Patent Application
20110154737
1. Field of the Invention
The present invention relates generally to energy collection and distribution and more particularly to improved methods and apparatus for accumulation, storage and controlled release of thermal energy.
2. Description of Related Art
In recognition of the ecological and cost impact of fossil fuels and other conventional energy sources, significant effort has been expended in developing and optimizing sources of energy that are more environmentally benign, including solar, wind, and geothermal energy sources. While these sources show considerable promise in helping to meet future energy needs, significant problems prevent more effective utilization of these types of energy sources.
One problem inherent to these types of sources relates to the timing and location of energy supply and demand. With energy sources such as solar, wind, and geothermal sources, the relative rates of energy supply and demand are not readily matched in terms of time and/or location. For example, for those living above certain degrees of latitude in parts of the northern or southern hemispheres, solar energy collection is not practical year-round and higher rates of energy are typically generated when energy demands themselves tend to be at lower levels. Wind energy is often limited by timing considerations; while wind energy can occur any time of day or any season, it is not controllable either in terms of timing or intensity. As with solar energy systems, many geothermal energy systems are similarly constrained by location considerations. So called “low temperature” geothermal energy systems still require proximity to extremely high temperature resources such as geologically hot rocks and hot springs which are often limited to areas near tectonic plate boundaries. Thus, there is a need for an economical means of storing the energy for effective utilization of energy sources in which the rates of energy supply and demand, timing, and location, are not generally well matched. Also, there is a need for economical and efficient means of utilizing energy sources that are well matched to the time and location of their use. In addition, there are also advantages to systems that can take advantage of waste energy from combustion or other sources.
A number of methods used for heat storage apply energy to increase the temperature of a medium, typically to high temperature levels that exceed acceptable levels for safe direct use and for human or animal contact, and maintain that elevated temperature until the stored heat can subsequently be used. With some approaches to the problem, only short-term storage is feasible, such as using sufficiently large water reservoirs with correspondingly costly insulation for energy storage. With solar collection, special and therefore costly solar collectors can be used if long-term storage is required, since in this case the high temperatures usually encountered are considered necessary for regeneration of the storage medium. In addition, regeneration of such a long-term store is in practice only possible in the summer months with strong direct solar radiation, so that the storage medium must have capacity that extends through the months in which heating is used.
Various chemical storage media have also been proposed for storing and releasing energy using hydration/dehydration cycles and similar techniques at high temperature. While such methods may provide large amounts of thermal energy for subsequent use, the regeneration of the storage medium also consumes large amounts of energy, amounts that may be difficult to obtain from the most desirable sources, particularly for use in low temperature conditions. High amounts of stored heat can also be generated from the storage media when releasing the stored energy, although it is generally at temperatures in excess of what is generally considered to be safe and comfortable for habitable spaces, for example. Thus, current practice often requires the use of heavily-insulated containers or conduits, which are expensive and can result in large losses of heat energy even during short periods of storage or distribution. Because of high levels for generated heat, current methods of heat storage can also require a good measure of isolation between the storage location and the location of use by occupants of a home, workplace, or other facility.
Goals for improved methods and apparatus for accumulating, storing, and releasing thermal energy for living quarters, work environments, and other habitation include the following:
A number of solutions have been proposed for energy storage and release using dehydration and hydration of metal salts. However, none of these solutions appears to satisfy the requirements listed in (i) to (vii) above.
For example, U.S. Pat. No. 4,303,121 entitled “Energy Storage by Salt Hydration” to Pangborn describes storage of solar energy or waste heat for later use using endothermic/exothermic cycles of dehydration/hydration of inorganic salts. The Pangborn '121 solution, however, is intended for and describes only high heat and high temperature applications and falls short of what is needed for goals (i), (iii), and (iv).
U.S. Pat. No. 4,291,755 entitled “Method and Apparatus for Accumulating, Storing, and Releasing Thermal Energy and Humidity” to Minto describes a heat storage system that employs polyvalent metal salts to generate heat that is used for drying grain. However, embodiments described in Minto '755 utilize compressed steam and heated oil in hydration and dehydration, providing a system that handles high temperatures, failing to satisfy (i) above, risks uncontrolled temperature elevation and heat evolution, failing to satisfy (iii) above, introducing some environmental concerns relative to (v) above, and not compatible with goal (vi) above. The efficiency of such a system is questionable, making it difficult to satisfy goal (vii) above.
