Phase change material for cooling air

Abstract

Aspects of the invention relate to phase change materials that can be used to cool air. In particular, the phase change material is a composition comprising dimethyl sulfoxide and a salt selected from the group consisting of sodium nitrate, potassium nitrate and lithium bromide. The phase change materials are designed for efficient storage and release of thermal energy, by use of which heat and cold can be preserved at low demand, nighttime periods with lower energy rates. Then, the stored energy is released during a peak demand period, so that the pressure on the power grid is reduced, and the energy-saving strategy is kept consistent with an energy-saving strategy using off-peak pricing.

Description

Technical Field

[0001] Several aspects of the present invention relate to phase change materials that can be used to cool air. Background Art

[0002] Phase change material (PCM) is a material that absorbs and releases thermal energy by undergoing a phase change, for example, from solid to liquid and back from liquid to solid. As PCM, organic materials such as fatty acids or paraffins, and inorganic materials such as salt hydrates have been used.

[0003] Through melting and solidification (eg, crystallization) of the PCM, the PCM is able to store and release a large amount of energy per unit mass, thereby providing an effective means for cooling the environment.

[0004] Cooling an environment, such as air conditioning, is a process that typically requires high energy input during periods of peak energy consumption. Standard air conditioning utilizes a liquid refrigerant within an evaporator coil. The liquid refrigerant is compressed and cooled by a compressor. Warm air from within the conditioned environment is then passed over the evaporator coil containing the cooled refrigerant, thereby cooling the air. The cooled air is then introduced into the conditioned environment, and the liquid refrigerant, heated by contact with the warm air, evaporates into the evaporator coil. The evaporated refrigerant then flows to a compressor, typically coming into contact with ambient, outdoor air, where it is compressed and cooled again, restarting the cycle of cooling the warm air. During hot daytime hours in a given region, many users of the power grid will run their air conditioning, placing heavy demands on power plants during peak demand periods. To accommodate this, power grids may implement variable daytime pricing programs to manage load and maintain supply.

[0005] Because PCMs are designed to efficiently store and release thermal energy, using them allows for the conservation of heating and cooling during low-demand, nighttime hours, taking advantage of lower energy rates. This stored energy can then be released during peak demand hours, reducing stress on the grid and aligning with energy conservation strategies that utilize off-peak pricing. Summary of the Invention

[0006] Described herein are solutions of inorganic salts in dimethyl sulfoxide (DMSO) suitable for use as PCMs, particularly for air conditioning applications. These solutions can be cooled to crystallization temperature during off-peak hours, and the solidified solutions can then be used to cool air during peak hours.

[0007] Specific inorganic salts suitable for mixtures and solutions of DMSO for PCM applications include lithium bromide, potassium nitrate, and sodium nitrate. Preferably, the DMSO solution for PCMs may contain 2% to 14% (by weight) of these salts, preferably 4% to 12% of these salts, for cooling warm air. Further embodiments relate to methods for cooling a warm air environment, comprising transferring air from a warm environment to the vicinity of a PCM to cool the air, and then transferring the cooled air to the warm air environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1A and 1B Shown is a temperature profile for pure DMSO;

[0009] Figure 2 Shown is a temperature profile graph for a DMSO solution containing 4 wt % ZnCl2;

[0010] Figure 3 shows a temperature profile for a DMSO solution containing 4 wt % KCNS;

[0011] Figures 4A-4B Shown are temperature profiles for DMSO (neat) and DMSO solutions containing 2 wt %, 4 wt %, 6 wt % and 8 wt % LiBr, corresponding to cooling (4A) and melting (4B);

[0012] Figures 5A-5B shows temperature profiles for DMSO (neat) and DMSO solutions containing 2 wt%, 4 wt%, 6 wt%, 6.6 wt%, 8 wt% and 10 wt% KNO3 (5K and 5L), corresponding to cooling (5A) and melting (5B); and

[0013] Figures 6A-6B Shown are temperature graphs for DMSO (neat) and DMSO solutions containing 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt% and 14 wt% NaNO3, corresponding to cooling (6A) and melting (6B). DETAILED DESCRIPTION

[0014] the term

[0015] Dimethyl sulfoxide (DMSO): A transparent, colorless liquid at 20°C with the structure: (CH3)2SO.

