The invention relates to a system and process for electricity generation using steam production by hydrogen combustion, and more particularly to a Rankine Cycle system and process for the generation of electricity using a primary pure hydrogen fuel source for the generation of steam in the boiler system. The Rankine Cycle system and process may also use one or more secondary fuel sources in combination with the primary hydrogen fuel source to supplement the primary pure hydrogen fuel if necessary. Additionally, the inventive system and process can use a flame temperature reducing fluid for lowering bulk flame temperature of a burner in the boiler system to increase equipment life and decrease equipment failure. The inventive Rankine Cycle system and process reduce emissions of carbon dioxide, nitrogen oxides, and other greenhouse gases into the atmosphere, and reduce bulk flame temperatures to increase equipment life and decrease equipment failure.