TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Methods: Heating the electrolyte in the second mode of operation comprises coupling the extracted heat from the hydrogen compressor to the electrolyte via recirculation of the electrolyte through a heat exchanger. The inventive method further comprises switching between the first and second modes of operation by controlling operation of valves associated with the electrolyzer, the hydrogen compressor, and the heat exchanger to alter flow paths of hydrogen and electrolyte. It includes storing a portion of generated hydrogen from the electrolyzer in a low pressure storage vessel (50); compressing the stored hydrogen via the hydrogen compressor during startup of the electrolyzer; and actively heating the electrolyte at startup of the electrolyzer by extracting heat from the compressed hydrogen to maintain or increase the temperature of the electrolyte. It further includes recuperating heat from an end use system coupled to the integrated hydrogen production and processing system for maintaining a desired temperature of the electrolyte.Preferred Components: The electrolyzer comprises an alkaline electrolyzer, a polymer electrolyte membrane (PEM) electrolyzer, a polybenzimidazole (PBI) electrolyzer, or a solid oxide electrolyzer. The heat exchanger is disposed within the electrolyzer. The circulation system comprises a pump configured to facilitate circulation of the electrolyte through the electrolyzer. The system further comprises a gas-liquid separator coupled to the electrolyzer, configured to receive a hydrogen-electrolyte mixture from the electrolyzer and to separate the electrolyte and the hydrogen from the mixture. It has an oxygen catalyst (54) downstream of the gas-liquid separator, configured to recombine any free oxygen in the hydrogen stream to form water and produce heat. It has a low pressure storage vessel upstream of the hydrogen compressor, configured to store hydrogen generated from the electrolyzer for use during startup of the electrolyzer or while the electrolyzer is in idle mode. It has high pressure storage vessel (52) downstream of the hydrogen compressor, configured to store compressed hydrogen from the hydrogen compressor for use by an end use system. The circulation system comprises valves associated with each of the electrolyzer, hydrogen compressor, and the heat exchanger for controlling the operation of the electrolyzer, hydrogen compressor, and the heat exchanger. The system further comprises a controller (62) configured to control the operation of the valves associated with each of the electrolyzer, hydrogen compressor, and the heat exchanger for transiently heating the electrolyte during different modes of operation. It includes an end use system coupled to the integrated hydrogen production and processing system, being transferred to the electrolyzer for heating the electrolyte to maintain or increase the temperature of the electrolyte. The end use system comprises gas turbine, steam turbine, fuel cell, hydrogen internal combustion engine, or hybrid power generation system.