My initial thought about this was that it's using fuel to make electricity, right? Rather than using sunlight/hydro/etc -- kinda like a generator, but without the mechanical aspect?
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Normally to produce electricity from fuel you would spin a turbine, either with a mechanical engine or using vapour. But here the energy is captured through a photo cell, and the author claims that mixing sodium into certain fuels leads to a very significant part of fuel energy going into light at specific wavelength.