A steam generator system configured to burn hydrogen and oxygen at stoichiometry along with a increased-pressure water and steam. Said steam generator system comprise a hydrogen source, an oxygen source, a nitrogen source, a water source, a steam source, a hydrogen-oxygen handling unit, a cooling unit, a one or more H2-O2 steam generators and a control unit. Said steam generator system is configured to provide said hydrogen source to said hydrogen-oxygen handling unit through an oxygen passage, said oxygen source to said hydrogen-oxygen handling unit through a hydrogen passage, and said nitrogen source to selectively purge said oxygen passage and said hydrogen passage. Said water source provide water to said cooling unit. Said cooling unit is configured to receive said water source and said steam source.