U.S. Pat. No. 4,484,617 entitled “Method of Using and Storing Energy from the Environment” to Sizmann describes heat storage using materials such as silica gel or zeolite, with applied water vapor for heat generation. However, some method of vapor generation must be included as part of the system, making it difficult to satisfy goal (i) above and along with large complex equipment, falling short of meeting goal (vii) above.
U.S. Pat. No. 4,179,493 entitled “Dehydration Process” to Sadan describes the production of dehydrated or anhydrous salts from higher hydrates of the same salt using solar energy. However, embodiments described in Sadan '493 utilize aqueous solutions and a solar pond to obtain the dehydrated or anhydrous salts failing to satisfy (ii) above since no energy release is performed and would require complex separation equipment to obtain the potentiated material for energy release, failing to satisfy (vii) above. In addition, (iv) and (vi) above are not satisfied as humidification cannot be controlled nor can energy generation and storage be co-located or conveniently moved.
Other solutions such as that described in U.S. Published Patent Application 2009/0020264 entitled “Method of Heat Accumulation and Heat Accumulation System” to Morita, and references therein, involve formation of and storage of liquid salt solution phases and require the use of complex and costly equipment such as vacuum pumps and compressors, thereby failing to satisfy (iv) and (vii) above.
In embodiments of the present invention, thermal energy is stored in a medium which can be maintained in a relatively high potential energy state for indefinitely long periods of time in uninsulated or partially insulated containers, and can be controllably liberated at another time or another place, while also being able to be used at or near the same location and used very shortly after storage of the energy, and the heat storage medium thereafter recharged or reactivated by the application of heat and/or dry air to the medium.
The invention provides an improved method of accumulating, storing and controllably releasing thermal energy with a storage medium at moderate temperatures in the 10-75° C. range and wherein the medium can be indefinitely recycled by regenerating the medium.
The invention uses a process that is self-regulating with respect to the maximum temperature reached by the medium. Apparatus of the present invention can be used to store energy from a range of sources including solar, wind, hydroelectric, nuclear, wave and geothermal energy. Additionally, energy sources from other processes, such as waste heat from a furnace or furnace ducts, oven, stove, clothes dryer, washer or fireplace, or waste engine heat may be used.
The present invention supplies heat and humidity to gas filled spaces by the addition of water to a dehydrated material that releases heat upon exposure to water, exposing the hydrated material to dry contacting gas which results in loss of water from the hydrated material to the contacting gas, the contacting gas being heated and humidified by such exposure, and subsequent dispersal of the added heat and humidity to the gas filled space. This sequence also results in regeneration of the dehydrated material so that these steps may be repeated. By limiting the total amount of water addition to the dehydrated material within a cycle of the process, less time and/or energy is required to regenerate the dehydrated material and finer control of resultant living space humidity may be possible.
a-4d are schematic diagrams showing variations for providing outside air in exemplary embodiments of the present invention.
It is to be understood that elements not specifically shown or described herein may take various forms well known to those skilled in the art. Figures provided herein are given to show overall function, operation, and relationships and are not drawn with the intention of showing components or elements to scale.
Various terms are used in the art to describe the process by which energy can be stored using materials that exhibit heat of hydration. In the context of the present disclosure, the term “dehydration” is used for the storage process and is considered to be essentially equivalent to the terms “regeneration” or “potentiation” that are sometimes used in the art.
Embodiments of the present invention utilize dry air or other type of dry gas as the gas that contacts hydrated material in order to perform dehydration. By “dry gas” is generally meant a contacting gas having sufficiently low moisture content to effect drying when it moves past a material that is at least partially hydrated. Roughly speaking, such dry gas should have a moisture content of less than about 10 grams per cubic meter and preferably less than about 6 grams per cubic meter. The less moisture content, that is, the lower the water vapor pressure, the faster the drying. As is well known, moisture content is a factor in determining relative humidity (RH), along with temperature.
The “equilibrium phase transition temperature” for salt hydrates is defined as the temperature at and above which a salt hydrate releases water such that a liquid phase forms under equilibrium conditions. The present invention, which operates at least partially under the non-equilibrium condition of low water vapor pressure above the salt during dehydration, enables dehydration to occur at temperatures at or below the equilibrium phase transition temperature.
Embodiments of the present invention contemplate an improved method and apparatus of handling thermal energy in which a metal salt or mixture of metal salts having different states of hydration, is utilized as a heat storage medium.
