WO2024184671A1

WO2024184671A1 - Refrigeration systems and refrigeration methods

Info

Publication number: WO2024184671A1
Application number: PCT/IB2023/052070
Authority: WO
Inventors: Chin Lee ONG; Miguel RICO LUENGO; Riccardo CLAVENNA; Szymon BIALON; Yuhang Liu
Original assignee: Freshape Sa
Priority date: 2023-03-06
Filing date: 2023-03-06
Publication date: 2024-09-12
Also published as: WO2024184794A1

Abstract

There is in particular described a refrigeration system (100) comprising a thermoelectric device (10) exhibiting a cold side (CS) and a hot side (HS) which are thermally coupled to first and second heat transfer structures (20, 30), respectively. The first heat transfer structure (20) that is coupled to the cold side (CS) of the thermoelectric device (10) acts as heat absorber to draw heat away from an adjacent location (1000) to be refrigerated or cooled, while the second heat sink (30) that is coupled to the hot side (HS) of the thermoelectric device (10) acts as heat rejector to reject the heat drawn from the adjacent location (1000). The second heat transfer structure (30) is placed within an airflow path (35) to draw heat away from the second heat transfer structure (30). The refrigeration system (100) additionally comprises an evaporative cooler (50) that is provided within the airflow path (35) to reduce a temperature of the hot side (HS) of the thermoelectric device (10), which evaporative cooler (50) is supplied with a coolant medium (W) that is caused to evaporate as a result of passage of airflow through the evaporative cooler (50). The refrigeration system (100) further comprises a supply of low humidity air to feed the evaporative cooler (50; 50*) and cause evaporation of the coolant medium (W) therein.

Description

REFRIGERATION SYSTEMS AND REFRIGERATION METHODS

TECHNICAL FIELD

The present invention generally relates to a refrigeration system and a corresponding refrigeration method. The present invention also relates to a combined dehumidification and refrigeration system and a corresponding combined dehumidification and refrigeration method embodying the same.

BACKGROUND OF THE INVENTION Refrigeration is a process involving the transfer of heat from one location to another, more specifically by transferring heat from a colder side to a warmer side to achieve cooling of a dedicated location.

Nearly all refrigeration systems and methods deployed today rely on vapor compressors that consume a considerable amount of valuable electrical energy. To an end-user, this easily accounts for a significant proportion of the end-user’s operating costs. By way of illustration, according to “Refrigeration - A guide to energy and carbon saving opportunities", The Carbon Trust, October 2019 (https://www.carbontrust.com/our-work-and-impact/guides-reports-and- tools/refrigeration-quide), the typical proportion of overall energy used by refrigeration by industry sector is estimated as follows:

There are accordingly opportunities to make significant energy consumption savings and to come up with more efficient refrigeration solutions. Figure 1 is a schematic flow diagram of a typical vapor-compression refrigeration cycle, which is the established and most widely employed technology for cooling/refrigeration purposes. The main components of a typical vapor-compression refrigeration system include (i) an evaporator, (ii) a condenser, (iii) a compressor and (iv) an expansion valve that are arranged in a refrigeration loop. Vapor-compression refrigeration loops use coolants, conventionally known and referred to as refrigerants, with typically low boiling points.

As schematically shown in Figure 1 , a typical vapor-compression refrigeration cycle involves absorption of heat by the evaporator from the location to be cooled/refrigerated and rejection of the heat into the environment by the condenser. More specifically, the typical vapor-compression refrigeration cycle includes: i. feeding of a liquid-vapor refrigerant mixture from the expansion valve to the evaporator inlet; ii. heat absorption at the evaporator from the location to be cooled or refrigerated, causing evaporation of the refrigerant, i.e. a phase change from liquid to vapor; iii. compression of the saturated vapor exiting the evaporator by the compressor to a higher pressure and temperature, resulting in superheated vapor; iv. condensation of the superheated vapor in the condenser (which may typically be air-cooled or water-cooled), resulting in the release of latent heat that is rejected into the environment and causing the refrigerant to cool and undergo a phase change from vapor to liquid; and v. routing of the liquid refrigerant through the expansion valve where it undergoes an abrupt reduction in pressure resulting in the adiabatic flash evaporation of part of the liquid refrigerant, which liquid-vapor mixture is fed back to the evaporator.

Vapor-compression refrigeration technology has the advantage of being a reasonably reliable, proven technology that exhibits exceptional cooling performance. Vapor-compression refrigeration systems can easily be scaled up to increase their refrigerating capacity. These refrigeration systems are also capable of reaching extremely low temperatures.

Vapor-compression refrigeration technology also has disadvantages, most notably: it requires use of specific refrigerants, including e.g. hydrofluorocarbon (HFC) refrigerants (which are environmentally unfriendly and can cause significant environmental damage), chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) refrigerants (which contribute to depletion of the ozone layer and are now banned in most countries), ammonia (which is highly toxic and flammable), propane (which is likewise flammable), and carbon dioxide (which requires a high pressure implementation); the compressor can be the costliest component in the vaporcompression refrigeration loop and includes moving parts that must be checked regularly to ensure optimal performance; the refrigeration loops are prone to refrigerant leakages during their lifetime, which can cause environmental, health and/or safety hazards and affect system efficiency; the refrigeration loop operates less efficiently when its size becomes smaller due to a lower refrigerant charge, smaller channels contributing to comparatively higher frictional pressure drop and thermodynamic losses; and it consumes “high grade” energy, namely electricity that is still largely generated by burning fossil fuels that contributes to carbon dioxide emissions, a major contributor to greenhouse gases emissions leading to climate change and global warming.

In effect, the compressor, whose role is to increase the refrigerant temperature difference between the evaporator and condenser (also known and referred to as “temperature lift”), represents the most energy intensive part of the vapor-compression refrigeration loop. This temperature lift of the compressor determines the amount of work required, which in turns defines the energy consumption. In general, a higher temperature lift involves more compressor work, which in turn causes an upsurge in energy consumption. Moreover, intermittent operation of vapor-compression refrigeration systems degrades system efficiency.

Alternatives to vapor-compression refrigeration systems are known in the art. One such alternatives is to use thermoelectric devices to drive the refrigeration process.

Figure 2 shows a schematic diagram of a thermoelectric refrigeration system, which uses so-called Peltier elements to drive the refrigeration process. It is a relatively simple system with no moving parts when compared against the aforementioned vapor-compression refrigeration system.

Thermoelectric cooling/refrigeration uses the Peltier effect to create a heat flux at the junction of two different types of materials. A thermoelectric device is in effect a solid-state active heat pump, made of an assembly of p-type and n- type semiconductor elements placed thermally in parallel to each other and electrically in series between a pair of electrodes (of e.g. copper), which heat pump transfers heat from one side of the device (the “cold side”) to the other (the “hot side”) using electrical energy, depending on the direction of the electrical current. The electrodes on each side are joined with a thermally conductive, electrically insulated plate (usually made of ceramic material), the cold and hot sides being typically switchable from one or the other side depending on the electrical polarity applied across the thermoelectric device.

Compared to vapor-compression refrigeration systems, thermoelectric refrigeration systems have a relatively low coefficient of performance (COP) and a comparatively higher energy consumption for a given refrigeration capacity. Thermoelectric refrigeration systems are therefore mainly used for applications where a relatively small refrigeration capacity is required and/or when the temperature lift is relatively low, i.e. in cases where the temperature difference between the hot and cold sides of the thermoelectric device is relatively small. Thermoelectric refrigeration technology nevertheless remains a particularly advantageous alternative to vapor-compression refrigeration technology in that its implementation is relatively simple since it operates without any moving parts, thereby imposing less servicing and maintenance requirements and being quieter to operate. Without the need for a compressor and associated refrigerant circuit, thermoelectric cooling/refrigeration systems are also lighter and exhibit a lower specific weight. It is furthermore an environmentally friendly technology since it does not rely on the use of potentially harmful refrigerants and will therefore not be prone to refrigerant leakages during its lifetime. Thermoelectric refrigeration also has the advantage of being more responsive compared to vaporcompression refrigeration in that temperature control can be easily achieved by varying electrical current through the thermoelectric device, thus reducing response time.

