COLD ENERGY STORAGE
1. A cold storage box comprising:
- a container for containing contents to be kept cool;
an evaporator chamber having thermally insulated walls surrounding the container and defining a space between the container and the chamber; and
an adsorber unit located above the evaporator chamber, the adsorber unit including adsorbent material, a mesh retaining the adsorbent material while permitting the adsorbent material to be exposed to vapor from the evaporator chamber, and a thermally conductive surface on a top or surrounding sides of the desorber unit.
Disclosed is a cold storage container able to keep its contents cool for long periods without using electricity by using the phenomenon of adsorption. An adsorbent material placed in a conductive material above an insulated vacuum chamber adsorbs water vapor from the melting ice surrounding or above a cold chamber where contents are kept cold. This generates continuous evaporation which cools the water and therefore the contents of the cold chamber.
- 1. A cold storage box comprising:
a container for containing contents to be kept cool; an evaporator chamber having thermally insulated walls surrounding the container and defining a space between the container and the chamber; and an adsorber unit located above the evaporator chamber, the adsorber unit including adsorbent material, a mesh retaining the adsorbent material while permitting the adsorbent material to be exposed to vapor from the evaporator chamber, and a thermally conductive surface on a top or surrounding sides of the desorber unit.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- 13. A cold storage box comprising:
a container for containing contents to be kept cool; an adsorber unit located above the evaporator chamber, the adsorber unit including adsorbent material and a thermally conductive surface on a top or surrounding sides of the desorber unit wherein the adsorbent material is plasma sprayed onto the conductive surface.
This invention relates to cold energy storage devices and, more particularly, to adsorption-based cold energy storage devices.
Continuous refrigeration is required to store and transport food, fruits, vegetables and health supplies. Bananas, for example, are stored at temperatures between 14 and 18° C.; and vaccines need to be stored in temperatures between 2° C. and 8° C. in order to keep their disease preventing properties. For places where access to electricity is limited, electricity-free cold storage solutions are often required.
A cold chain is a temperature-controlled supply chain that includes a series of refrigerated production and storages. A cold chain maintains a desired low-temperature range right from manufacturing to the end user. The cold chain consists of walk-in chillers, walk-in freezers, refrigerators, refrigerated trucks and cold storage boxes. Cold box storages are typically thermally insulated devices that allow transportation without electricity.
In rural areas, especially in developing countries, electricity is either not available or unreliable with voltage fluctuations. With such conditions, refrigerators cannot operate and products such as vaccines cannot be stored at the required temperatures. Refrigerators and chillers often use mechanical compressors which consume substantial amount of electricity and therefore difficult to operate in such areas. For example, in India, where 70% of the population is rural, only 2% of rural children receive vaccination.
There are different types of cold box storages. A typical cold box uses thermally insulating materials to reduce heat transfer between the content that needs to be kept cold and ambient temperature. This is perhaps the most dominant technology that is used for many applications.
There are other types of cold boxes that enhance the thermal insulation of this commonly used technology by adding a semi/full vacuum chamber around it. Some more advanced cold boxes not only provide thermal insulation, but also proactively generates cooling power for a limited time which significantly improves hold over time.
There are also a number of cold storages or cooling containers that operate based on the adsorption phenomenon. One example is a three-chamber configuration containing vaporized liquid, sorbent and vacuum (Sabin, Thomas, and Steidl, U.S. Pat. No. 5,048,301; 1991). In this system, adsorbent container in located inside the cold box where a valve can control the evaporation. However, in this configuration the dissipation of heat from adsorbent is not efficient. A second example is U.S. Pat. No. 4,759,191; 1988, where an insulated chamber containing the sorbent connected to the liquid chamber (evaporator) via a valve and a liquid-vapor separator. Another configuration is a single-bed adsorption system disclosed by Monma and Mizota having a refrigeration chamber in the middle surrounded by an evaporator containing the liquid and that is surrounded by an adsorbent bed (Monma, Mizota, JP2005299974; 2005). The wall between the refrigeration chamber and evaporator is thermally conductive, while the outer surface of the evaporator between evaporator and adsorbent bed is a thermally insulated layer. Opening a valve between the evaporator and adsorbent chamber starts the operation. However, this configuration can only operate with liquid refrigerants and insulation between the adsorbent bed and evaporator, which is not practically effective. This is due to the fact that even the best insulating materials still conduct heat, yet at lower rate. Therefore, in the by configuration suggested by Monma and Mizota, the heat of adsorption dissipates into the evaporator, which reduces cooling power. Different configurations using the same principle have also been suggested for self cooling drink containers and cans (Claydon, U.S. Pat. No. 6,829,902) (Hidaka, et al., JP2005098647), temperature controlled storage (Eckhoff, et al., U.S. Pat. No. 9,140,476) or a container cooling apparatus (Maier-Laxhuber et al., U.S. Pat. No. 5,440,896).
