Method and apparatus for determining the amount of hydrogen in a vessel

A method for determining the amount of hydrogen in a hydrogen storage vessel containing a known quantity of hydrogen storage media, while the hydrogen storage vessel is discharging hydrogen, comprising:

• measuring temperature at one or more points on the hydrogen storage vessel and calculating an average temperature for the hydrogen storage media;
• measuring mechanical strain at one or more points on the hydrogen storage vessel and computing the pressure inside the hydrogen storage vessel based on the measured mechanical strain;
• selecting a pressure, composition, temperature (PCT) operating curve from a family of PCT curves for the hydrogen storage media, based on the calculated average temperature;
• selecting an operating point on the selected PCT operating curve, corresponding to the computed pressure inside the hydrogen storage vessel;
• determining a value of hydrogen to metal ratio on the selected PCT operating curve corresponding to the selected operating point;
• and
• computing the quantity of hydrogen in the hydrogen storage vessel by multiplying the looked up hydrogen to metal ratio value by the quantity of hydrogen storage media.

A method for determining change in quantity of hydrogen in a hydrogen storage vessel containing a known quantity of hydrogen storage media in a known initial state, comprising:

• storing initial state parameters, comprising quantity of hydrogen in the hydrogen storage vessel, temperature of the hydrogen storage media at the initial state and pressure inside the hydrogen storage vessel at the initial state;
• measuring temperature at one or more points on the hydrogen storage vessel and calculating an average temperature for the hydrogen storage media;
• measuring mechanical strain at one or more points on the hydrogen storage vessel and computing the pressure inside the hydrogen storage vessel based on the measured mechanical strain;
• selecting van't Hoff parameters by referring to a lookup table for the hydrogen storage media;
• and
• computing the change in quantity of hydrogen using a differential form of van't Hoff relation Δ ⁢ ⁢ x = [ 2 ⁢ Δ ⁢ ⁢ H R ] [ Δ ⁢ 1 T Δ ⁢ ⁢ ln ⁢ ⁢ P ]
• wherein Δx is the change in quantity of hydrogen in the hydrogen storage vessel, Δ ln P is the difference between the pressure inside the hydrogen storage vessel at the initial state and the computed pressure inside the hydrogen storage vessel, Δ{fraction (1/T)} is the difference between reciprocal of the temperature of the hydrogen storage media at the initial state and the reciprocal of the calculated average temperature of the hydrogen storage media, R is the universal gas constant which has a value of 8.314 kiloJoule/kilomole Kelvin, and ΔH is the change in enthalpy of the hydrogen storage media;
• and
• updating the stored initial state parameters with the calculate average temperature, the computed pressure and the computed change in quantity of hydrogen.

A system to determine the quantity of hydrogen in a hydrogen storage vessel containing a known quantity of hydrogen storage media, comprising:

• a means for measuring pressure inside the hydrogen storage vessel;
• a means for measuring temperature at one or more points on the vessel and calculating an average of the measured temperatures;
• and
• a computational means for estimating the quantity of hydrogen in the hydrogen storage vessel;
• wherein the computational means
• selects a pressure, composition, temperature (PCT) operating curve from a family of PCT curves for the hydrogen storage media, based on the calculated average temperature;
• selects an operating point on the selected PCT operating curve, corresponding to the measured pressure inside the hydrogen storage vessel;
• determining a value of hydrogen to metal ratio on the selected PCT operating curve corresponding to the selected operating point;
• and
• computes the quantity of hydrogen in the hydrogen storage vessel by multiplying the looked up hydrogen to metal ratio value by the quantity of hydrogen storage media.