High conductive arrangement

Abstract

The invention relates to an electrical network comprising: an electrical conductor; and a refrigerant source configured to contain refrigerant, the refrigerant source being arranged such that, in use, refrigerant is provided to the conductor to maintain the conductor in a high conductivity state.

Description

Technical Field

[0001] The present invention relates to electrical networks. In particular, the present invention relates to such electrical networks that can be cooled using liquid hydrogen or other refrigerants to improve efficiency. It is well known that superconducting properties of certain materials can enable efficient electrical networks when their electrical resistance drops to zero below a critical temperature. Background Art

[0002] This superconducting behavior has many advantages, such as high component efficiency, low heat losses, and the use of liquid hydrogen is a known method of maintaining the superconducting behavior of components.

[0003] Propulsion systems are now shifting towards alternative fuels to reduce the environmental impact of emissions. Electric vehicles and hydrogen-powered vehicles are currently being developed for wider use.

[0004] In aircraft in particular, while hydrogen-powered flight has been discussed, the industry favors the use of gas turbines for propulsion for a number of technical reasons, including the additional power required to account for the takeoff and climb phases of flight and the ability to remain reasonably effective and efficient during cruise.

[0005] Therefore, while there are recognized environmental benefits to using alternative fuels, these benefits have not yet been universally applied. The efficiency gains that can be provided by using superconducting materials have not yet been accepted as a solution strong enough to encourage a departure from typical fuels and standard combustion. However, in the case of using alternative cryogenic fuels, the possible advantages to be gained from superconducting arrangements are very attractive.

[0006] Development is needed to encourage the use of alternative fuels and thereby reduce the environmental impact of transportation by means of transport, whether on land, sea or air.

[0007] Busbars and power cables of an aircraft or other vehicle are specific examples of components within an electrical network. Such a network may also include electrical converters, fuel cells, motors, generators, propellers, etc. Busbars and power cables are usually electrically isolated in the network by a dielectric layer or insulation, but this is not always the case in the case of busbars.

[0008] The inventors of the invention described herein have created a new solution for providing low temperature electrical efficiency that can be used with alternative fuel arrangements for vehicles to make alternative fuels more attractive. Summary of the invention

[0009] Various aspects of the invention are set out in the accompanying claims.

[0010] Viewed from a first aspect, there is provided an electrical network comprising: electrical conductors; and a refrigerant source configured to hold a refrigerant, the refrigerant source being arranged such that, in use, the refrigerant is provided to the conductors to maintain the conductors in a highly conductive state.

[0011] Such a network would have high electrical efficiency, be lightweight, and be more robust than modern systems using superconducting arrangements.

[0012] In one example, the electrical network also includes a fuel cell stack electrically connected to the electrical conductor, wherein the refrigerant source is arranged at a refrigerant upstream end of the network, the fuel cell stack is arranged at a refrigerant downstream end of the network, and wherein, in use, the refrigerant is in a liquid phase at the refrigerant source and in a gas phase at the fuel cell stack.

[0013] Such a network advantageously utilizes the refrigerant to improve electrical efficiency while increasing the temperature of the refrigerant so as to thereby render the refrigerant suitable for use in a fuel cell stack at the downstream end of the network. In this way, the cooling properties of the refrigerant are optimally utilized in the arrangements disclosed herein.

[0014] In one example, the electrical network further comprises a prime mover arranged for providing motion from electrical energy, wherein the prime mover is arranged between the upstream end of the refrigerant and the fuel cell stack, and wherein, in use, the refrigerant is provided to the prime mover in a liquid phase.

[0015] This arrangement allows the refrigerant to be delivered to the prime mover at the appropriate temperature, taking into account the starting temperature of the refrigerant and the ideal temperature for interaction with the prime mover. This, in turn, improves the overall efficiency of the system from both a thermal and electrical perspective.

[0016] In one example, the electrical network further comprises further electrical conductors arranged for conducting electrical energy at a lower voltage than the electrical conductors, wherein, in use, the further electrical conductors conduct the low voltage electrical energy to at least one electrical control unit.

[0017] In one example, the electrical energy conducted by the electrical conductor is approximately 270 volts, and the low voltage electrical energy conducted by the further electrical conductor is approximately 28 volts.

[0018] In one example, the further electrical conductor is formed from aluminium. We have found that aluminium is particularly advantageous for use in such a highly conductive arrangement.

[0019] In one example, the electrical conductor comprises a refrigerant transport portion which, in use, transports a refrigerant provided to the conductor by the refrigerant source.

[0020] In one example, the network is arranged to provide a closed loop system for the refrigerant. This way, there is no loss of refrigerant and the refrigerant can be reused. This allows for a more efficient system and reduces the need to top up the refrigerant after using the network.

[0021] In one example, the network is arranged to provide refrigerant to portions of the network so as to maintain the following portions at the following temperatures: refrigerant source at 25 Kelvin; electrical conductors at 25 Kelvin; coils of motors at 25 Kelvin; power electronics at 80 Kelvin; and hydrogen mixers at 300 Kelvin. This arrangement is efficient in terms of space, electrical, and refrigerant usage.

