The invention generally relates to a cooling element, e.g. a panel.

To cool housings, or an environment in general, various systems are known.

First, there is the roof-pond which however, to avoid problems related to water accumulation and hygiene maintenance, only exploits the heat capacity of retained water, sealed almost always in sterile and waterproof containers. In conjunction with the roof-pond an uncomfortable covering system is always needed. There are other systems, where the water is left exposed (roof pool), wherein the cooling effect occurs both as a result of the heat capacity and of evaporation, but with the need for water supply and hygienic maintenance. These systems also only work on flat roofs.

There are also similar thermal machines, such as air conditioners/ air- processors, which lower the temperature of the environment by directly injecting forced air conveyed through a wet filter. The water must be guided inside the system, and is then evaporated by blowing external air above it. Another disadvantage is that one interferes with the environment due to emissions of very humid air. In spray evaporators there are instead water sprayers that vaporize it over the covers. It is a hydro- mechanical system that consumes enormous amounts of water, and wherein the evaporation of the same firstly involves the atmospheric air and subsequently the covering surface of the building.

Then there are "green roofs" (also called roof gardens), which have excessive inertias, given the considerable layer of vegetal soil necessary to plants, have huge weight, are in need of maintenance and with the necessity of water supply if set in highly sunny regions. Here the process of evapo- transpiration is beneficial to the vegetal cover and only mildly to the rooms below. Another known method is the evaporation under photovoltaic panels, where the excess waste water deriving from the green roof is exploited, to convey it, for evaporative purposes, under the photovoltaic panels. This method can be used only on flat surfaces, without envisaging forms of water retention under the photovoltaic panel. It has in fact the same needs and disadvantages of green roof.

Finally, there are the dehumidifying mortars, almost all aimed to sorption by capillary action from the wall and/ or from the environment. They do not possess a high capacity to retain water and lack progressively of process reversibility for the co-presence of adsorbent processes that alter the initial porosity/ composition.

In the present specification, the following definitions are used:

phase transition (or change of state or passage of state or state transition) indicates the transformation of a thermodynamic system from one aggregation state (e.g. solid, liquid or vapor) to another;

sorption indicates generically a phenomenon of establishment of bonds between the molecules of two or more different phases, which involves both the surface and the interior of the phase;

absorption indicates in particular the retention of a material (absorbate) by another material (absorbent). Commonly it relates to gases, liquids or solids retained within a liquid or a solid. In the case of chemical absorption, there are established chemical bonds between the absorbent and the absorbate. In the case of physical absorption, due to the trapping of a fluid in gaps and interstices of the solids, there is no phase transition of the absorbate;

adsorption indicates a chemical-physical phenomenon which consists of the accumulation of one or more fluid substances (liquid or gaseous) on the surface of an adsorbent (solid or liquid) . In the phenomenon of adsorption the chemical species (molecules, atoms or ions) establish between each other an interaction of chemical-physical type (through Van der Waals forces or chemical intramolecular bonds) on the separation surface between two different phases. From a thermodynamic point of view, the adsorption can be described as a phase transition that occurs on the surface of the asdorbent. While the adsorption is a surface phenomenon, the absorption involves the entire mass in question.

JP 2002 103505 describes a film which does not requires special equipment, artificial feeding or water spray to obtain a cooling effect. The film is constituted by a first moisture-permeable layer with a reflectivity to infrared rays, laminated on a second layer having hysteresis characteristics and capable of adsorbing and releasing steam. Inside the second layer a state transition (condensation) occurs of the vapor from the gaseous phase to the liquid adsorbed phase.

US 2010/015430 generally describes an article having reversible properties of thermal regulation. It comprises a substrate and a phase change functional polymeric material having a thermal load capacity. There is no mention to specific applications, and no further layers are mentioned. In this case, too, a passage of state is used to tie the water vapor present in the gas phase to the polymeric material (adsorption) and obtain the cooling effect when the adsorbed water returns to a vapor state.

The main object of the invention is to provide a cooling system and method that is easy to build and with excellent thermal efficiency.

