Patent Description:
More particularly, the invention relates to a device for filling the tanks of fuel cell electric vehicles (FCEV), the device comprising a liquefied gas source, a transfer circuit in downstream fluid communication with the liquefied gas source and comprising at least one downstream end adapted and configured to be removably connected to a vehicle hydrogen tank to be filled.

Hydrogen gas refuelling stations using liquid hydrogen sources are known. These known devices make it possible to use refrigeration from the liquid hydrogen to produce pre-cooled pressurized hydrogen gas for rapid filling without experiencing an excessive increase in the temperature of the gas in the tank during filling.

For example, Daney, et al. proposed a conceptual refilling station that uses a vaporizer for providing ambient temperature, high pressure gaseous hydrogen that is subsequently cooled prior to being fed to the vehicle tank.

Another such station implemented at an urban bus refilling station utilizes a vaporizer that transfers heat from the ambient air to the pumped flow of liquid hydrogen to provide a flow of high pressure, gaseous hydrogen to the vehicle tank.

At atmospheric pressure, the boiling point of hydrogen is -<NUM>. Because the station disclosed in Raman, et al. uses a vaporizer that exchanges heat between the liquid hydrogen and ambient air, the skin temperature of the ambient air vaporizer is exceedingly low. As a result, water vapor from the ambient air condenses and freezes on surfaces of the ambient air vaporizer. Also air around the ambient air vaporizer condenses and drips on the equipment below. This creates a risk for the equipment below. Equipment may become thermally embrittled, especially equipment that is made of carbon steel, and plates may crack, structural beams may fail, and pipes may burst. Since oxygen will condense at a higher temperature than nitrogen, an oxygen enriched atmosphere may be created. There are of course many known risks presented by an oxygen-rich atmosphere. Furthermore, the condensing air exacerbates the cryogenic cloud around the equipment.

When the depth of the frozen water on the surface of the ambient air vaporizer reaches an unsatisfactory depth, thereby decreasing effective heat transfer, or even results in bridging in between adjacent vanes of the ambient air vaporizer, such a vaporizer must be defrosted before further use is continued. To solve this problem, two ambient air vaporizers may be used in alternating fashion so that while one is being defrosted, the other is used to vaporize the liquid hydrogen. While this solves the problem, it can unsatisfactorily increase capital costs because of the necessity of having two ambient air vaporizers for each filling circuit. For hydrogen filling stations located in areas where the real estate is costly and/or for hydrogen filling stations co-located at a retail gasoline station where the space for the station is leased from the retail gasoline station, capital expenses are also increased because the necessity of having two vaporizers doubles the footprint or space taken up by the liquid vaporization portion of the station.

Because the skin temperature of the ambient air vaporizer is so low, water vapour in the ambient air also condenses in regions surrounding the vaporizer, creating fogging conditions.

While fogging can be a nuisance for refilling stations isolated from the public, such as in an industrial area ordinarily far from consumers, fogging is a much more serious problem for more conspicuous refilling stations, such as at retail hydrogen refilling stations, open demonstration refilling stations, and hydrogen filling stations co-located with retail gasoline stations. This is because members of the public will view the fogging emanating from a hydrogen refilling station and incorrectly conclude that either a dangerous leak of hydrogen has occurred at the station or even that a fire has broken out at the station. Erroneous reports of disastrous leaks or dangerous fires to emergency responders will therefore require that the station be subjected to an emergency stop followed by a thorough safety assessment before the station may be declared safe for operation. For this reason, the use of ambient vaporizers can seriously impede the development of hydrogen refilling stations sourced by on-site tanks of liquid hydrogen and located in conspicuous areas viewable by the public,.

<CIT> and <CIT> disclose liquefied hydrogen dispensing systems.

An aim of the invention is to overcome all or some of the prior art disadvantages stated above.

There is disclosed a hydrogen refilling station in accordance with independent claim <NUM> and a method of filling a tank in accordance with independent claim <NUM>.

