TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Method: The method further comprises determining a target hydrogen mass flow rate mset for the volume of hydrogen produced by the hydrogen generator corresponding to iset; operating the hydrogen generator at an output level enough to produce a hydrogen mass flow rate approximating mset; controlling the amount of current drawn from the fuel cell; generating a hydrogen consumption control command based on a comparison of the measured pressure of the hydrogen within the flow path and pset; providing a power converter for controlling the amount of current drawn from the fuel cell, where the hydrogen consumption control command is delivered to the power converter; adjusting the rate of hydrogen consumed by the fuel cell at enough frequent intervals to ensure that the pressure of the volume of hydrogen in the flow path is between a minimum and a maximum pressure value; separating the output of the hydrogen generator into a hydrogen enriched gas stream delivered through the flow path to the fuel cell and a hydrogen depleted gas stream used to regulate the temperature of the hydrogen generator; and measuring the operating temperature of the hydrogen generator and adjusting the value of pset depending upon the measured operating temperature of the hydrogen generator. The hydrogen generator is operated at a hydrogen output level enough to enable the fuel cell to produce a current approximating the target output current iset by, measuring the current igross outputted by the fuel cell; generating a fuel supply control command based on a comparison of iset and igross; and delivering fuel from the fuel supply subsystem to the hydrogen generator in an amount corresponding to the fuel control command. It is also operated at a hydrogen output level enough to produce a hydrogen mass flow rate approximating mset by, measuring the current igross outputted by the fuel cell; estimating the mass flow rate of the volume of the hydrogen based on the measured pressure of the volume of the hydrogen and the measured current igross outputted by the fuel cell; generating a fuel supply control command based on a comparison of mset and the mass flow rate estimated above; and delivering fuel from the fuel supply subsystem to the hydrogen generator in an amount corresponding to the fuel supply control command. The hydrogen consumption control command is delivered to the fuel cell for controlling the amount of hydrogen consumed by the fuel cell. The amount of hydrogen consumed by the fuel cell is adjusted when the measured pressure of the hydrogen in the flow path differs from pset by a predetermined amount, and adjusted continuously as the measured pressure of the hydrogen in the flow path differs from pset.Preferred Condition: The hydrogen mass flow rate is estimated using a mathematical expression: min = (VdivideRasteriskT)asteriskdPdividedT + mout, where mout = nc - igrossdivide2asteriskF, and where min is the estimated mass flow produced by the hydrogen generator, mout is the estimated mass flow of hydrogen consumed by the fuel cell, V is the volume of hydrogen within the vessel, R is the universal gas constant, T is the temperature of the vessel, dPdividedt is the time rate of change of pressure in the vessel, nc is the number of cells in fuel cell stack, igross is the gross current produced by the fuel cell, and F is Faradays constant. Preferred Component: The hydrogen generator is a reformer. The hydrogen delivery vessel is an accumulator for storing a portion of the volume of the hydrogen at pressure. The hydrogen separator is a palladium membrane hydrogen separator. The first controller is a PID (sic) controller.