System and Method for Solar Powered Thermal Management and Transport

FIELD

Embodiments are directed to thermal and data management systems and methods, and more specifically, but not exclusively, to a system and method for providing scalable and intrinsic solar powered refrigeration for transportation and remote delivery of vaccines, pharmaceuticals, and other perishable items.

BACKGROUND

The World Health Organization (WHO) estimates that, globally, close to two million preventable deaths each year occur due to lack of immunizations in children under five. Thirty million children—roughly one in five born each year—globally remain unimmunized or under-immunized, and are at risk for vaccine-preventable communicable diseases that can cause debilitating and incapacitating health conditions or fatality.

Vaccines are highly sensitive biological materials that require strict storage and maintenance standards. For example, vaccines need to be stored in a very narrow temperature range (e.g., 2-8° C.) throughout their life to preserve their viability. Storing vaccines at improper temperatures can destroy the vaccines' viability and is one of the greatest unsolved problems faced in the vaccine cold chain in developing countries. Globally, half of vaccines are wasted, in large part due to temperature excursions beyond the aforementioned temperature range. Further, under-immunization is not due to high vaccine prices, but rather to breakdowns in the supply cold chain. Current solutions attempt to increase capacity and frequency of vaccine distribution from national source locations where infrastructure is sound.

However, despite the sound infrastructure at the national source locations, the other parts of the supply and distribution network in developing countries face serious infrastructure challenges (especially power and transportation) and are hard to reach. In an illustrative scenario, the first stop in distribution from the national source location would typically be to a regional store, which serves a large portion of the country. Often, there are fewer than ten regional stores in, for example, a mid-sized sub-Saharan African Country.

From the regional store, vaccines move to a District Store, where vaccines typically are stored for onward distribution to one or more remote places. District Stores unfortunately are equipped with inadequate power infrastructures and have only intermittent electricity. Power outages can result in storage temperatures exceeding the acceptable temperature range for vaccines. This exposure to heat can render vaccines ineffective.

A selected District Store may supply several “Health Centers,” which often are located in remote locations and similarly face intermittent, or no, electricity. Furthermore, outreach includes day-long trips by health workers to the most remote areas that are not in close reach of health centers. Locations served by outreach are often the areas where vaccines are most needed, because these locations have the least access to healthcare. These areas typically are the least developed in the cold distribution chain. Delivery of vaccines to these remote places requires potentially several miles or days of walking (or bicycle) transportation during which there are few ways available to maintain the viable temperature range for the vaccines. The segment of the cold chain from health centers to outreach, particularly in rural areas, is often referred to as the “last mile,” or the “last underserved mile” as these are the most challenging stages of vaccine distribution. The last mile is where the cold chain is weakest, and where immunization is most difficult to achieve. High-level barriers to 100% immunization revolve around access to cold chain equipment. Where refrigerators are unavailable to store vaccines, there is a no viable way to immunize children. This leaves many children unimmunized or under-immunized. In some cases, children are even “vaccinated” with vaccines that have either frozen or become too hot—a most egregious failure. Similar problems arise with other pharmaceutical products such as blood, oxytocin, perishable medicines and so on.

Conventional solutions for refrigeration in the vaccine cold chain face several challenges. Residential refrigerators are not viable candidates for vaccine storage—these refrigerators require alternating-current (AC) mains and lack precise temperature control and holdover capability (i.e., the ability to keep internal temperatures in the acceptable temperature range during periods without power). Current WHO-approved vaccine refrigerators that do not rely on electricity (e.g., kerosene-, gas-, and solar-based refrigerators), as a whole, tend to be expensive and have low holdover times. Gas- or kerosene-powered absorption vaccine refrigerators in particular are in common use, but are costly (e.g., recurrent operating and fuel costs), challenging to maintain, and are technically complex, resulting in frequent failures. Many African countries have recently issued policies against the future purchase of absorption refrigerators.

Solar-powered refrigeration can be used in areas with intermittent or non-existent electrical grid access. However, early solar-powered solutions have not only been expensive, but also required a rechargeable battery. The rechargeable battery charges during sunlight hours and is necessary to power the refrigerator when the sun is unavailable. Unfortunately, the rechargeable batteries can be costly to fix/replace, toxic, and subject to immediate failure without warning. Furthermore, some rechargeable batteries have a shorter lifetime in warmer ambient climates—as low as five years, compared to ten to twenty years for the refrigerator it powers. Any of these issues with the battery can lead to an entire vaccine payload being spoiled.

In an attempt to remedy battery issues, Solar Direct Drive (SDD) refrigerators use a thermal battery without the need of an external electrical battery. Stated in another way, SDD refrigerators freeze water (or another substance) to maintain required temperature ranges in the absence of solar power. In addition, current SDD refrigerators use a vapor compression cooling system. However, SDD refrigerators are heavy and large, with payloads of about 50 L-150 L. Additionally, SDD refrigerators are difficult to transport, and are priced beyond the reach of many communities.

As a further disadvantage, SDD refrigerators require a power surge to start running. Therefore, while the sun may rise as early as 5 am in the morning, it may be several hours before the solar radiation is strong enough for the SDD refrigerator to turn on, thus reducing the amount of the solar day during which the refrigerator can run.