U.S. Pat. No. 6,688,132 (Smith et al.) discloses another related design for a cooling container in which a mechanism is devised to control the flow of refrigerant and thus control the temperature or duration of cooling. The mechanism involves one or more liquid reservoirs and fluid restriction between the reservoir and evaporator. However, this design is also only usable with liquid refrigerants.
Another related adsorption cooling system is a temperature-controlled portable cooling unit (Eckhoff, et al., U.S. Pat. No. 9,170,053). Its evaporator chamber and desiccant chamber are separated by a vapor conduit where the vapor control unit (valve, controller and sensor) is located.
Innovations and improvements in electricity-free adsorption technology remain highly desirable.
The following presents a simplified summary of some aspects or embodiments of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention relates to a self-contained cooling storage, container or device comprising an adsorber unit, an evaporation chamber and an optional area for storage or container. The adsorber unit is located on the top of the system where its outside wall includes a thermally conductive material (e.g. aluminum). Therefore, the produced heat of adsorption can transfer effectively to the ambient air. The evaporator chamber is designed to enable the use of ice as well as other solid or liquid refrigerants. The use of ice provides a wider range of cooling temperature and/or prolonged duration of cooling. There is no valve between the evaporator and adsorbent chamber, which enables to provide a large surface area and therefore maximize the diffusion of vapor into the adsorbent. Furthermore, the thermal insulation between the evaporator and the adsorber unit is provided by vacuum to prevent the adsorption heat affecting the cooling storage.
This invention allows low temperatures to be maintained without continuous supply of electricity by providing a cold storage or carrier whose cooling effect is provided by an adsorption process. The full adsorption refrigeration cycle is not performed in the present cold storage as this system does not have any condenser units. The evaporation process provides the cooling effect and is essential for this operation. A desorption process is also performed during the charging process. The desorption process can be performed either by separating the adsorbent unit or in-situ. In the first case the adsorbent can be heated in the oven or any other heating device. For the second case (in-situ desorption) the adsorbent can be heated via contacting a hot device (e.g. an iron) to the top conductive layer or via turning on a set of heating wires located in the adsorbent.
This invention is a cold storage box which, in addition to the thermal insulation used in standard cold storage boxes, uses the phenomenon of adsorption to provide electricity free cooling power. In laboratory tests, the adsorption extended the hold over time of a standard cold storage box by more than 800%. This allows electricity free storage for several days, weeks or even months below 15° C. which is ideal for many fruits such as bananas. For other applications where lower temperatures are required, the duration of electricity free storage would be shorter depending on temperature requirements. The invention significantly decreases operating costs because of the reduction in electricity consumption, and also allows contents to be shipped over large distances without the need of refrigerated shipment. In addition, it allows for the storage of health supplies such as vaccines to improve accessibility for hard-to-reach populations in rural areas.
The present invention is a sorption-based portable thermal energy storage (TES) device to produce and maintain cooling within a closed space. There are many sorption-based TES devices currently in research and development, although most of them are large and full-scale systems aimed to produce space cooling and heating for buildings and locomotives (see e.g. Li, Hwang, and Radermacker, International Journal of Refrigeration, 2014; 44: 23-35). These systems are stationary devices installed near a heat source, which can be recovered to power the sorption cycles. Closed-loop sorption cycles are common in TES applications where the refrigerants are conserved and undergo thermodynamic cycles in a closed system. The present invention is different in a way that it is a portable cold storage device that is designed to be carried and transported either by manpower, automobiles or equivalent. The present invention only executes a single-stage thermodynamic process instead of a full thermodynamic cycle to produce cooling, thus providing portability by eliminating the condenser, desorber, heat exchanger and piping that are the essential components in large scale full-cycle systems.
The present invention is an adsorption-based cold storage box (or cold energy storage device) which can be used as a transportable carrier or static storage container for carrying or storing contents that are to be kept cool.
In the embodiment depicted by way of example in
In the embodiment shown by way of example in
When one cycle of cooling has been completed, the adsorber unit 101 is detached and the adsorbent 111 is dried by exposure to a heat source, e.g. an electric heater, fire, sun, etc. The adsorber unit 101 is then reinserted or reattached for the next cooling cycle. The cold storage box is refilled with ice and the space inside the evaporator chamber 102 holding the ice is depressurized using a vacuum pump. After this, the cold storage box can be reused for another cycle of cooling. Alternatively, the adsorber unit 101 can be recharged by heating in-situ. It can be done by heating the conductive surface 112 or by turning on heating wires inside the adsorber unit.
In some embodiments as shown by way of example in
The cold storage box has a similar configuration comparing to the carrier box except for that there is no lid 131 at the front of cold chamber (i.e. container 103) to allow excess of contents from outside. The lid shown in
It should be understood that, while water is an inexpensive, widely available, and non-harmful refrigerant, there is a possibility to readily use other available refrigerants or add additives to water to change the freezing point or other parameters of the refrigerant.
