NOVELTY - Exhaust heat utilizing hydrogen-oxygen system has water vapor-electric power-generating unit (1), exhaust heat utilizing heat electric power generating unit (5), water electrolysis unit (10), pure hydrogen liquefier (16) and oxygen liquefier (12), nitrogen re-liquefier (17) and liquid hydrogen storage tank (18) and liquid oxygen storage tank (14). The water electrolysis unit has a water purifier (13) for supplying pure water (25).    USE - Used as a power source for motor vehicles.    ADVANTAGE - The exhaust-heat utilizing hydrogen-oxygen system manufactures liquid hydrogen and oxygen, without ejection of carbon dioxide.    DETAILED DESCRIPTION - An exhaust heat utilizing hydrogen-oxygen system has a water vapor-electric power-generating unit (1), an exhaust heat utilizing heat electric power generating unit (5), a water electrolysis unit (10), a pure hydrogen liquefier (16) and an oxygen liquefier (12), a nitrogen re-liquefier (17), and a liquid hydrogen storage tank (18) and a liquid oxygen storage tank (14). The water electrolysis unit has a water purifier for supplying pure water. Water vapor and electric power are produced in the water vapor-electric power-generating unit. Electric power and coolant (23) are produced in the exhaust heat utilizing heat electric power generating unit using an operating medium having a boiling point lower than water and exhaust gas from the water vapor-electric power-generating unit. The electric power from the water vapor-electric power-generating unit and the exhaust heat utilizing heat electric power generating unit are purified in the water purifier and electrolyzed in the water electrolysis unit. The hydrogen gas and oxygen gas from the water electrolysis unit are cooled and liquefied in the respective liquefiers using coolant produced in the exhaust heat utilizing heat electric power generating unit, and stored in the respective storage tanks. The cooled hydrogen gas (30, 34) is liquefied again in the nitrogen re-liquefier, by circulating liquid nitrogen (31).    An INDEPENDENT CLAIM is also included for the manufacture of liquid hydrogen involving pressurizing liquid hydrogen (33, 35) stored in the liquid hydrogen storage tank of an exhaust-heat utilizing hydrogen-oxygen system, and carrying out adiabatic expansion to obtain liquid hydrogen. The hydrogen-oxygen system comprises a water vapor-electric power generation unit with a steam-generating unit (2), water vapor turbine (3) and generator (4), and an exhaust-heat utilizing cooling-heating electric power generating unit with an absorption refrigerator (9), operating medium steam generation unit (6), operating medium steam turbine (7) and generator (8).    DESCRIPTION OF DRAWING(S) - The figure shows the structure of the exhaust-heat utilizing hydrogen-oxygen system. (Drawing includes non-English language text).    Water vapor-electric path generating unit (1)    Steam generating unit (2)    Water vapor turbine (3)    Generator (4,8)    Exhaust-heat utilizing cooling-heating electric power generation unit (5)    Operating medium steam generating unit (6)    Operating medium steam turbine (7)    Absorption refrigerator (9)    Water-electrolysis unit (10)    Heat exchanger (11,15)    Oxygen liquefier (12)    Water purifier (13)    Liquid oxygen storage tank (14)    Pure hydrogen liquefier (16)    Nitrogen re-liquefier (17)    Liquid hydrogen storage tank (18)    Coolant (23)    Pure water (25)    Liquid oxygen (27,29)    Hydrogen gas (30,34)    Liquid nitrogen (31)    Liquid hydrogen (33,35)