Disclosed are embodiments relating generally to storage tanks, and in particular the cryogenic storage of liquid methane, as well as its delivery as fuel, for instance to power generation systems such as engines.
The storage of cryogenic materials, such as liquid methane, and its delivery as a fuel to engines and other power generation systems can present several technical challenges as compared to conventional, non-cryogenic liquid fuels such as diesel, gasoline, and butane.
For example, in terms of storage, to minimize the loss of methane gas through venting, a typical storage tank 100 is illustrated in
Because there is typically vacuum between the outer and inner vessels, and/or further because the inner vessel is typically pressurized, additional support structures may be required. For example, a cryogenic tank may require bunding. External structural supports may waste valuable footprint space, thereby limiting storage volume and increasing weight. Additionally, to accommodate pressure, existing designs may use heavy or thick materials, which can increase costs, lead to unwanted heat transfer, and limit applications. Thus, there remains a need for improved storage tank arrangements, including for use in vehicles.
Additionally, given the pressure constraints of existing systems, storage vessels must typically be cylindrical in cross-section, with a centrally located short pipe for output. One approach to non-cylindrical tank design is provided in WO 2019/102357 by Mann et al., titled “Liquid Methane Storage and Fuel Delivery System,” where embodiments utilize a rope suspension system. However, there remains a need for non-cylindrical shaped tank arrangements, for instance, with alternative support structures.
According to embodiments, structural supports are provided between an inner and outer vessel of a storage tank. For instance, rods may be fitted between the two. In certain aspects, the inner vessel has a pressure pushing outwards, and the outer vessel has a vacuum pulling inwards. In this arrangement, the tanks can mutually supporting each other. This can eliminate, for instance, the need for a cryogenic vessel to have large internal bunding on an inner tank and/or additional structural supports for an outer tank.
According to embodiments, a storage tank is provided that comprises an outer vessel, an inner vessel arranged within the outer vessel, and at least a first support system that connects the inner vessel to the outer vessel. The first support system may comprise, for instance, a plurality of rods where each of the plurality of rods is attached to a surface of the inner vessel and attached to a surface of the outer vessel. In certain aspects, the attachment may be a fixed or non-fixed arrangement. In some embodiments, each of the plurality of rods may be partially or completely hollow, for instance, in the form of a tube. In some embodiments, the tank also has a second support system that is located at least partially within the inner vessel, where the second support system comprises a webbing. This may be, for instance, a lattice of rods and/or rope. The storage tank may have a non-cylindrical cross section in some embodiments, and may be an operative component of a vehicle used for purposes other than just fuel delivery or fuel storage. For instance, it may be a wing, structural wall of a vehicle, or other component.
According to embodiments, a storage tank is provided that comprises an outer vessel having a first side surface and a second side surface, and an inner vessel arranged within the outer vessel and having a first opening and a second opening. The outer vessel may comprise a first rod extending between the first side surface and the second side surfaces, while the inner vessel comprises a first hollow tube between the first and second openings. The first rod can be within the first hollow tube. In some embodiments, the tank further comprises a second rod extending between a third side surface and a fourth side surface of the outer vessel, where the inner vessel comprises a second hollow tube arranged between a third and fourth opening and the second rod is located within the second hollow tube. Additionally, the tank may further comprise a third rod extending between a fifth side surface and a sixth side surface of the outer vessel, where the inner vessel comprises a third hollow tube arranged between a fifth and sixth opening and the third rod is located within the third hollow tube. In some embodiments, each of the first, second, and third tubes intersect and are orthogonal. Additionally, one or more of the openings, tubes, and rods can have a varying width (e.g., narrowing towards the center of the tank). For instance, each of opening of the inner vessel has a trumpet-like shape in some embodiments.
According to embodiments, at least one of the tanks described above is mounted on a vehicle and connected to an engine, such that the tank is arranged to deliver methane to the engine. In some embodiments, the tank is the wing of an aircraft. In some embodiments, the tank is part of a fuel delivery system. In some embodiments, the tank is a structural wall of the vehicle.
According to some embodiments, a method is provided. The method may begin with preparing an inner vessel of a storage tank. The method may further comprise preparing an outer vessel of a storage tank, attaching support rods between the inner and outer vessels, and connecting an internal support structure, where the internal support structure comprises webbing within the inner vessel. The webbing may comprise, for instance, rods or a lattice of rope. In some embodiments, connecting the internal support structure comprises tensioning the webbing.