Reliance upon ice packs in passively-cooled ice boxes to store or transport vaccines during outreach is an additional weakness with the existing distribution strategy, as vaccines can freeze—rendering them ineffective—when placed in close proximity to over-cooled (sub-zero) ice packs. Freezers are generally set to temperatures as low as −25 C in order to freeze ice-packs quickly.

The WHO publishes recommended immunization schedules for diseases that countries should vaccinate against. New introductions to these schedules have included vaccines that are bulkier and more expensive (e.g., Pneumococcal Conjugate Vaccine, Rotavirus Vaccine, Inactivated polio vaccines (IPV), and so on) that will further complicate the difficulty of last mile distribution, and the cost of vaccines that spoil due to heat or freezing.

Meeting the current and increasing demand for vaccine delivery to the broadest possible population requires a low-cost, sustainable, durable, portable vaccine refrigerator that can be powered by solar photovoltaic (PV) panels without the complications of an external battery, without a requirement for a high startup current, and that prevents any possibility of freezing of vaccines. Accordingly, a need exists for improved systems and methods for thermal management and vaccine (and other such vulnerable resources) transportation in an effort to overcome the aforementioned obstacles and deficiencies of prior art systems.

SUMMARY

In one embodiment, a refrigeration system for vaccine storage and/or transportation includes an inner chassis. One or more vertical lift carriages are positioned in the inner chassis and can house a plurality of vaccines, pharmaceuticals, and/or other perishable items. Each vertical lift carriage is contained in an isothermal chamber. One or more isothermal chambers surround a phase change reservoir (PCR), which is positioned at a central location of the inner chassis and contains frozen water or another phase change material.

In some embodiments, a thermal attenuation layer is disposed between the PCR and each isothermal chamber that moderates energy transfer between the chamber and the PCR, thereby controlling the temperature range in each isothermal chamber. Surrounding the inner chassis, an additional insulation layer can be disposed to reduce energy transfer from the ambient environment into each isothermal chamber.

The system advantageously provides for storage and transportation of vaccines, pharmaceuticals, and/or other perishable items in the absence of a reliable supply of electricity.

In some embodiments, the refrigerator uses at least one of solid-state thermoelectric heat pump or compact vapor compression cooling system to actively cool the PCR.

In some embodiments, the system is modular and can be scaled up or down to ensure a vaccine delivery system that is appropriate for a locations population size and climatic conditions. For instance, a scaled down (e.g., backpack) vaccine delivery system allows portability to easily service the final steps in the cold chain described above: the District/Regional Store; the Health Center; and last-mile Outreach.

In some embodiments, the vaccine storage and transport system includes application of data telemetry that allows electronic logging of vaccine temperatures, refrigerator system performance, GPS coordinates (allowing tracking of any individual immunization mission), equipment/vaccine inventory, and/or immunization records/epidemiological data. Data telemetry allows remote monitoring and control of each vaccine storage and transport system in the field. For instance, the system's power can be controlled remotely and alerts can be sent remotely in case of unacceptable temperatures or certain breakdowns.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary top-level block diagram illustrating a top view of an embodiment of a refrigeration and transport system;

FIG. 2A is detail drawing illustrating an embodiment of an isothermal chamber for the system of FIG. 1, wherein the isothermal chamber supports a lift-up carriage having a variety of storage compartments;

FIG. 2B is a detail drawing illustrating an alternative embodiment of the isothermal chamber of FIG. 2A;

FIG. 2C is a detail drawing illustrating an alternative embodiment of the refrigeration and transport system of FIG. 1;

FIG. 3A is a detail drawing illustrating a perspective view of an embodiment of the inner chassis of the refrigeration and transport system of FIG. 1;

FIG. 3B is a detail drawing illustrating a perspective view of an alternative embodiment of the inner chassis of the refrigeration and transport system of FIG. 1;

FIG. 3C is a detail drawing illustrating a perspective view of an alternative embodiment of the inner chassis of the refrigeration and transport system of FIG. 1;

FIG. 3D is a detail drawing illustrating a perspective view of yet another embodiment of the inner chassis of the refrigeration and transport system of FIG. 1;

FIG. 3E is a detail drawing illustrating a perspective view of another embodiment of the inner chassis of the refrigeration and transport system of FIG. 1;

FIG. 3F is a detail drawing illustrating a perspective view of another embodiment of the inner chassis of the refrigeration and transport system of FIG. 1;

FIG. 3G is a detail drawing illustrating a perspective view of another embodiment of the inner chassis of the refrigeration and transport system of FIG. 1;

FIG. 4A is a detail drawing illustrating the inner chassis of FIG. 1 including a heat pump module in accordance with one preferred embodiment;

FIG. 4B illustrates a system application of the inner chassis of FIG. 1 in accordance with one embodiment of the present invention;

FIG. 4C illustrates an alternative view of the system application of the inner chassis of FIG. 4B in accordance with one embodiment of the present invention;

FIG. 4D illustrates a cross-sectional view of the system application of FIG. 4B;

