Analytical expression of electric power was deduced in case of the large-scale thermoelectric device that consists of the cylindrical double tubes like roll cake and is exposed to the two thermal fluids. The output powers of 16 systems were mathematically described by the simultaneous equations based on heat exchange. The temperature profiles in the device depend on the flow directions of hot and cold fluids, but the flow directions did not change the output power. Resultantly, eight sets of solutions for the output power were deduced. The maximum output power was the largest in the two systems (V2CC-I and V2CC-II system), where two fluids flow in counter directions and one of the fluids goes into the system from the inside of the inner cylinder. These chosen systems can generate the thermoelectric power equivalent with the single cylinder system (V1C system) using only 36% material of V1C.