  I propose a design strategy to enhance the performance of heat engine via
absorption of thermal energy from the channel region. The absorption of thermal
energy can be actuated by inelastic processes and may be accomplished by an
energy restrictive flow of electrons into the channel. The proposed design
strategy employs dual energy filters to inject and extract electrons through
the contact to channel interface. The first filter injects a compressed stream
of electrons from the hot contact, at an effective temperature much lower than
the channel temperature. The compressed stream of injected electrons, then,
absorb energy via inelastic scattering inside the channel and are finally
extracted via a second filter at the cold contact interface. Rigorous
mathematical derivations demonstrate that an optimized performance for the
proposed design strategy demands the implementation of a box-car transmission
function at the electron injecting terminal and a unit-step transmission
function at the electron extracting terminal. Numerical simulation show that in
the proposed design strategy, the heat engine performance, under optimal
conditions, can surpass the ballistic limit when the required output power is
low compared to the quantum bound. The proposed concept can be used to
construct high efficiency thermoelectric generators in situations where the
source of usable heat energy is limited, but insulated from environmental
dissipation.