[0016] Onset of Melting: Non-ideal mixtures and substances will melt (fuse) and crystallize (solidify) within a certain temperature range, and each process has a beginning and an end. The onset of melting is the temperature at which a solid mixture or substance begins to transform into a liquid phase. Therefore, it marks the temperature at which a PCM begins to absorb heat.

[0017] Tykos Melting Point: This is the temperature Maria Telkes referred to simply as the melting point during her pioneering research on PCMs. This temperature can be measured by slowly melting a mixture in an ambient environment (such as warm air) and observing a so-called plateau on the curve of the mixture's temperature versus time. In the absence of a phase change, heating of the ambient environment causes the mixture's temperature to rise. As the mixture melts, it consumes latent heat, a process also observed as "releasing cold." Unless otherwise specified, the term "latent heat" used herein should be understood as "latent heat of fusion." Due to this process, the temperature of the mixture stops rising or rises more slowly. Under certain melting conditions, a distinct melting point is observed when the temperature of the mixture stops rising, which can be identified as the Tykos Melting Point, coinciding with the onset of melting. In other mixtures, the temperature of the mixture rises slowly. The Tykos Melting Point is calculated using two points: the point at which melting begins, when the slope of the temperature increase decreases, and the point at which the slope of the temperature increase increases again. The average of these two points is the Tykos Melting Point.

[0018] Crystallization temperature: As used herein, crystallization temperature or solidification temperature refers to the specific temperature at which a substance transitions from a liquid phase to a solid crystalline phase during a cooling process. When one measures the temperature of a mixture as a function of cooling time using a constant-temperature coolant, a plateau or local maximum is present. In the case of supercooling, this local maximum is observed. In that case, the crystallization temperature is considered to be the temperature at the local maximum. If there is no supercooling and a plateau is observed, the crystallization temperature is considered to correspond to the onset of the plateau, also known as the onset of crystallization.

[0019] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The singular terms "a", "an", and "the" include plural references unless the context clearly indicates otherwise. Similarly, the word "or" is intended to include "and" unless the context clearly indicates otherwise. Although methods and materials similar or equivalent to the methods and materials described herein can be used in the practice or testing of the present disclosure, suitable methods and materials will be described below. The term "comprising" means "including". The abbreviation "e.g., for example" is derived from the Latin exempligratia and is used herein to indicate a non-limiting example. Thus, the abbreviation "e.g., for example" is synonymous with the term "e.g.". The term "consisting essentially of..." limits the scope to the specific materials described and those materials that have no substantial effect on the basic and novel characteristics of the claimed invention.

[0020] In case of conflict, the present specification, including explanations of terms, will control. In addition, all materials, methods, and examples are illustrative and not intended to be limiting.

[0021] As mentioned above, conventional air conditioning systems require significant energy to operate compressors during peak hours, thereby cooling the air to a comfortable temperature of approximately 20-25°C in warm environments, such as those inside buildings or homes. One way to reduce energy costs and grid energy demand during peak hours is to use Tycos PCM, which has a melting point of 7–12°C. During off-peak hours, such as nighttime, when ambient temperatures are low and demand for air conditioning is low, energy is consumed to cool this PCM to below freezing. After freezing during low-demand periods, the PCM remains frozen until air conditioning is needed and grid demand is high.

[0022] The cooling system described herein preferably utilizes Tycos PCM, which has a melting point of 7–12°C, by transferring warm air over the PCM, for example, by using an air duct equipped with a pump or fan to transfer the warm air from the warm environment to the PCM storage area. The PCM melts, absorbs heat energy from the warm air, and cools the air. The air can then be transferred to the warm environment, for example, via the air duct, to cool the warm environment to a comfortable temperature of 20–25°C.