U.S. Patent No. US 5,737,923 A discloses a thermoelectric heat transfer system having a thermoelectric device coupled to a heat exchanger having an evaporating chamber and a condensing chamber. A working fluid is sealed within the heat exchanger to undergo a phase change, namely evaporation in the evaporating chamber and condensation in the condensing chamber. The thermoelectric device includes a plurality of thermoelectric elements disposed between a thermally conductive hot plate and a thermally conductive cold plate. A surface of the evaporating chamber is thermally coupled with the thermally conductive hot plate and provided with an enhanced heat transfer surface to promote boiling of the working fluid. A fluid flow path is provided between the evaporating and condensing chambers to allow working fluid in its vapor phase to flow from the evaporating chamber to the condensing chamber and working fluid in its liquid phase to flow from the condensing chamber to the evaporating chamber. More specifically, the condensing chamber comprises a plurality of hollow tubes with enhanced heat transfer surface formed on the interior of each hollow tube and a plurality of convection cooling fins disposed on the exterior of the hollow tubes to transfer heat from the hollow tubes to the surrounding environment. In other words, US 5,737,923 A essentially discloses a thermoelectric device whose hot side is thermally coupled to the evaporative part of a heat exchanger consisting of sealed evaporating and condensing chambers forming a closed loop circuit where working fluid undergoing a phase change is allowed to circulate.

U.S. Patent No. US 7,584,622 B2 discloses a localized refrigerator apparatus for a thermal management device including a sealed chamber having an evaporation portion and a condensation portion. The evaporation portion is thermally coupled to a heat generating device. A working fluid is housed in the sealed chamber and is adapted to facilitate heat transfer between the evaporation portion and the condensation portion by an evaporation and condensation cycle. The condensation portion is furthermore thermally coupled to one or more thermoelectric coolers and a heat sink that is exposed to ambient airflow to promote removal of heat and allow vapor condensation.

U.S. Patent No. US 10,655,910 B2 discloses a cooler for cooling a beverage fluid flow. The cooler includes one or more thermoelectric cooling modules arranged along the path of the beverage fluid flow, each thermoelectric cooling module comprising a fluid heat exchanger that is thermally coupled to the cold side of a thermoelectric device. The hot side of the thermoelectric device is thermally coupled to an evaporative heat sink having a water permeable membrane for evaporative cooling. More specifically, a flow of water is fed and continuously circulates through the water permeable membrane under the action of a water pump, which leads to a relatively complex and bulky arrangement. A fan is further provided to promote the flow of ambient air across the water permeable membrane and improve evaporation of water therein.

U.S. Patent No. US 6,845,622 B2 discloses a heat-transfer device having a sealed vapor chamber with a phase-change working fluid therein, and a thermoelectric element whose cold side is thermally coupled to a condensing portion of the vapor chamber and whose hot side is in contact with heatdissipation fins. The thermoelectric element decreases the temperature of the condensing portion of the vapor chamber and increases the temperature of the fins for improved efficiency. A heat source is in thermal contact with an evaporating portion of the vapor chamber to cause evaporation of the phasechange working fluid, which condenses in the condensing portion of the vapor chamber. In one embodiment, the vapor chamber is defined between concentrically positioned outer and inner tubes, and a tunnel region is located within the inner tube. Additional thermoelectric elements may be provided within the tunnel region to further dissipate heat. Korean Patent Publication No. KR 10-2008-0017674 A discloses a small refrigerator comprising a thermoelectric device for cooling the internal space of the refrigerator. More specifically, the cold side of the thermoelectric device faces the inner side of the refrigerator and is provided with a cooling radiation plate, while the hot side of the thermoelectric device is directed on the outer case of the refrigerator. A heat exchange pipe is used to absorb and transfer the heat from the hot side of the thermoelectric device to a plurality of plate-shaped fins that are stacked to provide a heat dissipation structure for heat exchange with ambient air. A water pan is further provided to collect condensed water forming around the cooling radiation plate and a non-woven fabric extends from inside the water pan to be exposed at a rear end of the refrigerator to allow evaporation of the condensed water.

U.S. Patent No. US 6,434,955 B1 discloses an electro-adsorption chiller comprising at least one condenser for cooling refrigerant (such as water, methanol or ammonia) and at least one evaporator for cooling a location to be cooled, the evaporator being connected to the condenser by a pressure isolation device to provide a refrigerant circuit. At least one pair of adsorber units, each capable of operating in adsorption and desorption cycles, is connected to the condenser and evaporator via on-off valves, and a thermoelectric device is coupled between each pair of adsorber units. In operation, the cold side of the thermoelectric device is coupled to that one of the adsorber units that undergoes an adsorption cycle to cause adsorption of refrigerant vapor that is fed from the evaporator, while the hot side of the thermoelectric device is coupled to that one of the adsorber units that undergoes the desorption cycle to cause desorption of refrigerant vapor that is fed to the condenser. Operation of the adsorber units and thermoelectric device is switched cyclically to alternate between adsorption and desorption cycles.

Korean Patent Publication No. KR 10-2005-0117046 A discloses a cooling apparatus combining a thermoelectric device and an absorbing-type cooling device. A fan is installed on the inner wall of a refrigerator to circulate cool air within the inner space of the refrigerator. A thermoelectric device is positioned at a rear side of the fan, with the cold side of the thermoelectric device facing the fan, to absorb heat. Absorbed heat is rejected to the outside via the hot side of the thermoelectric device which is coupled to a heat sink. The heat absorbed by the thermoelectric device and transferred to the heat sink is used as heat source to evaporate a refrigerant including a solution of ammonia and water that circulates in a dedicated closed-loop refrigerant circuit. Vaporized refrigerant rises to a separator where it is separated into pure ammonia vapor and a solution having a low concentration of ammonia. The pure ammonia vapor is fed to a condenser, while the solution with low concentration of ammonia is returned to a storage tank storing the refrigerant. The pure ammonia vapor is condensed in the condenser and then flows through an evaporator installed in the wall of the refrigerator to serve as an auxiliary cooling device. The ammonia vapor evaporated through the evaporator is then absorbed by an absorber and sent back to the storage tank.

Chinese Patent No. CN 109386912 B discloses a thermoelectric adsorption dehumidification device with a rotary structure. A thermoelectric module is interposed between first and second heat sinks that are mounted on both sides of a heat insulation rotating plate that is supported for rotation and coupled to the shaft a motor. The first and second heat sinks are each coated with a solid dehumidification material. The assembly formed of the thermoelectric module, heat insulation rotating plate and the two heat sinks is fitted within a cylindrical housing so as to be rotatable, cyclically, by half a turn under the action of the rotor. First and second fans are further positioned at one end of the cylindrical housing to blow air across the first and second heat sinks. In use, the rotating assembly is rotated so that one of the two heat sinks is positioned within the space to be dehumidified, while the other heat sink is exposed outside the space to be dehumidified.

A limitation of known thermoelectric refrigeration systems and methods resides in the fact that the coefficient of performance (COP) thereof drops significantly when temperature gradient between the hot and cold sides increases.

Furthermore, it is potentially more expensive to operate, compared to the more conventional vapor-compression refrigeration systems and methods, since the electrical energy consumption is comparatively higher for a given cooling/refrigeration capacity due to the lower operating COP.

Moreover, the efficiency of thermoelectric refrigeration systems and methods drops significantly for lower cold side temperatures.

There therefore remains a need for an improved solution.

SUMMARY OF THE INVENTION

A general aim of the invention is to provide a refrigeration system and method that obviates the limitations and drawbacks of the prior art solutions.

More specifically, an aim of the present invention is to provide such a solution that is more efficient to operate, while remaining reasonably cost-efficient to implement.

A further aim of the invention is to provide such a solution that is more environmentally friendly that conventional solutions based on vapor-compression refrigeration.

Another aim of the invention is to provide such a solution that is basically self-sufficient to operate beyond the electrical energy required to run the refrigeration process.

A further aim of the invention is to provide such a solution that can further be combined with and implement dehumidification of air and, especially, atmospheric water harvesting (AWH) for recovery of e.g. potable water.

These aims, and others, are achieved thanks to the solutions defined in the claims.

