Method and Apparatus for Hydrogen Pumping and Compression

1 . A hydrogen pumping and compression apparatus, comprising:

a first positive displacement first stage pump including a first pump element disposed in a first pump chamber having an inlet port and an outlet port;

a first stage driver coupled to the first pump element;

an inlet valve in flow communication with the inlet port of the first stage pump;

a positive displacement second stage pump including a second pump element disposed in a second pump chamber having an inlet port and an outlet port;

a second stage driver coupled to the second pump element; and

a transfer pipe interconnecting the outlet port of the first stage pump and the inlet port of the second stage pump.

wherein the first stage driver is configured to cause the first pump element to discharge at a first speed and to cause the first pump element to retract at a second speed in a single cycle, the first speed different from the second speed.

2 . The apparatus of claim 1 , wherein:

the transfer pipe communicates with a buffer volume; and

the buffer volume includes a vent valve communicating with at least one of the atmosphere and a bulk storage vapor space.

3 . The apparatus of claim 1 , wherein the inlet valve is actuator operated.

4 . The apparatus of claim 3 , further comprising an electronic controller operably connected to the first stage driver, the second stage driver, and the inlet valve.

5 . The apparatus of claim 1 , further comprising a pressure transducer, wherein:

the pressure transducer is operable to sense a hydrogen pressure in the transfer pipe and generate a signal representative thereof, and is operably connected to an electronic controller operably connected to the first stage driver and the second stage driver; and

the electronic controller is configured to control at least one of the first speed and the second speed using the generated signal.

6 . The apparatus of claim 1 wherein a ratio of a swept volume of the first stage pump to a swept volume of the second stage pump is variable between 1:1 and 50:1, inclusive.

7 . The apparatus of claim 1 , further comprising:

at least one further positive displacement first stage pumps each of the at least one further first stage pump including a respective pump element disposed in a respective pump chamber having a respective inlet port and a respective outlet port,

wherein the transfer pipe interconnects the respective outlet port of the at least one further positive displacement first stage pump with the inlet port of the second stage pump.

8 . The apparatus of claim 1 , wherein:

a tee is connected to the transfer pipe and the outlet port of the first stage pump;

a first shutoff valve is positioned between the transfer pipe and the tee; and

a second shutoff valve is positioned between the tee and a further pipe,

wherein the first and second shutoff valves are selectively configurable to direct flow from the first stage pump to the second stage pump and/or to a storage tank or to a vehicle directly receiving liquid hydrogen as fuel.

9 . A hydrogen pumping and compression method, comprising:

operating a first pump element of a first positive-displacement first stage pump using a first stage driver to draw hydrogen from a bulk fuel storage tank, as a liquid at a temperature of 18-25K and a pressure of 1-6 bar, and discharge it to a transfer pipe as a liquid at a temperature of 20-30K and a pressure of 2-20 bar, wherein the first stage driver is configured to cause the first pump element to discharge at a first speed and to cause the first pump element to retract at a second speed in a single cycle, the first speed different from the second speed; and

simultaneously, operating a second pump element of a positive-displacement second stage pump using a second stage driver which is independent of the first stage driver, to compress the liquid hydrogen from the first stage pump to a pressure of at least 350 bar, and discharge it from an outlet of the second stage pump.

10 . The method of claim 9 , wherein ratio of a swept volume of the first stage pump to a swept volume of the second stage pump is varied within a range of 1:1 to 50:1, inclusive, while operating the first pump element.

11 . The method of claim 9 , wherein:

the transfer pipe incorporates a buffer volume.

12 . The method of claim 11 , further comprising:

monitoring the pressure of the liquid hydrogen in the buffer volume; and

in response to the pressure exceeding a predetermined value, venting some of the liquid hydrogen to the atmosphere or to a bulk storage vapor space, through a vent valve, so as to reduce the pressure.

13 . The method of claim 9 , further comprising using an electronic controller to control the first stage driver and the second stage driver.

14 . The method of claim 13 , further comprising:

using a pressure transducer disposed downstream of the first stage pump, to sense a hydrogen pressure; and

controlling the first driver with the electronic controller to discharge at the first speed to maintain a target pressure, using feedback signals from the pressure transducer.

15 . The method of claim 9 , wherein two or more of the positive-displacement first stage pumps are operated, each with its own a first stage driver, to draw hydrogen from the bulk fuel storage tank, as a liquid at a temperature 18-25K and a pressure of 1-6 bar, and discharge it as a liquid at a temperature of 20-30K and a pressure of 2-20 bar.

16 . (canceled)

17 . (canceled)