[0023] Alternatively, the system described herein can use the cooled PCM described above to cool the coolant. The coolant can then be delivered to an area where it comes into contact with warm air, thereby cooling the warm air in a warm environment. According to one embodiment, the coolant is water.

[0024] The use of such a cooling system is beneficial for the environment because it eliminates the need to build new power plants to meet high demand during peak hours. Rather than using energy during peak hours, the cooling system described herein uses energy to solidify the PCM during off-peak hours, then uses it during peak hours to absorb heat through melting, thereby cooling the air and replacing a standard air conditioning system. Such a cooling system can be adapted to transfer heat to and from existing air conditioning systems, for example, using standard air conditioning system components such as compressors, condensers, heat pumps, storage tanks, and chillers, eliminating the need to replace the entire air conditioning system.

[0025] In many power grids, electricity costs are lower during periods of low demand. The system described herein can be very useful in providing energy-efficient and inexpensive air conditioning in warm environments. Preferred embodiments of the present invention may include DMSO in combination with one of lithium bromide, potassium nitrate, and sodium nitrate. When lithium bromide is used, the preferred weight percentage in DMSO is 2% to 6%. When potassium nitrate is used, the preferred weight percentage in DMSO is 2% to 6%. When sodium nitrate is used, the preferred weight percentage in DMSO is 4% to 12%.

[0026] In addition to inorganic salts, other additives may be added to the DMSO, for example additives that absorb water molecules and do not absorb salts and DMSO, to maintain a low water content and thus a homogeneous melt. Optionally, these additives are selected from molecular sieves and silica gel.

[0027] According to one embodiment, described herein is a composition for cooling air, comprising dimethyl sulfoxide and a salt selected from the group consisting of sodium nitrate, potassium nitrate, and lithium bromide. Optionally, the salt is sodium nitrate. Optionally, sodium nitrate is present in the composition in an amount of 4-12 weight percent. Optionally, sodium nitrate is present in the composition in an amount of 10-12 weight percent. Optionally, the salt is potassium nitrate. Optionally, potassium nitrate is present in the composition in an amount of 2-6 weight percent. Optionally, the salt is lithium bromide. Optionally, lithium bromide is present in the composition in an amount of 2-6 weight percent. Optionally, the composition is in solid form. Optionally, the composition consists essentially of dimethyl sulfoxide and a salt selected from the group consisting of sodium nitrate, potassium nitrate, and lithium bromide. Optionally, the composition consists of dimethyl sulfoxide and a salt selected from the group consisting of sodium nitrate, potassium nitrate, and lithium bromide. Optionally, no precipitation of the salt is observed after the composition solidifies and melts. Optionally, the composition has a latent heat that is less than 10% lower than the latent heat of pure dimethyl sulfoxide.