There is accordingly provided a refrigeration system, the features of which are recited in claim 1 , namely a refrigeration system comprising a thermoelectric device exhibiting a cold side and a hot side which are thermally coupled to first and second heat transfer structures, respectively. The first heat transfer structure that is coupled to the cold side of the thermoelectric device acts as heat absorber to draw heat away from an adjacent location to be refrigerated or cooled, while the second heat transfer structure that is coupled to the hot side of the thermoelectric device acts as heat rejector to reject the heat drawn from the adjacent location. The second heat transfer structure is placed within an airflow path to draw heat away from the second heat transfer structure. The refrigeration system additionally comprises an evaporative cooler that is provided within the airflow path to reduce a temperature of the hot side of the thermoelectric device, which evaporative cooler is supplied with a coolant medium that is caused to evaporate as a result of passage of airflow through the evaporative cooler. The refrigeration system further comprises a supply of low humidity air to feed the evaporative cooler and cause evaporation of the coolant medium therein.

Thanks to the invention, higher efficiency is achieved thanks to an increase of the coefficient of performance (COP) of the thermoelectric device. More specifically, thanks to the implementation of the evaporative cooler that is fed with low humidity air, enhanced evaporating cooling is achieved, leading to improved cooling of the hot side of the thermoelectric device. The hot side temperature can be lowered significantly, meaning that the temperature gradient between the hot and cold sides of the thermoelectric device can be reduced, leading to a higher COP. For a given COP, this implies that lower temperatures can be achieved on the cold side of the thermoelectric device.

In accordance with a first embodiment of the invention, the evaporative cooler is positioned upstream of the second heat transfer structure along the airflow path such that cold humid air exiting the evaporative cooler is channelled across the second heat transfer structure. In effect, the airflow can be cooled down to a point corresponding to its wet-bulb temperature, which wet-bulb temperature can be significantly reduced thanks to feeding of low humidity air at the inlet of the evaporative cooler.

In accordance with a second embodiment of the invention, the second heat transfer structure integrates the evaporative cooler which is thermally coupled to the hot side of the thermoelectric device, meaning that evaporative cooling takes place in direct thermal coupling with the hot side of the thermoelectric device. By way of preference, the second heat transfer structure and the evaporative cooler are integrated into a common thermally conductive structure that is thermally coupled to the hot side of the thermoelectric device and configured to channel the airflow therethrough and cause evaporation of the coolant medium directly within a core of the common thermally conductive structure. Various preferred and/or advantageous embodiments of this refrigeration system form the subject-matter of dependent claims 5 to 17.

Also claimed pursuant to claim 18 is a combined dehumidification and refrigeration system comprising a refrigeration system in accordance with the invention and a dehumidification system that is operatively coupled to the refrigeration system and configured to harvest moisture from hot humid air exiting the second heat transfer structure and supply dehumidified dry air that is fed to the evaporative cooler. In effect, this provides for active control and regulation of the relative humidity (RH) of the dehumidified dry air being supplied to the evaporative cooler.

Various preferred and/or advantageous embodiments of this combined dehumidification and refrigeration system form the subject-matter of dependent claims 19 to 31 .

There is also provided a corresponding refrigeration method, the features of which are recited in independent claim 32, namely a refrigeration method comprising:

(a) providing a thermoelectric device exhibiting a cold side and hot side;

(b) coupling the cold side of the thermoelectric device to a first heat transfer structure to act as a heat absorber to draw heat away form an adjacent location to be refrigerated or cooled;

(c) coupling the hot side of the thermoelectric device to a second heat transfer structure to act as a as heat rejector to reject the heat drawn from the adjacent location; and

(d) channelling airflow across the second heat transfer structure to draw heat away from the second heat transfer structure, wherein step (d) includes providing an evaporative cooler to reduce a temperature of the hot side of the thermoelectric device, supplying a coolant medium to the evaporative cooler, and feeding the evaporative cooler with low humidity air to cause evaporation of the coolant medium.

Various preferred and/or advantageous embodiments of this refrigeration method form the subject-matter of dependent claims 33 to 41 . Also claimed pursuant to claim 42 is a combined dehumidification and refrigeration method involving refrigeration or cooling of an adjacent location to be refrigerated or cooled in accordance with the refrigeration method of the invention, wherein the method includes harvesting moisture from hot humid air exiting the second heat transfer structure and feeding dehumidified dry air to the evaporative cooler.

Various preferred and/or advantageous embodiments of this combined dehumidification and refrigeration method form the subject-matter of dependent claims 43 to 55.

Further advantageous embodiments of the invention are discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will appear more clearly from reading the following detailed description of embodiments of the invention which are presented solely by way of non-restrictive examples and illustrated by the attached drawings in which:

Figure 1 is a schematic flow diagram illustrating operation of a known vapor compressor refrigeration cycle;

Figure 2 is a schematic diagram of a known thermoelectric refrigeration system;

Figure 3 is a schematic diagram of a refrigeration system in accordance with a first embodiment of the invention;

Figure 4 is a chart showing simulated wet-bulb temperature curves, as a function of ambient air pressure, illustrating the expected drop in temperature resulting from evaporative cooling for various illustrative values of airflow relative humidity and airflow temperature at the inlet of the evaporative cooler;

Figure 5 is a schematic diagram of a refrigeration system in accordance with a second embodiment of the invention;

Figure 6 is a schematic diagram of a refrigeration device suitable for use in the context of the refrigeration system of Figure 5, which refrigeration device includes the assembly of a thermoelectric device exhibiting a cold side and hot side that are thermally coupled to first and second heat transfer structures, respectively, wherein the second heat transfer structure integrates an evaporative cooler comprising a porous wick structure as a core element of the second heat transfer structure;

Figures 7A and 7B are explanatory diagrams illustrating wetting of the porous wick structure of the evaporative cooler and heat transfer occurring as a result of evaporative cooling;

Figure s is a schematic diagram of a combined dehumidification and refrigeration system in accordance with an embodiment of the invention; and

Figures 9A to 9C are schematic diagrams illustrating successive operating phases of a combined dehumidification and refrigeration system in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention will be described in relation to various illustrative embodiments. It shall be understood that the scope of the invention encompasses all combinations and sub-combinations of the features of the embodiments disclosed herein as defined by the appended claims.

As described herein, when two or more parts or components are described as being connected, attached, secured or coupled to one another, they can be so connected, attached, secured or coupled directly to each other or through one or more intermediary parts.

Embodiments of the invention will especially be described hereinafter with reference to Figures 3 to 9A-C.

Figure s is a schematic diagram of a refrigeration system 100 in accordance with a first embodiment of the invention. In the illustration of Figure 3, the refrigeration system 100 is shown coupled to a closed space 1000 to be refrigerated (such as e.g. the interior space of a refrigerator) which is surrounded by insulation material. The refrigeration system 100 comprises a thermoelectric device 10 exhibiting a cold side CS and a hot side HS which are thermally coupled to first and second heat transfer structures 20, 30, respectively, namely a pair of heat sinks 20, 30. The first heat sink 20 that is coupled to the cold side CS of the thermoelectric device 10 acts as heat absorber to draw heat away from the refrigerated space 1000, while the second heat sink 30 that is coupled to the hot side HS of the thermoelectric device 10 acts as heat rejector to reject the heat drawn from the space 1000. The thermoelectric device 10 may include one or more Peltier elements thermally coupled to the first and second heat transfer structures 20, 30.

In the illustration of Figure 3, the heat sink 20 is exposed to a flow of air circulating within the refrigerated space 1000 and a ventilation fan VF is located in the refrigerated space 1000 to cause circulation within the space 1000 of cold air exiting the heat sink 20 and force circulation of warmer air from the refrigerated space 1000 across the heat sink 20. As schematically illustrated, the refrigerated space 1000 may especially be provided with air suction manifolds to draw and channel the air to circulate across the heat sink 20 for efficient cooling of the air within the refrigerated space 1000.

