Mobile Fuel Filling Trailer
The present invention relates to the distribution of fuel. In particular, the present invention provides a method and an apparatus for filling hydrogen fuel tanks with hydrogen from "multi-cylinder packs" or commercial tube trailers.
Hydrogen is considered as a potential low-carbon alternative to fossil fuels. As well as fuelling stationary power supplies, hydrogen can also be used to fuel vehicles, providing a cleaner alternative to petrol-powered vehicles. However, a suitable hydrogen filling station infrastructure must first be established before the development of hydrogen-fuelled vehicles can proceed.
It is therefore desirable to have a system that allows quick installation of the necessary equipment for filling hydrogen-fuelled vehicles when no permanent hydrogen filling station infrastructure is available.
Hydrogen can be delivered in the form of "multi-cylinder packs" or commercial tube trailers, provided by industrial gas suppliers to any suitable location. Most packs deliver gas at a pressure of the standard "K" type cylinder at 200 bar (20MPa) . However, most vehicles that use hydrogen gas store the gas at a pressure of 350 bar or 700 bar (35/70 MPa) . Hydrogen gas from a tube pack therefore requires compression before it can be supplied to a hydrogen-fuelled vehicle.
If hydrogen is delivered on a truck or other vehicle, as for example in JP 2006/015765 (Tatsuno Corp) or JP 2007/100906 (Toho Gas KK) , a compressor can be provided on the vehicle powered by the vehicle's own power supply. However, the compressed hydrogen must then be stored at the filling station, because otherwise the vehicle is taken out of action.
On the other hand, a passive trailer left on site would require access to an electric power transmission grid in order to drive the compressor, which may not be available in some locations.
WO 2007/019948 (Linde) shows a mobile filling station which has a main storage tank, a compressor and an intermediate, high-pressure reservoir. A fuel cell is supplied by the storage tank to power the station. The entire apparatus is a unit which has to be shipped as a whole, which is cumbersome.
The present invention aims to provide a more versatile system and is defined in the claims, as a method and as an apparatus .
The invention in one aspect envisages a filling station for hydrogen-fuelled vehicles in which the same source of hydrogen is used to fill the fuel tanks of the hydrogen- fuelled vehicles, and to provide fuel to generate power to drive a pressure booster. Such systems do not require access to a power grid, and therefore their locations are not restricted. Another advantage of the invention is that a filling station can be installed at a new location quickly by pre-manufacturing a number of such stations and simply delivering one to a suitable location. Similarly, a trial gas filling station can be relocated easily when required.
In embodiments of the invention, a mobile trailer is provided for a hydrogen filling station, including one or more hydrogen fuel cells to power electrical equipment on or in or associated with the trailer. The electrical equipment will generally include an electric air compressor to provide compressed air and a booster pump powered by the compressor to boost hydrogen to a suitably high pressure by means of the compressed air.
The mobile trailer may have an inlet connection for connecting one or more "low-pressure" hydrogen storage means thereto and an outlet connection for onward connection to a hydrogen fuel tank, e.g. of a vehicle.
The hydrogen storage means may be a multi-cylinder pack including standard hydrogen cylinders at about 200 bar. One or more multi-cylinder packs may be connected to the trailer from a distance to provide hydrogen to the booster pump and to the hydrogen fuel cells.
In operation of embodiments of the invention, a stream of hydrogen is allowed to flow from a tube pack, through an inlet connection, to feed a compressor or booster pump on a trailer, while a small portion of the input flow is diverted to feed one or more hydrogen fuel cells. The cells power an electric compressor on the trailer which provides compressed air to operate the booster pump, the combination generally being referred to as a compressor. Hydrogen boosted to a suitably high pressure by the booster pump can then be provided to a hydrogen fuel tank of a vehicle through an outlet connection.
In an alternative aspect the invention provides a mobile gas filling apparatus for conveying gas in a stationary storage means at a given pressure to a container at a target, higher, pressure, comprising: a connector for receiving gas from the storage means; a compression device for compressing the gas thus received; an outlet leading, in use, from the compression device to the high-pressure container; two or more tanks for containing gas received from the storage means at approximately the said target pressure; and a valve system with pipework and valves, and a control device, for connecting the tanks in sequence to a vehicle tank to deliver gas at successively higher pressures approaching the target pressure, and for connecting the compression device to the tanks to refill them after a filling procedure.
This sequential filling process can be used with the fuel- diversion feature of the invention as described above, or independently. However, it exhibits its advantages best when used in a portable context, since otherwise a quick fill can be obtained simply by using larger apparatus.