FIG. 4E illustrates a cross-sectional view of a system application using an alternative active cooling system;

FIG. 5 illustrates a cross-section view of the heat pump module of FIG. 4A in accordance with one embodiment of the present invention;

FIG. 6 is an exemplary top-level block diagram illustrating an embodiment of the data flow between a data acquisition and telemetry system that can be used with an embodiment of the refrigeration and transport system of FIG. 1 and FIGS. 4A-E;

FIG. 7 is an exemplary top-level block diagram illustrating an embodiment of the data flow using the data acquisition and telemetry system of FIG. 6;

FIG. 8 is an exemplary schematic diagram illustrating an embodiment of backpacks that can be used with the refrigeration and transport system of FIGS. 4A-E;

FIG. 9A is an exemplary schematic diagram illustrating an embodiment of a carrier that can be used with the refrigeration and transport system of FIG. 1;

FIG. 9B is an exemplary schematic diagram illustrating an alternative embodiment of a carrier that can be used with the refrigeration and transport system of FIG. 1; and

FIG. 9C is an exemplary schematic diagram illustrating an alternative embodiment of a carrier that can be used with the refrigeration and transport system of FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As previously discussed, conventional vaccine storage and transport systems are ineffective for comprehensive global distribution. For example, current vaccine refrigeration and transport systems adhere to the familiar geometry of the front-opening-door refrigerator or the travel/picnic cooler geometry with a hinged top. All of these systems provide operator access to a centrally located interior compartment where vaccines are stored. Any thermal storage or phase change material typically is located around a perimeter of the interior storage compartment. Outside of the central storage and phase change material lining is insulation that attenuates heat flow from the environment. This geometry introduces risks of freezing vaccines and requires complicated controls to manage internal temperatures or the use of phase change materials that are expensive and often do not provide the same ability to store energy as water.

If water is used in this configuration, the water cannot be allowed to freeze, forfeiting the large thermal storage potential of water due to its heat of fusion and introducing reliance on closed loop thermal control systems. Phase change materials with higher phase transition temperatures than water/ice are often used instead although use of such materials carries a significant reduction in thermal storage capacity by mass and volume. Closed-loop thermal control systems constantly assess the real-time refrigerator temperature and control active cooling to manage temperatures according to user-defined settings.

Most conventional refrigerators circulate refrigerant very near to the lining of the vaccine storage chamber. Without adequate air circulation, hot spots and cold spots can emerge, creating a risk of damaging vaccines. Even with adequate circulation and/or other systems to create an acceptable internal temperature, the temperature of the chamber lining often dips or in some cases is required to be below 2° C., posing a freezing threat. Many refrigerators instruct the user to place the vaccines away from the floor and walls to prevent freezing, but user compliance cannot be ensured. Often removable baskets are supplied with refrigerators to keep vaccines off of the chamber floor and walls, but this approach is prone to user misuse.

For this reason, the WHO insists upon several vaccine packaging and placement requirements—as a precaution against freezing—that limit the density with which vaccines can be held, thus increasing the minimum size storage or transport system needed to immunize a given size population. Many conventional refrigerators also suffer from low holdover times during extended absence of power, such as at night or inadequate sunlight. Transportation options in current art (especially for extended time or long distances) usually rely solely on ice packs in vaccine carriers/cold boxes, which offer a limited holdover time.

Turning to FIG. 1, one preferred embodiment of a system 100 for refrigeration and/or transport for overcoming the aforementioned obstacles is illustrated. The thermal geometry of system 100 advantageously prevents freezing of vaccines as well as ensures their viability by maintaining a predetermined temperature range (e.g., 2-8° C.). FIG. 1 shows that the system 100 can include a shell 190 for enclosing an inner chassis 110. The shell 190 can be insulated and includes a material that can be selected based on the temperature profile of the intended location of use. Examples of material that can be used with the shell 190 include, without limitation, extruded polystyrene (XPS), expanded polystyrene (EPS), phenolic foam, vacuum insulated panels (VIP) (panels 410 shown in FIG. 4C), and so on.

As shown in FIG. 1, the inner chassis 110 is disposed within a cavity formed by a top opening of the shell 110. A phase change reservoir (PCR) 150 is disposed at a central location within the inner chassis 110. In one embodiment, the PCR 150 can hold water and/or other water-based liquids. However, other phase change materials (i.e., substances with a high heat of fusion such that heat is absorbed or released when the substance changes from solid to liquid and from liquid to solid) can be used.

In some embodiments, the PCR 150 and the enclosed water (or phase change material) can be removed from the refrigeration system 100 to be cooled through an external chiller (not shown). In another embodiment, the PCR 150 can include ice packs (not shown) to bring the temperature of the PCR 150 down to near 0° C. The ice packs can act as a “thermal battery,” which continue to draw energy out of one or more isothermal chambers 140 for many days (even at a high ambient temperature). Additionally and/or alternatively, if water is used in the PCR 150 and is fully frozen, acceptable vaccine temperatures can be maintained for five to seven days without any additional active cooling. The PCR 150 can include a single reservoir or comprise a number of smaller reservoirs that form the PCR 150.