Another object is to provide a cooling system and method using materials which are readily available commercially. Another object is to provide a cooling system and method which achieves an isolation/ insulation system not based on thermal transmittance but on the heat capacity of water, in order to then exploit the latent heat of the same water in an evaporation phase. A coating element or coating layer is proposed as defined in the appended claims, i.e. an element or layer, e.g. for coating applications in buildings, able to cool the coated space or the object it is in contact with, comprising a support means, e.g. with lattice or mesh structure,

a sorption material, contained between void spaces of the support means, able (i) to absorb and retain water always in the liquid state, and (ii) to release it in the form of steam when heated; and

at least a second layer, superimposed to the first, which is preferably formed by inert material and is equipped with channels passing through its thickness (i.e. that run through the thickness to form channels), for the passage of water and steam to and from the first layer.

In this way the insulation effect of the element and the absorption and evaporation phenomena of the water inside it are improved. The water retained in the element, mainly by the action of said material, acts in the first place as a thermal flywheel, therefore as an insulation, by its ability to accumulate energy, but also and above all as a cooling agent, due to its high latent vaporization heat when, e.g. by the sun and wind, the water evaporates.

This is made possible both by the use of a water- sorpting material (through a process of physical absorption) in the first layer (such as for example polyacrylic acid, polyacrylate salts, etc.) or other solid substances, capable of receiving and retaining large quantities of water in the liquid state, possibly forming a gelatinous-looking mass, and of retaining it even in conditions of slope, and by an optional adsorbent material comprised in the second layer. The release of water from said element in the form of steam results in a high heat disposal.

The support means or the support layer may be e.g. a condensed gravel or a sponge mortar or a grout or a stone conglomerate. The support means or support layer may also be a mortar, preferably with a high porosity. Advantageously, the coating element or coating layer, or the support means or the support layer, may have alveolar or reticular structure so as to form cells in which the sorption material is contained. The aim is to improve the retention in the layer of sorption material, which can comprise - or be in the form of - gel.

The second layer has the following advantages and effects:

- with its porous or alveolar or ducted structure it acts as a filter with respect to the sorption material. If atmospheric impurities (dust or powder) or those contained in the water or rain would reach the sorption material it would get dirty, thereby resulting in loss of performance and/ or a drastic reduction of useful operating life;

- it prevents the total dispersion of moisture towards the environment when the moisture is released from the sorption material. The moisture trapped in the channels or alveoli may (i) condense again, to be again captured by the sorption material "reloading" it, or may (ii) leave the second layer towards the environment subtracting heat to said element or coating layer;

- it acts as a thermal flywheel and may in itself be the place of evaporation (by water vapor adsorbed or absorbed inside it), thereby assisting the cooling by means of heat dissipation. Advantageously, the second layer may have an alveolar or lattice structure to form cells communicating with each other. The filter effect and water recovery effect is thus amplified.

According to another possible embodiment, the coating layer comprises mortar or grout containing inside the sorption material. The effect is to form a breathable, cooling panel for buildings.

The coating element or coating layer may also be optionally covered by or coupled to:

- a first waterproof, particularly breathable and/ or reflective, membrane or barrier; and/ or - a second breathable and/ or filtering membrane; and/ or

- a rigid cover element provided with pass-through openings.

Preferably between the second layer and the support means or support layer there is a third, breathable layer, e.g. consisting of or comprising a three-dimensional mesh or in general an alveolar material with alveoli bigger than those present in the second layer, so as to allow a better passage of air inside it. Experimentally it has been observed that the absence of direct contact between the second layer and the support means or layer amplifies the cooling effect, especially if between said two layers there passes air, since the sorption material is able to release water, in vapor form, in the air flow in a more efficiently way. Furthermore, such layer is able to enhance the filtration effect of the water toward the underlying sorption material.

Preferably between the third layer and the support means or support layer there is a fourth, porous and breathable layer which has the function of retaining the sorption material (e.g. in granules) and to adduce water. The fourth layer has alveolar structure, or provided with channels, whose alveoli or channels preferably have dimensions smaller than those of the third layer. Through the fourth layer, e.g. by capillary effect, water can be introduced into the coating element or coating layer to load and supply with liquid the sorption material. In general one may also envisage a means or conduit to load and supply with water the sorption material, where the means or conduit extends inside any one or more layers that make up the coating element or coating layer. In general, in the elements defined herein the alveoli may be of regular or irregular shape.

