CRYO-COMPRESSED HYDROGEN STORAGE MULTI-TANK SYSTEMS AND THEIR THERMAL MANAGEMENT

A method of operating a cryo-compressed storage system is disclosed. The system includes a plurality of cryogenic tanks adapted to store a supply of hydrogen. The method includes dividing the hydrogen into a plurality of portions, storing each of the portions in respective first and second cryogenic tanks of the plurality of cryogenic tanks; withdrawing at least part of a first portion of the plurality of portions from the first cryogenic tank; responsive to the first cryogenic tank containing a remainder of the first portion, such that the first respective cryogenic tank is at least partially depleted, withdrawing a first amount of hydrogen of the second portion from the second cryogenic tank; heating, via a heater external to the plurality of cryogenic tanks, the first amount of hydrogen; and providing the first amount of hydrogen to the first cryogenic tank such that the first amount of hydrogen heats the remainder.

TECHNICAL FIELD

The present application relates to hydrogen storage. In particular, the present application relates to multi-tank cryo-compressed hydrogen storage systems optimized for heavy-duty transportation utilization, such as by fuel cell trucks and marine vessels.

BACKGROUND

Decarbonization of the heavy-duty transportation industry, which is responsible for approximately 10% of global CO2emissions, is a daunting challenge that needs to be addressed in order to prevent catastrophic climate change outcomes. In contrast to the light-duty transportation sector, heavy-duty trucks, marine vessels, and aircraft demand remarkable power for long-route operations and consequently need to store magnitudes more fuel onboard. Thus, solutions that can mitigate CO2emissions resulting from fuel consumption in the light-duty transportation sector may not be effective in heavy-duty applications. For example, electrification with batteries is not sufficient in many operations, as the low energy-density limits the range of heavy-duty trucks and the long and demanding charge times constrains operational flexibility, and places substantial pressure on the local grid.

One known possible solution is natural gas as a heavy-duty fuel. Natural gas may be stored onboard as a liquid. While the energy density can meet demands across industries, and it can provide some CO2abatement, natural gas is ultimately not a low-emission fuel. It does not enable a scalable, full decarbonization of the industry. Natural gas is best thought of as a bridge fuel, buying more time to find the appropriate zero-emission fuel solution.

Liquid ammonia stored in low-pressure tanks is another possible fuel solution. Liquid ammonia exhibits a lower energy density than liquid natural gas, but is nonetheless considered by maritime industry, as an example. However, low carbon liquid ammonia has a high production cost, emits NOxcontaminants, and introduces human health risks during accidental exposures. These factors may slow and constrain liquid ammonia as a low-carbon emission fuel.

A third possible solution is liquid hydrogen. Hydrogen can be a truly zero-emission fuel and the infrastructure exists today to initiate adoption by truck fleet and shipping operators. Liquid hydrogen can meet the energy demands of truck routes and many shipping segments, as its density is about 70 g/L (2.3 kWh/L) at 1 bar. One problem with liquid hydrogen as a fuel is its high cost in many parts of the world today. Transportation of goods is a low-margin industry and fuel cost is one of the most important financial metrics. Furthermore, distribution of liquid hydrogen from a centralized liquefaction facility will present serious logistical issues. For instance, many deep-sea ships could require 20 or more liquid hydrogen tanker trucks to be at the port at a precise moment for refueling. Compound this problem with simultaneous refueling of multiple deep-sea ships at a given port and port space becomes a seemingly intractable issue. The same scenario may also be problematic when refueling heavy-duty truck fleets and aircraft at an airport. A second problem with liquid hydrogen storage is that the resulting system density ends up being much lower than 70 g/L, a result of numerous factors, including the resulting internal density is actually lower than 70 g/L at storage conditions, volume space in the storage vessel is left vacant for liquid vapor, and due to the large ΔT between the environment and the liquid hydrogen, a thick insulation layer is required.

More recently, a fourth possible solution has been posited: compressed hydrogen. Various pilot projects have operated by storing hydrogen at 350 bar or 700 bar, both at room temperature.FIG.4shows that on-site hydrogen compression to about 350 bar is more than 50% cheaper than liquefaction and delivery to a refueling terminal, assuming the compressed hydrogen was produced on-site and incurs no delivery costs. While compressed hydrogen may serve some limited market segments, its poor volumetric density will prevent broader adoption. Compressed 350 bar hydrogen does not meet the energy demands of many truck and vessel routes. At a hydrogen system density of 20 g/L (0.7 kWh/L) and 4 wt % (1.3 kWh/kg), truck range is typically limited to below 300 miles and there may not be enough volume onboard most marine vessels to store sufficient hydrogen for regular operations. The challenge is exacerbated given that current options today call for simply stacking multiple single tanks into “pods”, which creates significant void space, and overall can result in system densities that are even lower, 8 g/L (0.3 kWh/L). While 350 bar compressed hydrogen may be used by early adopters as demonstrations, its broad application is are limited. Compressed 700 bar storage vessels, with a system density of 25 g/L (0.8 kWh/L) and 6 wt % (2 kWh/kg), may be more suitable, but still faces similar challenges.