Advantageously, keeping a core of the PCR 150 initially at a low (e.g., 0° C. or subzero) temperature allows use of high thermal storage capacity materials (e.g., water-based PCR materials)—despite those materials having a lower phase change transition temperature than is normally acceptable for vaccines—substantially reducing cost and weight while improving safety.

Within the inner chassis 110, the one or more isothermal chambers 140 surround the PCR 150. In some embodiments, a thermal attenuation layer 170 is provided between the PCR 150 and each isothermal chamber 140 to moderate energy transfer between the PCR 150 and the isothermal chambers 140. The thermal attenuation layer 170 (of which the material, size, and so on can be customized to local geo-climate conditions) between the PCR 150 and the isothermal chambers 140 creates a protective insulation between the PCR 150 and each isothermal chamber 140, preventing stored vaccines from freezing.

The shell 190 forms a chamber around the chassis 110 and can include one or more vacuum insulated panels 410 (e.g., shown in FIG. 4C) to provide powerful insulation from fluctuating ambient temperatures. The chambers 140 advantageously can be isothermal and made from materials with a high thermal conductivity, thereby enabling a stable narrow temperature range within each chamber 140 even as energy is entering the chamber 140 from the external environment as energy is leaving the chamber 140 to the PCR 150. Stated in another way, heat reaches the isothermal chambers 140 from the environment primarily on one or more sides of the chambers 140 that face the exterior of the refrigerator system 100. This heat—which arrives primarily on one or two of the four sides of the chamber—is rapidly conducted around all four sides of the isothermal chamber through the highly conductive material so that one side is not hotter than the other. As a result, the temperature at all points within the isothermal chambers 140 is consistent.

Each isothermal chamber 140 is configured to receive a vertical lift-up carriage 120 (shown in FIGS. 2A-C). As the temperature is uniform throughout the chamber 140 (in a manner that does not require air circulation power), the vertical lift-up carriage 120 can be filled completely with vaccines without concern for packing the vaccines too tightly. Packing the vaccines too tightly could threaten the required thermal environment of vaccines in conventional refrigeration systems.

The thermal geometry of the refrigeration system 100 creates a thermal gradient between the frozen core in the PCR 150 (0° C. or lower) and the external environment (ambient temperatures typically are about 32-43° C.). The thermal attenuation layer 170 and the insulation in the shell 190, together, moderate the flow of energy across this thermal gradient. The characteristics, such as choice of materials and thickness, of the thermal attenuation layer 170 may be influenced by the applicable ambient climate as well as the size of the PCR 150 and/or the size and capacity of the system 100. The thermal attenuation layer 170 can be made of a suitable material including metals, open or closed cell foams, plywood, synthetic polymers, extruded polystyrene (XPS), neoprene, and so on. Plywood, for example, may be suitable for warmer climates, while neoprene is insulating and can be suitable for use in colder climates. Furthermore, the thermal attenuation layer 170 can exist in a solid, liquid, and/or gaseous state.

By placing the isothermal chamber 140 between the appropriate thermal attenuation layer 170 and the appropriate external insulation 190, the temperature in the isothermal chamber 140 where the vaccines are stored can be kept constantly within an acceptable range (e.g., 2-8° C. for vaccines) even across a wide range of environmental temperatures. The risk of accidental freezing thereby is limited.

In some embodiments, the system 100 provides proper vaccine protection at ambient temperatures, for example, between 48° C. and 5° C. (i.e., a single thermal attenuation layer 170 and a single insulation chamber 140 in the shell 190 covers most of the regions where system 100 is used). Rather than relying on active feedback systems and control loops, fundamentals of heat transfer and material properties maintain the narrow range of acceptable temperatures. Accordingly, the refrigeration system 100 preferably is an example of providing a passive cooling system.

Turning to FIG. 2A, the vertical lift-up carriage 120 can be removed from the refrigeration system 100 via an opening formed at a selected portion of the chamber 140. Once the vertical lift-up carriage 120 is raised, one or more storage compartments 130 are accessible. The storage compartments 130 can be used to store any number and/or type of payloads (not shown). Non-limiting examples of payloads that can be used with system 100 include vaccines, medical consumables (e.g., oxytocin, antibiotics, and so on), other pharmaceuticals, perishable items, and so on. During continuous use, nesting the storage compartments 130 into the vertical lift-up carriage 120—accessible from the exterior of the system 100—protects both the payloads from a temperature rise and the PCR 150 from the heat gain associated with continuous chamber access events. In some embodiments, the storage compartments 130 supports 0.5-60 L of various payloads.

FIG. 2B illustrates an alternative embodiment of the vertical lift-up carriage 120 of FIG. 2A, when the vertical lift-up carriage 120 cooperates with the inner chassis 110. Similarly, FIG. 2C illustrates an embodiment of the inner chassis 110, wherein the inner chassis 110 is removably disposed within the shell 190. Although shown as a vertical-lift up carriage 120 that can slide vertically, other configurations can be used to provide access to the storage compartments 130 from the isothermal chambers 140. For example, the payload can be housed in spring-loaded tubes that can be placed upright directly in the isothermal chamber 140 and/or directly placed in the isothermal chamber 140 without the need for the vertical lift-up carriage 120.