The second heat sink 30 is placed within an airflow path 35 to draw heat away from the second heat sink 30. According to this first embodiment, an evaporative cooler 50 is provided within the airflow path 35 and positioned upstream of the second heat sink 30. The evaporative cooler 50 is supplied with a coolant medium W (preferably water) that is caused to evaporate as a result of passage of airflow through the evaporative cooler 50. The resulting cold humid air exiting the evaporative cooler 50 is accordingly channelled across the downstream-located second heat sink 30, thereby reducing the temperature of the hot side HS of the thermoelectric device 10. As a result, hot humid air exits the second heat sink 30, as schematically depicted in Figure 3.

In accordance with the invention, the refrigeration system 100 further comprises a supply of low humidity air to feed the evaporative cooler 50. As this will be explained in greater detail hereafter, this helps enhancing the cooling efficiency of the evaporative cooler 50, which helps decreasing the wet-bulb temperature of the airflow exiting the evaporative cooler 50 and flowing across the second heat sink 30, thereby decreasing further the temperature of the hot side HS of the thermoelectric device 10 and promoting enhanced heat rejection.

By way of preference, the evaporative cooler 50 includes a thermally conductive porous wick structure 500 that is wetted by means of the coolant medium W and is exposed to the airflow to cause evaporation of the coolant medium W. The coolant medium W may be supplied to the porous wick structure 500 by means of a suitable coolant dispensing system configured to wet the porous wick structure 500 by capillary action. Even more preferably, as schematically illustrated in Figure 3, the porous wick structure 500 is structured to form a plurality of channels 500A through which the airflow is channelled. Any suitable structuring may be contemplated, especially such structuring that promotes exposure of the wetted porous material to airflow to enhance evaporation of the coolant medium W.

In accordance with a particularly preferred embodiment, the supply of low humidity air is a supply of dehumidified dry air exhibiting a relative humidity (RH) that is lower than that of ambient air. Expressed in terms of relative humidity (RH), it is especially contemplated to supply dehumidified dry air exhibiting a relative humidity (RH) of less than 20%, even more preferably of less than 10%. The lower the inlet relative humidity, the better the evaporative cooling performance, as evaporative rate - and therefore cooling efficiency - is increased. Production of the dehumidified dry air may especially be ensured by a suitable dehumidification system operatively coupled to the refrigeration system 100, as described hereafter with reference to Figures 8 and 9A-C. Such dehumidification system may furthermore be configured to harvest moisture from the hot humid air exiting the second heat transfer structure 30 (as well as from ambient air), which ensures self-sufficiency with respect to the supply of the low humidity air and coolant medium W required to feed the evaporative cooler 50.

Figure 4 is a chart showing simulated wet-bulb temperature curves (eight such temperature curves being shown by way of illustration), as a function of ambient air pressure p, in adiabatic conditions, illustrating the expected drop in temperature resulting from evaporative cooling for various illustrative values of airflow relative humidity RHin and airflow temperature Tin at the inlet of the evaporative cooler. The horizontal lines with round markers at 30°C (dotted curve) and 20°C (continuous curve) are representative of the relevant temperatures at 100% relative humidity, which equals the relevant dry-bulb temperatures that are considered for the sake of illustration. The two curves with x markers, immediately below the aforementioned horizontal lines, are illustrative of the relevant web-bulb temperature at 90% relative humidity for the same airflow temperatures at the inlet of the evaporative cooler, namely 30°C (dotted curve) and 20°C (continuous curve). As expected, the drop in temperature resulting from evaporative cooling is relatively minor when the inlet relative humidity remains high.

The four remaining curves are illustrative of the expected drop in temperature resulting from evaporative cooling considering illustrative values of inlet relative humidity RHin of 10% (curves with square markers) and 0% (curves with diamond markers), respectively, and the same illustrative values of airflow temperature Tin at the inlet of the evaporative cooler, namely 30°C (dotted curves) and 20°C (continuous curves).

As can be seen from Figure 4, the wet-bulb temperature of the airflow is significantly affected by airflow relative humidity of the airflow at the evaporative cooler’s inlet. As a rule of thumb, a lower RH indicates a better capacity of water uptake per unit volume of air. In other words, a low airflow relative humidity is desirable as it results in increased evaporation, i.e. enhanced evaporative cooling. In effect, the lower the airflow relative humidity at the inlet, the better.

Considering the above, a lower wet-bulb temperature can be achieved with lower inlet relative humidity. Referring to Figure 4, considering by way of illustration an airflow pressure of 100 kPa, an inlet relative humidity of 10% (RHin = 0.1 ) and a dry-bulb temperature Tin of the inlet airflow of 20°C, the wetbulb temperature is of 7.8°C and is reduced down further to about 6°C if inlet relative humidity is reduced further to 0% (RHin = 0.0), meaning that the expected drop in temperature will be of AT1 = 12.2°C and AT2 = 14°C, respectively, i.e. a difference of about 1.8°C. At 30°C, this difference is increased even further to about 2.7°C.

A colder airflow temperature is ideal to reduce the temperature of the hot side of the thermoelectric device, yielding a reduced temperature gradient between the hot and cold sides and, hence, achieving a better COP.

As a rule of thumb, considering the embodiment of Figure 3, convective heat transfer coefficients are usually constant through the process. Hence, lowering the temperature of the airflow fed across the second heat sink 30 will lower the temperature of the hot side HS by a similar magnitude. Figure 4 also shows that a reduction of airflow pressure yields a lower wetbulb temperature. In other words, operating the refrigeration system 100 of Figure 3 such that the airflow path 35, second heat transfer structure 30 and evaporative cooler 50 are maintained at sub-ambient pressure would yield a further improvement in cooling efficiency and therefore a further improvement of the COP.

Referring again to Figure 3, low humidity air (in particular pre-dried) is fed to the evaporative cooler 50 and channelled through the channels 500A of the wetted porous wick structure 500 causing evaporation of the coolant medium W. The airflow accordingly undergoes evaporative cooling, with its temperature dropping significantly as it passes through the wetted porous media. Airflow temperature can be cooled to a point corresponding to its wet-bulb temperature. The resulting cold humid air is then channelled across the second heat transfer structure 30 which is thermally coupled to the hot side HS of the thermoelectric device 10. The colder air temperature therefore increases heat transfer, resulting in a lower hot side temperature. The resulting reduction in temperature gradient between the hot side HS and cold side CS of the thermoelectric device 10 accordingly yields a better coefficient of performance (COP) or, for a given COP, a lower cold side temperature of the thermoelectric device 10.

As discussed in greater detail hereafter, the hot humid air exiting the second heat transfer structure 30 is preferably fed to a dehumidification system, such as an adsorber system containing adsorbents, to harvest moisture therefrom, which can be recovered and recycled as coolant medium W that is supplied to the evaporative cooler 50.

One will appreciate that Figure 3 in essence shows an embodiment involving indirect evaporative cooling of the thermoelectric device 10. In accordance with another embodiment of the invention, a direct evaporative cooling of the thermoelectric device 10 may alternatively be contemplated, as shown e.g. by Figure 5.

Figure 5 is a schematic diagram of a refrigeration system 200 in accordance with a second embodiment of the invention. In the illustration of Figure 5, the refrigeration system 200 is again shown coupled to a space 1000 to be cooled or refrigerated (such as e.g. the interior space of a refrigerator), which space 1000 is only partly shown in Figure 5 and may be similar to the space 1000 shown in Figure 3. The refrigeration system 200 likewise comprises a thermoelectric device 10 exhibiting a cold side CS and a hot side HS which are thermally coupled to first and second heat transfer structures 20, 30*, respectively. The first heat transfer structure 20 is here again shown as a heat sink 20 that is coupled to the cold side CS of the thermoelectric device 10 to act as heat absorber to draw heat away from the refrigerated space 1000, while the second heat transfer structure 30* that is coupled to the hot side HS of the thermoelectric device 10 again acts as heat rejector to reject the heat drawn from the space 1000.

In the illustration of Figure 5, the heat sink 20 is likewise exposed to a flow of air circulating within the refrigerated space 1000 and a ventilation fan VF is also located in the refrigerated space 1000 to cause circulation of air within the space 1000, as already discussed with reference to Figure 3.