Another method of storing hydrogen is through cryo-compression and storage in suitable storage vessels, such as that described in the prior art, including U.S. Pat. No. 6,708,502B1. Cryo-compressed hydrogen (CCH2) storage tanks have been developed for light-duty applications. While they have never reached commercial application, they have been demonstrated to work at lab and pilot scale, for example by BMW in their hydrogen7vehicle. In these examples, a single tank is used, with a storage volume of around 150 L, and the overall system size, with valves and other essential components, is around 200 L. Under these cryo-compressed hydrogen conditions, the tanks can store 5-10 kg of hydrogen and feature a system density of around 35 g/L (1.2 kWh/L) and 7 wt. % (2.3 kWh/kg). The single on-board tanks feature an in-tank heat exchanger for thermal management, as described in prior art, such as that in DE102014207300.

Simply combining multiple of these light-duty tanks to enable storage of more hydrogen would not be a suitable solution for most of heavy-duty transportation applications. There are numerous limitations to this approach and are all related to the arrangement of possible tanks, as well as their thermal management. Consider that for small and medium size ship types, hundreds to even thousands of these cryo-compressed tanks would be required. This introduces a large amount of void space between tanks. This greatly decreases the overall system volumetric density to the point where cryo-compression no longer makes sense, as precious cargo space would have to be converted to fuel storage space. Importantly, having at least one valve per tank will result in having hundreds to thousands of individual valves, which drives up the cost substantially. Notably, half of the storage system cost is the balance-of-systems, of which the primary contribution are valves. Additionally, for every valve required there is a higher probability of a leak point. In cryo-compressed hydrogen storage, many of these valves will need to be vacuum insulated, and consequently, any hydrogen leak will result in heat leaking into the system. Given the complexity in valves and potential leak points, hydrogen's high diffusivity and conductivity, this is a probable occurrence with current designs which can result in substantial venting and a loss of most of the fuel. This is unacceptable for maritime and aviation operations. Similarly, having an in-tank heat exchanger inside every tank is a prohibitively expensive thermal management operation for heavy-duty hydrogen storage quantities. Any components inside the storage vessel, such as a heat exchanger, will face harsh stresses. Typically heat exchangers are tubular structures that may vibrate substantially under on-road, or on-vehicle conditions. In order to avoid possible failure modes, such a cracking of the heat-exchanger, a notable amount of support material and thick connections are required. As described in prior art DE102015219984, one proposed solution includes having an additional hydrogen storage tank dedicated to storing hot hydrogen and using it for thermal management with the main hydrogen storage tank. While this may avoid using an in-tank heat exchanger, it still introduces complexity (an additional tank, valve, piping, e.g.) and adds more volume to the storage unit which does not contribute to the usable hydrogen capacity to power the on-board fuel cell or other hydrogen consuming device. Furthermore, the auxiliary tank needs to operate at a different pressure, and requires a distinct filling event from the main tank, which increases operational complexity. Prior art U.S. Ser. No. 11/137,116 similarly proposes using auxiliary tanks to help with thermal management. Overall, these strategies drive up cost while minimizing useful volume to store cryo-compressed hydrogen. A different multi-tank arrangement and its thermal management is thus required.

In sum, there is no solution that meets all the desired criteria to capture the 4.3 gigaton CO2abatement opportunity of the heavy-duty transportation industry that exists today. Cryo-compressed hydrogen storage holds great promise but new designs for multi-tank systems and their efficient thermal management are required to drive down costs and increase performance.

SUMMARY

A method of operating a cryo-compressed storage system is disclosed. The system includes a plurality of cryogenic tanks adapted to store a supply of hydrogen, the method includes: dividing the hydrogen into a plurality of portions; storing each of the portions in respective first and second cryogenic tanks of the plurality of cryogenic tanks; withdrawing at least part of a first portion of the plurality of portions from the first cryogenic tank; responsive to the first cryogenic tank containing a remainder of the first portion, such that the first respective cryogenic tank is at least partially depleted, withdrawing a first amount of hydrogen of the second portion from the second cryogenic tank; heating, via a heater external to the plurality of cryogenic tanks, the first amount of hydrogen; and providing the first amount of hydrogen to the first cryogenic tank such that the first amount of hydrogen heats the remainder of the first portion.

Optionally in some embodiments the method includes providing a second amount of hydrogen of the second portion to a hydrogen consumption device.

Optionally in some embodiments the temperature of the first amount of hydrogen after heating is based on a characteristic of the remainder of the first portion.

Optionally in some embodiments, the characteristic comprises at least one of a temperature, a pressure, or an amount of the remainder.

Optionally in some embodiments responsive to the first cryogenic tank being at least partially depleted, ceasing the withdrawal of the first portion; and withdrawing a second amount of hydrogen of the second portion.

Optionally in some embodiments the method includes heating the second amount of hydrogen.

A method of thermal management of a cryo-compressed hydrogen storage system is disclosed. The method includes: storing cryo-compressed hydrogen in a plurality of tanks, wherein each tank of the plurality of tanks is in fluid communication with a shared hydrogen conduit; withdrawing the cryo-compressed hydrogen from the system at a withdrawal rate; conveying a portion of hydrogen in a controlled rate from a first tank of the plurality of tanks to a heater external to the plurality of tanks; heating the portion of hydrogen via the heater; conveying the portion of hydrogen from the heater to a second tank of the plurality of tanks. The first tank has a first pressure of hydrogen therein, the second tank has a second pressure of hydrogen therein, the second pressure is lower than the first pressure, the controlled rate is based at least on the withdrawal rate, and the portion of the hydrogen warms the second tank.