Other characteristic features and advantages will emerge upon reading the following description, with reference to the figures in which:.

As best shown in <FIG>, liquid hydrogen from a liquid hydrogen source <NUM> is fed to a filling circuit <NUM>, via an upstream end thereof, that includes a first heat exchanger <NUM>, a pressure control valve <NUM>, a second heat exchanger <NUM>. The downstream end of the filling circuit <NUM> is removably connected to a tank of a hydrogen fuel cell electric vehicle (FCEV) <NUM>. Heat transfer fluid flows in a heat transfer fluid circuit <NUM> that includes a heat transfer fluid pump <NUM>, a temperature sensor <NUM>, and a liquid hydrogen pump <NUM>.

The source optionally includes a pressure building circuit for building pressure in a headspace of the source by controlling amounts of liquid hydrogen from the source to exit the source and enter into a line in thermal connection with ambient air, using a flow control valve. The liquid hydrogen vaporizes in the line and is directed into the headspace. A pressure sensor measures a pressure inside the headspace. A controller is used to actuate the flow control valve based upon the measured headspace pressure so as to reach a desired pressure in the headspace.

The liquid hydrogen pump <NUM> is used to feed and pressurize the liquid hydrogen from the source and into the filling circuit. The use of a liquid hydrogen pump <NUM> allows the liquid hydrogen to be pumped to the supercritical pressures that are desired for high pressure fills of the tanks of the hydrogen-fuelled vehicle <NUM>. For example, liquid hydrogen stored in the source <NUM> at a pressure of around <NUM> bar may be easily pumped to a pressure of <NUM> bar or even higher. The properties and features of the particular liquid hydrogen pump <NUM> employed are ordinarily driven by the desired maximum pressure to be provided to the tank of the FCEV <NUM> and the desired filling capacity of the refilling station. Preferably, each liquid hydrogen pump <NUM> is characterized by the following operating conditions: a net positive suction head of <NUM>-<NUM> psi (<NUM>,138bar - <NUM>,345bar), a nominal flow capacity of <NUM>/h, a <NUM> psi (<NUM>,895bar) par liquid hydrogen suction pressure, and a maximum discharge pressure of about <NUM>,<NUM> psi (<NUM>,2bar).

Liquid hydrogen fed into the filling circuit <NUM> from the source <NUM> is vaporized at the first heat exchanger <NUM> to provide pressurized, gaseous hydrogen for filling the tank of the FCEV <NUM>. The first heat exchanger <NUM> exchanges heat between the heat transfer fluid flowing in the heat transfer fluid circuit <NUM> and the liquid hydrogen flowing in the filling circuit <NUM>, thereby vaporizing the liquid hydrogen (yielding cold hydrogen in supercritical fluid state) and cooling the heat transfer fluid. The vaporized liquid hydrogen constitutes the pressurized, gaseous hydrogen used to filling the tank of the hydrogen-fuelled vehicle <NUM>. Either a driver/customer of the FCEV <NUM> or an operator of the refilling station may access the nozzle (at the downstream end of the filling circuit <NUM>) conveniently located at an interface typically found at a standard gasoline station (i.e., a gas pump) which includes a display of the price of the hydrogen, the quantity of hydrogen delivered, and a start/stop button.

The cooled heat transfer fluid is warmed at the second heat exchanger <NUM> and pumped back to the first heat exchanger <NUM> using the heat transfer fluid pump <NUM>. The second heat exchanger <NUM> may be an ambient air vaporizer in which the cooled heat transfer fluid is warmed with the heat from the ambient air blown onto the ambient air vaporizer with the blower. Optionally, the second heat exchanger may be an electric heater.

While any known heat transfer fluid that is in the liquid phase at nominal pressures down to at least -<NUM>, a non-limiting and particularly suitable example of one is available from Eastman under the brand name Therminol VLT®. Therminol VLT® is a mixture of methylcyclohexane and trimethylpentane and has a reported liquid heat capacity ranging from <NUM> kJ/(kg·K) at -<NUM> to <NUM> kJ/(kg. K) at <NUM>.