The valve system preferably includes a bypass layout allowing feed directly from the storage means to the target container, bypassing both the compression device and the tanks, for use when the target container is at a low pressure; and/or a route from the tanks through the compression device, for final pressure top-up.
A sequential system is known from WO 2009/013415 (Air Liquide) , but this uses the compressor continuously.
An embodiment of the invention will now be described by way of an example with reference to the accompanying drawings, in which:
Figure 1 shows a booster trailer in accordance with the present invention, in use for filling a car with high-pressure hydrogen; Figure 2 schematically shows the fluid circuit of the trailer;
Figure 3 shows the electrical circuit of the trailer;
Figure 4 shows an alternative embodiment in circuit form with a separate trailer for storage and a sequential fill method; and
Figure 5 shows the physical form of the second embodiment .
As shown in Figure 1, the filling equipment is mounted in an enclosed movable trailer 1. The trailer or "pod" is designed to be easily movable, so that it can be delivered by road to the site, such as a fuel station, and moved
around the site as required. A standard industrial multi- cylinder pack 100 is connected to it by a hose 50 typically about 4m in length, and a vehicle 200 is being filled by a high-pressure hose 150, likewise about 4m long.
An inlet connection 3 is provided on the trailer to connect the multi-cylinder pack. Hydrogen enters at a pressure of up to 200 bar and passes through a safety solenoid arrangement, not shown, which shuts off the hydrogen supply when required in the event of an emergency. The hydrogen then enters a WT" piece 9, one branch of which diverts some of the input stream to one or more hydrogen fuel cells 20 to power an electric compressor 12 and other electrics on the trailer. In this example there are two 5-kW cells.
The other branch of the "T" piece feeds a booster pump 10 fitted with appropriate trip valves, safety systems and interlocks. For safety the booster pump should be nonelectrical. Here a pneumatically powered pump is used. The inlet to the booster pump is 6mm-diameter welded stainless steel pipework of the appropriate grade. The booster pump is operated by compressed air, and its materials are suitably chosen to prevent any possible contamination of the hydrogen therein. Also the separation of the booster from the electric circuits represents an additional safety measure. The combination of compressor and booster pump can be denoted "compression device".
The compressed air required for the operation of the booster pump is provided by the electric compressor 12 powered by the fuel cells 20 on the trailer. A suitable hydrogen detection system (not shown) is provided for emergency shutdown in the event of hydrogen leakage. For vehicle use, a hydrogen filling nozzle is provided on the trailer as an outlet, and a facility for recharging hydride canisters is also provided.
Figure 2 shows the fluid circuit of the trailer 1. The pipework is made by welded fittings except for the compression fittings on the booster pump. The figure shows the various pressure regulators P, gauges G, non-return valves NV, relief valves RV and trip valves V, that are incorporated into the system. These are linked to a gas detection system to produce a complete fail-safe unit, the unit shutting down if a hydrogen leakage is detected.
The hydrogen enters at the port Hl in the top right, via the flexible hose 50, and is fed by the hydrogen booster 10 to the outlet port H2, shown at bottom left, where it enters the vehicle at the higher pressure. As can be seen by the dotted lines, the booster 10 is powered by compressed air from the compressor 12; this compressed air also operates the various valves. A branch line from the inlet Hl via a valve Pl feeds fuel cells 20 that power the compressor via an inverter, and another branch via a valve P2 leads to another outlet H3 and a further flexible hose 250 for filling hydride cylinders such as are used, for example, on fuel-cell-powered bicycles.
The trailer does not carry an on-board hydrogen reservoir; the main locations where hydrogen is stored are either the external multi-cylinder pack 100, or the hydrogen tank of the vehicle 200 after it has been filled. An arrangement for filling hydride canisters is provided separately on the trailer, by a hose 250, to provide hydrogen at a lower pressure. Again, no hydrogen storage is associated with this facility. As a result, the transit of the trailer does not involve the transport of hydrogen gas.
Figure 3 shows the electrics of the trailer 1, including a gas detection/control instrumentation section A, power conditioning section B, air compression and motor control section C, and other general trailer electrics.
The gas detection/control instrumentation section A comprises a two-zone leak detection system linked directly to an emergency stop and shut-down circuit, which stops hydrogen flow and closes down the air compressor 12, booster pump 10, and fuel cells 20 in the event of a gas leak.
The power conditioning section B comprises start-up batteries, DC-to-DC converters, and a main fuel cell inverter, which inverts the output voltage of the fuel cells 20 up to 110V AC, which is in turn transformed to 240V AC for supplying motors of the air compressor 12.
Note that when the trailer 1 is being powered externally by the mains, the fuel cells 20 and associated inverters are bypassed.