Preferably said coating element or coating layer is comprised in, or consists of, (i) a mat to be applied on an object to be cooled, (ii) a wall panel, or (iii) a tile. The following description refers to a preferred embodiment of cooling element or cooling layer and will further highlight its advantages, by reference to the accompanying drawings in which:

Fig. 1 shows a vertical cross-section of a coating element capable of cooling; Fig. 2 shows a vertical cross-section of another coating element capable of cooling, with features identical to the first but where the functions of absorption and adsorption of water do not take place in different layers but together.

In the figures same numerals indicate same or similar parts, and the element is described as being in use. In order not to crowd the drawings, not all equal elements are marked.

A coating, cooling element or layer 100, for example a panel, able to cool, is shown in figure 1.

The layer 100 comprises a lattice support 102, e.g. a mesh or alveolar structure, like e.g. a filamentous mass, a 3D fabric, glass wool, or a (plastic or iron) mesh or a spongy or honeycomb-shaped layer. Inside the lattice 102 there is an element 104 capable of absorbing water, and optionally there is a water adsorbing element 106.

The panel 100 can have the form e.g. of a mat to be applied on an object to be cooled, or of a wall panel, or of a tile.

The absorbent material 104, e.g. in the form of granules or powder, may be or comprise for example polyacrylic acid, polyacrylate salt, etc., optionally mixed with aluminum powder and lime (see below).

Overall, the layer 100 is capable of sorption, that is capable of absorbing water, and of retaining the water, and possibly also capable of adsorption thanks to the material 106 (see below). To do this, preferably the support lattice 102 may comprise containment cells C that contain the water- absorbing material 104, e.g. in gel form, or e.g. in dry or hydrated form. The cells, e.g. formed by the empty spaces in the lattice 102, may have straight or inclined walls, or e.g. may be in the form of pockets, bags or cavities in the mesh or alveolar structure, or may generally be formed by a three- dimensional lattice or by pockets or alveoli of varying size as long as they can hold the material 104 in various conditions of use. Shape, number and spatial arrangement of the cells may vary.

To prevent the absorbent material 104 from getting out of the layer 100, it is preferred to put a filtering and/ or breathable and/ or reflective membrane 108 on the upper surface of the layer 100. The membrane 108 allows the passage of steam or water but not of the material 104.

Under the layer 100 a membrane /layer/ plate /sheath 1 10 may be applied, preferably but not necessarily breathable, not insulating from a thermal point of view. The membrane 1 10 also serves to retain the absorption material 104 inside the lattice or cell 102.

The thickness of the layer 100 can be overall between 2 mm and 100 mm, so as to allow a considerable accumulation of water even in case of prolonged drought.

The material 106 may be formed by inert materials and, to a varying extent, by water adsorbent materials, e.g. a cement aggregate with inert material of various nature (e.g. gravel, expanded clay, zeolite, earthenware, etc.) having controlled granulometric curve, or by a natural conglomerate/ agglomerate (e.g. pudding-stone, tuff, materials of volcanic origin, etc.).

It is preferable that the material 106, especially when used in the absence of the membrane 108, has asperities/ surface porosities so as to offer a greater surface area to facilitate condensation/ adsorption of dew, fog or humidity in general. These latter can be important surrogates of atmospheric precipitation, managing to capture significant amounts of water, especially from night dew.

What has been said for the material 106 may also apply in general to the aforementioned support means or layer. OPERATION

The layer 100 is able to capture and retain water, e.g. in the form of rain or after being wet. The material 104 allows a complete reversibility of the absorption/ evaporation process given by the hysteretic behavior of the absorbent material.

The element 100 has various functions.

It constitutes a thermal inertial mass with the ability to cope with heat propagation due to solar radiation S in all seasons, especially in summer. In essence, the layer 100 behaves like a confined layer of water. Having the water a high heat capacity, a lot of heat is necessary to raise the temperature of the layer 100 and that of the object or space H on which such element is applied. In other words, given a certain heat flux S hitting on the layer 100, the water contained in it will heat little, thereby isolating said object H a lot. In winter or in cold places, the possible freezing of the water contained in the material 104, through the "igloo" effect, prevents the spread of extreme temperatures towards the object H underlying the layer 100, or - equally - an excessive heat flow in the reverse direction, with considerable advantages, especially compared to conventional insulators. Besides, because of the heat coming from the outside (mainly in the form of solar radiation, see arrow S) and hitting on the layer 100, the water contained in the material 104 can evaporate, and the vapor thus generated leaves the layer 100. The evaporation cools very effectively the space H below the layer 100. Note that the element or layer 100 is automatically active when one really needs to cool, that is during times of peak heat when the temperature is high and solar radiation is maximum. The high latent vaporization heat of water ensures both high heat dissipation from the underlying object H, and high thermal transmission, benefiting both the underlying environments and the above elements (e.g. solar panels placed above the element 100, which will in part be cooled).