[0022] In one example, the network further includes at least one converter, at least one inverter, and at least one circuit breaker to control the transmission of electrical energy through the network.

[0023] From another aspect, a method for providing propulsion in a vehicle is provided, comprising: cooling an electrical conductor to a high conductivity state with a liquid refrigerant; cooling a prime mover with the liquid refrigerant; evaporating the liquid refrigerant via heat exchange; transferring the gaseous refrigerant to at least one fuel cell; generating electrical energy in the at least one fuel cell; providing the electrical energy from the at least one fuel cell to the electrical conductor for conduction to the prime mover; and generating propulsion from the electrical energy provided to the prime mover. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] One or more embodiments of the present invention will now be described, by way of example only, and with reference to the following drawings, in which:

[0025] Figure 1A shows a cross-sectional schematic diagram of a standard electrical transmission arrangement for a vehicle;

[0026] Figure 1B A schematic cross-sectional view of a new electrical transmission arrangement for a vehicle is shown;

[0027] Figure 2A A schematic cross-sectional view of a new electrical transmission arrangement for a vehicle is shown;

[0028] Figure 2B Shows Figure 2A A simplified enlarged version of Section D of Figure 2A A new electrical transmission arrangement for a vehicle is shown;

[0029] Figure 3 A schematic example of a highly conductive electrical network is shown;

[0030] Figure 4A schematic example of a highly conductive electrical network is shown;

[0031] Figure 5 A flow chart is shown showing the budget of liquid hydrogen in an electrical network along with power losses and temperatures; and

[0032] Figure 6 A flow chart illustrating the budget of gaseous helium in an electrical network as well as power losses and temperatures is shown.

[0033] Any reference to prior art documents in this specification should not be regarded as an admission that such prior art is widely known or forms part of the common general knowledge in the field. The words "comprise", "comprising" and similar words used in this specification should not be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including but not limited to". The present invention is further described in conjunction with the following examples. It will be understood that the claimed invention is not intended to be limited in any way by these examples. It will also be appreciated that the present invention includes not only a single embodiment, but also a combination of these embodiments described herein.

[0034] The various embodiments described herein are presented only to aid in understanding and teaching the claimed features. These embodiments are provided only as representative samples of embodiments and are not exhaustive and / or exclusive. It should be understood that the advantages, embodiments, examples, functions, features, structures and / or other aspects described herein should not be regarded as limitations on the scope of the invention as defined by the claims or limitations on the equivalents of the claims, and other embodiments and modifications may be used without departing from the spirit and scope of the claimed invention. Various embodiments of the present invention may appropriately include, consist of, or consist essentially of appropriate combinations of elements, components, features, parts, steps, devices, etc. other than those specifically described herein. In addition, the present disclosure may include other inventions that are not currently claimed but may be claimed in the future. DETAILED DESCRIPTION

[0035] The invention described herein relates to electrical networks. In particular, the invention relates to electrically efficient, cooled electrical transmission lines in the network and the arrangement of these cooled electrical transmission lines. Such electrical transmission lines may be cables for conducting electricity. The cables described herein may also carry refrigerants. These networks may be used for vehicles, and the refrigerants used therein may be used for both cooling and generating propulsion.

[0036] Electrical conductors may be cooled using cryogenic fluids, such as liquid helium (between about 0 Kelvin and about 4 Kelvin), liquid hydrogen (between about 14 Kelvin and about 20 Kelvin), liquid neon (between about 24 Kelvin and about 27 Kelvin), liquid nitrogen (between about 63 Kelvin and about 77 Kelvin), and liquid oxygen (between about 55 Kelvin and about 90 Kelvin). Cryogenic gaseous helium may also be used. A number of superconducting materials are known, which are materials that have a resistance that drops to zero (particularly zero resistance under direct current [DC] conditions, where alternating current [AC] encounters some slight resistance) once the material is cooled beyond a certain "supercooled" temperature (taking into account critical values ​​of an external magnetic field and a current being carried).

[0037] These materials offer highly electrically efficient transport systems. However, there are difficulties in using superconductors in vehicle arrangements. In particular, superconductivity relies on the material being permanently maintained in a superconducting phase. If a material leaves its superconducting phase, the material's resistance increases from zero. In this case, the passage of current through a material with a non-zero resistance causes heating of the material. This, in turn, causes the material's resistance to increase, which in turn causes more heat. When this occurs, a positive feedback loop causes a rapid increase in the material's temperature. This heat is transferred to a nearby coolant (liquid hydrogen, etc.) and is then largely evaporated. This is referred to in some circles as a "quench". A "quench" also occurs if the current through a superconducting material exceeds the material's critical current value.

[0038] Such "quench" events can be very dangerous, causing serious damage to electrically connected components and potentially wasting large amounts of refrigerant. In particular, if these events occur on an aircraft or other similar vehicle, they can jeopardize the safety of passengers.

