Analytical expression of electric power was deduced in case of the large-scale
cylindrical thermoelectric tubes exposed to two thermal fluids. The output
powers of the proposed six geometrical arrangements were mathematically solved
from heat transfer theory, and compared with the flat panel systems. The maximum
output was the largest in the ideally cooled systems. In the other realistic
systems, it was the largest for the system of the counter flow with a single
thermoelectric tube. The multiplication of thermoelectric panels can shorten
significantly the device length, although the output from the multi-tubes
decreases only a little. For example, the double helical tubes (T2CH system) can
generate 96 pct output by 35 pct length, compared with the single tube in the
counter flow (T1C system).