According to some embodiments, a method is provided. The method may begin with preparing an inner vessel of a storage tank having one or more hollow tubes. The method may further comprise preparing an outer vessel of a storage tank, suspending the inner vessel within the outer vessel using a rope suspension system, and inserting one or more rods through the hollow tubes of the inner vessel to fasten the inner and outer vessel together. In some embodiments, the inner and outer vessel each comprises one or more trumpet-shaped openings.
According to some embodiments, one or more designs described herein are scalable to any desired volume, for instance, by adjusting the number and spacing of support elements.
According to some embodiments, the pressure in an inner vessel is used to force the outer vessel walls out via thin walled composite tubes, which, by entering into the inner tank, for instance via recess, can be long and therefore have minimal heat loading.
According to some embodiments, an internal structure can support higher pressures than the outer by incorporating laced rigging internally. This may be made of, for example, rope made of a para-aramid synthetic fiber such as Kevlar®. In certain aspects, a loop is added at the internal junction between a composite tube and outer stainless steel tube between the inner and outer tanks and pulled tight before welding the inner tank shut. The wall thickness can then be made thin as the pressure of the inner tank is used to force the outer out until the rope rigging pulls tight. According to embodiments, a material such as Kevlar's strength will increase dramatically as it gets cold, and thus, higher pressures can be contained and even thinner walls use. This can allow, in some embodiments, the tank to be formed by pressing thin sheets of stainless steel.
According to embodiments, a vehicle is provided. The vehicle may be, for example, a car, lorry/truck, or tractor. Other examples may include sea or air vehicles, such as boats and aircraft. The vehicle comprises an engine and a tank according to any of the foregoing embodiments, where the tank is configured to deliver fuel to the engine. In certain embodiments, the fuel is methane. In some embodiments, the engine is a combustion engine. Other engines may be used, including a flameless heat engine that runs, for instance, on methane.
According to some embodiments, disclosed designs can allow arbitrary shape to be configured and the tank operated at relatively high pressure. The pressure in the tank pulling against the rigging provides counteracting forces that give it additional strength, meaning the tank can be used as a structural support. One example would be an aircraft wing. Another might be a space rocket fuselage. Another example is a complicated fuel tank for a car, lorry/truck, or tractor. By way of example, applications can relate to any arrangement that uses an inner and outer skin.
According to embodiments, a fuel delivery system is provided, comprising: a storage tank according to any of the foregoing; one or more compressors coupled to the storage tank and configured to pressurize methane from the storage tank; and a power unit coupled to at least one of the compressors. The power unit is configured to operate using pressurized methane from the at least one compressor. The power unit may be an engine.
According to embodiments, a method of operating a vehicle is provided, where the vehicle has a storage tanking according to any of the foregoing. The method may include, for example, filling the storage with methane and operating the vehicle with an engine powered by the methane. In some embodiments, the storage tank has a square or rounded rectangular shape in cross-section and at least 6 sides.
According to embodiments, a method of operating a vehicle is provided, where the vehicle has a storage tanking according to any of the foregoing. The tank may be, for example, a low pressure tank. The method may include: extracting methane from the tank; generating pressurized methane by compressing the extracted methane; and operating a power unit of the vehicle using the pressurized methane. In some embodiments, the storage tank has a square or rounded rectangular shape in cross-section. In some embodiments, the method comprises processing the extracted methane with a heat exchanger. Additionally, the method may comprise delivering one or more of the extracted methane and the pressurized methane to a buffer, and passing methane stored in the buffer to the storage tank. This delivery can include the use of a pressure booster and second compressor. In some embodiments, the method comprises generating energy with an auxiliary power unit using methane from the storage tank, and performing one or more of heating a vehicle passenger area, operating the heat exchanger, and starting up the vehicle using the generated energy from the auxiliary power unit. Additionally, in certain aspects, one or more of the extracting, processing, generating pressurized methane, delivering, passing, generating energy, and performing can be in response to a demand for gaseous methane. The methane from the storage tank can be one or more of the methane stored in the buffer and the methane processed by the heat exchanger.
The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments.
Together with the description, the drawings further serve to explain the principles of the disclosure and to enable a person skilled in the pertinent art to make and use the embodiments disclosed herein. In the drawings, like reference numbers indicate identical or similar functionally.
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According to embodiments, the recesses 308, 310 are tube-shaped regions with end plates 312. Other recess shapes may be used. In the arrangement of
According to some embodiments, for instance depending on rod material, a recess may not be required. That is, pins may be located on an outer surface 307 of vessel 300 without a recess. In some embodiments, the pins may be made of the same materials as the respective vessel. For example, the pins 202, 204 may be made of steel and welded to a surface of the outer vessel 200.