The second heat transfer structure 30* is once again placed within an airflow path 35 to draw heat away from the second heat transfer structure 30. According to this second embodiment, an evaporative cooler 50* is likewise provided within the airflow path 35, but, unlike the first embodiment discussed previously, the second heat transfer structure 30* integrates the evaporative cooler 50* which is thermally coupled to the hot side HS of the thermoelectric device 10. More specifically, in the illustrated example, the second heat transfer structure 30* and the evaporative cooler 50* are advantageously integrated into a common thermally conductive structure that is thermally coupled to the hot side HS of the thermoelectric device 10 and configured to channel the airflow therethrough and cause evaporation of the coolant medium W directly within a core of the common thermally conductive structure.

The refrigeration system 200 likewise further comprises a supply of low humidity air to feed the evaporative cooler 50* to enhance the cooling efficiency of the evaporative cooler 50*, which similarly helps decreasing further the temperature of the hot side HS of the thermoelectric device 10, thereby promoting enhanced heat rejection. By way of preference, the evaporative cooler 50* likewise includes a thermally conductive porous wick structure 500 that is wetted by means of the coolant medium W and is exposed to the airflow to cause evaporation of the coolant medium W. The coolant medium W may again be supplied to the porous wick structure 500 by means of a suitable coolant dispensing system configured to wet the porous wick structure 500 by capillary action (see also Figure 6). Even more preferably, as also schematically illustrated in Figure 5, the porous wick structure 500 is likewise structured to form a plurality of channels 500A through which the airflow is channelled.

In this other embodiment, low humidity air (in particular pre-dried) is fed to the evaporative cooler 50* and channelled through the channels 500A of the wetted porous wick structure 500 causing evaporation of the coolant medium W. As a result of evaporative cooling, heat is drawn away from the thermally conductive porous wick structure 500 and, by way of consequence, from the hot side HS of the thermoelectric device 10, increasing heat transfer and thereby achieving a lower hot side temperature. The resulting reduction in temperature gradient between the hot side HS and cold side CS of the thermoelectric device 10 likewise yields a better coefficient of performance (COP) or, for a given COP, a lower cold side temperature of the thermoelectric device 10.

In a manner similar to the first embodiment of Figure 3, hot humid air exiting the second heat transfer structure 30* is preferably fed to a dehumidification system, such as an adsorber system containing adsorbents, to harvest moisture therefrom, which can be recovered and recycled as coolant medium W that is supplied to the evaporative cooler 50*.

Figure 6 is a schematic diagram of a refrigeration device suitable for use in the context of the refrigeration system of Figure 5, which refrigeration device includes the assembly of a thermoelectric device 10 exhibiting a cold side CS and hot side HS that are thermally coupled to first and second heat transfer structures 20, 30*, respectively, namely a heat sink 20 and a heat transfer structure 30* that integrates an evaporative cooler 50* comprising a porous wick structure 500 as a core element of the second heat transfer structure 30*. Much like the evaporative cooler 50* shown schematically in Figure 5, the porous wick structure 500 shown schematically in Figure 6 is similarly structured to exhibit a plurality of channels 500A to channel airflow through the heat transfer structure 30* to cause evaporation of the coolant medium directly within a core of the common thermally conductive structure that integrates the second heat transfer structure 30* and the evaporative cooler 50*.

Also shown in Figure 6 is a coolant dispensing system 550 configured to wet the porous wick structure 500 by capillary action, which coolant dispensing system 550 here takes the form of a coolant medium manifold adapted to drip coolant medium W on top of the porous wick structure 500.

Figure 6 also shows first and second layers of thermal interface material TIM interposed respectively between the cold side CS of the thermoelectric device 10 and the heat sink 20, and between the hot side HS of the thermoelectric device 10 and the heat transfer structure 30*, namely between the hot side HS and the porous wick structure 500 in the illustrated example.

Figure 6 is only one possible illustrative example of a refrigeration device suitable for use in the context of the refrigeration system 200 of Figure 5. In other embodiments, the porous wick structure could be formed on a support structure, likewise made of a thermally conductive material, that is thermally coupled to the hot side of the thermoelectric device.

Figure 7A schematically illustrates the wetting process taking place within the evaporative cooler 50* (likewise shown as being thermally coupled to the hot side HS of the thermoelectric device 10 via a layer of thermal interface material TIM), which wetting process involves the supply of coolant medium W to the porous wick structure 500 from the top of the structure. The coolant medium W is distributed throughout the porous wick structure 500 by capillary action. Figure 7A similarly shows the channels 500A through which the airflow is channelled to cause evaporative cooling directly within the core of the combined structure integrating the heat transfer structure 30* and evaporative cooler 50*.

The porous wick structure 500 is preferably made of sintered porous material, metallic foam, ceramics or other materials containing voids. By way of preference, the porous wick structure 500 has a porosity of approximately 20% to 80% and preferentially exhibits pores having an average size comprised between approximately 5 pm and 200 pm. A thickness of the porous wick structure 500 is furthermore advantageously of about 0.5 mm to 5 mm, depending on the packaging and relevant structuring.

Figure 7B schematically illustrates the cooling process taking place as a result of evaporation of the coolant medium W. Heat conduction from the hot side HS of the thermoelectric element 10 causes a corresponding heat flow within the porous wick structure 500. Evaporation of the coolant medium W occurs within the channels 500A at the interface between the airflow and the exposed surface of the porous wick structure 500, resulting in the production of moist airflow that is progressively channelled through the channels 500A. Heat is thus extracted as a result of evaporation, vapor absorbing heat which is extracted as hot humid air exiting the core of the combined structure integrating the heat transfer structure 30* and evaporative cooler 50*. In effect, moisture content progressively increases from inlet to outlet of the combined heat transfer/evaporative cooler structure 30*/50*.

Figure s is a schematic diagram of a combined dehumidification and refrigeration system DRS in accordance with an embodiment of the invention. In the right-hand part of Figure 8, there is schematically shown the refrigeration system 100 coupled to the space 1000 to be refrigerated, including the thermoelectric device 10 with its cold and hot sides CS, HS thermally coupled to the first and second heat transfer structures 20, 30, respectively, as well as the successive arrangement, within the airflow path 35, of the evaporative cooler 50 and the second heat transfer structure 30 as already described with reference to Figure 3. It is to be appreciated however that the refrigeration system 200 discussed with reference to Figure 5 is equally applicable, the sole difference residing in the integration of the evaporative cooler 50* and the second heat transfer structure 30* as a single, integrated structure. In both instances, as already mentioned, dehumidified dry air is fed to the evaporative cooler 50, resp. 50*, as the relevant supply of low humidity air, and hot humid air exits the second heat transfer structure 30, resp. 30*.

The combined dehumidification and refrigeration system DRS shown in Figure s further comprises a dehumidification system 300 that is operatively coupled to the refrigeration system 100 (or 200) and configured to harvest moisture form the hot humid air exiting the second heat transfer structure 30 (or 30*) and supply the dehumidified dry air that is fed to the evaporative cooler 50 (or 50*). In the illustrated example, a ventilator VT is further provided to force circulation of the dehumidified dry air through the evaporative cooler 50 (resp. 50*).

The illustrated dehumidification system 300 fulfils more than a dehumidification function, namely it also advantageously recovers coolant medium Wfrom the hot humid air, which is recycled to the evaporative cooler 50 (resp. 50*). To this end, the dehumidification system 300 advantageously includes an adsorber system 600 coupled to the airflow path 35 of the refrigeration system 100 (or 200) and configured to recover the coolant medium W from the hot humid air. In that regard, the dehumidification system 300 preferably further comprises a collection reservoir 700 to collect coolant medium W recovered by the adsorber system 600 and from which the coolant medium W is supplied to the evaporative cooler 50 (resp. 50*). The adsorber system 600 may especially be a multi-stage/multi-effect adsorber system as discussed in greater detail below.

As will be explained hereafter with reference to the preferred embodiment shown in Figures 9A-C, the adsorber system 600 may be configured to partly reject the dehumidified dry air produced thereby into the environment and to partly recycle the dehumidified dry air to the evaporative cooler 50 (resp. 50*). In practice, only a portion of the dehumidified dry air produced by the adsorber system 600 may be required to adequately feed the evaporative cooler 50 (resp. 50*).

