A fuel, e.g. gasoline, is used to heat an emitting
surface to approximately 1500K, and the emitter in turn radiates
high-energy photons. The PV cells on which this spectrum is
incident converts the photons with energies higher than the
bandgap of the PV cell into electricity. The remaining portion of
the spectrum which cannot be converted is dissipated as heat in
the PV cell.
Using a GaSb PV cell, with a bandgap energy of
0.7eV, (1.7µm in wavelength) requires a filter which passes
photons whose wavelengths are shorter than 1.7 µm to the PV cell
while reflecting the remaining photons back to the emitter.