[0039] The invention described herein relates to an electrical network for cooling of efficient electrical transmission devices. The network has also improved safety by significantly reducing the risks associated with typical electrical solutions and superconductors. The network disclosed herein occupies less space than current solutions. As described above, the network of the present invention utilizes electrical transmission devices, which can be busbars or cables with a new design.

[0040] Reference now Figure 1A , shows a typical electrical transmission device 10, which includes a series of cables 11, 12, 13, 14, 15, 16. The typical cables may be made of copper, each having a diameter A of about 16 mm for a transmission device having a diameter B of about 55 mm.

[0041] In electrical buses commonly found on aircraft, the conductors are in ambient air conditions or sometimes have blown air for cooling purposes. Heat transfer from such current-carrying conductors can be achieved by conduction (usually dominated by axial conduction into a cold compartment), convection cooling (which is limited at flight altitudes in non-pressurized compartments (usually about 20,000 to 40,000 feet)), or radiant heat emission. Heat is lost axially when the conductor is hotter than the compartment into which the conductor is entering. Axial conduction of heat into a cold compartment occurs along the conductor from a warmer structural boundary to a cooler structural boundary.

[0042] Therefore, the heat transfer of such conventional bus and power cabling systems is limited. Typically, the power bus system is routed in the fuselage of the aircraft and routed in the non-pressurized area of ​​the aircraft. For aircraft using electric propulsion, i.e., aircraft using alternative fuels as described above, this routing of the power bus is primarily in the non-pressurized area of ​​the aircraft.

[0043] Due to these limitations, and to achieve high power transmission of, for example, 1 MW of electricity, the design may require 6 conductors with a total cross-sectional area of ​​643 mm 2 Copper OFF 4 / O specification cable. This is Figure 1A Here 4 / O refers to the American Wire Gauge rating, where 4 / O is 0.46 inches or 11.684 millimeters (mm) in diameter.

[0044] One way to reduce the effects of Joule heating is to use higher voltages. The highest DC voltage seen in aircraft today is 270V DC. For some potential electric propulsion aircraft, voltages considered range from 700V DC, 1kV DC, up to about 3kVDC. These very high voltages are challenging because at voltages above 327V, partial discharge effects can occur at any pressure or distance (327V is the minimum breakdown voltage at any pressure or distance in air). This leads to greater challenges in integrating such high voltage systems into electrical transmission arrangements or networks.

[0045] Some modern propulsion systems use refrigerants, for example in fuel cell systems. In such systems, there is a refrigerant that can be routed to cool the cable. In this way, the resistivity of the copper is reduced, so gains can be made in terms of increasing the current carrying capacity of the cable while maintaining the same current carrying capacity, or in terms of reducing the size of the cable.

[0046] Modern operating temperatures for networks or network parts (e.g. power bus systems) are between -55°C and +260°C, which are usually defined by the aircraft environment and operating conditions. In this range, the electrical conductivity of aluminum is lower than that of copper, i.e. the electrical resistance per unit area of ​​aluminum is higher. However, in an arrangement using a refrigerant, the temperature of the power bus system can be cooled to temperatures below this range.

[0047] The inventors of the present invention have recognized the risks associated with superconducting regions, in addition to seeing the obvious benefits of using them, and have proposed a new system for improving electrical transmission and networks. Aluminum has a lower density than copper and at cryogenic temperatures (approximately less than 100 Kelvin) it has a resistivity similar to or lower than copper.

[0048] Below 100 Kelvin, we refer to aluminum as being in a "highly conductive" state until the temperature reaches 1.175 Kelvin, at which point it becomes a superconductor. We define a highly conductive material as a typical conductive material that experiences a sharp or nonlinear drop in specific resistivity at cryogenic temperatures (less than 100 Kelvin) without reaching a superconducting state. The present invention exploits this highly conductive state to provide a robust yet electrically efficient and effective electrical transmission system and network.

[0049] Aluminum has a lower density than copper, which means that when the room temperature ( Figure 1A ) and the dimensions of standard copper cable routing in highly conductive areas ( Figure 1B ) when compared with aluminum cable run arrangements, the size of the cable run is significantly reduced.

[0050] In particular, cooling aluminum to 20 Kelvin increases the conductivity by about 3500 times compared to room temperature. The conductivity of aluminum at 77 Kelvin is about 324 times higher than the conductivity of aluminum at room temperature. When comparing the resistivity of aluminum at 20 Kelvin to copper at room temperature, the resistivity of aluminum has increased by a factor of 2246. This is equivalent to a 5000-fold and 2246-fold decrease in the mass of the conductor of aluminum or copper at room temperature, respectively. See Table 1 for experimental details on the resistivity of aluminum and copper at different cryogenic temperatures.

[0051] Table 1 - Shows the resistivity of aluminum and copper at different temperatures

[0052]

[0053] Therefore, significant gains can be gained by using coolant that may already be present in the propulsion system to convert the cable material to a highly conductive state.