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According to embodiments, different materials may be used for the tank, including for the inner vessel, outer vessel, and support structures. For example, the inner and outer vessels may be made of one or more of a composite, stainless steel, aluminum, and copper. The connection pins may be made of similar materials, and in some embodiments, made of stainless steel welded to a surface of the inner and/or outer vessels. The rods may be made of similar materials, and in some embodiments, the rods are made of Kevlar® or a similar para-aramid synthetic material, including a hollow Kevlar® tube. In some embodiments, the outer vessel is made of a metal or composite and the pins are made of the same material as the vessel.
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The support structure can provide additional support for an inner vessel, such as inner vessel 300, enabling, for example, higher pressures, intricate vessel shapes, and/or thinner sidewalls for the vessel. In some embodiments, for instance where the inner and outer vessels are connected by a plurality of rods, the internal support structure similarly supports the outer vessel 200. This can enable, for example, reduction of the outer vessel wall, elimination or reduction in bunding, improved footprints, and material cost savings. The internal support structure 602 may be made of para-aramid synthetic materials such as Kevlar®; however, other materials such as stainless steel or other composites may be used. In some embodiments, the components 604, 606, 608 of the support structure 602 are rope, such as Kevlar® rope or rope of another material. In some embodiments, the components 604, 606, 608 of the internal support structure 602 are rods. For instance, according to embodiments, tanks can be implemented that do not use any rope elements for the internal or outer support systems. The rods of the internal support system may be hollow tubes in some embodiments.
According to embodiments, the internal support structure 602 is comprised of at least horizontal and vertical components 606, 608. The components 606, 608 may be orthogonal to each other such that they form 90 degree angles. However, other embodiments may use components 606, 608 at different angles. Longitudinal components 604 may also be used, and may also be orthogonal to components 606, 608. In certain aspects, the outer support system comprises an n×m×o array of rods in recesses connected to pins, and the inner support system comprises an a×b×c array of rods or ropes having an orthogonal arrangement. In some embodiments, n×m and a×b arrays may be used, respectively. Additionally, one or more of the support systems may be applied in a single direction in some embodiments. For instance, an internal support structure may comprise only components 604, or 606, or 608 in some examples.
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Another view of the assembly shown in
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Although illustrated with trumpet shapes in
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According to embodiments, the inner and outer vessels 710, 720 may be made of one or more of a composite, stainless steel, aluminum, and copper. The trumpets, rods, and/or tubes may be made of similar materials, and in some embodiments, made of stainless steel welded to a surface of the inner or outer vessels. They may also be made of similar materials, and in some embodiments, made of Kevlar®, including a hollow Kevlar® tube or rod.
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In step 810, an inner vessel is prepared. This may include manufacturing or otherwise obtaining an inner vessel, such as vessel 300. Such manufacture may include, for instance, rolling steel, shaping one or more recesses and their end plates, welding or otherwise attaching pins, or applying an insulation or vacuum wrap.
In step 820, an outer vessel is prepared. This may include, manufacturing or otherwise obtaining an outer vessel, such as vessel 200. Such manufacturing may include, for instance, rolling steel and attaching guide pins. As with step 810, an insulation wrap may be applied.
In some embodiments, a step 825 is provided, in which a tube or rod is attached to at least the inner vessel. This could include, for instance, placing one or more rods or tubes 430 over connection pins 302, 304.
In step 830, the inner vessel is enclosed by the outer vessel.
In step 840, support structures are attached to the outer vessel. This could include, for instance, welding an end of the rods or tubes 430 and alignment/connection pins 202, 204 to the outer vessel. The end of rods or tubes 430 may be placed over pins 202, 204. According to embodiments, one or more washers or an adhesive can be used for attachment. In certain aspects, the attachment is a fixed or non-fixed arrangement.
In some embodiments, a step 845 is provided, in which an internal support structure, such as support structure 602, having a webbing or rope lattice, is connected. This may include one or more of tensioning the support structure and fastening the support structure, for instance, to the inner or outer vessel. According to embodiments, step 845 may be performed after step 840. However, step 845 may be performed at other times, including as part of preparing the inner vessel 810 or enclosing step 830. The support structure 602 may comprise one or more rods.
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In step 860, an inner vessel is prepared. This may include, manufacturing or otherwise obtaining an inner vessel, such as vessel 720. For instance, the inner vessel may have one or more trumpet and tube support elements.
In step 870, an outer vessel is prepared. This may include, manufacturing or otherwise obtaining an outer vessel, such as vessel 710. For instance, the outer vessel may have one or more openings for a trumpet and rod support element.
