Self-saturating liquefied natural gas delivery system utilizing hydraulic pressure

1. A method comprising:

filling a main tank with a cryogenic liquid while an overflow tank remains empty;

coupling a tank apparatus with a use device, the tank apparatus comprising:

(a) the main tank and the overflow tank contained within the main tank, wherein the main tank contains a vapor head above the cryogenic liquid;

(b) a withdrawal line that passes through a first vaporizer and that leads to the use device;

(c) a vapor line having a first end positioned within the vapor head in the main tank and a second end that communicates with an overflow line via a first pressure regulator such that vapor from the vapor head can pass through the vapor line to the overflow tank via the overflow line and the first pressure regulator, and wherein the vapor line also connects with the withdrawal line;

(d) the overflow line having a first end positioned inside the overflow tank, wherein the overflow line communicates with the withdrawal line;

(e) a liquid line with a first end positioned inside the main tank and a second end positioned outside the main tank, the second end of the liquid line connected to a second vaporizer outside the main tank;

(f) a condensing line having a first end connected to the second vaporizer and a second end connected to the withdrawal line, wherein the condensing line passes through the main tank in contact with the cryogenic liquid in the main tank;

(g) a check valve located between where the vapor line connects to the withdrawal line and where the condensing line connects to the withdrawal line;

flowing liquid cryogen through the liquid line toward the use device and vaporizing the liquid cryogen at the second vaporizer to form a resulting vapor;

passing the resulting vapor through the condensing line and through the main tank toward the use device such that heat is transferred from the resulting vapor to the liquid cryogen in the main tank thereby causing the liquid cryogen in the main tank to expand such that hydraulic pressure in the main tank exceeds a threshold pressure of the first pressure regulator to cause the first pressure regulator to open;

upon the first pressure regulator opening, flowing liquid cryogen out of the main tank through the vapor line and to the overflow tank via the first pressure regulator and the overflow line while the check valve remains closed;

increasing a saturation pressure within the main tank until the check valve opens such that cryogenic fluid flows from the overflow tank and the vapor head toward the use device via the overflow line, the withdrawal line, and the check valve;

causing a saturation pressure in the main tank to equalize to a saturation pressure in the overflow tank as a result of a thermal interconnect between the overflow tank and the main tank while the tank apparatus is in operation, wherein the saturation pressure in the main tank and the overflow tank exceeds a pressure that causes the check valve to open; and

causing cryogenic fluid to flow from one of the overflow tank and the main tank toward the use device through the open check valve to provide a continuous supply of the cryogenic fluid to the use device from the main tank or the overflow tank.

2. The method of claim 1 , wherein the use device is an automobile engine.

3. The method of claim 1 , wherein the cryogenic liquid is liquid natural gas.

4. The method of claim 1 , wherein:

the continuous supply of cryogenic fluid is facilitated by the hydraulic pressure of the main tank when the hydraulic pressure in the main tank is more than the saturation pressure in the main tank; and

the continuous supply of cryogenic fluid is facilitated by the saturation pressure of at least one of the main tank and the overflow tank when the hydraulic pressure in the main tank is one of less than and equal to the saturation pressure in the main tank.