The temperature of the heat transfer fluid may be controlled as follows. A controller (not illustrated) controls the speed of the heat transfer fluid pump <NUM> (such as by increasing or decreasing the speed of a variable frequency drive of the pump <NUM>) based upon the temperature of the heat transfer fluid sensed by temperature sensor <NUM>. If the temperature of the heat transfer fluid just upstream of the first heat exchanger <NUM> is unsatisfactorily high, it will impair the ability of the heat transfer fluid to warm the liquid hydrogen flowing through the first heat exchanger <NUM>. On the other hand, if the temperature of the heat transfer fluid is too low, it may become too viscous or even frozen. The controller is typically a computer or programmable logic controller. More specifically, the temperature of the heat transfer fluid downstream of the first heat exchanger may be controlled within a temperature range or according to a temperature set point.

Inside the first exchanger <NUM>, the flow of liquid hydrogen is surrounded by the flow of heat transfer fluid. This prevents an exterior skin temperature of the first exchanger <NUM> from reaching the exceedingly cold temperatures experienced by ambient air vaporizers of conventional liquid hydrogen-source hydrogen filling stations. Thus, condensation of water vapor upon the first heat exchanger <NUM> and consequent frosting (and the associated problems of defrosting in the prior art as discussed above) is avoided. Also, condensation of water vapor in regions surrounding the first exchanger <NUM> (and the associated problems of fogging in the prior art as discussed above) is avoided. Typically, the configuration of the first heat exchanger <NUM> is tube-in-tube where the liquid hydrogen flows through the inner tube and the heat transfer fluid flows in the outer tube. For pressures of about <NUM> bar, a tube in tube heat exchanger is less complex and less costly than a shell and tube heat exchanger. The first heat exchanger may instead be a shell and tube heat exchanger in which the tube fluid is liquid hydrogen and the shell fluid is the heat transfer fluid. Types of heat exchangers other than the pipe-in-pipe or shell and tube configurations may be used for the first heat exchanger <NUM> may be used with the invention so long as the liquid hydrogen is surrounded by heat transfer fluid and/or the skin temperature of an exterior of the first heat exchanger <NUM> does not reach the exceedingly low temperatures of conventional ambient air vaporizers and fogging and frosting are avoided. Portions of the filling circuit upstream of the first heat exchanger may be vacuum-jacketed to prevent the frosting and fogging problems.

The pressure of the hydrogen used to fill the tank of the FCEV <NUM> may be controlled with a pressure control valve <NUM>. While the particular manner in which the tank is filled is not limited, typically the tank is filled according to a standard filling scheme such as the Society of Automotive Engineers (SAE) standard J2601. The pressure control valve <NUM>.

As best illustrated in <FIG>, the hydrogen filling station may also include one or more buffer containers <NUM> for containing high pressure hydrogen, downstream of the first heat exchanger. Each of the buffer containers may be provided with a pressure building circuit in order to maintain a desired pressure within. The vaporized hydrogen is fed to the buffer containers via a leg <NUM> appending from the filling circuit <NUM>. The pressure control valve <NUM> may be used to fill the tank of the hydrogen-fuelled vehicle using a filling algorithm as discussed above. As in <FIG>, the liquid hydrogen is pumped to high pressure by liquid hydrogen pump <NUM> and heated by the heat transfer fluid at the first heat exchanger <NUM>. Shut-off valve <NUM> is closed, shut-off valve <NUM> is open, and one or more of the shut-off valves <NUM> are open. Instead of being fed to the FCEV directly, the cold supercritical hydrogen is used to fill one more of the buffer containers <NUM>. Optionally, one of the buffer containers <NUM> is at medium pressure while another is at high pressure. By selective opening or closing of the shut-off valves <NUM>, the buffer container <NUM> at high pressure may be filled first and the buffer container <NUM> at medium pressure filled second. Unless one or more of the buffer containers <NUM> is at an undesirably low pressure, the liquid hydrogen pump <NUM> need not be continuously run. If the buffer containers <NUM> are full, the tank of the FCEV <NUM> may be filled with hydrogen stored in the buffer containers <NUM> in a cascade fill in which the buffer container <NUM> at medium pressure is pressure-equalized with the tank of the FCEV <NUM> and subsequently the buffer container <NUM> at high pressure is pressure-equalized with the tank as is known in the art.