In some embodiments, a step 875 is provided, in which an inner vessel is suspended within an outer vessel. This could include, for instance, suspending vessel 720 within vessel 710 using rope connection points 718, 728.
In step 880, the inner vessel is enclosed by the outer vessel.
In step 890, support structures, such as the rods, are attached. This could include, for instance, inserting one or more rods 714 through the assembly, and then welding one or more trumpets 712 into place on the outer vessel 710 along with the rods 714.
According to embodiments, step 890 may be performed as part of a different step, or at a different time in the process 850.
According to some embodiments, a storage tank may be implemented on a vehicle. As used herein, the term vehicle includes, but is not limited to, ground-based vehicles, such as cars, trucks, motorcycles, and tractors; sea-based vehicles, such as boats; and air-based vehicles, such as airplanes or drones.
According to embodiments, a fuel delivery system for a vehicle can be implemented with or more tanks, such as tanks 400, 700, or vessels 200, 300, 710, 720. In embodiments, one or more of tanks 400, 700 and their respective vessels have inlets and outlets for liquid or gaseous fuels. For instance, piping from one or more faces of the tanks 400, 700 may be used for access or decanting. The piping need not be centrally located on a given face. For instance, fuels may enter or exit the tank near an edge.
Although some examples are described with respect to Kevlar®, other fibrous materials, including synthetic fibers such as other para-aramid synthetic fibers can be used. For instance, other materials that maintain strength and resilience over a broad temperature range, including down to cryogenic temperatures may be used. According to some embodiments, the rope material used for the support system of the inner tank can have the specific properties of high strength, and very low thermal conductivity and low elasticity over many years. For some vehicle applications, the UN R110 regulations require that the tank must be able to withstand an impact deceleration or acceleration of 9G in any axis. The testing process also includes a 9 meter drop without liquid release for 60 minutes, which can result in even higher forces in order for the support system to survive and yet not allow rapid heat ingress. Therefore, in certain embodiments, the material is not only able to support the tank and pressure under normal conditions, but orders of magnitude more. In addition, the integrity of the vacuum insulation must be maintained to avoid heat ingress, as well as the quality of the stored liquid or gas (e.g., methane), and so the material has low outgassing properties in some embodiments. According to embodiments, the tank is designed to withstand 5G in the horizontal directions.
According to embodiments, an assembly method is described. In certain aspects, assembly may include preparing an inner vessel (e.g., with support webbing), connecting pins and tubing, preparing an outer vessel around the inner vessel, attaching supports to the inner vessel, and attaching supports to the outer vessel. This may include tensioning or otherwise fixing the support webbing. In some embodiments, this may be a part of process 800. According to some embodiments, support elements may be attached using one or more connection points on a surface of the inner or outer vessel.
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According to embodiments, including those discussed with respect tank 400,
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The system may also include a heat exchanger 1306, an auxiliary power unit 1308, a liquefaction/refrigeration circuit 1316, a gas compressor 1310, and a high pressure buffer and booster 1314 and 1312. The system may be configured so that the liquid methane is held at the lowest possible temperature, thereby increasing the energy density to its maximum.
In some embodiments, upon receiving a demand for gaseous methane, the compressor 1310 is powered up, forcing gas into the engine 1304. The engine may be a combustion or non-combustion engine according to embodiments. In some embodiments, a flameless heat engine is used, in which a catalyst is used to heat the gas before passing it to a gas turbine. Gas may also be forced back into the tank via a regulator, pressurizing the tank to force more liquid methane out through the heat exchanger 1306, where it is vaporized before being compressed and forced into the engine to continue the cycle. That is, gas may be passed to the tank 1302 from compressor 1310 (or 1311) via regulator 1313. In this way, the components of system 1300 may be used in conjunction to simultaneously deliver the necessary fuel to unit 1304, such as an engine, while ensuring that additional fuel will be vented from tank 1302 for sustained delivery and use.
According to some embodiments, a second compressor 1311 may be used. The second compressor can be coupled to the tank 1302. In some embodiments, the second compressor 1311 is placed in parallel with the first compressor 1310. It may be used, for example, to deliver methane gas under high demand. In some embodiments, the second compressor 1311 may be arranged to act independently of the first compressor 1310 to supply methane gas to a pressure booster, such as booster 1312. This may be, for instance, to achieve high pressure for storage in the high pressure buffer 1314 or to drive a cooling unit, such as refrigeration circuit 1316. As illustrated in
By way of example, during normal vehicle cruising operation one compressor, such as compressor 1310, could be sufficient to deliver methane at a first level, such as at 8 grams per second to the engine. In this instance, the second compressor, such as compressor 1311, could be reserved for additional tasks, as required. As an example, the second compressor could be used to supply gas to a regulator, or a pressure booster and fill a high pressure buffer. According to some embodiments, when there is a need to cool a fuel stored in a tank, such as liquid methane in tank 1302, high pressure methane from the buffer or from the output of a pressure booster can be passed through a refrigeration element, such as a Joule Thompson refrigeration circuit inside the tank, re-condensing the methane to a liquid that is colder than the main reservoir. This could increase the hold time left before the methane would need to be vented, or make additional space available for fresh fuel because the colder methane is denser.