Even further, each vertical lift-up carriage 120 and/or storage compartment 130 can house a different type of payload (e.g., food versus vaccines) and/or a group of similar payloads (e.g., all vaccines in a selected vertical lift-up carriage 120). Therefore, depending on the specific need, the system 100 enables selective need-based access of a selected vertical-lift up carriage 120, reducing the access frequency and minimizing heat gain into core of the system 100 during clinic events.

Each vertical lift-up carriage 120 can maintain a predetermined number of storage compartments 130. For example, the storage compartments 130 can include trays 131A (shown in FIG. 3A) and/or drawers 131B (shown in FIG. 3B). Turning to FIG. 3A, the trays 131A can be useful for storing a number of vaccine vials. The trays 131A can be light-weight and provide high-density packing that is customizable at the individual tray level for allowing sizable populations to be immunized, for example, by human-scale end-of-cold-chain transport. The trays 131A prevent freezing of the individual vaccines, enabling more vaccines to be transported without a need to increase system volume. Further, the storage compartments 130 can be made of a suitable material including metal, plastic, wood, rubber, and/or any other suitable material compatible with the system construction.

FIG. 3B illustrates an alternative embodiment of the inner chassis 110. In this embodiment, the inner chassis 110 is similar to that shown in FIG. 3A; however, the inner chassis 110 of FIG. 3B includes drawers 131B allowing conventional vaccine vial packing. The same payload volume can also be used, as illustrated in FIG. 3A, with boxes of vaccines stored in the drawers 131B, which will fit single or multi-dose vial boxes efficiently just as-is, but can be removed to accommodate larger boxes as well. Although not illustrated, the vertical-lift up carriage 120 can also include shelves upon which the vaccines and other payload can be directly stored or stacked in their packaging.

FIGS. 3C-G illustrate alternative embodiments of the vertical lift-up carriage 120. Turning first to FIG. 3C, the inner chassis 110 is shown as being modular, which enables scaling in size and easy integration with other vaccine transportation systems that are built with similar geometry (e.g., a backpack vaccine transporter (shown in FIGS. 7-9B-C), which uses the same design and components as the inner chassis 110). Turning to FIG. 3D, the vertical lift-up carriage 120 is easily and readily removable for minimizing heat gain into the core of the system 100 during clinic events. FIG. 3E further illustrates that the tray 131A can be densely packed at the individual tray level, without sacrificing temperature changes, for allowing sizable populations to be immunized.

In some embodiments, the vaccine type can be presorted by tray color, tray size, and elevation in the vertical lift-up carriage 120, advantageously, helping reducing the risk of errors in immunization, while reducing the time vaccines are exposed to ambient temperatures. Vaccine vials can be prepackaged into high density trays 131A, which themselves nest into high density arrays, such as the arrays shown in FIG. 3F.

By using a predetermined size for the storage compartment 130, the modular trays 131A can provide flexibility (e.g., holding various sizes of single-dose and multi-dose vials and single-use syringes). Turning to FIG. 3G, the modular trays 131A can include a variety of trays 132A-C, each for receiving a different payload. For example, tray 132A includes vaccine cavities of about 14 mm in diameter for holding about sixty small vaccine vials. Tray 132B includes vaccine cavities of about 17 mm in diameter for holding about forty-five mid-sized vaccine vials. Similarly, tray 132C includes cavities of about 11 mm in diameter to hold about sixty single-use syringes. Advantageously, the modular trays 131A can be customized by region and/or pre-packaged at the vaccine manufacturing lab. Color-coding (or labeling) can provide a simple identification scheme and ease of use during clinical trials. Each modular tray 131A can have uniform cavity sizes and/or cavities of varying sizes to accommodate any number and/or type of payload stored in the tray 131A. As shown in FIGS. 3E-G, the trays 131A can be stackable to accommodate various heights of vials.

In some embodiments, selected components in system 100 can be modular. Exemplary modular components can include: a) the vertical lift-up carriage 120 within the isothermal chambers 140, further sub-modularized by storage compartments 130 (e.g., vaccine vials in high density trays 131A); b) PCRs 150, the sizing and number of which can determine hold-over time; and/or c) thermal attenuation layer 170. The modularity of these components allows system 100 to be scaled to fit different regions where system 100 may be used. For example, a 10-liter payload capacity may be an appropriate capacity in some areas. Each of these components can be combined in a configuration that matches a selected need (e.g., longer or shorter hold-over times, larger or smaller populations to be served, storage capacity needed at any given location, distance to be traveled on foot at the end of the cold chain, etc.). This modular design also simplifies manufacturing because the same basic components are used in varying combinations to build many different products as needed.