The sequence diagram of
Conventional approaches using heat of hydration, such as those noted above in the Description of Related Art, for example, attempt to maximize heat output. Such an approach, however, also consumes considerable energy in order to store energy for future use. The Inventor, however, has adopted an alternative approach to energy storage, operating over an energy range that neither delivers the peak amounts of heat energy possible from hydration of the material, nor requires higher temperatures and overall energy input for the purpose of storing energy by dehydration. By working over a more moderate energy storage/output range, methods of the present invention can take advantage of lower energy requirements and simpler equipment configurations in order to affect energy storage.
By way of example, the difference between the solutions proposed in the present invention and those taught in the Morita et al. '264 disclosure are illustrated in the comparative graph of
In contrast, the energy transition used in the present invention does not require this energy input, as shown by a solid line 96 with starred endpoints. As the graph of
For the process used herein, the degree of dehydration that is attainable is a direct function of the temperature to which the salt is subjected and is an inverse function of the partial pressure of water vapor in the fluid (typically air) that is in contact with the salt. The applied fluid can be some other gas than air, for example nitrogen, oxygen, argon, neon, helium or carbon dioxide may be used.
Particularly useful in the dehydration is warming of outdoor air having a temperature below about 20° C. prior to warming. Such warming may occur by methods such as earth-air heat exchange or through the use of another renewable energy source. Similarly, cool indoor air which has gone through warming from a furnace, radiator or other space heating apparatus may also be particularly useful.
During the dehydration, supplemental heat may be applied by a heater or heat from some other source. Preferably, unlike other methods that have been described in the art, such as that taught in the Morita et al. '264 application that require dehydration above the equilibrium phase transition temperature of a hydrated salt, dehydration is done with the temperature of the hydrated salt at or below its equilibrium phase transition temperature in embodiments of the present invention, as was shown with reference to
However, the process of the present invention may alternately be used in conjunction with a process in which the storage medium temperature is brought slightly above the equilibrium phase transition temperature during some part of the process and/or utilize vacuum for a portion of the dehydration step. Use of vacuum for the dehydration step may be particularly useful at times when additional humidification of the surroundings or nearby living spaces is not desired. In such a case, it may be possible to increase the rate of dehydration. Once sufficient water is removed, the storage medium temperature may be decreased to at least the equilibrium phase transition temperature and the current inventive process may be continued.
In energy storage step 20 of
Referring to
The contacting gas 16 may optionally be obtained by warming, using heater 44a, of source gas 15 with naturally derived heat such as from solar energy or geothermal sources, from heat pumps or by waste heat sources, such as suitable flue gas ducts, furnace ducts, ovens, stoves, fireplaces, washing machines, or clothes dryers, or by electric heaters including those whose electricity is derived from solar photovoltaic, wind, hydroelectric, nuclear energy, or stored in electrical batteries, which may be rechargeable or single use, or fuel cells, and may be used directly, or along with any other source of gas.
Alternatively, the source gas 15 may be derived from a storage cylinder of compressed dry gas which may be used either directly without warming or, optionally with application of heat from a heat source, to become the dry contacting gas 16.
This process may be used either in a continuous flow or a batch mode of operation. In a continuous flow operation, the source gas may be dried by causing the gas to contact a strongly hygroscopic or desiccant material (41 in
During hydration of the dehydrated material, the total amount of water that is added is limited to that which favorably generates heat with little or no excess liquid solution formed after the water addition. The volume percentage of the water/storage medium mixture that is solid should be greater than 50% following the water addition, preferably it is greater than 90% and most preferably greater than 99%. For the preferred materials, the amount of water added to the dehydrated material should be less than about 60% by weight and often can be less than about 35% by weight.
However, for the most preferred cases, the weight percentage of water added to the dehydrated storage medium 12, such that little or no excess liquid solution forms, is dependent upon the chemical composition of the storage medium and the extent to which it has been dehydrated. Thus, if the dehydrated storage medium has a composition approximating sodium carbonate monohydrate, anhydrous sodium sulfate, sodium tetraborate pentahydrate or magnesium sulfate tetrahydrate, the weight percent of added water to the dehydrated storage medium should most preferably be less than about 50%, 20%, 35%, or 30%, respectively.
Additionally, if too little water is added or if the rate of water addition is too slow, insufficient storage medium heat generation temperature increase is obtained. The minimum weight percent of added water to the dehydrated storage medium should be at least about 5%, preferably at least about 10% and most preferably at least about 15%.