[0054] Table 1 shows that below 77 Kelvin, as lightweight aluminum enters the highly conductive region, the resistivity of aluminum drops below that of copper. Therefore, the system can advantageously use liquid hydrogen to cool aluminum components because the temperature of liquid hydrogen is below 30 Kelvin. Therefore, using liquid hydrogen as a coolant enables the aluminum to be cooled sufficiently to make it more conductive than copper. Using liquid or gaseous helium can also provide this.

[0055] As can be readily appreciated, as the resistivity of aluminum drops below that of copper, and given the lower density of aluminum compared to copper, significant gains can be made in terms of the overall size and mass of the cable required.

[0056] Reference now Figure 1B , shows a highly conductive electrical transmission device 100 comprising an aluminium 1 MW cable 110 at 270 V DC (below Paschen minimum). The highly conductive electrical transmission device 100 is configured for use in a highly conductive network. Compared to the six copper cables 11, 12, 13, 14, 15, 16 having a diameter of 16 mm (forming a total transmission device 10 having a diameter of 55 mm), the highly conductive equivalent 110 has a diameter of about 2.4 mm; see Figure 1B The measurement C in Figure 1A The transmission device 10 to Figure 1B This is a significant size reduction in the size of the electrical transmission device. In addition, considering the relative density, the conductor mass per unit length of the electrical transmission device 100 is about 16.5 g / m, compared to the conductor mass per unit length of the transmission device 10 of about 7.2 kg / m. Therefore, when using Figure 1B The weight is also significantly reduced when using the high-conductivity arrangement shown.

[0057] Thus, the proposed system 100 is approximately 400 times lighter than current systems and is electrically more efficient, using less than half the voltage ( Figure 1A Use 700V AC, and Figure 1B Using 270V DC). Therefore, a network using the transmission device 100 can benefit from these weight gains. Tables 2 and 3 show the calculated results of this significant weight reduction.

[0058] Therefore, significant benefits can be achieved when using a high-conductivity electrical transmission device. This may also be called a high-conductivity electrical bus, a high-conductivity bus, or a high-conductivity cable.

[0059] One option for cooling the cable to the high conduction region is to immerse the cable in liquid hydrogen, but this may not be the most efficient or effective method. Therefore, examples of efficient and effective cable construction are now discussed.

[0060] Reference now Figure 2A and Figure 2B , showing a schematic diagram of a new electrical transmission arrangement 200 for an electrical network of a vehicle. Figure 2A A cross-sectional schematic diagram of an electrical transmission arrangement 200 is shown. Figure 2B Shows Figure 2A An enlarged schematic diagram of part D in FIG.

[0061] Figure 2A A transmission device 200 is shown. The transmission device 200 has a central core of a cryogen, such as liquid hydrogen 210. The transmission device 200 has an aluminum layer 220 surrounding the hydrogen 210. The transmission device 200 has a dielectric layer 230 surrounding the aluminum layer 220. The transmission device 200 has an outer surface of an insulating portion 240. The insulating portion 240 surrounds the dielectric 230.

[0062] Figure 2A The cable arrangement 200 allows both electrical signals and refrigerant 210 to be transmitted, so the cable provides dual purpose in a system that uses refrigerant and needs to transmit refrigerant. In addition, the transmission of refrigerant also provides the function that the aluminum cable 220 is cooled.

[0063] For clarity, Figure 2B Shows Figure 2A The layers are clearly shown as the refrigerant 210 ( Figure 2B ), followed by aluminum 220, dielectric 230, and insulation 240 on the outermost layer ( Figure 2B of the display).

[0064] The layers of dielectric 230 and insulation 240 provide electrical isolation for the electrical energy carried in electrical conductor 220. Refrigerant 210 may also serve as an electrical insulator.

[0065] In use, the aluminum 220 contains the refrigerant 210, which can be pressurized liquid hydrogen or cryogenic gaseous hydrogen (or liquid or gaseous helium), while also carrying electrical current to the required load. The aluminum tube 220 will then be surrounded by a layer of dielectric 230 and insulation 240. To simplify manufacturing, this can be spray foam or cryogenic blankets and / or vacuum, as this will allow leaks to be detected and is a suitable insulator. This structure and construction technique reduces the complexity of manufacturing compared to an electrical transmission device immersed in liquid hydrogen, which would require mechanical support.

[0066] The aluminum tube 220 is partially supported by the refrigerant 210, as tensile strength increases by up to 40% at cryogenic temperatures. The aluminum tube 220 may also be strengthened by doping it with graphene, which has a negligible effect on the conductivity of the tube 220. The aluminum 220 may also be supported by a simple, inert, and lightweight molding, such as glass reinforced plastic, which will contribute to the robustness of the aluminum 200. Thus, these manufacturing steps may be taken to improve the robustness of the design of the cable 200.

[0067] Reference now Figure 3 , a schematic diagram of a new electrical network 300 for a vehicle is shown.