As discussed above, system 100 provides an example of a passive cooling system. Stated in another way, the thermal geometry of system 100 advantageously allows maintaining appropriate temperatures for extended periods without an active cooling system. An alternative embodiment of the system 100 can include an active cooling system. FIGS. 4A-C show the system 100 that includes the active cooling system. In FIG. 4A, for example, the water (or other phase change material) in PCR 150 can be cooled through the active cooling system, such as a heat pumping system 160 (also optionally modular). As shown, the heat pumping system 160 includes at least one (or more) thermoelectric (TE) heat pump module 160A. In some embodiments, each TE heat pump module 160A can be placed on the exterior of the inner chassis 110 for easier access and maintenance.

In an alternative embodiment, the heat pumping system 160 (e.g., the thermoelectric modules and fan as well as fluid circulating pump shown in FIG. 5) can be powered through direct DC-DC charging by a solar photovoltaic system (not shown). The heat pumping system 160 can be connected directly to solar panels (not shown) via a microcontroller 641 (shown in FIG. 6) without the need for intermediary power conditioning/battery storage/buffering. The solar insulation level of the system 100 is tracked and the input voltage is controlled by the microcontroller 641 to regulate the function of the heat pumping system 160. Instead of storing electrical energy in a battery, the refrigeration system 100 can use a thermal battery as the PCR 150 to maintain payload temperatures within the predetermined range (2-8° C.). For example, under certain conditions such as at night or during cloudy, rainy weather, the well-insulated cool storage of system 100 maintains acceptable temperatures for many days. Further, the use of solar power makes the system 100 even more independent from unreliable power grids, improves portability of the system 100 and increases reliance on clean energy.

FIG. 5 is a detail drawing of one embodiment of the TE heat pump module 160A that can be used with the system 100. Turning to FIG. 5, the TE heat pump module 160A consists of a thermoelectric module 210, a heat transfer fluid recirculation pump 220, and a heat rejection fan 230 (only two moving parts). The heat transfer fluid recirculation pump 220 is the innermost part of the TE heat pump 160A and couples the TE heat pump module 160A—specifically the coldest point on the TE heat pump module 160A where energy is extracted—and a fluidic circuit 420 (shown in FIGS. 4B and 4D). The thermoelectric module 210 extracts energy from the heat transfer fluid recirculation pump 220, which chills a coolant circulating through the heat transfer fluid recirculation pump 220.

Therefore, turning to FIG. 4B, to reduce temperature in the PCR 150, the heat pump module 160A extracts heat from the fluidic circuit 420, which then runs sub 0° C. liquid through the PCR 150. As shown in FIG. 4B, the fluidic circuit 420 includes an array of copper fins 421. With reference to FIG. 4D, a cross-sectional view of the refrigeration system 100 is shown. FIG. 4D also shows the active cooling system (e.g., an array of TE heat pump modules 160A), which can pump chilled fluid (e.g., coolant) into PCR 150 via the heat transfer fluid recirculation pump 220. Specifically, a fluidic pump tube system 422 runs along the height of the system 100 and connects the heat transfer fluid recirculation pump 220 to the copper fins 421 in the PCR 150 at a top portion 422A.

The coolant passes along the height of system 100, through the fluidic pump tube system 422 of the fluidic circuit 420 and into the copper tubes 421 that are located inside the PCR 150. Therefore, the coolant through the fluidic pump tube system 422 cools the water or other phase change material contained within the PCR 150. The TE heat pump module 160A pushes energy extracted at the heat transfer fluid recirculation pump 220 through the module to the heat rejection fan 230, which then dissipates the heat into the atmosphere. Thus, the PCR 150 is brought to, and maintained at, a temperature close to 0° C. Combined with the thermal attenuation layer 170, the PCR 150 enables the entire system 100 to maintain payloads within the predetermined temperature range.

In an alternative embodiment, rather than using the fluidic circuit 420, a solid state heat extraction is used (i.e., without the need for fluid). The TE thermoelectric heat pumps 160A are situated on, or very near to, the PCR 150. Therefore, heat extraction occurs through the walls of the PCR 150 and/or using heat pipes (not shown) to extract heat from within the core of the PCR 150 without the need for fluid. A break in the thermal pathway can be achieved by creating a physical separation between the cold side 240 of the TE thermoelectric heat pump 160A and the PCR 150 when the system 100 is not actively powered. In some embodiments, the heat pump module 160A transfers this heat into the environment through the array of copper fins 421 and a fan (e.g., the heat rejection fan 230) at the base of the refrigerator. The heat pump module 160A is configured to be easily replaceable by medical staff with minimal engineering or technical skill.

Turning back to FIG. 4B, the refrigeration system 100 is shown as including the inner chassis 110 having the PCR 150 at the core. FIG. 4B illustrates that the refrigeration system 100 has two PCRs 150, but the refrigeration system 100 can have any suitable number of modular PCRs 150, as desired. Similarly, four isothermal chambers 140 are shown to surround the PCRs 150. Each isothermal chamber 140 receives a vertical lift-up carriage 120 that is shown to support a stack of trays 131A.

FIG. 4C shows the refrigeration system 100 with the placement of inner chassis 110 into an insulated shell 190, which can comprise vacuum insulated panels 410 that form an opening at a top portion of the shell 190 for receiving the inner chassis 110. Once received, a top access door 430 can be used to access the vertical lift-up carriages 120 from each isothermal chamber 140.