A storage system is disclosed. The system includes a plurality of tanks in fluid communication with one another via a manifold; a first of tank of the plurality of tanks is fluidically coupled to a valve that controls a flow of cryo-compressed hydrogen flow in and out of the first tank; a second tank of the plurality of tanks is in direct fluid communication with the manifold; a heater is disposed in the manifold such that hydrogen can be exchanged between the first tank and the second tank while being heated by the heater.

Optionally, in some embodiments, each tank of the plurality of tanks includes an outer wall; a support layer disposed inside and spaced apart from an inner surface of the outer wall, wherein the inner surface of the outer wall and an outer surface of the support layer define an insulation compartment therebetween; and a liner disposed inside an inner surface of the support layer, wherein the liner forms a closed storage volume.

Optionally in some embodiments, the closed storage volume is at least 100 liters.

A hydrogen storage system is disclosed. The system includes two or more tanks configured to store pressurized cryogenic hydrogen; an insulation layer encapsulating the two or more tanks; a continuous outer jacket encapsulating the single insulation layer; a conduit, disposed inside the single insulation layer, and in fluid communication with the two or more tanks, which conduit extends to an exterior of the outer jacket; and a control valve disposed in, and operative to control a flow of hydrogen in the conduit.

Optionally in some embodiments the insulation operates at atmospheric pressure.

Optionally in some embodiments the discharge of hydrogen from the storage system cools a remainder of hydrogen in the system and compensates for a lower insulation performance of the insulation, relative to high-vacuum insulation system.

In one aspect, a pressure vessel optimized for storing hydrogen in its cryo-compressed state, of sufficient size to accommodate use by heavy-duty transportation, such as marine vessels or trucks, the pressure vessel includes A long, cylindrical body such that the tank length is much greater than the tank radius A long, cylindrical body that enables the tank to scale to store sufficient hydrogen without requiring thick outer walls and decreasing the overall system density A metallic liner that provides durability over many hydrogen refueling cycles Hollow fittings on the tank exterior that enable facile movement of tank and rapid swapping if required for refueling Tank walls and vacuum space that provide the means for optimal density at the optimal pressure-temperature envelope for heavy-duty transport applications.

In one aspect, a multi-tank system with a manifold optimized for storing hydrogen in its cryo-compressed state, of sufficient size to accommodate use heavy-duty transportation, such as marine vessels or trucks, the system includes Of two or more tanks, where each individual tank valve is connected to a main manifold A manifold that contains channels that enable fluidic communication between tanks A manner to enable hydrogen exchange via the manifold, which enables a temperature exchange pathway and provides the means for obviating the need for an in-tank heat A manifold that decreases the number of valves per tank, decreasing failure points and cost

In one aspect, a multi-tank system with a manifold optimized for storing hydrogen in its cryo-compressed state, of sufficient size to accommodate use heavy-duty transportation, such as marine vessels or trucks, the system includes Of two or more tanks, where each individual tank valve is connected to a main manifold A manifold that contains a heat exchanger, enabling the warming up of hydrogen being exchanged between tanks, and obviates the need to have an in-tank heat exchanger A manifold that provides the means for increasing usable hydrogen capacity without decreasing the available storage fuel space

In one aspect, a multi-tank system with one vacuum layer and suitable for use in heavy-duty transportation, such as marine vessels or trucks, the system includes Of two or more tanks A single insulation layer encapsulating the tanks, and correspondingly, a single continuous outer jacket. A multi-tank system with a single insulation layer provides a means for decreasing the amount of space required for on-board storage relative to individual insulated, compressed tanks.

In one aspect, a pressure vessel for storing supercritical hydrogen includes a cylindrical body defining an internal storage volume for storing the supercritical hydrogen, the cylindrical body having a length and a diameter, where the length is greater than or equal to 6 times the diameter, an overwrap surrounding the cylindrical body, a jacket spaced apart from and surrounding the overwrap and defining an insulation layer between the overwrap and the jacket, where the insulation layer is configured to contain a vacuum.

The pressure vessel may also include where a portion of the overwrap has a first radial thickness near a longitudinally central portion of the cylindrical body and a second radial thickness near an end portion of the cylindrical body, where the first thickness is greater than the second thickness

The pressure vessel may also include where the cylindrical body is metallic.

A system may include a plurality of vessels where the plurality of vessels include respective insulation layers in fluid communication with one another.

The system may also include where the respective internal storage volumes of the plurality of pressure vessels are in fluid communication with one another via a manifold.

The system may also include where the plurality of pressure vessels are configured to exchange hydrogen with one another via the manifold.

The system may also include where the exchange of hydrogen between the respective pressure vessels provides a heat exchange pathway between the respective pressure vessels.