[0028] Further described herein is a method of cooling air in a warm air environment, comprising: solidifying a composition comprising dimethyl sulfoxide and a salt selected from the group consisting of sodium nitrate, potassium nitrate, and lithium bromide; causing warm air to flow from the warm air environment to the environment of the composition, thereby forming cool air; and causing the cool air to flow from the environment of the composition to the warm air environment, thereby cooling the air in the warm air environment. Further described herein is a method of cooling air in a warm air environment, comprising: solidifying a composition comprising dimethyl sulfoxide and a salt selected from the group consisting of sodium nitrate, potassium nitrate, and lithium bromide; contacting a coolant with the composition; causing warm air to flow from the warm air environment to the environment of the coolant, thereby forming cool air; and causing cool air to flow from the environment of the coolant to the warm air environment, thereby cooling the air in the warm air environment. Optionally, solidification is achieved using electricity drawn from the grid during off-peak electricity demand periods. The present invention further includes the following embodiments: 1. A composition for cooling air, comprising dimethyl sulfoxide and a salt selected from the group consisting of sodium nitrate, potassium nitrate and lithium bromide. 2. The composition of embodiment 1, wherein the salt is sodium nitrate. 3. The composition of embodiment 2, wherein the sodium nitrate is present in the composition in an amount of 4-12% by weight. 4. The composition of embodiment 3, wherein the sodium nitrate is present in the composition in an amount of 10-12% by weight. 5. The composition of embodiment 1, wherein the salt is potassium nitrate. 6. The composition of embodiment 5, wherein the potassium nitrate is present in the composition in an amount of 2-6% by weight. 7. The composition of embodiment 1, wherein the salt is lithium bromide. 8. The composition of embodiment 7, wherein the lithium bromide is present in the composition in an amount of 2-6 wt%. 9. The composition according to any of the preceding embodiments, which is in solid form. 10. The composition of any of the preceding embodiments, consisting essentially of dimethyl sulfoxide, and a salt selected from sodium nitrate, potassium nitrate, and lithium bromide. 11. The composition according to any of the preceding embodiments, consisting of dimethyl sulfoxide and a salt selected from sodium nitrate, potassium nitrate and lithium bromide. 12. The composition according to any of the preceding embodiments, wherein after solidification and melting of the composition, no precipitation of the salt is observed. 13. The composition of any of the preceding embodiments, having a latent heat greater than 10% less than the latent heat of pure dimethyl sulfoxide. 14. A method of cooling air in a warm air environment, comprising: a. solidifying the composition according to any one of the preceding embodiments; b. causing warm air to flow from the warm air environment to the environment of the composition, thereby forming cool air; and c. allowing the cool air to flow from the environment of the composition to the warm air environment, thereby cooling the air in the warm air environment. 15. A method of cooling air in a warm air environment, comprising: a. solidifying the composition according to any one of embodiments 1-13; b. contacting the coolant with the composition of step a; c. causing warm air to flow from the warm air environment to the coolant environment, thereby forming cool air; and d. Allowing cool air to flow from the coolant environment to the warm air environment, thereby cooling the air in the warm air environment. 16. The method according to embodiment 14 or 15, wherein solidification is achieved by using electricity drawn from the grid during off-peak electricity demand periods. Example

[0029] The following examples are provided to illustrate certain specific features and / or embodiments. These examples should not be construed as limiting the disclosure to the specific features or embodiments described.

[0030] Example 1: Solidification and melting of DMSO

[0031] One apparatus comprises a jacketed reactor with an internal volume of approximately 300 milliliters (ml) and equipped with a jacket into which a coolant can be introduced, and a temperature sensor within the internal volume. The temperature within the jacket is set and measured by a dynamic temperature control system / circulatory thermostat. The coolant used to cool the reactor is ethylene glycol or polyethylene glycol. The coolant can also serve as a heating medium when the contents of the internal volume are melted. To prevent heat loss, the reactor jacket is protected by a second vacuum jacket.

[0032] About 300 ml of the reactor's internal volume was filled with DMSO. The DMSO, which had a temperature of about 30° C., was cooled by introducing a coolant, which was maintained at 3° C., circulating through the jacket. Figure 1A In the graph, the temperature of the internal volume (represented by the upper line) and the temperature of the coolant in the external jacket (represented by the lower solid line) are tracked over time from the start of the experiment (x-axis). In the experiments depicted in the figure, the internal volume is designated as "mixture" even when DMSO alone is used. As shown, at this temperature, crystallization is measured at 18.3°C over a longer period of time, indicating that the coolant is extracting heat energy from the DMSO in the reactor, while the DMSO remains at the same (crystallization) temperature.

[0033] Then, the DMSO crystallized at about 4°C was heated by circulating the heating medium, and its temperature was increased from 3°C at a rate of 3.5°C / hour in a temperature-programmed manner until the entire contents of the reactor were completely melted. As the temperature in the jacket and the temperature of the contents of the reactor in the internal volume increased, the difference between them was measured. Figure 1B The relationship between this difference and the temperature of the internal volume is described in Figure 1B The temperature difference between the jacket and the reactor interior increases at approximately 15.5°C, indicating the onset of melting, which absorbs heat from the surrounding environment. At approximately 18.5°C, the temperature difference between the jacket and the reactor interior begins to decrease, as indicated by the peak in the curve. At approximately 28.5°C, melting is complete, as indicated by the curve, reaching a constant temperature difference between the jacket and the interior.