As best shown in <FIG>, the second heat exchanger <NUM> may be an ambient air vaporizer, the filling circuit <NUM> may also include an optional chiller <NUM> and pressure and temperature sensors <NUM>, <NUM>, and the heat transfer fluid circuit <NUM> may include a heat transfer fluid reservoir <NUM> and a temperature sensor <NUM>. The tank of an FCEV may be filled using the pressure control valve <NUM> as described above, based upon the pressure and temperature sensed by pressure and temperature sensors <NUM>, <NUM>. The heat transfer fluid circuit <NUM> is provided with a primary line <NUM> in which the second heat exchanger <NUM> is disposed. The cooled heat transfer fluid is warmed with the heat from the ambient air blown onto the second heat exchanger <NUM> with a blower <NUM>. Optionally, there is also a bypass line <NUM> that branches off of the primary line <NUM> such that a portion of the cooled heat transfer fluid is not warmed at the second heat exchanger <NUM>. In such an optional case, the warmed heat transfer fluid in the primary line <NUM> is combined with the non-warmed heat transfer fluid in the bypass line <NUM> using a three-way control valve <NUM>. Because the ambient air temperature blown by the blower <NUM> will vary with the time of year, the three-way control valve <NUM> may be controlled according to a control scheme which varies by the season. For example, during the winter in the northern hemisphere, the entirety of the flow of the heat transfer fluid may be fed through the primary line <NUM> and be heated at the second heat exchanger <NUM>, whereas during the summer, a portion or all of the flow of the heat transfer fluid may be fed through the bypass line <NUM> in order to yield a colder heat transfer fluid for storage in a heat transfer fluid reservoir <NUM>. This is helpful during especially hot weather in the summer when heat leaks impair the ability to maintain the heat transfer fluid below a maximum predetermined temperature.

The temperature of the combined flow of heat transfer fluid from the three-way control valve <NUM> may alternatively be controlled in the following manner. A controller (which may be the same as or different from the controller used to control the temperature of the heat transfer fluid downstream of the first heat exchanger <NUM>) controls actuation of the three-way control valve to achieve a ratio of the flow of warmed heat transfer fluid in the primary line and non-warmed heat transfer fluid in the bypass line based upon the temperature measured by the temperature sensor of the heat transfer circuit.

The pressure and temperature sensors <NUM>, <NUM> may be used to input a pressure and temperature of the hydrogen delivered to the FCEV tank as variables into a filling algorithm as described above. In particular, the filing algorithm is in compliance with SAE standard J2601.

As best in shown in <FIG>, the features of the embodiments of <FIG> and <FIG> may be combined.