The minimum rate at which water should be added to the dehydrated material is greater than about 0.1 weight percent per second based on the dehydrated material, preferably greater than about 1 weight percent per second based on the dehydrated material, and most preferably greater than about 10 weight percent per second based on the dehydrated material.
It will be understood that where the term “weight percentage” is used herein, what is meant is a weight of water being added as a percentage of the weight of the solid material to which it is being added at that time. Any additional material which is isolated from the material to which the water is being added—whether by having the other material in one or more separate containers, or by isolating the material with some kind of barrier within the same container, such that the added water does not reach the other material—would not be considered when the “weight percentage” was being determined within the teaching of the invention.
The schematic block diagrams of
The system is comprised of a storage medium 12 that may be held in trays or otherwise supported by fine wire mesh, fabric or yarn. Furthermore, the storage medium 12 may be free standing or surrounded by a chamber 36 that may be partially thermally insulating and partially thermally conductive or entirely thermally conductive.
A water supply 32 provides water for hydration. Although droplets are shown in
As the dashed line indicates, both hydration for releasing energy and dehydration for storing energy can be executed within the same environment 30, such as the same room, building or general area. The use of non-hazardous materials enables the system of the present invention to be used within a habitat, such as a house, office building or workplace, for example. Alternately, using the appropriate support components, hydration for heat generation can be done at one location, with dehydration performed at a different site.
After water addition is completed, source gas 15 can be drawn from outside the area 30 through an outside inlet or conduit 64, or an optional valve 40 can allow drawing some or all of the source gas 15 through an inside inlet 104 within the area 30. A blower 42 draws the gas in, and propels it into the chamber 36 where the dry contacting gas 16 flows across and contacts the material 12. It should be noted that source gas 15 and blower 42 may be replaced by a cylinder of compressed gas and a valve. Preferably, source gas 15 has a temperature of less than about 20° C.
Heat generation can be used to heat the ambient room air surrounding storage medium 12 or to heat another transport medium. In the embodiment shown in
Dry contacting gas 16 removes moisture from hydrated storage medium 12. The water content of the dry gas increases as it contacts the hydrated form of storage medium 12.
Optionally, a heater 44a can be provided for heating the source gas 15 to form the dry contacting gas 16, or heater 44b can be provided for heating the hydrated storage medium 12 which may also cause heating of the source gas 15 and/or dry contacting gas 16.
Water vapor 18 is expelled from chamber 36 to a valve 50 that can direct the output moisture either to an outlet 111 in the same room 30 that contains the thermal energy storage and release system or to a different room, or to the outside 112. One or more optional sensors 46 are used in one embodiment, to sense the humidity of the expelled gas.
Sensor 46 (or a second such humidity sensor) may also be used to measure the relative humidity (RH) of the ambient air in a room or building 30, to determine whether or not to control valve 50 to direct moist gas back into the room or building or expel the moisture to the outside or other room 112 or repeat the method. For example, measuring the water vapor in the heated contacting gas with sensor 46, the water vapor may first increase, then reach a peak value, then decline. When the water vapor level stops declining after it has begun decreasing would provide an indication that the process may be repeated. Alternatively, if it is found that at least 85% of the water added in the hydration step has been removed during dehydration, for example by sensing the weight change of the storage medium, the process may be repeated.
An optional filter 52 helps to inhibit the emission of salt particles into the surrounding environment. Optionally, water vapor expelled during dehydration that is not needed for increasing room humidity is condensed and re-used for subsequent hydration or other use.
The operation of both valves 50 and 101 could also be set, if desired, to allow a blend of contacting gas 111 and heated bypass air 110 to flow into the room 30 in modes a or b, above. Valve 40 could be set in modes a or b to allow some or all of the intake air 15 to be drawn from the room 30.
Dry air serves as the drying agent in one embodiment of the present invention. The air that is in communication with blower 42 or other type of air mover may be obtained in any of several ways.
a to 4d show a number of options for providing air that is at suitable temperature and humidity levels.