[0034] For the avoidance of doubt, Figure 1BThe entire process is described in , not as a time course, but in relation to the temperature of the inner volume during the temperature-programmed heating. The temporal evolution of the melting follows a general trajectory: the temperature of the jacket heating the inner volume always exceeds the temperature of the inner volume itself. Before the onset of melting, the temperature of the inner volume rises more slowly compared to the temperature-programmed heating of the jacket. After the onset of melting, the inner volume starts to absorb heat and experiences heating at a decreasing rate, thereby amplifying the temperature difference between the jacket and the inner volume. After a certain point in time, the temperature corresponding to Figure 1B At the peak in , the heating of the inner volume accelerates again, indicating that the melt strength has begun to decrease. At the end of the process, after melting is complete, the heating rate of the inner volume approaches the rate of temperature-programmed heating, while the temperature difference remains.

[0035] For DMSO, when the experiments were performed, the following physical parameters were found, as shown in Table 1:

[0036] Table 1:

[0037] The latent heat of pure DMSO was obtained from literature (Gaylord Chemical) and used to estimate the latent heat of the salt mixture. This estimate was based on the assumption that the latent heat of the mixture is proportional to the area under the curve of the temperature difference between the jacket and the mixture versus time. This assumption assumes that the weight and volume of the mixture are approximately the same in all experiments, and other conditions are also the same. Calibration was performed using pure dimethyl sulfoxide and a reference value for the latent heat of pure dimethyl sulfoxide, and the curve was numerically integrated to obtain the area under the melting curve of the temperature difference between the jacket and the mixture versus time.

[0038] As can be seen from Table 1, the melting point of Tycose is 16.75°C, which is higher than the ideal range for high-efficiency PCM.

[0039] Example 2A: Solidification and melting of DMSO + zinc chloride salt solution.

[0040] An attempt was made to prepare a solution of ZnCl2 in order to lower the melting point of DMSO. Initially, a 2 wt% ZnCl2 solution was prepared at room temperature and subjected to cooling and heating cycles as described in Example 1. The melting curves showed heterogeneous melting, making it difficult to determine the onset of melting and other characteristic temperatures, but it was clear that melting occurred at temperatures above the desired range. The term "heterogeneous melting" is used herein to refer to the process by which a solid transforms into a liquid phase in a non-uniform manner throughout its volume and / or through an intermediate phase and / or when the solid consists of multiple phases. This phenomenon often occurs when there is a range of melting points. Unlike homogeneous melting, where the entire material melts uniformly at a specific temperature, heterogeneous melting occurs in different parts of the material at different temperatures. When melting occurs without any phase transitions other than a single transition from solid to liquid, this type of melting is referred to as "homogeneous melting" or "simple melting." This latter type of melting is often described as ideal and theoretical. Non-uniform melting is not a problem unless it results in multiple melting points and results in a low latent heat. This is the case with zinc chloride in dimethyl sulfoxide. In general, inhomogeneous melting occurs in mixtures that are not well suited for use as PCMs. Figure 2 The heating of dimethyl sulfoxide containing 4 wt% zinc chloride is shown. The higher the concentration, the more pronounced the heterogeneous melting.

[0041] Example 2B: Solidification and melting of DMSO + iodide salt solution.

[0042] Solutions of potassium iodide (KI) of varying concentrations were prepared, expressed as weight % KI. The solutions were subjected to cooling and heating cycles as described in Example 1. Table 2 lists the data obtained from these cycles:

[0043] Table 2:

[0044] As shown in the table, even with the addition of relatively large amounts of KI, the melting point did not reach the target Tycos melting point, which is between 7 and 12 °C. The latent heat was observed to be reduced to approximately 80% of that of pure DMSO, indicating that solutions of KI in DMSO are not ideal PCMs due to their relatively low heat storage per unit mass.