As best illustrated in <FIG>, the filling circuit includes a primary line <NUM> and a bypass line <NUM> that branches off of the primary line. The portion of the liquid hydrogen fed to the primary line <NUM> is vaporized at the first heat exchanger <NUM> while the portion of the liquid hydrogen fed to the bypass line <NUM> is not. The two flows of hydrogen are combined at a point <NUM> downstream of the first heat exchanger <NUM> to provide the pressurized, gaseous hydrogen. The temperature of the pressurized, gaseous hydrogen may be controlled by controlling the flows of liquid hydrogen into the primary and bypass lines <NUM>, <NUM> with temperature control valves <NUM>, <NUM>. The temperature control valves <NUM>, <NUM> may be controlled with a controller (not shown but examples include a computer or a programmable logic controller which may be the same as or different from controller(s) that controls operation of the three-way control valve <NUM> and/or the liquid hydrogen pump variable frequency drive) based upon the temperature measured by the temperature sensor <NUM>. The skilled artisan will recognize that, when the temperature sensed by the temperature sensor is too low (high), the flow of liquid hydrogen to the primary line <NUM> may be increased (decreased) and the flow of liquid hydrogen to the bypass line <NUM> may be decreased (increased) by a corresponding amount. Thus, control of the temperature of the pressurized, gaseous hydrogen may be performed without the optional chiller <NUM> or the optional chiller <NUM> may provide supplemental refrigeration only. In this embodiment, the flow of gaseous hydrogen to the FCEV tank is controlled by pressure control valve <NUM>, optionally based upon the pressure and temperature sensed by the pressure and temperature sensors <NUM>, <NUM> as explained above. If the FCEV tank is not being filled with hydrogen from the buffer containers <NUM>, shut-off valves <NUM> are closed and the two flows of hydrogen are combined at a point <NUM> downstream of the first heat exchanger <NUM> to provide the pressurized, gaseous hydrogen for filling the FCEV tank. If one of the buffer containers <NUM> is being used to fill the FCEV tank, one of the shut-off valves <NUM> is closed, one of the shut-off valves <NUM> is open and a flow of hydrogen from one of the buffer containers <NUM> is combined with a flow of liquid hydrogen from the bypass line <NUM> at the point <NUM> downstream of the first heat exchanger <NUM>. During such a fill, the pump <NUM> may keep running or optionally it may be turned off. Regardless of whether the vaporized hydrogen is obtained directly from the primary line <NUM> or from one of the buffer containers <NUM>, the temperature of the pressurized, gaseous hydrogen may be controlled by controlling the flows of liquid hydrogen in the primary and bypass lines with temperature control valves <NUM>, <NUM>. The temperature control valves <NUM>, <NUM> may be controlled with a controller (not shown but examples include a computer or a programmable logic controller which may be the same as or different from controller <NUM>) based upon the temperature measured by the temperature sensor. The skilled artisan will recognize that, when the temperature sensed by the temperature sensor is too low (high), the flow of liquid hydrogen to the primary line <NUM> may be increased (decreased) and the flow of liquid hydrogen to the bypass line <NUM> may be decreased (increased) by a corresponding amount. Thus, control of the temperature of the pressurized, gaseous hydrogen may be performed without the optional chiller or the optional chiller may provide supplemental refrigeration only. In this embodiment, the flow of gaseous hydrogen to the FCEV tank is controlled by pressure control valve based upon the pressure sensed by the pressure sensor.

In a variant of the embodiment of <FIG> and as best illustrated in <FIG>, the station may have two filling circuits <NUM>', <NUM>". This allows the liquid hydrogen from the source <NUM> to be supplied to either of the liquid hydrogen pumps <NUM> and compressed liquid hydrogen may be supplied to either of the two filling circuits <NUM>', <NUM>" from either liquid hydrogen pump. Although not illustrated, a single set of buffer containers <NUM> may be shared in common with each of the filling circuits <NUM>', <NUM>" allows the size of the buffer containers to be optimized, thereby decreasing capital costs.

In each of the foregoing embodiments, it should be noted that the downstream end may be equipped with at least two nozzles. Each of the nozzles is adapted and configured to be removably connected with the tank of a FCEV for filling of the tank with. While any known configuration of nozzle may be used, typically the nozzle is part of a hydrogen dispenser available from Tatsuno Corporation for use in retail hydrogen refilling stations.

