  Thin-film thermoelectric generators with a novel folding scheme are proposed
for large-area, low energy-density applications. Both the electrical current
and heat transfer are in the plane of the thermoelectric thin-film, yet the
heat transfer is across the plane of the module - similar to conventional bulk
thermoelectric modules. With such designs, the heat leakage through the module
itself can be minimized and the available temperature gradient maximized.
Different from the previously reported corrugated thermoelectric generators,
the proposed folding scheme enables high packing densities without compromising
the thermal contact area to the heat source and sink. The significance of
various thermal transport, or leakage, mechanisms in relation to power
production is demonstrated for different packing densities and thicknesses of
the module under heat sink-limited conditions. It is shown that the power
factor is more important than ZT for predicting the power output of such
thin-film devices. As very thin thermoelectric films are employed with modest
temperature gradients, high aspect-ratio elements are needed to meet the -
usually ignored - requirements of practical applications for the current. With
the design trade-offs considered, the proposed devices may enable the
exploitation of thermoelectric energy harvesting in new - large-area -
applications at reasonable cost.