[0045] Similarly, we also tested salts prepared with sodium iodide (NaI), but we determined that even with the addition of relatively large amounts of NaI, up to 8 wt%, they were unable to reach the target Tycos melting point of 7 to 12°C. The lowest achievable melting point at 8 wt% was 15.4°C. Similar to KI, at these concentrations, the addition of NaI lowered the latent heat of DMSO, and the mixture melted unevenly.

[0046] Example 2C: Solidification and melting of DMSO + potassium thiocyanate solution.

[0047] Solutions of potassium thiocyanate (KCNS) were prepared at various concentrations, expressed in weight percent. The solutions were subjected to cooling and heating cycles as described in Example 1. Table 3 lists the data obtained from these cycles:

[0048] Table 3:

[0049] In the case of 4% KCNS, non-uniform melting was observed. As shown in the table, in the case of 4% KCNS, its latent heat was observed to drop to a level significantly lower than that of pure DMSO, indicating that KCNS solutions in DMSO are not ideal PCMs due to their relatively low heat storage per unit mass. Figure 3 Shown is the heating of DMSO containing 4 wt % KCNS.

[0050] Example 3: Solidification and melting of DMSO + lithium bromide (LiBr) salt solution.

[0051] Solutions of lithium bromide (LiBr) of varying concentrations were prepared, expressed in weight percent. The solutions were subjected to cooling and heating cycles as described in Example 1. Table 4 lists the data obtained from these cycles:

[0052] Table 4:

[0053] As shown in the table, the target Tycos melting point was achieved at all tested concentrations between 2% and 8%. At 6%, a supercooling temperature of 7°C was observed. Solutions between 2% and 6% are favorable because they have relatively high latent heats and do not experience extreme supercooling. Furthermore, salt precipitation was evident at 8% LiBr.

[0054] Figures 4A-4B Temperature profiles of DMSO / LiBr solutions with different concentrations during cooling (4A) and melting (4B) are shown.

[0055] LiBr is hygroscopic and requires special storage and handling conditions.

[0056] Example 4A: Solidification and melting of DMSO + potassium nitrate (KNO3) salt solution

[0057] Solutions of KNO3 with varying concentrations were prepared, expressed in wt %. The solutions were subjected to cooling and heating cycles as described in Example 1. Tables 5A and 5B list the data obtained from these cycles:

[0058] Table 5A:

[0059] Table 5B:

[0060] As shown in Tables 5A and 5B, the target Tycos melting point was achieved at all tested concentrations between 4% and 10%. In some of the temperature profiles shown below, two crystallization events were observed during both cooling and heating. This indicates the presence of two distinct melting stages. The latent heat of the composition remains relatively high, approaching that of dimethyl sulfoxide. Precipitation of KNO3 was observed at salt concentrations above 6%. Overall, KNO3 is an acceptable PCM, but only up to a concentration of 6%. Figures 5A-5B Temperature plots of DMSO / KNO3 solutions of varying concentrations relative to pure DMSO during cooling (5A) and melting (5B) are shown.

[0061] Example 4B: Solidification and melting of DMSO + sodium nitrate (NaNO3) salt solution

[0062] Prepared different concentrations of NaNO3 solution, expressed in weight %. As described in Example 1, the solution was subjected to cooling and heating cycles. Tables 6A and 6B list the data obtained by these cycles:

[0063] Table 6A:

[0064] Table 6B: pilot projects <![CDATA[10%NaNO3]]> <![CDATA[12%NaNO3]]> <![CDATA[14%NaNO3]]> Subcooling temperature 10.07 7.45 5.0 Crystallization temperature (℃) 11.06 / 6.9 9.15 / 6.5-7.0 7.2 Onset of fusion / melting (℃) 7.0 6.1 5.9 End of fusion / melting (℃) 20.0 18.4 18.6 Maximum value on the melting curve (℃) 8.67 8.93 9.01 Tycos melting point (℃) 7.8 7.45 7.35 Latent heat (estimated, (kJ / kg)) 179 175 151