In accordance with a preferred implementation, the coolant medium W is water and the adsorber system 600 also operates as atmospheric water harvesting system, extracting water from ambient air, as well as recovering such water from the hot humid air exiting the second heat transfer structure 30 (resp. 30*). In effect, water could be recovered and collected in the collection reservoir 700 and be used not only as coolant medium W, but also as a potential source of potable water for consumption. In the illustrated example, the combined dehumidification and refrigeration system DRS further comprise an ambient air intake to channel ambient air to the adsorber system 600 and, as the case may be, to the evaporative cooler 50 (resp. 50*).

Turing to Figures 9A to 9C, one will now describe a particularly preferred embodiment of the combined dehumidification and refrigeration system DRS as generically discussed with reference to Figure 8. In effect, Figures 9A to 9C are schematic diagrams illustrating successive operating phases of the combined dehumidification and refrigeration system DRS in accordance with this preferred embodiment of the invention. As shown in Figures 9A-C, the adsorber system includes first and second adsorber units 610, 620 that are each configured to undergo successive adsorption and desorption cycles. More specifically, the first adsorber unit 610 is coupled to an input side of the relevant refrigeration system 100, resp. 200, namely to an input side of the evaporative cooler 50, resp. 50*, while the second adsorber unit 620 is coupled to an output side of the refrigeration system 100, resp. 200, namely to an output side of the second heat transfer structure 30, resp. 30*.

The combined dehumidification and refrigeration system DRS is configured to operate cyclically in accordance with the following sequence of operation phases as represented by Figures 9A to 9C.

During a first operating phase, as shown in Figure 9A, the first and second adsorber units 610, 620 are both operatively coupled to the refrigeration system 100, resp. 200, and each operated to undergo an adsorption cycle such that dehumidified dry air produced by the first adsorber unit 610 is fed to the evaporative cooler 50, resp. 50*, and hot humid air exiting the second heat transfer structure 30, resp. 30*, is fed to the second adsorber unit 620. During this first phase, ambient air is preferably fed to the first adsorber unit 610 and moisture contained in the ambient air is adsorbed by the adsorbents of the first adsorber unit 610. Moisture contained in the hot humid air that is fed to the second adsorber unit 620 is likewise adsorbed by the adsorbents of the second adsorber unit 620. By way of preference, dehumidified dry air produced by the second adsorber unit 620 is partly rejected into the environment and partly fed back to the evaporative cooler 50, resp. 50*.

As the hot humid air exiting the second heat transfer structure 30, resp. 30*, contains a larger proportion of moisture, the second adsorber unit 620 is expected to reach saturation earlier than the first adsorber unit 610. As a consequence, during a second operating phase, triggered once the second adsorber unit 620 reaches saturation, as shown in Figure 9B, the second adsorber unit 620 is uncoupled from the refrigeration system 100, resp. 200, and operated to undergo a desorption cycle. During this second operating phase, water recovered as a result of desorption is advantageously collected in the collection reservoir 700. Furthermore, part or all of the hot humid air exiting the second heat transfer structure 30, resp. 30*, which is not anymore fed to the second adsorber unit 620, may be rejected into the environment. This assumes that the coolant medium W is not environmentally harmful, which is particularly the case in the event water is used as the coolant medium W. Preferably, at least part of the hot humid air exiting the refrigeration system 100, resp. 200, is mixed to ambient air and recycled to the first adsorber unit 610 which is still undergoing the adsorption cycle.

Finally, during a third operating phase, triggered once the first adsorber unit 610 also reaches saturation, as shown in Figure 9C, the first adsorber unit 610 is uncoupled from the refrigeration system 100, resp. 200, and likewise operated to undergo a desorption cycle. During this third operating phase, water recovered as a result of desorption in the first adsorber unit 610 may similarly be collected in the collection reservoir 700. Moreover, as the production of dehumidified dry air is interrupted during this third phase, ambient air is preferably fed to the evaporative cooler 50, resp. 50*, meaning that the refrigeration system will work with a suboptimal coefficient of performance (COP) only during this third phase. Normal operation is restored as soon as the adsorber units 610, 620 have completed their desorption cycle and the adsorbents contained therein have been fully regenerated to be ready to adsorb moisture again.

Alternatively, the thermoelectric part of the refrigeration system 100, resp. 200, may be rendered non-operational during the third operating phase, leading to intermittent operation of the refrigeration system 100, resp. 200, namely only during the first and second operating phases. Contrary to the conventional vaporcompression solutions, such intermittent operation does not drastically impair system efficiency.

The adsorber units 610, 620 may be constructed in any desired way to fulfil their intended functions. By way of preference, the adsorber units 610, 620 are advantageously constructed as multi-stage/multi-effect adsorber units in accordance with the principles disclosed in International (PCT) Application No. PCT/IB2021/059253 of October 8, 2021 , titled “ATMOSPHERIC WATER GENERATION SYSTEM AND METHOD”, and International (PCT) Application No. PCT/IB2021/061229 of December 2, 2021 , titled “MULTI-STAGE ADSORBER DEVICES AND USES THEREOF FOR CHILLING AND/OR ATMOSPHERIC WATER HARVESTING”, both in the name of the present Applicant and the contents of which are incorporated herein by reference.

Various modifications and/or improvements may be made to the abovedescribed embodiments without departing from the scope of the invention as defined by the appended claims.

For instance, while water is preferably used as coolant medium, other coolant mediums could possibly be contemplated. Water is however preferred in view of its totally harmless nature from an environmental perspective, which does not require any particular measure should e.g. hot humid air be rejected into the environment. Use of water also opens up the possibility to design the combined dehumidification and refrigeration system in such a way as to additionally implement the ability to perform atmospheric water harvesting and use the recovered water as a potential source of potable water.

Furthermore, while the embodiments of the refrigeration systems have been described with particular reference to refrigeration of a closed space, such as the interior space of a refrigerator, the cold side of the thermoelectrical device and the associated heat transfer structure could be designed in any other suitable way depending on the adjacent location to be refrigerated or cooled. For instance, the first heat transfer structure could be configured to draw heat away from a liquid circulating through the first heat transfer structure, rather than by convection of air.

LIST OF REFERENCE NUMERALS AND SIGNS USED THEREIN

10 thermoelectric device

20 first heat transfer structure (e.g. heat sink)

30 second heat transfer structure (e.g. heat sink - first embodiment)

30* second heat transfer structure (combined heat sink and evaporative cooler - second embodiment)

35 airflow path

50 evaporative cooler placed within airflow path 35 upstream of second heat transfer structure 30 (first embodiment)

50* evaporative cooler placed with airflow path 35 and forming an integral part of the second heat transfer structure 30* (second embodiment)

100 refrigeration system (first embodiment)

200 refrigeration system (second embodiment)

300 dehumidification system operatively coupled to refrigeration system 100, resp. 200 (atmospheric water harvesting system)

500 porous wick structure of evaporative cooler 50, resp. 50*

500A airflow channels formed in porous wick structure 500

550 coolant dispensing system (e.g. coolant medium manifold) for wetting of porous wick structure 500

600 adsorber system (dehumidifier)

610 first adsorber unit coupled to input side of refrigeration system 100, resp. 200

620 second adsorber unit coupled to output side of refrigeration system 100, resp. 200

700 collection reservoir for coolant medium W

1000 adjacent location to be refrigerated or cooled (e.g closed space)

W coolant medium (preferably water) supplied to evaporative cooler

50, resp. 50* I coolant medium for wetting of porous wick structure 500 CS cold side of thermoelectric device 10 that is thermally coupled to first heat transfer structure 20

HS hot side of thermoelectric device 10 that is thermally coupled to second heat transfer structure 30, resp. 30* TIM thermal interface material

VF ventilation fan for circulation of air within closed space 1000

VT ventilator for force circulation of dehumidified dry air produced by adsorber system 600 through airflow path 35

DRS combined dehumidification and refrigeration system (combined atmospheric water harvesting and refrigeration system)

Claims

1. A refrigeration system (100; 200) comprising a thermoelectric device (10) exhibiting a cold side (CS) and a hot side (HS) which are thermally coupled to first and second heat transfer structures (20, 30; 20, 30*), respectively, wherein the first heat transfer structure (20) that is coupled to the cold side (CS) of the thermoelectric device (10) acts as heat absorber to draw heat away from an adjacent location (1000) to be refrigerated or cooled, while the second heat transfer structure (30; 30*) that is coupled to the hot side (HS) of the thermoelectric device (10) acts as heat rejector to reject the heat drawn from the adjacent location (1000), wherein the second heat transfer structure (30; 30*) is placed within an airflow path (35) to draw heat away from the second heat transfer structure (30; 30*), wherein the refrigeration system (100; 200) additionally comprises an evaporative cooler (50; 50*) that is provided within the airflow path (35) to reduce a temperature of the hot side (HS) of the thermoelectric device (10), which evaporative cooler (50; 50*) is supplied with a coolant medium (W) that is caused to evaporate as a result of passage of airflow through the evaporative cooler (50; 50*), and wherein the refrigeration system (100; 200) further comprises a supply of low humidity air to feed the evaporative cooler (50; 50*) and cause evaporation of the coolant medium (W) therein.