In a preferred embodiment, the active heat pumping element 160 is a self-contained unit that can: a) include “thermal diode” properties (discussed below) to minimize standby losses; b) be replaced easily by an unskilled staff member; and/or c) be used in the quantity needed for either high or low power systems (multiple TE heat pump modules 160A provide for redundancy and allow the system 100 to operate even if one TE heat pump module 160A fails).

A low thermal resistance path can present a thermal liability when the heat pump 160 is not active. That is, the highly thermal conductive pathway that enables the heat pumps 160 to efficiently extract energy when the refrigeration system 100 is running can also allow heat to enter the refrigeration system 100 when the refrigeration system 100 is not running (e.g., at night). In order to minimize the standby heat losses, to achieve a long hold-over with a practical amount of thermal storage, the conduction path can be broken with a “thermal diode” configuration shown in the refrigeration system 100 in FIG. 4D and FIG. 5. For example, TE heat pump module 160A can be physically disconnected from the PCR 150. Similarly, the TE heat pump module 160A and the PCR 150 can be connected through a fluidic circuit 420. While the TE heat pump module 160A can be effective at moving energy both out of the system (when active) and into the system (when inactive), the fluidic circuit efficiently moves energy when the fluid is circulating. This way, when the system is “off” and the fluidic circuit 420 is static, the PCR 150 is isolated from the TE heat pump module 160A and its high thermal conductivity path to environmental heat.

The fluidic circuit 420 connects the cold side 240 of the TE thermoelectric heat pump 160A, the point from which energy is extracted, and the PCRs 150. Accordingly, when the refrigeration system 100 is off, there is no highly conductive path linking the external environment and the PCR 150. The fluidic circuit 420 can be turned “off” to provide a break in the thermal pathway between the outside environment and the PCR 150.

Thermoelectric heat pumping modules advantageously enable: a) portable, rugged, reliable operation, promoting an easily repaired and modular system; b) light weight and solid states, using no refrigerants; c) unlike in a vapor-compression heat pump, starting does not require a surge of power, thus enabling it to run continuously, and proportionately to the magnitude of solar insulation. It is also designed to couple tightly with a wide range of solar PV panel outputs.

With reference now to FIG. 4E, an alternative embodiment of the refrigeration system 100 having the active cooling system is shown. Turning to FIG. 4E, the refrigeration system 100 is shown as including a vapor compression cooling system 160B. The vapor compression cooling system 160B includes an air cooled condenser 162, at least one evaporator 163, and small-scale compressor 164. A refrigerant isobutane (or other) in alternating liquid and vapor form is routed through the small-scale compressor 164, condenser 162, capillary tubes and evaporator 163, which extracts heat from the central PCR 150. As discussed above, the vapor compression cooling system 160B can alternatively be powered through direct DC-DC charging by a photovoltaic system. The vapor compression cooling system 160B advantageously provides a smaller and lighter compressor than conventional compressors and generates a relatively smaller power surge.

In another embodiment, data telemetry can be used to log and transmit data from the refrigeration system 100 to a centralized location for remote monitoring. Turning to FIG. 6, using a Graphic User Interface (GUI) 610, a remote administrator can monitor data and send commands to the refrigeration system 100. In this embodiment, a microprocessor (not shown) embedded in a controller 641 of the refrigeration system 100 autonomously collects data from various sensors in the refrigeration system 100 (including, but not limited to, temperature sensors 642, photovoltaic (PV) array state, etc). Supercapacitors 643 with a memory card and a display (for readings and diagnostics) connected to the controller 641 can record/store status information when there is no sunlight and PV source. These logs provide diagnostics as well alarms if the temperatures (from the temperature sensors 642 located at selected points in the refrigeration system 100) go outside the predetermined temperature range in absence of a PV source. Additionally and/or alternatively, a local user interface (UI) 644 may be linked to the controller 641 and can be used to manually enter data, for example, regarding vaccine administration, vaccine inventory, immunization records, etc. The controller 641, via a serial port for example, transmits the information through a cellular modem 645 (which can have a global positioning system (GPS) receiver for identifying location data of the refrigeration system). Transmission infrastructure for telemetry to a centralized location (e.g., over a data network 630 such as via cloud computing) allows for remote monitoring, early alerts, early fault detection, and early response to any anomalies.

A backend data processor 620 can also perform analytics and be used to send commands to the refrigeration system 100 via the same bidirectional transmission channel (e.g., over data network 630). The GUI 610 allows the remote administrator to monitor and manage the controls of the refrigeration system 100. On the end of the refrigeration system 100, the commands are received by the controller 641, which in turn controls various refrigeration system 100 functions 646, including the power convertors, heat pumps and fan function in the refrigeration system 100. In some embodiments, the power convertors, heat pumps, and fan functions in the refrigeration system 100 are modular and their number can be selected depending on the capacity of the refrigeration system 100.

Data collection and telemetry of vaccine payload temperatures, system performance, physical location, and vaccine payload access profile enables remote monitoring of broadly distributed fleets of vaccine refrigerators and vaccine backpacks to ensure the most successful vaccine campaigns as possible (shown in FIG. 7).