The system may also include where as a first pressure vessel of the plurality of pressure vessels is filled with hydrogen, a first quantity of the hydrogen boils to gaseous hydrogen, and the gaseous hydrogen is routed via the manifold from the first pressure vessel to a second pressure vessel of the plurality of storage vessels to cool the second pressure vessel. Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

DETAILED DESCRIPTION

Cryo-compressed hydrogen, or CCH2, is a fuel that can accelerate decarbonization in the heavy-duty transportation sector. Some examples include heavy-duty trucks, marine vessels, aviation, hydrogen delivery vehicles, and/or other applications of hydrogen storage. More specifically, the present disclosure is directed to multi-tank systems and methods of storing and utilizing CCH2 on-board heavy-duty vehicles.FIG.1andFIG.2detail the CO2abatement and market opportunity in heavy-duty trucks and in maritime, respectively. Overall, it is a massive economic opportunity with great environmental imperative. Cryo-compressed hydrogen can provide fuel densities comparable to and even higher than liquid hydrogen without the cost of liquefaction, offering sufficiently high density at a cost lower than liquid hydrogen. The tradeoff between hydrogen cost and volumetric density may in general be optimized for cryo-compressed hydrogen at about 80 K and 300 bar. Note that the pressure-temperature envelope that enables similarly high densities extends beyond this one point, and for example can occur at combinations including but not limited to 50 K and 145 bar, 60 K and 200 bar, 90 K and 375 bar. Depending on the particular end case, the optimal density may be higher or lower than this.

FIG.3illustrates that at these conditions, utilizing storage systems of the present disclosure, hydrogen may be stored on-board vessels within the existing fuel storage volumes used for hydrocarbon fuels. As an example, hydrogen stored in a storage system described herein can provide enough energy to power a large container ship for 2 trips, with fuel left over. While a traditional hydrocarbon fuel stored in the same volume would power such a ship for more trips, this type of stored hydrogen enables zero-emission power with minimal changes to logistics and ship scheduling. It was previously thought that only liquid hydrogen would be a possible solution for container and cargo ships.

Notably, the cryo-compressed hydrogen used can be cheaper than liquid hydrogen.FIG.4compares the compression of hydrogen at a refueling facility versus the centralized liquefaction and delivery to the refueling facility. Cryo-compressed hydrogen at about 80K and 300 bar, or more generally within the pressure-temperature envelop previously described, will likely fall in between these two prices, requiring less energy than liquefaction but slightly more energy, and cost, than compression. As decentralized compressed hydrogen can be around 60% cheaper, cryo-compression may likely also be cheaper than liquid. Importantly, decentralized hydrogen production will need to happen in order to meet global CO2reduction targets.

Many examples of the present disclosure on multi-tank systems minimize the number of tanks per amount of hydrogen stored, as well as minimize the number of valves per tank, so that the void spaces are minimized, the amount of fuel stored and utilized is maximized, failure and leak points are minimized, and overall storage cost is decreased.

The individual storage vessels that make up the multi-vessel system, according to the present disclosure, may be designed to accommodate larger storage volumes. In one of many embodiments, a storage vessel (e.g., a tank) includes a liner3which encloses the internal storage volume2, as depicted for example inFIG.5A. The liner3may be surrounded by a support layer, or overwrap4. The support layer4may be formed of a composite material, such as a fiber (e.g., glass, aramid, and/or carbon fiber, etc.) and a polymer resin. An outer wall or jacket,8, may surround the support layer4and may be separated by a distance from the support layer so as to define an insulation compartment5. The insulation compartment5may contain an insulating material such as metal foil, perlite, fiberglass, foam (e.g. expanded polystyrene or the like), silica fibers, or similar materials that can inhibit the transfer of heat between the environment and the internal storage volume2. In many examples, the insulation compartment5may be evacuated of gases or other fluids to form a vacuum. The vacuum may act like an insulating material to inhibit heat transfer.

As shown inFIGS.5A and5B, the liner encloses the inner volume that stores a gaseous fuel such as hydrogen. The liner is typically metallic, such as stainless steel or/and aluminum. It can also be polymeric or other materials. At lower temperatures, metallic liners may perform more reliably and may have a longer lifetime than polymeric liners. However, polymeric liners may offer weight saving benefits. If a polymeric liner is used, the insulation layer can be foam, or a non-vacuum type of insulation. This avoids the issue of hydrogen permeation through the plastic liner which degrades the vacuum insulation layer performance. As such, polymeric liner and foam insulation is a suitable combination that is appropriate only for high and constant consumption rates, such as in autonomous trucking, as the self-cooling effect from tank discharge will compensate for the weaker insulation performance of non-vacuum foam. The liner3is typically the same level of thickness throughout the entire encapsulation of the inner void space. While thinner liners can be beneficial to maximize overall system hydrogen storage densities, the thickness may scale with stability, and will depend on the amount of support layer utilized. Typically, the support layer provides the majority of pressure stability. The optimal thickness depends on the tank dimensions but may be between 3 mm and 30 mm.

The overwrap4may be made of a lightweight material and serves the function of providing support, thereby increasing stability and lifetime of the tank. The composite material may be carbon-fiber, Kevlar™ (aramid), glass, or another carbon-based material that typically contains a fiber reinforced resin matrix build. The overwrap4may be manufactured by wrapping a fiber material embedded in a resin matrix over the liner and then curing the resin matrix, or by other suitable methods. A cryogenic-temperature resin can be used to further extend the lifetime of the tank. Resins that are not suitable at these temperature may crack, resulting in carbon fiber movement and thus lower fatigue life for the tank. The overwrap thickness may vary throughout the encapsulation of the liner.