In
As shown in
The rate of dehydration and consequent energy storage is a function of both the temperature and relative humidity of the dry contacting gas 16. Advantageously, embodiments of the present invention do not require extreme temperatures in order to provide energy storage, but can efficiently store energy even using dry air as the source gas at temperatures that are at or below room temperature. In one embodiment, shown as air input subsystem 60 in
The schematic diagram of
There are a number of options for providing heat storage medium 12. In one embodiment, chamber 36 is a replaceable canister or other easily removable container that can be used to generate heat for a room or other location. Once the canister has been hydrated and its stored heat obtained, the canister may be removed and returned to a recharging site at which dehydration takes place. This type of arrangement makes it possible, for example, to take advantage of higher energy sources than might be usable near human habitation or than might be available at the time and/or location of its use for generating heat. An example of such use would be to move the canister of hydrated storage medium 12 to a furnace area of a building for dehydration. When dehydration is complete, the canister can be brought back to a room for hydration and heat evolution. Such a replaceable canister may contain one or more trays or other support means for the storage medium 12.
Optional heating devices 44a and 44b used with embodiments of the present invention can use heat from any of a number of sources, in addition to heating elements. Waste heat from combustion, such as from a furnace, radiator, hot water heater, fireplace, stove, oven, clothes washer or dryer, or excess heat from a nuclear or industrial process can be used, for example. The heat used for heating the source gas 15 or for heating the heat storage medium 12 can be from a renewable source, such as solar thermal, geothermal, wind, or hydroelectric power, for example. Batteries and fuel cells can be used to generate heat, coupled with various types of resistive or thin-film heating devices. Another source of heat may be from the addition of water to anhydrous salts of calcium chloride, magnesium chloride, magnesium sulfate or sodium carbonate which may also be subsequently dehydrated for re-use, though under higher temperature conditions than those employed in the present invention.
In one embodiment of the present invention, heat storage medium 12 was, initially, fully hydrated sodium tetraborate decahydrate, commonly known as borax or with the alternative formula Na2[B4O5(OH)4].8H2O, in a tray that was housed within an insulated container. Outdoor air at −7° C. and 80% relative humidity (RH) was brought through a conduit through a wall of a room that was at 9° C. and 61% relative humidity. The tubing was connected to the inlet of a blower that simultaneously heated the air. The outlet of the blower was connected to tubing, the end of which was placed at the bottom of the insulated container. The top of the container was partially open to allow air, with the added moisture from its dehydrating action on the hydrated salt, to leave the container.
The heated outdoor air moved through the container containing the tray of borax for about five hours, during which time the temperature of the borax had increased to about 48° C. After this time, the borax was found to have lost about 23% of its weight, indicating conversion of the borax from its original decahydrate to a composition having a similar empirical formula to sodium tetraborate pentahydrate. Addition of water to the dehydrated composition in a weight ratio of 1:3.2 at 22° C. resulted in a temperature rise of the hydrated sodium tetraborate to about 45° C. with a concomitant rise in the temperature and humidity of the air in the insulated container.
Another specific example of the present method with the above apparatus is similar to that just described, except that the tray in the insulated container contained partially hydrated sodium sulfate containing about 13% water, by weight. Dehydration was carried out with outdoor air that was at −7° C. and 80% RH brought by intermittent use of a blower, such that the blower did not heat the outdoor air, through a conduit through a wall of a room having indoor air at 9° C., 63% RH. With a heater in contact with a tray containing the partially hydrated sodium sulfate, the salt temperature rose to about 32° C., resulting in a weight loss of about 13% indicating conversion to predominantly anhydrous sodium sulfate. Addition of water to the dehydrated composition in a weight ratio of 1:5 at 19° C. resulted in a temperature rise of the hydrated sodium sulfate to about 25° C. with a concomitant rise in the temperature and humidity of the air in the insulated container.
Another specific example of the present method used magnesium sulfate heptahydrate, which was converted by dehydration to magnesium sulfate hexahydrate. This was accomplished using outdoor air at 2° C. and 88% RH. Continuous blowing and heating of this air through a conduit surrounded by indoor air at about 7° C. and 64% RH resulted in air entering the insulated chamber at about 55° C. and 2% RH. Additional heating was supplied by a heater in contact with the magnesium sulfate heptahydrate so that the salt temperature was about 45° C. After a short time the salt experienced a 7% weight loss, indicating conversion to a composition approximating magnesium sulfate hexahydrate. Further treatment under the same conditions resulted in a total weight loss of about 14%, indicating conversion to a composition with the empirical formula approximating magnesium sulfate pentahydrate.