[0065] As shown in Tables 6A and 6B, the target Tycos melting point was achieved at all tested concentrations between 4% and 14%. Figures 6A-6BThe temperature profiles corresponding to this example are shown in Figure 2. In some of the temperature profiles shown below, two crystallization events were observed during both cooling and heating. The mixture had two freezing points. As the NaNO3 concentration increased, the higher freezing point decreased from 18.6°C to 9.15°C. The lowest freezing temperature was reached at a NaNO3 concentration of 12%. Accordingly, there were two melting points, or two melting phases. At NaNO3 concentrations above 8%, there was effectively only one melting phase. The lower of the two freezing temperatures was almost independent of NaNO3 concentration, remaining between 6.5°C and 7°C. No salt precipitation was observed during the cycling process. Even at high concentrations of approximately 12%, the latent heat remained relatively high, approaching that of pure dimethyl sulfoxide. A higher salt concentration (14%) exhibited a single freezing point at 7.2°C, but its latent heat was relatively low: only 77% of that of pure DMSO. Overall, this salt offers excellent performance as a PCM, even outperforming KNO3. A potential disadvantage of using high concentrations of NaNO3 is that above 10 wt% NaNO3 in DMSO may be explosive.

[0066] Given that the principles of the disclosed invention can be applied to many possible embodiments, it should be recognized that the illustrated embodiments are merely preferred examples of the invention and should not be construed as limiting the scope of the invention. Rather, the scope of the invention is determined by the appended claims. We therefore claim protection for our invention to the full extent that comes within the scope and spirit of these claims.

Claims

1. Use of a composition for cooling air, said composition comprising dimethyl sulfoxide and a salt selected from the group consisting of sodium nitrate, potassium nitrate and lithium bromide.

2. Use of the composition according to claim 1, wherein the salt is sodium nitrate.

3. The use of a composition according to claim 2, wherein the sodium nitrate is present in the composition in an amount of 4-12% by weight, Specifically, the sodium nitrate is present in the composition in an amount of 10-12 wt %.

4. Use of the composition according to claim 1, wherein the salt is potassium nitrate.

5. Use of the composition according to claim 4, wherein the potassium nitrate is present in the composition in an amount of 2-6% by weight.

6. Use of the composition according to claim 1, wherein the salt is lithium bromide.

7. Use of the composition according to claim 6, wherein the lithium bromide is present in the composition in an amount of 2-6% by weight.

8. Use of a composition according to any one of the preceding claims, wherein the composition is in solid form at a temperature below 7°C, in particular below 10°C.

9. Use of a composition according to any one of the preceding claims, wherein at least 98% (w / w), in particular at least 99% (w / w) of the composition consists of dimethyl sulfoxide and a salt selected from sodium nitrate, potassium nitrate and lithium bromide.

10. Use of a composition according to any one of the preceding claims, wherein the composition consists of dimethyl sulfoxide and a salt selected from sodium nitrate, potassium nitrate and lithium bromide.

11. Use of a composition according to any one of the preceding claims, wherein after solidification and melting of the composition no precipitation of the salt is observed.

12. Use of a composition according to any one of the preceding claims, wherein the latent heat of fusion of the composition is equal to or greater than 90% of the value of the latent heat of fusion of pure dimethyl sulfoxide.

13. A method of cooling air in a warm air environment, comprising: a. solidifying the composition as defined in any one of the preceding claims; b. causing warm air to flow from the warm air environment to the environment of the composition, thereby forming cool air; and c. allowing the cool air to flow from the environment of the composition to the warm air environment, thereby cooling the air in the warm air environment.

14. A method of cooling air in a warm air environment, comprising: a. solidifying the composition as defined in any one of claims 1-12; b. contacting the coolant with the composition of step a; c. causing warm air to flow from the warm air environment to the coolant environment, thereby forming cool air; and d. Allowing cool air to flow from the coolant environment to the warm air environment, thereby cooling the air in the warm air environment.

15. A method according to claim 13 or 14, wherein solidification is achieved by using electricity drawn from the grid during off-peak electricity demand periods.

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