NOVELTY - A carbon dioxide energy source apparatus has solid oxide fuel cell (10), in which carbon dioxide is cracked into carbon monoxide and water, and solid oxide fuel cell (11). Overall chemical reaction in fuel cell (10) is performed as follows. Hydrogen (gaseous form) and carbon dioxide (gaseous form) are reacted, to obtain water (gaseous form) and carbon monoxide (gaseous form). Overall chemical reaction in fuel cell (11) is performed as follows. Carbon monoxide (gaseous form) and half mole of oxygen (gaseous form) are reacted, to give carbon dioxide (gaseous form).    USE - Carbon dioxide energy source apparatus is used in solid oxide fuel cell-carbon dioxide-energy conversion cycle (claimed).    ADVANTAGE - The solid oxide fuel cell-carbon dioxide-energy conversion cycle is performed using the apparatus, without emission of carbon dioxide.    DETAILED DESCRIPTION - A carbon dioxide energy source apparatus has solid oxide fuel cell (10), in which hydrogen is introduced to anode (A1), carbon dioxide is introduced to cathode (A2), carbon dioxide is cracked into carbon monoxide and water, and a solid oxide fuel cell (11) connected in series to the solid oxide fuel cell (10). In anode (A1), hydrogen (gaseous form) gives hydrogen (anode), which in turn gives two protons (anode) and 2 electrons, and the obtained two protons (anode) and oxide ion (anode) are reacted, to obtain water (gaseous form). Overall chemical reaction at anode (A1) is performed as follows. Hydrogen (gaseous form) and oxide ion (anode) are reacted, to obtain water (gaseous form) and two electrons. Main chemical reaction at cathode (A2) is performed as follows. Carbon dioxide (gaseous form) gives carbon dioxide (cathode), which in turn gives carbon monoxide (cathode) and half mole of oxygen (cathode). The carbon monoxide (cathode) gives carbon monoxide (gaseous form). Half mole of oxygen (cathode) and two electrons are reacted, to obtain oxide ion (cathode). Main chemical reaction in an electrolyte of solid oxide fuel cell (10) is oxygen ion conduction, which is performed as follows. Oxide ion (cathode) gives oxide ion (anode). Overall chemical reaction in the solid oxide fuel cell (10) is performed as follows. Hydrogen (gaseous form) and carbon dioxide (gaseous form) are reacted, to obtain water (gaseous form) and carbon monoxide (gaseous form). The carbon monoxide generated in solid oxide fuel cell (10) is introduced to anode (B1) of the solid oxide fuel cell (11), and carbon dioxide (after power generation) generated in solid oxide fuel cell (11) is introduced into the cathode (A1). Main chemical reaction at anode (B1) is performed as follows. Carbon monoxide (gaseous form) gives carbon monoxide (anode), which is reacted with oxide ion (anode), to give carbon dioxide (anode) and two electrons. Main chemical reaction at cathode of solid oxide fuel cell (11) is performed as follows. Half mole of oxygen (gaseous form) gives half mole of oxygen (cathode) and two electrons, which in turn gives oxide ion (cathode). Main chemical reaction in electrolyte of solid oxide fuel cell (11) is oxygen ion conduction, which is performed as follows. Oxide ion (cathode) gives oxide ion (anode). The overall chemical reaction in solid oxide fuel cell (11) is performed as follows. Carbon monoxide (gaseous form) and half mole of oxygen (gaseous form) are reacted, to give carbon dioxide (gaseous form). An INDEPENDENT CLAIM is included for method for using carbon dioxide energy source.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the carbon dioxide energy source apparatus.    Solid oxide fuel cells (10,11)