NOVELTY - Controlling a process for generation of hydrogen by reforming a hydrocarbon-containing feed at elevated temperature in the presence of water involves generating hydrogen at rate within a first rate to accumulate hydrogen in the reservoir, changing the rate of hydrogen generation to a second rate insufficient to maintain the first amount of hydrogen, and changing the rate of hydrogen generation to a rate within the first rate.    USE - For controlling a process for generation of hydrogen and for generating electrical power (claimed) useful for residential uses including for electricity generation and vehicle refueling, small-scale hydrogen distributors or for small chemical processes.    ADVANTAGE - In the control methods, the rate of hydrogen generation is not directly related to demand for hydrogen. Hence, peak hydrogen demands may be satisfied without requiring large hydrogen generator capacities. And the sophistication of control for chemical reaction unit operations that must be performed by the hydrogen generator can be minimized without undue sacrifice in economy of operation or hydrogen product quality. The reservoir contains sufficient hydrogen for use on an episodic basis such as for refueling quickly an automobile, and the used hydrogen can be replaced over time by the operation of the hydrogen generator once the reserve of hydrogen falls below a predetermined amount. The capacity of the reservoir may be relatively small and sized only to accommodate the time for the transition between the rate within the second (net production loss) rate range and the rate within the first (net hydrogen make) rate range. Thus, the amount of hydrogen storage can be nominal and lags in turn-up response by the hydrogen generator can be tolerated while still fully supplying hydrogen demand. The hydrogen generator need only be operated within rate ranges. The methods are relatively insensitive to the conditions of the raw materials and the hydrogen generator. There is no need for the hydrogen generator to precisely and reproducibly meet a hydrogen production rate specification. Indeed, so long as the first rate is net hydrogen make rate and the second rate is a net production loss rate, subject to maintaining product quality, the absolute production rate within each range is relatively immaterial. The control for the fuel cell can be independent of the control for the hydrogen generator thereby reducing complexity.    DETAILED DESCRIPTION - Controlling a process for generating hydrogen involves:    (a) generating hydrogen at a rate within a first rate range sufficient to accumulate hydrogen in the reservoir;    (b) upon a predetermined first amount of hydrogen being accumulated in the reservoir, changing the rate of hydrogen generation to a rate within a second rate range insufficient to maintain the first amount of hydrogen in the reservoir; and    (c) upon a predetermined second amount of hydrogen being in the reservoir, the second amount being less than the first amount, changing the rate of hydrogen generation to a rate within the first rate range.    The hydrogen is generated by reforming a hydrocarbon-containing feed at elevated temperature in the presence of water to produce a reformate containing carbon monoxide (at least 3 vol.% on dry basis), reducing the carbon monoxide content of the reformate to provide a purified hydrogen product having less than 100 ppm by volume of carbon monoxide (dry basis), maintaining a reservoir of hydrogen from reforming, and withdrawing hydrogen from the reservoir.    INDEPENDENT CLAIMS are included for the following:    (1) controlling a combined process for generating hydrogen and using hydrogen for generating electrical power involving step (A) - (C). The hydrogen is generated by reforming the hydrocarbon-containing feed, providing the reformate at a pressure and temperature for pressure swing adsorption to obtain a purified hydrogen stream, recovering hydrogen from the reformate by pressure swing adsorption to provide a purified hydrogen product stream containing at least 98 vol.% hydrogen and less than 100 ppm by volume of carbon monoxide (dry basis) at least a portion of which purified hydrogen product stream is used to generate electrical power by reaction with oxygen in a fuel cell and to provide a purge stream containing hydrogen and carbon monoxide at least a portion of which purge stream is combusted to provide heat for the reforming, and maintaining a reservoir of the purified hydrogen product stream;    (2) generation of hydrogen involving reforming a hydrocarbon-containing feed at elevated temperature in the presence of water and nitrogen and oxygen-containing gas so that a portion of the feed is partially combusted to provide heat for reforming to produce a reformate containing water, hydrogen, nitrogen, carbon dioxide and at least 3 vol.% (dry basis) carbon monoxide, providing the reformate at a pressure and temperature for pressure swing adsorption to obtain a purified hydrogen stream, recovering from the reformate during an adsorption cycle of a pressure swing adsorber hydrogen a purified hydrogen product stream containing at least 98 vol.% hydrogen and less than 100 ppm by volume of carbon monoxide (dry basis) and provide during a purge cycle a purge stream containing nitrogen, carbon dioxide, hydrogen and carbon monoxide at least a portion of which purge stream is combusted to provide heat for the reforming, in which the rate of hydrogen production is changed from a first rate to a second rate and a substantially constant pressure swing cycle time is maintained for the adsorption at each such rate and the purity of the purified hydrogen stream varies.