The layer between the overwrap4and the outer wall8is the insulation layer5. The insulation layer5may be a void space that contains a vacuum, typically established by utilizing a high-vacuum source, reaching 1 μbar or less. The function of the insulation layer5is to attenuate heat transfer from the external environment to the internal, stored hydrogen. The thickness of the insulation layer5and the vacuum pressure determine the extent of heat transfer mitigation. As is also known in the art, multilayer vacuum insulation, or superinsulation, may also be used to serve this purpose. As previously mentioned, depending on operating conditions, different insulation materials may be used, including those not requiring high vacuum. These ambient-pressure insulation materials, such as foam, may be compatible with non-metallic liners.

An outer wall, jacket, or outer shell8may enclose the insulation layer5. The outer shell8may mirror the shape of the interior vessel. However, it can also deviate from the shape; for instance, it may have caps that are less rounded. The insulation layer5thickness may therefore not be consistent throughout the entire encapsulation of the overwrap. The jacket8is typically metallic, for example stainless steel or aluminum but may be made of other materials. The thickness of the jacket8is usually less than that of the liner3and less than that of the overwrap4thickness.

The jacket8is kept in place and prevented from making contact with the overwrap4by support structure7. Support structures7can be various shapes, such as rods or rings, and may include insulating materials with high compression strength.

Fluid flows in and out through valve10, which may contain two separate and isolable channels. The valve may function mechanically, pneumatically, hydraulically, or electronically. Each channel can be controlled by a flow control valve, and may provide control at a 500 mbar to 1 bar resolution. The valve10can be connected to fluid lines for refueling or for fuel consumption, at the end of the two isolable channels. The valve may also be a single channel, which enables flow in and out of the tank.

As shown inFIGS.5A and5B, the overwrap4is formed over the liner3. Support structures7may be added, and the jacket8may be mounted. Vacuum may be established after construction by connecting a vacuum pump to the vacuum valve6.

The tank1may be used on-board a truck or other heavy-duty transportation modalities, including ships or planes. A tank1may also be used off-board, for instance to provide hydrogen fuel for backup power generation. The tank system is agnostic to the downstream hydrogen consumption method. Typically, for on-board use, the tank1is connected via appropriate piping up to the refueling infrastructure. In one specific example, hydrogen flows in through valve10. If supercritical hydrogen is used, it may warm up. To mitigate temperature increase due to this flow work, the hydrogen may be flowed through the tank to quickly pre-cool the tank. In such a scenario, one of the two channels in valve10will let in hydrogen flow, which the other channel enables hydrogen to leave. Upon filling, one of the two channels is then connected to the desired hydrogen fuel consumption method. The transducer11enables electronic monitoring and control of hydrogen pressure flow required for the consumption method.

In one example, a proposed cryo-compression tank may have a high length-to-diameter ratio, L/D, such that the inner tank diameter remains small relative to the length, typically 40-80 centimeters, and the tank length to be long, typically 5-12 meters. In another set of embodiments, suited more for truck on-board storage, the diameter may be 20-60 centimeters and a length ranging from 1-3 meters. In various examples, the L/D ratio may be about 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or higher. The relatively thin diameters may enable the use of a relatively thin overwrap4and liner3, which may increase volumetric hydrogen system densities.FIG.6Ashows one embodiment in a longitudinal cross-sectional view. An example size includes an external radius of roughly 40 centimeters and an overall volume of 2500 to 3000 liters. This tank1is capable of storing around 190 kg of hydrogen. The tank1may have a long, thin cylindrical shape with a cap18at each end formed with or attached to the cylindrical section. The cap18may be hemispherical. The caps18and the cylindrical section may define inner storage volume2. The inner storage volume2may make up a majority of the system volume. The inner wall material, or liner3, is typically metallic, for example aluminum or stainless steel. As the lifetime of onboard marine vessels is longer than on-land transportation, polymeric liner, utilized in light-duty applications, may not meet duration standards.

In one exemplary embodiment, such as that inFIG.5A, there is a vacuum valve6to ensure vacuum is maintained in the insulation layer5. On the outside are two hollow fittings9built such that they facilitate the picking up and swapping of tanks onboard a vessel. These fittings can be metallic, or other materials with high tensile strength. There can be more than two fittings. In this embodiment valve10contains two controllable flow channels. There may be a pressure transducer11and/or a temperature transducer which may be in fluidic communication with the internal storage volume2, and operate to measure the temperature and or pressure of the fluid in the internal storage compartment2. As previously mentioned, in another embodiment, there may be only one channel for hydrogen to flow in and out.

FIG.6shows another exemplary embodiment of an individual tank that can subsequently make up a multi-tank system, this one embodiment containing a second valve12at the hemispherical cap end opposite the valve10. The valves10and12may facilitate fluid flow-through between multiple tanks. For example, a daisy-chained configuration may be used during refueling events to pre-cool one or more tanks.

FIG.7shows an exemplary embodiment of a multi-tank system. The jacket16, typically stainless steel or aluminum, contains multiple tanks, and in this example two tanks, but three, four, five, six or more may be used. Overall, this approach can be extended to more than two inner tanks. This arrangement may result in increased volumetric density relative to traditional multi-tank arrangements, as void spaces between tanks are minimized. In particular, one insulation layer is shared between multiple tanks, further decreasing storage volume.