[0068] The network 300 has a cryogen storage 310. The cryogen storage 310 may be arranged for holding liquid hydrogen (LH2) or other similar cryogen for use in the network 300. The cryogen may be used to cool electrical cables and other components in the network.

[0069] Liquid refrigerant can be provided from the refrigerant reservoir 310 to a series of fuel cell stacks 320 (once suitably heated, such heating can occur during cooling of a high-conductivity cable or the like or via a heat exchanger). In the example shown, the refrigerant reservoir 310 is in fluid communication with four fuel cell stacks 322, 324, 326, 328. The fuel cell stacks 322, 324, 326, 328 can each consist of a 350kW fuel cell stack. This makes the total network 300 a 1MW high-conductivity network 300.

[0070] Each of the fuel cell stacks 322, 324, 326, 328 is electrically connected to an electrical converter 332, 334, 336, 338. The converters 332, 334, 336, 338 are connected to an electrical transmission device 340, which may be an electrical bus bar or the like. The electrical bus bar 340 may have a configuration such as Figure 2A The arrangement shown. Converters 332, 334, 336, 338 are used to regulate the voltage before the high voltage bus 340. The fuel cell stacks 322, 324, 326, 328 are connected to the converters 332, 334, 336, 338 through cryogenic cooling circuit breakers 352, 354, 356, 358. The circuit breakers 352, 354, 356, 358 are cooled by the refrigerant in the refrigerant storage 310. Liquid refrigerant from the hydrogen cryogenic storage tank 310 is provided to the converter 330 and then provided to the bus 340.

[0071] The electrical bus bar 340 is arranged to effectively and efficiently carry electrical signals through the network 300. The electrical bus bar 340 is connected to the refrigerant reservoir 310, and the refrigerant from the refrigerant reservoir 310 is arranged to maintain the bus bar 340 in a high conductivity state. In this way, the advantages of high conductivity are introduced into Figure 3 network.

[0072] The electrical bus 340 distributes electrical power from the fuel cell stacks 322, 324, 326, 328 to the motors 362, 364 that produce thrust or to a low voltage (LV) bus 370 that powers a full authority digital engine control (FADEC) 372, a fuel cell (FC) control 374, and a cabin and cargo load 376. The voltage of the LV bus 370 may be approximately 28 VDC, while the voltage of the electrical bus 340 may be approximately ±270 V DC.

[0073] In use, the network 300 may have a system composed of cryogenically cooled batteries and supercapacitors (in Figure 3 In the example of FIG. 1 , additional power for takeoff is shown as provided by auxiliary power storage 380. In this example, auxiliary power storage 380 may contain enough energy for an additional go-around required during an aborted or delayed landing. Bus 340 may be controlled by bus controller 390, which may also include passive means for cryogenic cooling. All conductors from fuel cell stacks 322, 324, 326, 328 to inverter and LV bus 370 may be formed of highly conductive aluminum.

[0074] The electrical bus bar 340 is connected to the motors 362, 364 that generate thrust via circuit breakers and inverters. All of these elements can be cooled by the refrigerant from the refrigerant storage 310. The motors 362, 364 that generate thrust are each connected to a fan or propeller 366, 368. The motor and fan / propeller 362, 364, 366, 368 combination acts as a prime mover. The prime mover receives electrical energy and converts the electrical energy into kinetic energy. In particular, in the case of motors 362, 364 and fans / propellers 366, 368, electrical energy is received, rotational energy is generated in the fans / propellers 366, 368 by the motors 362, 364, and this provides thrust to the system 300 in which the fans / propellers 366, 368 are arranged.

[0075] Figure 3Examples include heat exchangers 395. Heat exchangers 395 can thermally connect motors 362, 364 and / or fans / propellers 366, 368 and refrigerant storage 310. The refrigerant may have been changed from liquid hydrogen (for example) to hydrogen in gaseous form while providing a heat exchange function on the elements in network 300. In this case, after providing a heat exchange function for the motor and fan / propeller elements 362, 364, 366, 368, the gaseous hydrogen can be provided to the fuel cell stacks 322, 324, 326, 328 for use.

[0076] The present high conductivity network provides substantial efficiency gains compared to current systems. In particular, when compared to a more electric aircraft (MEA) network or even a high voltage (HV) network, the high conductivity network leads to increased efficiency and reduced mass. An aluminum high conductivity network at 20 Kelvin was compared to a MEA and HV network at room temperature, delivering 1 MW of power, as shown in Table 2.

[0077] Table 2 - shows the characteristics of the currently disclosed high-conductivity network relative to the MEA network and the HV network

[0078]

[0079] Clearly, the high conductivity network of the present disclosure provides gains in electrical efficiency. The system in Table 2 is a 1 MW electrical network that uses 10 m of aluminum bus bars.

[0080] Furthermore, there are structural gains that are particularly relevant to weight. Table 3 uses the same parameters as Table 2, and only allows the system to heat up by 5°C in 1 minute.