2. The refrigeration system (100) according to claim 1 , wherein the evaporative cooler (50) is positioned upstream of the second heat transfer structure (30) along the airflow path (35) such that cold humid air exiting the evaporative cooler (50) is channelled across the second heat transfer structure (30).

3. The refrigeration system (200) according to claim 1 , wherein the second heat transfer structure (30*) integrates the evaporative cooler (50*) which is thermally coupled to the hot side (HS) of the thermoelectric device (10).

4. The refrigeration system (200) according to claim 3, wherein the second heat transfer structure (30*) and the evaporative cooler (50*) are integrated into a common thermally conductive structure that is thermally coupled to the hot side (HS) of the thermoelectric device (10) and configured to channel the airflow therethrough and cause evaporation of the coolant medium (W) directly within a core of the common thermally conductive structure.

5. The refrigeration system (200) according to claim 3 or 4, wherein the evaporative cooler (50*) is thermally coupled to the hot side (HS) of the thermoelectric device (10) via a layer of thermal interface material (TIM).

6. The refrigeration system (100; 200) according to any one of the preceding claims, wherein the evaporative cooler (50; 50*) includes a thermally conductive porous wick structure (500) that is wetted by means of the coolant medium (W), which porous wick structure (500) is exposed to the airflow to cause evaporation of the coolant medium (W).

7. The refrigeration system (100; 200) according to claim 6, wherein the evaporative cooler (50; 50*) includes a coolant dispensing system (550) configured to wet the porous wick structure (500) by capillary action.

8. The refrigeration system (100; 200) according to claim 6 or 7, wherein the porous wick structure (500) is structured to form a plurality of channels (500A) through which the airflow is channelled.

9. The refrigeration system (100; 200) according to any one of claims 6 to 8, wherein the porous wick structure (500) is made of sintered porous material, metallic foam, ceramics or other materials containing voids.

10. The refrigeration system (100; 200) according to any one of claims 6 to 9, wherein the porous wick structure (500) has a porosity of approximately 20% to 80%.

11. The refrigeration system (100; 200) according to any one of claims 6 to 10, wherein the porous wick structure (500) exhibits pores having an average size comprised between approximately 5 pm and 200 pm.

12. The refrigeration system (100; 200) according to any one of claims 6 to 11 , wherein a thickness of the porous wick structure (500) is of about 0.5 mm to 5 mm.

13. The refrigeration system (100; 200) according to any one of the preceding claims, wherein the first heat transfer structure (20) is a heat sink (20) exposed to a flow of air circulating within a space (1000) to be refrigerated or cooled, and wherein the refrigeration system (100; 200) further comprises a ventilation fan (VF) located in the space (1000) to be refrigerated or cooled to cause convection of air within the space (1000), namely circulation of cold air exiting the heat sink (20) and of warmer air from the space (1000) to be refrigerated or cooled across the heat sink (20).

14. The refrigeration system (100; 200) according to any one of the preceding claims, wherein the first heat transfer structure (20) is thermally coupled to the cold side (CS) of the thermoelectric device (10) via a layer of thermal interface material (TIM).

15. The refrigeration system (100; 200) according to any one of the preceding claims, wherein the thermoelectric device (10) includes one or more Peltier elements thermally coupled to the first and second heat transfer structures (20, 30; 20, 30*).

16. The refrigeration system (100; 200) according to any one of the preceding claims, wherein the supply of low humidity air to feed the evaporative cooler (50; 50*) is a supply of dehumidified dry air exhibiting a relative humidity (RH) that is lower than that of ambient air.

17. The refrigeration system (100; 200) according to any one of the preceding claims, wherein the supply of low humidity air is a supply of low humidity air exhibiting a relative humidity (RH) of less than 20%, preferably of less than 10%.

18. A combined dehumidification and refrigeration system (DRS) comprising a refrigeration system (100; 200) in accordance with any one of the preceding claims and a dehumidification system (300) that is operatively coupled to the refrigeration system (100; 200) and configured to harvest moisture from hot humid air exiting the second heat transfer structure (30; 30*) and supply dehumidified dry air that is fed to the evaporative cooler (50; 50*).

19. The combined dehumidification and refrigeration system (DRS) according to claim 18, further comprising a ventilator (VT) to force circulation of the dehumidified dry air through the evaporative cooler (50; 50*).

20. The combined dehumidification and refrigeration system (DRS) according to claim 18 or 19, wherein the dehumidification system (300) includes an adsorber system (600; 610, 620) coupled to the airflow path (35) of the refrigeration system (100; 200) and configured to recover coolant medium (W) from the hot humid air, which is recycled to the evaporative cooler (50; 50*).

21. The combined dehumidification and refrigeration system (DRS) according to claim 20, further comprising a collection reservoir (700) to collect coolant medium (W) recovered by the adsorber system (600; 610, 620).

22. The combined dehumidification and refrigeration system (DRS) according to claim 21 , wherein the evaporative cooler (50; 50*) is supplied with coolant medium (W) from the collection reservoir (700).

23. The combined dehumidification and refrigeration system (DRS) according to any one of claims 20 to 22, wherein the adsorber system (600; 610, 620) is configured to partly reject the dehumidified dry air produced by the adsorber system (600; 610, 620) into the environment and to partly recycle the dehumidified dry air produced by the adsorber system (600; 610, 620) to the evaporative cooler (50; 50*).

24. The combined dehumidification and refrigeration system (DRS) according to any one of claims 20 to 23, further comprising an ambient air intake to channel ambient air to the adsorber system (600; 610, 620) and, as the case may be, to the evaporative cooler (50; 50*).

25. The combined dehumidification and refrigeration system (DRS) according to claim 24, wherein the coolant medium (W) is water and wherein the adsorber system (600; 610, 620) also acts as atmospheric water harvesting system configured to harvest water from the ambient air.

26. The combined dehumidification and refrigeration system (DRS) according to any one of claims 20 to 25, wherein the adsorber system (600; 610, 620) includes first and second adsorber units (610, 620) that are each configured to undergo successive adsorption and desorption cycles, wherein the first adsorber unit (610) is configured to be selectively coupled to an input side of the evaporative cooler (50; 50*), wherein the second adsorber unit (620) is configured to be selectively coupled to an output side of the second heat transfer structure (30; 30*), wherein the combined dehumidification and refrigeration system (DRS) is configured such as to operate cyclically in accordance with the following sequence of operating phases: (i) a first operating phase during which the first and second adsorber units (610, 620) are both operatively coupled to the refrigeration system (100; 200) and each operated to undergo an adsorption cycle such that dehumidified dry air produced by the first adsorber unit (610) is fed to the evaporative cooler (50; 50*) and hot humid air exiting the second heat transfer structure (30; 30*) is fed to the second adsorber unit (620);

(ii) a second operating phase, triggered once the second adsorber unit (620) reaches saturation, during which the second adsorber unit (620) is uncoupled from the refrigeration system (100; 200) and is operated to undergo a desorption cycle; and

(iii) a third operating phase, triggered once the first adsorber unit (610) also reaches saturation, during which the first adsorber unit (610) is uncoupled from the refrigeration system (100; 200) and is likewise operated to undergo a desorption cycle.