FIG.8Aillustrates another embodiment for a multi-tank system. Here, the manifold17is connected to one outer tank valve20. Thus, one valve can be used for multiple tanks. This concept can be extended to three or more tanks. The manifold17connects to a valve that controls fluidic flow to each tank, as shown inFIG.8B. A transducer14near the valve monitors pressure. This arrangement may serve multiple functions. The system ofFIG.8Amay have certain advantages. First, if there is a leak within the manifold17it can be more effectively contained as vacuum surrounds the valves. Second, this system halves the number of valves that are repeatedly connected and disconnected, decreasing probability of leaks and other failure modes, as there is only one outer valve20. This can accelerate operations in a safe manner in examples where the tanks are frequently removed from the vehicle (i.e. tank swapping). Third, as the hydrogen line may sometimes need to be insulated, its placement within the insulation layer makes more efficient use of space. It can be appreciated that three or more tanks may be connected to a single internal manifold which is then connect to one outer valve. This may be important in the case of tank removal from onboard the vessel, or tank swapping, as it may greatly decrease the time to disconnect tanks. In other embodiments, no transducer is required, so that two, or more tanks, are in thermal equilibrium, and constitute one continuous storage volume for hydrogen. In such an embodiment, valve20controls the flow in and out of hydrogen. This type of arrangement minimizes hydrogen leaks altogether, minimizes failure modes, and minimizes cost.

Placing a heat exchanger within a tank has been previously proposed, e.g., for single-tank systems for light-duty vehicle onboard application. For on-board application, where the capacity of hydrogen is greater, (e.g. 10× greater in heavy-duty trucks, >100× greater in maritime and aviation), placing a heat exchanger inside each tank will in sum represent a large decrease in the total hydrogen storage space. Furthermore, each heat exchanger inside a tank likely introduces new potential gas or thermal leaks, and drives up storage cost. In contrast, the operating method for the multi-tank system ofFIG.9avoids an internal heat exchanger and can, for example, warm up hydrogen as it exchanges between two tanks. Overall, this fluidic exchange operating method can result in higher usable hydrogen capacities (amount of hydrogen discharged/initial total amount of hydrogen stored in system) compared to a system without a heat exchanger. Importantly, as additional components are not required for each tank, and as the amount of usable capacity increases, on a cost per usable capacity of the system, this approach may be less costly than a system with no thermal management operations. Prior art systems have unsuccessfully tried to address the problem of withdrawing hydrogen from vessels by adding auxiliary, non-cryogenic hydrogen tanks to the system. These auxiliary hydrogen tanks are dedicated to store hydrogen at sub-critical or non-cryogenic conditions, are not cryo-compressed hydrogen tanks, and do not contribute to the usable capacity of the system. Additionally, the need to package an auxiliary hydrogen tank that does not contribute to the system storage capacity results in a lower overall specific system storage capacity in both gravimetric and volumetric terms compared to systems of the present disclosure (e.g., lower kg H2/m3and kg H2/kg of the storage system) both of which are important metrics in the viability of any fuel storage system for mobile applications.

FIG.9is a simplified diagram of a fuel storage system900. A method1000of operating the system900is discussed with respect toFIG.10to describe the method of thermal management operation of one embodiment of the cryo-compressed multi-tank storage system described in this present disclosure. While four tanks are shown, the basic operations described here can be used for more or fewer tanks. The tanks can comprise of those depicted inFIG.6,FIG.7,FIG.8, or varying combinations, with no modifications or with some modifications.

In the present example, cryo-compressed storage tanks100,101, and102are in direct fluid communication with each other and with a hydrogen manifold (e.g., the tanks do not have individual hydrogen control valves), and as such all three tanks in this example can be thought of as one storage space, or one portion of stored hydrogen. In this example, multiple cryogenic pressure tanks serve as one stored hydrogen portion. Having one stored portion across multiple tanks decreases the number of balance-of-plant components and minimizes cost. Additionally, using more, smaller tanks aids packaging flexibility, compared to one larger tank. Furthermore, it can decrease the probability of leaks, such as those that occur from hydrogen control valves into the insulated vacuum system. Rather than having four hydrogen control valves, only tank103has a dedicated hydrogen control valve106.

To refuel, cryo-compressed hydrogen enters at supply line112and passes a check valve111. Typically, the supply line112is insulated, such as by high-vacuum insulation. The hydrogen enters the tanks100,101, and102. Valves105and106are open during the refueling operation, so tank103is also filled. Valves104,107, and113remain closed during refueling operations.

During vehicle operation, tanks100,101, and102can be the first storage volume, or stored hydrogen portion, to be discharged. Once the fuel cell or other hydrogen-consuming device or system requires hydrogen, valves105and113are opened. In examples discussed herein, it is understood that a fuel cell may be replaced with any other device or system that consumes hydrogen. The hydrogen is conveyed to a heat exchanger114, and ultimately enters the fuel cell.

The heat exchanger114can utilize thermal waste from the fuel cell to warm up the hydrogen towards ambient temperatures, before it enters the fuel cell. Once this set of tanks, tanks100,101, and102, are close to, or reach their minimal operating pressure, which in some cases is 5-15 bar, valve105is closed. As the temperature is very low (e.g., 30 K) in tanks100,101, and102, a notable amount of hydrogen can remain in this portion. For example, as much as 20% of the tank hydrogen capacity may remain in the tank and inaccessible. It is beneficial to extract as much hydrogen as possible from the system, for example to achieve higher vehicle range or autonomy.