[0081] Table 3 - shows the characteristics of the currently disclosed high-conductivity network relative to the MEA network and the HV network

[0082]

[0083] Table 3 clearly shows the advantages of the highly conductive electrical network disclosed herein in terms of weight and volume.

[0084] As shown above, highly conductive aluminum can be used as conductor for busbars and feeder cables. The aluminum can be cooled by LH2 from liquid refrigerant storage, or by being completely immersed in LH2 or used as a current carrying tube, see Figure 2. The highly conductive body will then be enclosed in dielectric and insulation to produce beneficial behavior when handling high voltages.

[0085] exist Figure 3In the arrangement in, liquid refrigerant in a refrigerant reservoir 310 provides both a fuel function and a coolant function for the network 300. Liquid refrigerant (which may be LH2, LHe [liquid helium], or gaseous helium) may be stored at about 20 Kelvin in a refrigerant reservoir 310, which may be a tank. Depending on the pressure within the refrigerant reservoir 310, the refrigerant may be stored at about 28K or no more than 28K. The refrigerant serves as a coolant for the highly conductive network 300 and its components, including power electronics. The refrigerant may then be used to cool drive and motor components before returning along the network 300. In particular, in Figure 3 , the return phase is shown by heat exchanger 395. After providing the heat exchanger function and possibly entering the gas phase, the refrigerant is fed to the fuel cell stack 322, 324, 326, 328 to be used as fuel. In the journey from the refrigerant storage 310 to the fuel cell stack 322, 324, 326, 328, the refrigerant is passively heated by the losses in the components of the network 300, and at some point, it will become gaseous. In this way, the network 300 is effectively arranged to maximize the use of the refrigerant in the refrigerant storage 310.

[0086] To achieve a particularly efficient arrangement, the temperature of the LH2 is about 0°C (273K) prior to use as fuel for the fuel cell stacks 322, 324, 326, 328. If the LH2 is not heated to an optimum temperature by use as a coolant, a heat exchanger (hydrogen mixer) may be used to assist in bringing the coolant to a predetermined temperature, such as 0°C.

[0087] Figure 4 The cryogenic coolant budget is shown in , which gives the estimated temperature rise for each step. Figure 4 An example is shown of how the refrigerant changes temperature through the network to bring it to a suitable temperature for the fuel cell stack. The temperature increase of the refrigerant is directly related to the losses in the network, which are considered as the cause of the temperature increase in the network components. These temperature increases are caused by the cooling function of the refrigerant.

[0088] Figure 4 A schematic diagram of a new electrical network 400 for use in a vehicle is shown.

[0089] Figure 3 Many features of Figure 4 See the example in . Figure 4 and Figure 3 is different in that it uses the main cryogen reservoir 410 as helium instead of hydrogen (such as Figure 3The liquid helium is provided to the converter 430 to provide cooling and then to the electrical bus 440. The helium is then provided to the inverter and motors 462, 464.

[0090] The helium stream is then passed to heat exchanger 495 and encounters the fluid stream from hydrogen refrigerant storage 412 - at Figure 3 The hydrogen and helium are combined and the hydrogen stream (now in a gaseous state) is provided to the fuel cell 420 for use in the fuel cell 420 .

[0091] like Figure 5 As shown in the example of , in the budget 500, the refrigerant storage is at 28 Kelvin and 5 atmospheres. The temperature and pressure can be different from the specific values ​​selected in this example. For example, in the case of using 28K, the value can be about 23 to 28 Kelvin. The temperature values ​​provided in the example will also vary depending on the relevant pressure.

[0092] In the example shown, this is the hydrogen tank 510. At this point, the refrigerant is in the liquid phase. The refrigerant reservoir feeds the refrigerant to the HTS current leads 1 520. The HTS current leads are extensively arranged in a network where the ambient temperature conductors are combined with the refrigerant from the tank. It is advantageous to have the HTS located in this position because the HTS has high electrical conductivity and low thermal conductivity. In this way, Figure 5 The example advantageously arranges HTS current leads 1 520 to improve electrical conduction and reduce the negative effects of heat losses. The HTS current leads 1 520 are maintained at a temperature of about 28 Kelvin (depending on the pressure). The power loss associated with this part of the network is about 0.25kW.

[0093] After the HTS current lead 1 520 has been cooled, the refrigerant can be delivered to the electrical network 530. The refrigerant can cool the electrical network 530 to about 25 to 30 Kelvin (in one example, this can be 28 Kelvin). The power loss associated with this portion of the network is in the order of a few watts, up to about 100 watts (0.1 kW). In this portion of the network, the refrigerant is still in the liquid phase.

[0094] The refrigerant is then fed to the coil 540 of the network. The coil 540 is maintained at a temperature of about 28 Kelvin and about 3 atmospheres of pressure. The power loss associated with this portion of the network is about 6 kW. This is a significant amount of power as the refrigerant cools. The refrigerant may be gaseous after the coil 540 portion of the network.

