cooling modules, that is, compares the hourly PV temperatures between the PV panels with and without the present invention throughout the year in Hong Kong. FIG. 9 clearly demonstrates that the PV temperature can be effectively reduced by the novel module. By reducing the temperature of the PV module, the efficiency of the PV cell is increased. FIG. 9 demonstrates that the membrane-based desorption cooling system provides energy-free, high-flux, and high-reliability thermal management.

Example 2

[0062] FIG. 10 depicts the dynamic temperatures of PV panels with direct dissipation, a H.sub.2O/LiBr solution module, and a H.sub.2O/ionic liquid solution module. In one embodiment, the ionic liquid solution is [DMIM][DMP]. Between 6 to 16 hours, the PV temperature of a PV panel only (that is, with no cooling system) reaches around 70-80° C.; the PV temperature of a panel including a H.sub.2O/LiBr solution module reaches around 50-60° C.; the PV temperature of a panel including a H.sub.2O/[DMIM][DMP] solution module reaches around 35-50° C. As for the electricity output, the PV panel with no cooling outputs around 150 W between 6 to 16 hours; the PV panel with a H.sub.2O/LiBr solution module outputs around 165-180 W between 6 to 16 hours; the PV panel with a H.sub.2O/[DMIM][DMP] solution module outputs around 175-190 W between 6 to 16 hours. When comparing the PV panel with no cooling to the PV panel with a H.sub.2O/LiBr solution module, the efficiency of the PV panel with a H.sub.2O/LiBr solution module improved by 10-17%. When comparing the PV with no cooling to the PV panel with a H.sub.2O/[DMIM][DMP] solution module, the efficiency of the PV panel with a H.sub.2O/[DMIM][DMP] solution module improved by 16-23%.

[0063] In daytime, the PV efficiency is greatly improved by desorption-absorption passive cooling, especially using ionic liquid solutions.

Research Methods and Results:

[0064] PV thermal management:

[0065] FIGS. 11A and 11B depict the simulation results of a membrane-based desorption cooling module for PV thermal management. Compared with the basic PV module (PV only), the PV with 12 mm solution layer can achieve a significant temperature drop because the desorption process provides high-flux cooling due to the large heat of vaporization. As the desorption continues, the solution gets concentrated. At night, the PV is cooled down and the concentrated solution holds a lower vapor pressure, which enables the vapor to pass through the membrane from the air to the solution. Comparisons between FIG. 11A and FIG. 11B indicate that a thicker solution layer can achieve a lower temperature; this increased temperature drop is attributed to the higher cooling capacity of the larger solution volume.

[0066] FIGS. 12A-12C demonstrate the laboratory test of a basic PV module (REF) and a PV module with thermal management (with cooling). Under the 1.4 sun illumination provided by the solar simulator, this module provides an average temperature drop of 18° C.

[0067] FIGS. 12D-12E present the field test results of a basic PV module (REF) and a PV module with thermal management (with cooling). Under the transient ambient conditions, the temperature of the novel PV module with thermal management is always lower than that of the basic PV module, especially in high-irradiance conditions on a sunny day. The geometry design and solution composition of this module can be optimized to further improve the performance.

[0068] Battery thermal management:

[0069] As shown in FIG. 13A, a membrane-based battery thermal management prototype is developed, aiming for a 18650 lithium battery. In the experimental study, an electric heater is used to emulate the real battery, which is a common experimental method. FIG. 13B compares the temperatures of three cases: battery without thermal management, battery with the proposed module using LiBr solution, and battery with the proposed module using LiCl solution. The period with heating means that the battery is in operation. It is found that both the two hygroscopic solutions have a significant temperature reduction of ˜30° C.

[0070] Electronics thermal management:

[0071] An experimental prototype is developed for the electronics thermal management module, using a heater to emulate the heat generation of electronics in the lab. FIG. 14 depicts the surface temperature and solution mass evolution under 50 wt % LiBr solution, 25° C. ambient temperature, and 60% relative humidity. FIG. 14A shows that the maximum temperature differences between the baseline (without LiBr solution) and the novel module with different solution thicknesses are 36.9° C., 38.8° C., and 41.1° C., respectively. A bigger temperature reduction is achieved as the solution thickness increases, which can be attributed to the higher moisture desorption rate, as shown in FIG. 14B.

INDUSTRIAL APPLICABILITY

[0072] The present invention provides a membrane-based desorption cooling module which achieves energy-free, high-flux, and high-reliability thermal management due to the following advantages: [0073] (1) The naturally-driven desorption-absorption processes involving large vaporization enthalpy yield high heat flux without energy consumption. [0074] (2) The microporous polymeric membrane features high specific areas that contribute to high mass flux in a compact structure. [0075] (3) The module structure is simple and the working fluid is stable, maintaining the high reliability of the passive thermal management method.

[0076] Compared with conventional and emerging passive thermal management technologies (including finned structure, floating PV, spectrum splitting, radiative cooling, phase change material, and adsorptive hydrogel), the membrane-based desorption cooling method shows much higher cooling power and temperature drop.

[0077] While the present disclosure has been described and illustrated with reference to specific embodiments thereof, these descriptions and illustrations are not limiting. It should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the present disclosure as defined by the appended claims. The illustrations may not necessarily be drawn to scale. There may be distinctions between the artistic renditions in the present disclosure and the actual apparatus due to manufacturing processes and tolerances. There may be other embodiments of the present disclosure which are not specifically illustrated. The specification and the drawings are to be regarded as illustrative rather than restrictive. Modifications may be made to adapt a particular situation, material, composition of matter, method, or process to the objective, spirit and scope of the present disclosure. All such modifications are intended to be within the scope of the claims appended hereto. While the methods disclosed herein have been described with reference to particular operations performed in a particular order, it will be understood that these operations may be combined, sub-divided, or re-ordered to form an equivalent method without departing from the teachings of the present disclosure. Accordingly, unless specifically indicated herein, the order and grouping of the operations are not limitations.