According to some embodiments, initial start-up of a vehicle, including for instance starting power/vehicle unit 1304, can be achieved using fuel stored in a high pressure buffer, such as buffer 1314, which can store methane gas. This could allow, for example, the first compressor 1310 to start independently of the pressure in the main tank 1302, which may be low according to some embodiments. In certain aspects, once the compressor 1310 is running, a regulator 1313 can be used to bleed some gas into the main tank. In some embodiments, gas is bled to the main tank 1302 at 3 bar. In some respects, the main tank pressure is therefore set independently of the liquid methane vapor pressure. According to embodiments, for instance in situations that require high gas flow, a pressure raising circuit can be incorporated. This can enable the pressure of the tank to be increased by boiling off some of the liquid, for example through a heat exchanger attached to the inside wall of an outer vacuum vessel. In this way, pressure in the tank can be maintained during periods of high usage
In certain aspects, auxiliary power unit 1308 can serve a number of roles. According to embodiments, it can be positioned anywhere on a vehicle and connected via the necessary pipes. It can be used to extract energy from the methane gas that would otherwise have to be vented when the pressure in the methane tank is rising but the vehicle or generator is not being used. Electrical energy may be generated by unit 1308, for instance, with a fuel cell arrangement and/or a secondary engine by using some of the methane. The electrical energy can be stored in a battery.
According to some embodiments, auxiliary power unit 1308 can be also be used to provide power and/or heat to a vehicle's quarters, including for instance a cabin or “hotel” load when the driver is sleeping overnight. For very cold starts, for example, it can be run exclusively from the high pressure buffer to generate heat for the heat exchanger, e.g. heat exchanger 1306, that vaporizes the liquid methane before the vehicles main engine is sufficiently warm.
According to some embodiments, system 1300 may operate in a state in which a tank is at an increased pressure. For example, they system may operate when the storage tank 1302 has been left for a period of time allowing heat to boil the stored fuel, such as liquid methane, thereby increasing the pressure. According to embodiments, a valve is opened for feeding the excess methane gas to an auxiliary power unit (such as a combustion engine or fuel cell) where power is generated and stored in a battery. This could be unit 1308, for instance. Power from the battery can then be used to power a compressor to take excess gas from the tank and pass it through a pressure booster (e.g., booster 1312) and cooling unit (e.g., refrigeration circuit 1316) to re-liquefy excess gas and return it to the main reservoir. This can advantageously reduce the main reservoir's temperature and extend its non-venting storage time. Alternatively, and according to some embodiments, a compressor and booster can be used to take low pressure gas from the main tank and store it in a highly compressed gaseous state in a high pressure buffer, such as buffer 1314, that acts as an independent reservoir that can be used to initiate the starting sequence of the main engine or supply the auxiliary power unit as required.
Although one larger low pressure compressor could be used, according to some embodiments, to supply sufficient gas to the engine when under maximum demand the use of two lower flow compressors acting independently may be used. In some cases, under normal operation, one compressor can fulfil the sufficient fuel delivery, saving energy. Further, to provide a high pressure buffer volume, the second compressor can be used independently. By pumping gas through a pressure booster, a high pressure reservoir can be filled. This can then be used to either power the engine during a cold start or keep the liquid reservoir cold by passing through a Joule Thompson refrigeration system positioned within the inner liquid methane tank. This system can be used to keep the main reservoir cold, thereby sustaining low pressure operation.
Although methane is used as an example, the storage elements described herein can be used for storage, including cryogenic storage, of other materials as well. For instance, hydrogen fuels may be used, and other materials (e.g., oxygen, helium, argon, and nitrogen) may be stored according to the embodiments described herein. Similarly, fuel storage and delivery systems according to embodiments also apply to non-methane fuels.
While various embodiments of the present disclosure are described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
Additionally, while the processes described above and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps may be performed in parallel.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2021/050274 | 1/15/2021 | WO |
Number | Date | Country | |
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62962414 | Jan 2020 | US |