[0095] The refrigerant in gaseous form is delivered to both the inverter / drive portion 550 and the stator 560. The inverter / drive 550 is maintained at a temperature of about 80 Kelvin. The power loss associated with the inverter / drive portion 550 of the network 500 is about 10 kW to 20 kW due to 1% to 2% losses, i.e., 98% to 99% efficiency. In refrigerant cooling, this is another considerable amount of power to consider. The refrigerant is gaseous after the inverter / drive 4550 portion of the network 500.

[0096] The refrigerant in gaseous form may also be delivered to the stator 560. The stator 560 (in one example, the iron stator portion 560) may receive the refrigerant, depending on how much refrigerant is held in the system. The power loss associated with this portion of the network is about 6 to 9 kW. In refrigerant cooling, this is another significant amount of power to consider. The refrigerant is gaseous after the stator 560 portion of the network 500. The system may include a permanent magnet motor.

[0097] The gaseous refrigerant passes from the inverter / driver 550 and stator 560 to the electrical network 570. The refrigerant leaves the inverter / driver 550 at approximately 115K (in the figure, shown as 113.5K) and is delivered to the power electronics 570 of the network.

[0098] The power electronics 570 of the network are maintained at a temperature of about 113.5 to 220 Kelvin. The refrigerant is heated (from about 115K) to a temperature of about 220K during thermal interaction with the power electronics, leaving the power electronics. The power loss associated with this part of the network is about 10 to 21 kW. In refrigerant cooling, this is another considerable amount of power to consider. The refrigerant remains in gaseous form after the power electronics 570 portion of the network and can be delivered to the hydrogen mixer 580 at about 220 Kelvin to 300 Kelvin (suitable for use in the fuel cell stack of the network 500). Alternatively, the gaseous refrigerant can be delivered from the power electronics 570 of the network back to the cryogenically cooled energy storage 590. More generally, the refrigerant is gaseous after this electrical network portion of the network and can be delivered to the hydrogen mixer at about 300 Kelvin (suitable for use in the fuel cell stack of the network).

[0099] therefore, Figure 5 The budget shown in the example of exemplifies how refrigerant can be routed through a network to provide effective and efficient cooling to components requiring such cooling and ultimately be delivered to a hydrogen mixer at a temperature suitable for a fuel cell.

[0100] Reference now Figure 6 , Figure 6 An alternative flow chart is shown which illustrates the use of cryogenic helium instead of using Figure 5 The hydrogen budget in Figure 6 In the case of a hydrogen / helium heat exchanger, the helium is cooled for Figure 6 The remaining elements of the heat exchanger are heated while the hydrogen is heated, possibly for use in a fuel cell or the like. The heat exchanger is shown at 610. The exchanger may be maintained at 25 Kelvin and 10 atmospheres.

[0101] The helium exits the exchanger at or about 25 Kelvin. The helium arrives at the HTS current lead 1 620 and provides cooling so that the helium is delivered to the high conductivity conduit 620 at a temperature of about 28 Kelvin. The helium is delivered through the conduit and exits at a temperature of about 29 Kelvin and is then delivered to the stator coil 640 and provides further cooling. The helium exits the coil 640 at a temperature of about 35 Kelvin and is delivered to the inverter / driver 650. The helium provides significant cooling for the inverter / driver 650 and brings the inverter / driver 650 to a temperature of about 120 Kelvin. The helium is then delivered to the (or earlier) heat exchanger 660 to be cooled by the liquid hydrogen source. This then allows the helium to be delivered to additional components (or as Figure 6 In this way, a significant amount of cooling can be provided to the network in a closed loop system. Figure 6 In the arrangement of Figure 5 The same benefits exist in .

[0102] Another advantage that exists when using highly conductive networks is the opportunity to integrate cryogenically cooled power electronics (CCPE).

[0103] It has been found that cooling some semiconductors to cryogenic temperatures significantly reduces conduction losses, in some cases reducing on-resistance by a factor of 5, while switching losses are reduced by 31.25%. Reducing both conduction and switching losses reduces the amount of cooling required, thereby reducing the weight of the CCPE device. For example, using liquid hydrogen as a coolant means that no additional cooling is required, and therefore further reduces the overall weight of the network.

[0104] We have found that the preferred temperature for the CCPE is about 80 Kelvin, as temperatures below 50 Kelvin cause losses to start rising again. This development can be beneficially integrated into the network of the present disclosure by selecting when to cool the CCPE by the coolant based on the preferred temperature of the coolant. In a preferred arrangement, the coolant cools the motor and the network to provide high efficiency at low temperatures. When cooling the motor and network, the temperature of the coolant increases so that the coolant can then be used for the CCPE at the preferred temperature of about 80 Kelvin. This is as Figure 4 The arrangement shown. Therefore, Figure 4 The arrangement is particularly advantageous with regard to the delivery and delivery sequence of the refrigerant to the network components.