The element or layer 100 further has the following advantages, i.e. it manages to:

· absorb and utilize the water produced by condensation of atmospheric moisture (e.g. dew);

• provide greater storage capacity and retention of rainwater even with high inclinations typical of roofs;

• be lightweight and easy to mount, especially if the sorption material 104 is initially in dry form;

• constitute a significant barrier to fire, since it is a material having extinguishing nature;

• achieve a strong reduction of sound waves and electromagnetic waves. OPTIONS

According to a variant, the sorption material 104 is in dry or hydrated form, or may be incorporated in another material 1 12, such as e.g. mortar or grout (shown partially in figure 1), preferably with a high porosity. The material 1 12 is distributed or dispersed in the lattice 102 or in a cell/ pocket.

The porosity characteristics for the material 1 12 can be achieved by the use of (a) rapid-setting binders (cement, trass, etc.) and/or (b) by adding a mixture of sand and/ or gravel, and/ or expanded clay, and/ or zeolite, and/ or earthenware. The porosity is chosen so as to leave space to the sorption material 104, in the form of granules or powder (such as polyacrylic acid, polyacrylate salt, etc.) mixed with micronized aluminum powder and lime.

What has been said for the material 1 12 may also apply in general to the aforementioned support means or support layer. Such mixture, during the packaging phase, first will produce a reaction of the aluminum powder with the lime, and the consequent development of hydrogen will generate small alveoli/ bubbles, which will find accommodation between the spaces of the component (b) . The action of the cement binder (a) will only occur successively, and simultaneously to the action of water sorption by the sorption material 104.

The sorption material 104 will remain inside the alveoli generated by the reaction of the aluminum, also as a result of a drying process of the layer 100, while remaining however capable of water sorption and of retaining water subsequently supplied during the working life of the element 100.

This variant involves an increase of the water sorption capacity of the layer 100, especially when used in the case of coverings with steep gradients or set vertically, when as a lattice 102 a very holding material is not used, such as e.g. a three-dimensional mesh, or in the case where the sorption material 104 is not placed within pockets or cells of various nature.

In general, the sorption material 104 can be mixed as indicated above to mortar or grout and can be applied directly (without other layers), forming the layer 100 on the wall or object H to be cooled.

The lattice 102 may also be formed or replaced by the same element 104. See now figure 2 for another variant.

A cooling, coating element or layer 10, e.g. a panel, capable of cooling is made by the superposition of two layers 20, 40.

The layer 20 is constituted by sorption material and made e.g. as the aforesaid layer 100, i.e. is capable of absorbing and retaining water. To do this, the layer 20 has a structure with containment cells 22, with walls 22b, which contain water sorption material 24 (equivalent to the material 104 of figure 1).

To prevent the sorption material 24 from getting out of the layer 20, it is preferred to arrange a breathable/ filtering and/ or reflecting membrane 26 placed between the layer 20 and the layer 40. The membrane 26 allows the passage of the steam or of the liquid water.

On the bottom of the layer 20 one can apply a membrane/ layer/ plate 28, possibly but not necessarily breathable and/ or reflective, but not insulating from a thermal point of view. The membrane 28 also serves to retain the sorption material 24.

For the thickness of the layer 20, what has been said for the thickness of the layer 100 of figure 1 holds.

The layer 40 is in general permeable, with drainage cavities or channels 42 which traverse the thickness thereof. It can be formed by inert materials, and to a varying extent by water adsorbing materials 44, e.g. a cement conglomerate with inert materials of various nature (e.g. gravel, expanded clay, zeolite, earthenware, etc.) having controlled granulometric curve, or by a natural conglomerate/ agglomerate (e.g. pudding-stone, tuff, materials of volcanic origin, etc.).

It is preferable that the materials 44 forming the layer 40 have surface roughness and/ or porosity so as to offer a greater surface area to facilitate condensation/ adsorption of dew, fog or humidity in general. The latter can be important surrogates of atmospheric precipitation, managing to capture significant amounts of water, especially from night dew.