Regardless of the particular embodiment, while the refilling station may be located anywhere FCEV tanks need refilling, it is of particular usefulness when located at a retail fuel station fitted with hydrogen dispensers for use by drivers of FCEVs who do not necessarily have any training in the handling and dispensing of high pressure hydrogen. In a preferred filling sequence, after the nozzle is connected in gas-tight fashion with the FCEV tank, gaseous hydrogen is first fed from the lowest pressure buffer container (that is at a pressure higher than that of the hydrogen in the tank) and into the tank in order to decrease the impact of the Joule-Thomson effect. The particular manner in which the filling is performed is dictated by the filling algorithm, such as one compliant with the SAE J2601 standard. Control of the pressure of the gaseous hydrogen from the nozzle is done with a pressure control valve based upon the pressure of the gaseous hydrogen by a pressure sensor in the nozzle or in the tank. When the lower pressure buffer container and the tank are essentially pressure-equalized, gaseous hydrogen is instead dispensed from a higher pressure buffer container and into the tank. This is continued until completion of the fill, according to the algorithm, is indicated. Before another FCEV tank is filled, the liquid hydrogen is pumped from the source to the first heat exchanger and the result pressurized gaseous hydrogen is used to refill the buffer containers.

The invention provides several advantages.

The vaporizer used in the invention need not be very tall. Indeed, it can remain under <NUM>' (<NUM>,<NUM>) in height. This is important because, in urban locations, the presence of overhead power lines, telephone lines, or trees restricts the vertical space that may be taken up by conventional ambient air vaporizers. In contrast to the vaporizer used in the invention, conventional ambient air vaporizers often exceed <NUM>' in height.

In comparison to ambient air vaporizers, the vaporizer used in the invention allows more precise control of the outlet temperature of the hydrogen at the dispenser that is necessary for meeting stringent temperature control profiles required by many hydrogen filling protocols, such as the SAE J2601. Because conventional ambient air vaporizers exchange heat with liquefied cryogenic gases in a largely passive manner, the temperature of the vaporized cryogen will highly depend upon the ambient temperature. In the invention, the temperature of the heat transfer fluid exiting the second heat exchanger may be precisely controlled through precise control of the blower speed or the electrical power supplied to a heater. This in turn allows more precise control of the vaporized hydrogen exiting the first heat exchanger after exchanging heat with the temperature-controlled heat transfer fluid.

Claim 1:
A hydrogen refilling station, comprising a liquid hydrogen source (<NUM>) adapted and configured to store liquid hydrogen, a filling circuit (<NUM>), and a heat transfer fluid circuit (<NUM>), wherein
the filling circuit (<NUM>) has an upstream end in downstream fluid communication with the liquid hydrogen source (<NUM>) to allow a flow of liquid hydrogen from the source (<NUM>) into the filling circuit (<NUM>), a downstream end adapted and configured to be removably connected with a hydrogen-fuelled vehicle tank (<NUM>) for filling of the tank with, and a first heat exchanger (<NUM>) disposed between the upstream and downstream ends of the filling circuit (<NUM>);
the heat transfer circuit (<NUM>) comprises, in flow order, an upstream end in downstream flow communication with the first heat exchanger (<NUM>), a second heat exchanger (<NUM>), a heat transfer fluid pump (<NUM>), and a downstream end in upstream flow communication with the first heat exchanger (<NUM>), the heat transfer fluid pump (<NUM>) being adapted and configured to receive a heat transfer fluid from the second heat exchanger (<NUM>) and direct it to the first heat exchanger (<NUM>), the heat transfer fluid being in liquid phase at nominal pressures down to at least -<NUM>;
the second heat exchanger (<NUM>) is adapted and configured to warm cooled heat transfer fluid received from the first heat exchanger (<NUM>); and
the first heat exchanger (<NUM>) is adapted and configured to exchange heat between the heat transfer fluid flowing through the heat transfer circuit (<NUM>) and liquid hydrogen in the filling circuit (<NUM>) so as to cool the heat transfer fluid and vaporize the liquid hydrogen to provide the pressurized, gaseous hydrogen for filling the tank (<NUM>), the flow of liquid hydrogen inside the first heat exchanger (<NUM>) being surrounded by the flow of the heat transfer fluid.