As an additional advantage, the refrigeration system 100 are much more affordable to a much wider population base than competing alternatives and are able to store vaccine vials at off-grid locations in the vaccine cold chain for extended periods. For example, in an 18 L version, the refrigeration system 100 can maintain thermal stability for about five days without requiring external power, such as solar or grid power. The ability to reliably hold thermally-protected vaccines at such locations for weeks or months on solar power can fundamentally change immunization campaigns in areas that could previously only provide occasional and very time-limited clinics for immunization.

FIGS. 9A-C illustrates alternative embodiments for the refrigeration system 100. As shown in FIG. 9B, for example, the refrigeration system 100 can be disposed in a conventional carrier, such as an ergonomic, form-fitting backpack vaccine transporter 920, designed specifically for outreach. In one embodiment, the backpack vaccine transporter 920 uses the modular, scaled down “passive” thermal geometry components. As shown in FIG. 9C, a universal backpack 930 is equipped with standard ice packs without the need for the PCR 150, offering the additional advantages of cost and wide accessibility, while still preventing freezing of vaccines. A cooler box 910 is shown in FIG. 9A, which houses an inner chassis 110 and provides for ease of transportability (e.g., wheels, handles, modular PCR 150, and so on).

In an alternative embodiment shown in FIG. 8, active cooling (TE or vapor compression based) can additionally be used in a backpack vaccine transporter similar to the backpack vaccine transporter 920.

Advantageously, the carrier configurations (shown in FIGS. 8 and 9A-C) allow compatibility with the inner chassis 110 in the refrigeration system 100 for easy transfer and exchange of vaccine carriages, which aids last-mile outreach, longer holdover times than the current art, and the increased portability allowing greater outreach to rural areas.

The following are some of the additional advantages of the refrigeration system 100.

It allows vaccine delivery and outreach to regions with unreliable or no grid power with an easily transported, lower capital cost system than is currently available.

Its modular system design allows country/region-specific optimization for: a) vaccine capacity; b) holdover time; c) ambient temperature range variation; and/or d) serving population size; e) compatibility between higher and lower capacity units.

Its active heat pump elements include “thermal diode” characteristics to minimize stand-by heat losses, as well as provide unitized, easily serviced “Plug and Play” modules that can be accessed at the exterior of the refrigerator/backpack by unskilled staff.

Holdover time in this system exceeds WHO minimum requirement of 20 hours over 3 days in ambient temperature ranges of ˜32-43° C. ambient.

It is lightweight and can be moved by an average-sized transporter, carried by two averaged-sized transporters, and easily transported by bicycle or motorcycle.

It has high fault-tolerance, with minimal and easily replaced mechanical parts, modular heat pump redundancy and ease of repair by a health worker with minimal training.

It is designed to be shock resistant and durable, with an expected 10 years life span, and therefore quite robust.

It utilizes green technology, inasmuch as solid state cooling does not require refrigerants, “thermal battery” core is a phase change system using simple non-toxic materials and no batteries are required other than those for data logging (i.e., low power, non-critical).

It allows continuous vaccine vial temperature monitoring, with regular reporting via data telemetry (in locations where infrastructure enables this feature). In an alternative embodiment, labeling/tracking of individual vaccine vials can also be integrated.

Other industries that might use the refrigeration system 100 include, but are not limited to, medical equipment manufacturers in developed nations—the system 100 could be useful also in high-resource countries, particularly as a transport unit—as well as other pharmacological/biological products refrigerator manufacturers (e.g., for blood samples, oxytocin, serums, organs for transplantation, etc.).

The language used to disclose various embodiments describes, but should not limit, the scope of the claims. For example, in the preceding description, for purposes of clarity and conciseness of the description, not all of the numerous components shown in the schematic are described. The numerous components are shown in the drawings to provide a person of ordinary skill in the art a thorough enabling disclosure of the disclosed embodiments. The operation of many of the components would be understood and apparent to one skilled in the art. Similarly, the reader is to understand that the specific ordering and combination of process actions described is merely illustrative, and the disclosure may be performed using different or additional process actions, or a different combination of process actions.

Each of the additional features and teachings disclosed herein can be utilized separately or in conjunction with other features and teachings to provide a solar powered storage and transport system. Representative examples using many of these additional features and teachings, both separately and in combination, are described in further detail with reference to the attached drawings. This detailed description is merely intended for illustration purposes to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the claims. Therefore, combinations of features disclosed in the detailed description may not be necessary to practice the teachings in the broadest sense, and are instead taught merely to describe particularly representative examples of the present disclosure. Additionally and obviously, features may be added or subtracted as desired without departing from the broader spirit and scope of the disclosure. Accordingly, the disclosure is not to be restricted except in light of the attached claims and their equivalents.

The described embodiments are susceptible to various modifications and alternative forms, and specific examples thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the described embodiments are not to be limited to the particular forms or methods disclosed, but to the contrary, the present disclosure is to cover all modifications, equivalents, and alternatives.

System and Method for Solar Powered Thermal Management and Transport

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