The thickness of the layer 40 may be comprised overall between 20 mm and 1000 mm, so as to provide also a thermal inertial mass. The layer 40 rests and/ or is joined, or glued, or otherwise secured, on the layer 20.

Optionally there can be a layer 60 on the layer 40, adapted to improve the resistance to wear and the filtering of rainwater. The layer 60 can also be made out of micro-perforated or perforated metal sheet, or any other perforated or permeable material.

Note another advantage of the layer 40: it increases the surface area in contact with air, and thus it increases the amount of captured water e.g. from rain or from condensation of dew at night, and at the same time it improves the vapor flow from the element 10 towards the surrounding air.

The layer 40 may be replaced, for reasons of aesthetics, lightness and practicality, directly by the layer 60, e.g. in the case of sandwich metal sheet or tiles, floating floors, roof tiles or bent tiles, in each case having always spaces between each other to allow the passage of water.

OPERATION

The layer 20 operates according to the principles already described for the layer 100 of figure 1 , and is able to capture and retain water, e.g. in the form of rain, coming from the upper layer 40 and/ or 60 via channels or holes, and filtered e.g. by the membrane 26, with a complete reversibility of the absorption/ evaporation process given by the hysteretic behavior of the sorption material 24 contained in it.

The layer 20 has various functions: - it constitutes an inertial thermal mass with the ability to cope with the heat propagation mainly due to the solar radiation S, and in parallel, through the "igloo" effect, it prevents the spreading of extreme temperatures towards the space H underlying the element 10;

- in addition, especially because of the external heat flow S transferred from the layer 40 and/ or 60 towards the layer 20, the water contained in the material 24 evaporates, and the vapor can escape through the layers 40 and/ or 60 via the channels /holes present in these (some part of it can condense, leak and be recovered again by the sorption material 24). Evaporation cools very efficiently the space H under the layer 20. The two coupled layers 20, 40 have synergistic action, the layer 60 has only aesthetic and/ or protective action with optional filtration functions. In the water accumulation phase, i.e. the cold period of the day or during rain, the water absorption by the sorption material 24 and the possible adsorption or vapor condensation on the materials present in the layer 40 of the element, develop generally a weakly exothermic reaction, which is in any case negligible compared to that which is manifested during the evaporation phase (warm period of the day) by which a strong endothermic reaction takes place. Note that such process does not take place as in PCMs (Phase Change Materials), and their known state changes, at constant temperature and confined areas, but the water absorbed in the various layers has a change of state necessarily in different settings, with a negative energy flow within the coating elements or layers, while the balancing of the energy balance takes place in the atmosphere. Therefore it always requires a renewed supply of water as well as of heat, while in the traditional uses of PCMs these materials remain constantly trapped in closed areas, without any supply of new material.

Note also that the element 10 is automatically active when actually it serves to cool the space H (e.g. a house) that is in the times of greatest heat, when the temperature is high and solar irradiation is maximum. The high latent vaporization heat of water ensures both high heat dissipation of the underlying zone H and a high thermal transmission, benefiting both the underlying environments and the overlying elements (e.g. solar panels placed on the element 10, which will in part be cooled). An advantage resulting from the implementation of the element 10 by means of reversible coupling of the layers 20, 40, 60 (without mixing them or penetrating one within the other) consists of the possibility, in the heat disposal phase, to be able to recover and group separately the different materials constituting the layers 20, 40, 60. The sorption material 24 may exhibit the same characteristics of composition and production already described for the material 104 of figure 1.

As a further variant, whenever one wishes to increase the surface adsorption capacity of the aggregates 44 in the layer 40, it is possible to process the entire mass of the layer 40 with wetting agents (e.g. surfactants) in order to improve the ability of the solid material to capture the atmospheric humidity.

What has been said for the material 40 may also apply in general to the aforementioned support means or support layer. Besides the advantages already expressed for the layer 100 of figure 1 , the layer 10 is able to also bring the following benefits:

• draining rainwater thereby hindering partially the effects of excessive/ sudden rainfalls, with gradual release over time of water towards the underlying element. The element 10 therefore also acts as a collecting basin;

• partially purifying waters, especially those of the first rain;

• significant barrier to acoustic and electromagnetic waves.