To continue fuel cell operations, valve106opens (valve105remains closed), discharging some of the hydrogen from tank103. Some of the flow is conveyed through valve113and into the heat exchanger114. Depending on fuel cell needs, the remaining hydrogen flow, which can be a percentage of the flow being conveying to the fuel cell, is conveyed through valve107, and into a heat exchanger, or heater,108. Valve107can be a flow regulating valve and for example, conveying about 25% of the flow that goes towards the fuel cell, through valve107. Valve107is opened when the first stored hydrogen portion, (e.g., the hydrogen in tanks100,101, and102), should be warmed up to extract more hydrogen.

The heat exchanger or heater108can use a minor amount of the thermal waste heat arising at the fuel cell, or other suitable heat source such as an electric heater. In one embodiment, heating powers as low as 0.1 kW can be utilized. This energy is transferred to the hydrogen which warms up, passes through check valve110and is introduced to tanks100,101, and102via the main supply line. The warm hydrogen consequently warms up this storage space, or portion, greatly increasing the pressure in the system containing tanks100,101, and102. For example, the pressure in the tanks100,101, and102may increase from 8 bar to 50 bar. The hydrogen released from tank103and passing through the heat exchanger108functions as a heat carrying medium which obviates the need for an in-tank heat exchanger. Furthermore, the system900avoids the need to have auxiliary stored hydrogen tanks for which the only purpose is to store and provide warm hydrogen, but which cannot store cryogenic hydrogen. Such an approach is not efficient from a usable capacity point of view. In contrast, the system900has tanks which all can store cryo-compressed hydrogen and all contribute to power the fuel cell. This warming up process can occur simultaneously as the fuel cell is fed hydrogen from tank103. Once tank103reaches its minimum operation pressure, typically 5-15 bar, valve106and107is closed, and valve105is opened, which discharges the now warm and greater pressure hydrogen from tanks100,101, and102. The system900and operating method increases the amount of hydrogen that is usable for consumption, and thus the useable capacity of the storage system. In one embodiment, this can increase usable hydrogen capacity by 10% compared to prior systems. Minimal operating valves are used, thereby reducing cost, weight, volume, control complexity, and leak points, no in-tank heat exchangers are used, and no auxiliary tanks are required. It is appreciated that different number of tanks and various operation sequences can be utilized beyond the one described herein. Furthermore, the system900is suitable to supply hydrogen to a fuel cell or other hydrogen consumption device at a rate of 5 kg/hour our higher.

FIG.10describes a method1000of operating the cryo-compressed storage system. The method1000may begin in operation1002and the hydrogen is divided into two or more portions, such as by automatic control of one or more valves by a processing element1102of the system900. A given portion can be stored in one tank, or a plurality of tanks. For example, one portion may be stored in the tanks100,101, and/or102and a second portion may be stored in the tank103.

The method1000may proceed to operation1004and hydrogen is withdrawn from a first portion of the two or more portions. In one example, the hydrogen is withdrawn to power a fuel cell on board a vehicle. In another example, the hydrogen is withdrawn and conveyed to an internal combustion engine. For example, the valves105and113may be opened by a processing element of the system900enabling a flow of the first portion of hydrogen from the tanks100,101, and/or102.

The method1000may proceed to operation1006and the system900determines whether a tank, or tanks, storing the first portion of hydrogen has reached a low operating pressure threshold. If the first portion of hydrogen is not at a low pressure threshold, the method1000may return to the operation1004and continue withdrawing hydrogen. Alternately, the system900may stop the withdrawal of hydrogen, such as if the hydrogen demand from a fuel cell or other device is removed. In one example, once a portion of the stored hydrogen is at or close to (e.g., within 10%) of a low operating pressure threshold (e.g., 5-15 bar), the method may proceed to operation1008.

In operation1008, hydrogen is withdrawn from a second portion (e.g., the portion stored in the tank103). For example, the valve105may be closed and the valve106may be opened by a processing element1102of the system900. Based on pressure and temperature sensors1114, a processing element1102of the system900can determine when a stored portion can benefit from increasing the temperature in that portion. In one example, a portion may have hydrogen below the low operating pressure threshold, and so increasing the temperature will result in a higher pressure, enabling the system900to use more hydrogen from this given stored portion. In another example, a stored portion of hydrogen may be above the low operating pressure threshold but may nonetheless benefit from increased temperature as it will ultimately allow more hydrogen to be withdrawn for this given portion.

The method1000may proceed to operation1010and a portion of the hydrogen withdrawn in operation1008is conveyed through the heater or heat exchanger108and heated. In one example, this heat exchanger108is distinct from the heat exchanger114used to warm up hydrogen for end-use operations. In another example, the heat exchangers108and114are the same the same heat exchanger.

The method1000may proceed to operation1012and the hydrogen warmed in operation1010is conveyed back into the storage system and is introduced into the portion that would benefit from warm hydrogen, thereby releasing additional hydrogen from that portion. In one example, the warming operation occurs simultaneous as hydrogen is withdrawn for end use, such as powering a fuel cell. It is also possible that the warmed hydrogen enters the portion from which hydrogen is being withdrawn. This may be enabled by an outlet tube and an inlet tube to this given portion. The method1000may be executed in different orders than that described. Some operations may be omitted and some operations may be executed in parallel with one another. InFIG.10, the order shown is presented for clarity, but can be executed in different orders.