An alternative batch method used to dehydrate magnesium sulfate heptahydrate was performed in which the magnesium sulfate heptahydrate was placed in a container with anhydrous calcium chloride. The air in the container was about 22° C. and 15% relative humidity prior to heating the magnesium sulfate heptahydrate in a tray with a heater. Upon heating the hydrated magnesium sulfate reached about 45° C. and was dehydrated to a composition approximating magnesium sulfate tetrahydrate as evidenced by a total weight loss of about 28%. In the absence of the calcium chloride, addition of water to this dehydrated sample in a weight ratio of about 1:3.6 at about 22° C. resulted in a temperature rise of the rehydrated magnesium sulfate to about 50° C. with a concomitant rise in temperature and humidity of the air in the container.
Another specific example of the present method with the above apparatus used partially hydrated sodium carbonate containing about 25% by weight water which was converted to predominantly sodium carbonate monohydrate. With intermittent use of the blower as described above for sodium sulfate, the salt temperature was about 30° C., with weight loss of about 13%. In this specific example, the outdoor air was 0° C. at 70% RH and the indoor air was about 10° C., 50% RH.
A further specific example of the present method was carried out using indoor air as the source gas at about 20° C. and about 20% RH. The air is heated by a hot water radiator that is part of a home heating system to about 40° C. and 5% RH, then is blown across a free standing tray holding sodium sulfate, partially hydrated with water to about 20% by weight, reaching a temperature of about 30° C. This resulted in about 20% weight loss from the partially hydrated sodium sulfate. Rehydration of this material by water addition in a weight ratio of 1 part water to 5 parts dehydrated sodium sulfate at about 20° C. led to a temperature rise of the rehydrated sodium sulfate to about 32° C.
Preferred materials for use as the storage medium are those that give off heat when exposed to water and are capable of releasing water at temperatures well below the boiling point of water when exposed to dry gas. Such materials include those that incorporate water into their crystal structures such as inorganic salts that form hydrates. Such materials include those having an equilibrium phase transition temperature in the range from above 30° C. to about 100° C., and preferably in the range of 30° C. to 85° C. Preferably, the hydrated forms of the salt or salts utilized are capable of efflorescence at moderate temperatures within the range from about 10° C. to about 70° C. or are capable of dehydration with the release of heat in this temperature range.
Included among these materials are hydrates listed in Table 1. The hydrated and dehydrated materials listed below may refer to empirical compositions that may be mixtures of thermodynamically stable hydrates or to the thermodynamically stable hydrates themselves. For example, magnesium sulfate tetrahydrate and pentahydrate, while described as products of efflorescence, may also each correspond to a mixture of magnesium sulfate hexahydrate and monohydrate in the respective appropriate ratio.
While these salts are among those preferred, compositions having other degrees of hydration may also be present in the potentiated and hydrated states of the process and both the preferred potentiated and preferred hydrated salts may be present at the same time. Any of a number of types of alternate materials that exhibit heat evolution upon hydration and loss of water upon exposure to dry gas can be used, including as hydrated forms of the materials, sodium thiosulfate pentahydrate or dihydrate; copper sulfate pentahydrate; zinc sulfate heptahydrate or hexahydrate; potassium aluminum sulfate dodecahydrate; trisodium phosphate dodecahydrate; disodium hydrogen phosphate dodecahydrate or heptahydrate; sodium dihydrogen phosphate dihydrate; tri-(sodium metaphosphate) hexahydrate; calcium chloride tetrahydrate; calcium acetate dihydrate; magnesium acetate tetrahydrate or mixtures thereof. Preferred salts are stable in the presence of water and air so that they are able to undergo a larger number of cycles without degradation in performance or formation of undesirable amounts of impurities.
The storage medium 12 can be formed so that it provides a favorable surface for energy transfer at a given rate. In one embodiment, for example, the medium is provided within chamber 36 as a canister, with the medium formed in a shape in which at least one dimension is small, such as for example, less than about 0.7 cm, and the other dimensions are longer, such as extending along the length and width of a canister, for example.
Liquid water is generally preferred for forming the hydrated salts, since it can help to release energy more quickly, thus providing a larger temperature increase of the storage medium 12 and not requiring use of added energy for vaporization, as would be needed to use water vapor. The water for water supply 32 can be from gravity or line feed and may be added in drop-wise or in continuous fashion.
The method and apparatus of the present invention overcomes the deficiencies of the methods and mechanisms heretofore proposed for a number of reasons, including at least the following:
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention as described above, and as noted in the appended claims, by a person of ordinary skill in the art without departing from the scope of the invention. Various methods could be used for drying the air or applied gas.
Thus, what is provided is an apparatus and method for more efficient accumulation, storage and controlled release of thermal energy and humidity.
Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.