[0105] Thus, an effective and efficient electrical network is described herein. The system provides many of the advantages described above. By enabling easier use of the transport of refrigerants and the use of high voltages, there are other forms of advantage, namely, it is easier to integrate the use of clean fuels into the generation of propulsion, either via the combustion of the refrigerant or via the generation of electricity via fuel cells. Thus, the system incidentally helps to reduce harmful emissions in modern propulsion systems.

[0106] The use of pure cryogenic oxygen and hydrogen enables significantly smaller (higher power density) and lighter mass (higher specific power) propulsion generation to replace modern propulsion systems. The use of liquid hydrogen and oxygen (ie, as cryogens) also has advantages in terms of power density and cooling factor.

[0107] Although the electrical transmission means used in the power network described herein are discussed as being primarily used for propulsion systems in the case of aircraft, other vehicles, such as spacecraft and submarines, etc. may carry oxygen, liquid oxygen, or gaseous or liquid hydrogen for propulsion systems using prime movers. Each of these will benefit from the presently disclosed network arrangements.

[0108] Generating propulsion from refrigerants rather than via fossil fuels has many advantages. The production of water replaces harmful gas emissions (NO x , CO2, etc.), which has obvious related advantages. In addition, the operation of the vehicle can be carried out at a significantly reduced noise level. In a specific example, due to the absence of high-speed exhaust, the take-off and landing phases of an aircraft can occur at a significantly reduced noise level.

[0109] Therefore, applications of this network arrangement may include automotive, space, home or commercial, etc.

[0110] As disclosed herein, a further benefit of using fuel cells compared to combustion engines is that microbial colonization that occurs in existing aircraft kerosene fuel tanks is avoided. Currently, cleaning such tanks requires the use of detergent-containing, pesticide-containing cleaning agents that are somewhat damaging to the environment. In some cases, such cleaning may be performed after each long-distance flight. Therefore, reducing cleaning work has further environmental benefits.

Claims

1. An electrical network comprising: Electrical conductors; and A refrigerant source is configured to contain a refrigerant, the refrigerant source being arranged such that, in use, the refrigerant is provided to the conductor to maintain the conductor in a highly conductive state.

2. The electrical network of claim 1, further comprising a fuel cell stack electrically connected to the electrical conductor, wherein The refrigerant source is arranged at a refrigerant upstream end of the network, The fuel cell stack is arranged at the refrigerant downstream end of the network, and in, In use, the refrigerant is in a liquid phase at the refrigerant source and in a gas phase at the fuel cell stack.

3. An electrical network according to claim 2, further comprising a prime mover arranged to provide motion from electrical energy, wherein The prime mover is arranged between the refrigerant upstream end and the fuel cell stack, and Wherein, in use, refrigerant is provided to the prime mover in liquid phase.

4. An electrical network according to any one of claims 1 to 3, further comprising a further electrical conductor arranged to conduct electrical energy at a lower voltage than the electrical conductor, wherein In use, the further electrical conductor conducts electrical energy at a low voltage to at least one electrical control unit.

5. An electrical network according to claim 4, wherein: In use, the electrical energy conducted by the electrical conductor is approximately 270 volts and the low voltage electrical energy conducted by the further electrical conductor is approximately 28 volts.

6. An electrical network according to claim 4 or 5, wherein: The further electrical conductor is formed from aluminium.

7. An electrical network according to any one of claims 1 to 5, wherein: The electrical conductor comprises a refrigerant carrying portion which, in use, carries refrigerant provided to the conductor by the refrigerant source.

8. An electrical network according to any one of claims 1 to 6, arranged as a closed loop system for providing a refrigerant.

9. An electrical network according to any one of claims 1 to 7, arranged to provide refrigerant to parts of the network in order to maintain the following parts at the following temperatures: a refrigerant source at 25 Kelvin; Electrical conductors, at 25 Kelvin; The motor's coils, at 25 Kelvin; Power electronics at 80 Kelvin; and Hydrogen mixer at 300 Kelvin.

10. An electrical network according to any one of claims 1 to 8, further comprising at least one converter, at least one inverter and at least one circuit breaker to control the transmission of electrical energy through the network.

11. An electrical network according to any one of claims 1 to 9, further comprising an electrical insulation arranged to form an outer layer of the electrical conductor.

12. An electrical transmission device according to any one of claims 1 to 10, further comprising a dielectric arranged to provide electrical insulation within the electrical conductor.

13. An electrical network according to any one of claims 1 to 11, wherein: The electrical conductor is formed from aluminum.

14. An aircraft electrical system comprising an electrical network according to any one of claims 1 to 13.

15. An aircraft comprising an electrical network according to any one of claims 1 to 13.

16. A method of providing propulsion in a vehicle, comprising: Cooling an electrical conductor to a high conductivity state using a liquid refrigerant; cooling the prime mover with the liquid refrigerant; evaporating the liquid refrigerant via heat exchange; delivering a gaseous refrigerant to at least one fuel cell; generating electrical energy in the at least one fuel cell; providing electrical energy from the at least one fuel cell to the electrical conductor for conduction to the prime mover; Propulsion is generated by electrical energy provided to the prime mover.

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