The operating method of thermal management described here has numerous benefits relative to standard, isolated cryo-compressed tanks, that costs as much, if not more, than present disclosure. As shown inFIG.12, the system usable hydrogen capacity (amount of hydrogen discharged/initial total amount of hydrogen stored in system) is greater across the full operating cycle of a typical long-range heavy-duty truck, such as one driving more than 500 miles a day. By day three, a steady-state operating temperature is reached, which is colder than that reached in day one. As a result, the thermal management operation has an even greater effect when steady-state conditions are realized.

FIG.11illustrates a simplified block diagram for a controller1100of the system900. The controller1100may automatically execute any operation of any method disclosed herein including the method1000, such as by automatic operation of the valves or other equipment of the system900, reading of sensors, or the like. As shown, the controller1100may include one or more processing elements1102, an optional display1108, one or more memory components1112, a network interface1104, optional power supply1110, and an optional input/output (I/O) interface1106, and/or one or more sensors1114. The various components may be in direct or indirect communication with one another, such as via one or more system buses, contract traces, wiring, or via wireless mechanisms.

The one or more processing elements1102may be substantially any electronic device capable of processing, receiving, and/or transmitting instructions. For example, the processing elements1102may be a microprocessor, microcomputer, graphics processing unit, or the like. It also should be noted that the processing elements1102may include one or more processing elements or modules that may or may not be in communication with one another. For example, a first processing element may control a first set of components of the system900and a second processing element may control a second set of components of the system900where the first and second processing elements may or may not be in communication with each other. Relatedly, the processing elements1102may be configured to execute one or more instructions in parallel locally, and/or across the network, such as through cloud computing resources.

The display1108is optional and provides an input/output mechanism for devices of the controller1100, such as to display visual information (e.g., images, graphical user interfaces, videos, notifications, and the like) to a user, and in certain instances may also act to receive user input (e.g., via a touch screen or the like). The display may be an LCD screen, plasma screen, LED screen, an organic LED screen, or the like. The type and number of displays may vary with the type of devices (e.g., smartphone versus a desktop computer).

The memory components1112store electronic data that may be utilized by the controller1100, such as audio files, video files, document files, programming instructions, and the like. The memory components1112may be, for example, non-volatile storage, a magnetic storage medium, optical storage medium, magneto-optical storage medium, read only memory, random access memory, erasable programmable memory, flash memory, or a combination of one or more types of memory components.

The network interface1104receives and transmits data to and from a network to the various devices of the system900. The network interface1104may transmit and send data to the network directly or indirectly. For example, the networking/communication interface may transmit data to and from other computing devices through the network. In some embodiments, the network interface may also include various modules, such as an application program interface (API) that interfaces and translates requests across the network to the controller110or other components of the system900. The network interface1104may be any suitable wired or wireless interface. For example, the network may be an Ethernet network, Wi-Fi, Bluetooth, Wi-Max, Zigbee network, Controller Area Network (“CAN”), the internet, microwave link, or the like.

The various devices of the system900may also include a power supply1110. The power supply1110provides power to various components of the controller1100. The power supply1110may include one or more rechargeable, disposable, or hardwire sources, e.g., batteries, power cord, AC/DC inverter, DC/DC converter, or the like. Additionally, the power supply1110may include one or more types of connectors or components that provide different types of power. In some embodiments, the power supply1110may include a connector (such as a universal serial bus) that provides power to the computer or batteries within the computer and also transmits data to and from the device to other devices.

The I/O interface1106allows the system900devices to receive input from a user and provide output to a user. In some devices, the I/O interface1106may be optional. For example, the I/O interface1106may include a capacitive touch screen, keyboard, mouse, stylus, or the like. The type of devices that interact via the input/output interface1106may be varied as desired.

The sensors1114may include any number of temperature, pressure, weight, force, proximity, limit, or other sensors. The sensors1114may be integrated with the controller1100or may be separate devices in communication with the controller1100such as by direct wired communication, wireless communication, the network interface1104, or the like. In many embodiments the sensors1114may measure fluid conditions in the system900such as in one or more tanks, in a heat exchanger, or the like.

From the description above, a number of advantages of the present disclosure become evident:(a) By having a valve at each end of the hemispherical cap, pre-cooling by flowing gas through is possible, and this may take less time than other pre-cooling methods.(b) A combination of non-vacuum insulation and a plastic liner may be the lowest cost option for high-utilization on-board storage applications, such as autonomous trucks(c) The self-cooling from hydrogen high-flow discharge, such as operative in autonomous trucks, can compensate for the lower performance of non-vacuum insulation(d) A resin suitable for cryogenic temperature may extend the fatigue life of tanks, as it prevents carbon fiber movement over many cycles(e) The described manifold enables hydrogen exchange between the tanks. This can obviate the need of in-tank heat exchangers and auxiliary tanks, which decrease system density, introduce failure modes for hydrogen leaks, and increases costs.(f) The described thermal management operations do not require an in-tank heat exchanger or auxiliary storage tanks that only contribute to thermal management but not to usable capacity.(g) The heating power in this described manifold is minimal, yet it can increase usable hydrogen capacity, and thereby range.(h) The storage systems are substantially cheaper as they have less valves per tank than other multi-tank arrangements, do not require in-tank heat exchangers, and the thermal management requires simple operations(i) The hydrogen line can be part of the tank insulation layer, which increases system volumetric density(j) The minimal number of insulated hydrogen control valves decreases the probability of hydrogen leaking into the insulated manifold