The air compression and motor control section C controls the supply of power, by means of switches Sl/1 and Sl/2, between fuel cells 20 and external supply (mains) . The air compression and motor control section C comprises a motor control circuit, which includes a staggered start facility for reducing the requirement of a high start-up current demanded by two 2.6IkW motors. The motors drive a twin compressor to produce a free air delivery of 25 CFM. An air receiver of 250 litres capacity stores the compressed air, used to drive the hydrogen booster pump 10 and various air- operated control and trip valves.
In this embodiment, a mains hook-up facility is incorporated into the electrical circuit such that the unit can run either on the fuel cells 20 or on mains power, controlled by the switches Sl/1 and Sl/2.
In a filling station, the multi-cylinder packs 100 can simply be delivered and suitably stored until needed. The trailer 1 can be connected to a pack and moved to a suitable position where vehicles can be filled. The trailer needs no other source of power than the fuel itself, though it is envisaged that an electric power supply could also be
fitted, such as a connection to the mains, as shown by the embodiment of Figure 3.
In another embodiment, a battery can be incorporated into the trailer electrics to provide back-up power for the control and safety systems, and to provide power for the initial start-up and shut-down of the fuel cells 20. However, as with a battery on a petrol-powered internal combustion engine car, the battery does not provide power to run the complete system.
In this way a filling station can easily be equipped to supply hydrogen or other gaseous fuel at high pressure, simply by providing a trailer 1 and delivering the required gas in bottles as required.
While the system desired is effective in filling a vehicle fuel tank to a desired high pressure, for commercial purposes it can be slow, because the high-pressure hydrogen is provided directly by the compression device. In a second embodiment, therefore, shown in Figure 4, a system is described that speeds the filling process to levels comparable to liquid-fuel systems.
The system, known as a sequential fast-fill system, comprises a storage container 300 in which are located three hydrogen tanks 310, 312, 314. These tanks can be standard 74-litre 350-bar tanks exactly like the ones commonly used in vehicles. The tanks are connected in parallel between an inlet side 320 and an outlet 330. Various valves V1-V12, NRVl-7 are shown, and gauges PGl-PGβ; also present is a PLC (control unit) 400, opening and closing the valves in a programmed sequence determined by the PLC system in response to signals received from the PTX' s (pressure transmitters) .
The container 300 is preferably also a free-standing trailer and is designed to be operated with an H2 booster trailer 1 similar to that shown in Figures 1-3. However, here the
outlet of the compression device does not go directly to the tank but is fed through a valve V3, located in the storage container, that is only opened during direct filling, for instance when the vehicle tank is at a low pressure below that of the hydrogen pack, or when it is nearly up to the required pressure, as will be described. The container 300 also contains a bypass route via a valve V2 (and non-return valve NRV3) leading straight from the MCP to the outlet 330.
Operation of the system is as follows. First, assuming the vehicle tank in the vehicle 200 is nearly empty, the cylinder pack 100 is connected to the outlet via the bypass valve V2 and valve V3, monitored by gauges PG2 and PG6. The booster 10 is preferably idle at this point. The pressure in the tank thus reaches about 165 bar (16.5 MPa), if a 17-cylinder MCP is used.
Then V2 and V3 are closed and V9 is opened, and the hydrogen in the first tank 310 is connected to the vehicle tank, resulting in a final pressure of about 257 bar. Again, the compression device is not operating, or is not connected. V9 is then closed and VlO is opened to the second tank, equilibrating at 303 bar, and similarly VlO is then closed and VIl opened, resulting in a pressure of 326 bar. This process takes a few minutes.
Such a pressure may be adequate for the user. However, if a completely full tank is desired, the system continues by switching the three-way valve V12 from the left to the right, in the drawing, so that the outlet of the third tank 314 is connected to the compression device 11 including the booster 10. The booster is started and valve V3 opened to complete the filling process. Here the booster does not have to do much work, as the pressure is not far off final pressure (within about 10%), so this stage also does not take long.
After the vehicle draws away, the compression device refills the three tanks 310-314, ready for the next vehicle.
Although the storage trailer 300 is designed as a unit separate from the compressor/booster trailer, and similarly portable, as shown in Figure 5, the two could be incorporated into one. Moreover, although three identical hydrogen tanks are shown by way of illustration, a different number could be used, and they could be different from each other and/or from a standard vehicle tank. However, for a simple solution to the problem of providing a hydrogen filing station at short notice the apparatus described is suitable .
The fast-fill system shown is also applicable to other systems for refilling with gaseous fuel, and indeed for any other high-pressure gas filling process.
The invention is not restricted to hydrogen; any suitable gaseous fuel can be compressed, with an appropriate fuel cell (or using the mains connection) .