Active venting control system for hydrogen fuel tanks

A liquid hydrogen tank module assembly, comprising:

• a module housing;
• a liquid hydrogen fuel tank within the housing and configured to contain liquid hydrogen at cryogenic conditions and gaseous hydrogen in a headspace above the liquid hydrogen, wherein the hydrogen fuel tank has a tank volume;
• a plurality of sensors operatively coupled to the hydrogen fuel tank and configured to measure a liquid temperature, a vapor temperature, a tank pressure, and a hydrogen mass, wherein the liquid temperature is a temperature reading of the liquid hydrogen, wherein the vapor temperature is a temperature reading of the gaseous hydrogen, wherein the tank pressure is a pressure reading of an interior of the hydrogen fuel tank, and wherein the hydrogen mass is a total mass of the liquid hydrogen and the gaseous hydrogen;
• a passive pressure relief valve coupled to the interior of the hydrogen fuel tank and configured to automatically move to a first open position when the tank pressure exceeds a relief pressure threshold;
• and
• an active venting control system coupled to the hydrogen fuel tank, the active venting control system comprising:
• an active venting valve operatively coupled to the hydrogen fuel tank and being in communication with the gaseous hydrogen, the active venting valve being movable between a closed position and a second open position;
• and
• a controller configured to receive outputs from the sensors and calculate a vapor density based on the vapor temperature and the tank pressure, a liquid density based on the liquid temperature and the tank pressure, an average density based on the hydrogen mass and the tank volume, and an effective fill level based on the vapor density, the liquid density, and the average density,
• wherein the controller is configured to move the active venting valve from the closed position to the second open position when the effective fill level exceeds an initial fill level threshold, and move the active venting valve to the closed position when a secondary threshold is reached after reaching the initial fill level threshold.

A liquid hydrogen tank assembly, comprising:

• a liquid hydrogen fuel tank configured to contain liquid hydrogen at cryogenic conditions and gaseous hydrogen in a headspace above the liquid hydrogen, wherein the hydrogen fuel tank has a tank volume;
• a plurality of sensors operatively coupled to the hydrogen fuel tank and configured to measure a liquid temperature, a vapor temperature, a tank pressure, and a hydrogen mass in the tank;
• and
• an active venting control system coupled to the hydrogen fuel tank, the active venting control system comprising:
• an active venting valve operatively coupled to the hydrogen fuel tank and being in communication with the gaseous hydrogen, the active venting valve being movable between a closed position and an open position;
• and
• a controller configured to receive outputs from the sensors and calculate a vapor density based on the vapor temperature and the tank pressure, a liquid density based on the liquid temperature and the tank pressure, an average density based on the hydrogen mass and the tank volume, and an effective fill level based on the vapor density, the liquid density, and the average density,
• wherein the controller is configured to cause the active venting valve to move from the closed position to the open position when the effective fill level exceeds an initial fill level threshold, and the controller is configured to cause the active venting valve to move the active venting valve to the closed position when a secondary threshold is reached after reaching the initial fill level threshold.