27. The combined dehumidification and refrigeration system (DRS) according to claim 26, wherein the combined dehumidification and refrigeration system (DRS) is further configured such that, during the first operating phase, dehumidified dry air produced by the second adsorber unit (620) is partly fed back to the evaporative cooler (50; 50*) and partly rejected into the environment.

28. The combined dehumidification and refrigeration system (DRS) according to claim 26 or 27, wherein the combined dehumidification and refrigeration system (DRS) is further configured such that, during the second operating phase, hot humid air exiting the second heat transfer structure (30; 30*) is at partly rejected into the environment and partly fed to the first adsorber unit (610).

29. The combined dehumidification and refrigeration system (DRS) according to any one of claims 26 to 28, wherein, during the first and second operating phases, the first adsorber unit (610) is fed with ambient air from the environment.

30. The combined dehumidification and refrigeration system (DRS) according to claim 29, wherein, during the third operating phase, the evaporative cooler (50; 50*) is fed with ambient air from the environment.

31. The combined dehumidification and refrigeration system (DRS) according to any one of claims 26 to 30, wherein the combined dehumidification and refrigeration system (DRS) is further configured such that, during the second and third operating phases, coolant medium (W) is recovered from each adsorber unit (610, 620) undergoing the desorption cycle for supply to the evaporative cooler (50; 50*).

32. A refrigeration method comprising:

(a) providing a thermoelectric device (10) exhibiting a cold side (CS) and hot side (HS);

(b) coupling the cold side (CS) of the thermoelectric device (10) to a first heat transfer structure (20) to act as a heat absorber to draw heat away form an adjacent location (1000) to be refrigerated or cooled;

(c) coupling the hot side (HS) of the thermoelectric device (10) to a second heat transfer structure (30; 30*) to act as a as heat rejector to reject the heat drawn from the adjacent location (1000); and

(d) channelling airflow across the second heat transfer structure (30; 30*) to draw heat away from the second heat transfer structure (30; 30*), wherein step (d) includes providing an evaporative cooler (50; 50*) to reduce a temperature of the hot side (HS) of the thermoelectric device (10), supplying a coolant medium (W) to the evaporative cooler (50; 50*), and feeding the evaporative cooler (50; 50*) with low humidity air to cause evaporation of the coolant medium (W).

33. The refrigeration method according to claim 32, wherein the evaporative cooler (50) is positioned upstream of the second heat transfer structure (30) such that cold humid air exiting the evaporative cooler (50) is channelled across the second heat transfer structure (30).

34. The refrigeration method according to claim 31 , wherein the second heat transfer structure (30*) integrates the evaporative cooler (50*) which is thermally coupled to the hot side (HS) of the thermoelectric device (10).

35. The refrigeration method according to claim 34, involving evaporation of the coolant medium (W) directly within a core of a common thermally conductive structure integrating the second heat transfer structure (30*) and the evaporative cooler (50*).

36. The refrigeration method according to any one of claims 32 to 35, further including providing the evaporative cooler (50; 50*) with a thermally conductive porous wick structure (500), wetting the porous wick structure (500) with the coolant medium (W), and exposing the wetted porous wick structure (500) to the airflow to cause evaporation of the coolant medium (W).

37. The refrigeration method according to claim 36, wherein the porous wick structure (500) is wetted by capillary action.

38. The refrigeration method according to claim 36 or 37, wherein channelling the airflow through the evaporative cooler (50; 50*) includes channelling the airflow through channels (500A) formed in the porous wick structure (500).

39. The refrigeration method according to any one of claims 32 to 38, further comprising: exposing a heat sink (20) acting as the first heat transfer structure (20) to a flow of air circulating within a space (1000) to be refrigerated or cooled; and blowing cold air exiting the heat sink (20) into the space (1000) to be refrigerated or cooled to force circulation of warmer air from the space (1000) to be refrigerated or cooled across the heat sink (20).

40. The refrigeration method according to any one of claims 32 to 39, wherein feeding the evaporative cooler (50; 50*) with low humidity air includes feeding of dehumidified dry air exhibiting a relative humidity (RH) that is lower than that of ambient air.

41 . The refrigeration method according to any one of claims 32 to 40, wherein feeding the evaporative cooler (50; 50*) with low humidity air includes feeding of dehumidified dry air exhibiting a relative humidity (RH) of less than 20%, preferably of less than 10%.

42. A combined dehumidification and refrigeration method involving refrigeration or cooling of an adjacent location (1000) to be refrigerated or cooled in accordance with any one of claims 32 to 41 , wherein the method includes harvesting moisture from hot humid air exiting the second heat transfer structure (30; 30*) and feeding dehumidified dry air to the evaporative cooler (50; 50*).

43. The combined dehumidification and refrigeration method according to claim 42, further including forcing circulation of the dehumidified dry air through the evaporative cooler (50; 50*).

44. The combined dehumidification and refrigeration method according to claim 42 or 43, wherein ambient air drawn from the environment is temporarily fed to the evaporative cooler (50; 50*) in the event dehumidified dry air cannot be supplied thereto.

45. The combined dehumidification and refrigeration method according to any one of claims 42 to 44, wherein harvesting moisture from the hot humid air exiting the second heat transfer structure (30; 30*) includes subjecting the hot humid air to adsorption.

46. The combined dehumidification and refrigeration method according to any one of claims 42 to 45, wherein the dehumidified dry air is produced at least partly as a result of subjecting ambient air drawn from the environment to adsorption.

47. The combined dehumidification and refrigeration method according to claim 45 or 46, further comprising recovering adsorbed water by subsequent desorption for use as the coolant medium (W).

48. The combined dehumidification and refrigeration method according to claim 47, further comprising collecting the water recovered by desorption in a collection reservoir (700) for supply to the evaporative cooler (50; 50*).

49. The combined dehumidification and refrigeration method according to any one of claims 45 to 48, wherein the dehumidified dry air produced as a result of adsorption is partly rejected into the environment and partly recycled to the evaporative cooler (50; 50*).

50. The combined dehumidification and refrigeration method according to any one of claims 45 to 49, including selectively coupling first and second adsorber units (610, 620) respectively to an input side of the evaporative cooler (50; 50*) and to an output side of the second heat transfer structure (30; 30*), and cyclically operating the first and second adsorber units (610, 620) in accordance with the following sequence of operating phases:

(i) a first operating phase during which the first and second adsorber units (610, 620) are both operated to undergo an adsorption cycle such that dehumidified dry air produced by the first adsorber unit (610) is fed to the evaporative cooler (50; 50*) and hot humid air exiting the second heat transfer structure (30; 30*) is fed to the second adsorber unit (620); (ii) a second operating phase, triggered once the second adsorber unit (620) reaches saturation, during which channelling of the hot humid air to the second adsorber unit (620) is interrupted and the second adsorber unit (620) is operated to undergo a desorption cycle; and

(iii) a third operating phase, triggered once the first adsorber unit (610) also reaches saturation, during which production of dehumidified dry air by the first adsorber unit (610) is interrupted and the first adsorber unit (610) is likewise operated to undergo a desorption cycle.

51 . The combined dehumidification and refrigeration method according to claim 50, wherein, during the first operating phase, dehumidified dry air produced by the second adsorber unit (620) is partly fed back to the evaporative cooler (50; 50*) and partly rejected into the environment.

52. The combined dehumidification and refrigeration method according to claim 50 or 51 , wherein, during the second operating phase, hot humid air exiting the second heat transfer structure (30; 30*) is at partly rejected into the environment and partly fed to the first adsorber unit (610).

53. The combined dehumidification and refrigeration method according to any one of claims 50 to 52, wherein, during the first and second operating phases, ambient air is fed to the first adsorber unit (610).

54. The combined dehumidification and refrigeration method according to claim 53, wherein, during the third operating phase, ambient air is fed to the evaporative cooler (50; 50*).

55. The combined dehumidification and refrigeration method according to any one of claims 50 to 54, wherein, during the second and third operating phases, coolant medium (W) is recovered from each adsorber unit (610, 620) undergoing the desorption cycle for supply to the evaporative cooler (50; 50*).