The following features can be applied to both carrier and storage box configurations.
The temperature of the cold box could be controlled, in one embodiment, to maintain the temperature at a certain predetermined level, or within a certain temperature range, by controlling the amount of exposure between the adsorbents and refrigerants. An electrical valve or similar flow control device that connects the adsorber unit 101 and the evaporator chamber 102 could be installed along with temperature and/or pressure sensors inside the evaporator chamber to facilitate the feedback temperature control process. Controlling the exposure area between the adsorber unit 101 and the evaporator chamber 102 effectively controls the rate of adsorption through evaporation. Thus this technique enables the cooling power to be matched with the desired demand.
One or more temperature sensors could alert the user when the temperature has exceeded the desired level. The user is thus able to set the temperature level depending on one or more requirements. Pressure sensors could detect air leakages and warn the user whenever a leak occurs.
A fixed or detachable manual vacuum pump could be installed on the evaporator chamber 102 to achieve either the manual desorption process or re-depressurization once the vacuum has been released. Premature vacuum release occurs when adsorbents have not yet reached full capacity and could result from accidentally opening the pressure release valve during the transportation process or by minor system leakages. The system could be re-vacuumed under either situation via the manual vacuum pump. A cold trap can be located between the vacuum pump and valve.
When the adsorbents have reached their full capacity and an additional amount of cooling time is required, the manual vacuum pump could then be operated to reduce the vacuum pressure inside the adsorption unit, thus inducing desorption through the de-pressurization process. Desorbed refrigerant vapor could be released through the vacuum pump and regeneration energy will be supplied from the ambient temperature. A proper ambient temperature is required for a successful manual desorption process.
In another embodiment of this invention, multiple adsorbents (such as silica gel and zeolite) may be used at the same time. Since each adsorbent performs better at a specific temperature and vapor pressure, this allows more continuous generation of cooling power at different vapor pressures and temperatures. Therefore, this configuration can help enhancing the efficiency of the cold box and prolonging the hold-over time.
A series of performance tests have been conducted using the storage box configuration shown in
Furthermore, the cold box with zeolite adsorbent outperformed the one without adsorbents by 8.8 times with a total hold-over time of 216 hours. As shown in the graph, the temperature lines of adsorption cases reaches the first plateau at 11° C., and thus the adsorbents in these tests are able to activate at around 11° C. without any control.
The following documents are incorporated herein by reference: (i) Claydon, P. C., “Self-Cooling Can,” U.S. Pat. No. 6,829,902; (ii) Eckhoff, P. H., Peterson, N. R., Tegreene, C. T., Wood, L. L. , “Temperature-controlled Portable Cooling Units,” U.S. Pat. No. 9,170,053; (iii) Eckhoff, P. H., Gates, W., Hyde, R. A., Jung, E. K. Y., Myhrvold, N. P., Peterson, N. R., Tegreene, C. T., Whitemer, C., Wood, L. L., et al., “Temperature-controlled storage systems” U.S. Pat. No. 9,140,476; (iv) Hidaka, H. Kakiuchi, H., Iwade, Y., Takewaki, T., Yamazaki, M., Watanabe, N., “Adsorption Type Cooler,” JP2005098647; (v) Maier-Laxhuber, P., Schwarz, J., Winter, E. R. F., Soltes, J., “Apparatus for cooling a medium within a container,” U.S. Pat. No. 5,440,896; (vi) Monma, T. Mizota, T., “Adsorption Type Refrigerator,”, JP2005299974; (vii) Smith, D. M., Roderick, K. H., Perkes, R. G., Sinclair, V., Warren, L. X., “Cooling Device and Temperature-Controlled Shipping Container Using Same,” U.S. Pat. No. 6,688,132; (viii) Sabin, C. M., Thomas D. A., Steidl, G. V., “Vacuum Insulated Sorbent Driven Refrigeration Device,” U.S. Pat. No. 5,048,301; (ix) Thomas D. A., Sabin, C. M., Cover, J. H., “Miniaturized cooling device and method of use,” U.S. Pat. No. 4,759,191; and (x) Li, G., Hwang, Y., and Radermacker, R., “Experimental Investigation on Energy and Exergy Performance of Adsorption Cold Storage for Space Cooling Application,” International Journal of Refrigeration, 44; 23-35, 2014.
It is to be understood that the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a device” includes reference to one or more of such devices, i.e. that there is at least one device. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of examples or exemplary language (e.g. “such as”) is intended merely to better illustrate or describe embodiments of the invention and is not intended to limit the scope of the invention unless otherwise claimed.
While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.
In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure.
Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the inventive concept(s) disclosed herein.