well, they didn't take into account the energy produced by the ambient temperature (the exact temperature was not mentioned in the article, and the paper is behind a paywall, but they do say it was rather high)
> [it] instead took advantage of small amounts of excess heat to emit more power than consumed. This heat arises from vibrations in the device’s atomic lattice, which occur due to entropy.
> [it] instead took advantage of small amounts of excess heat to emit more power than consumed. This heat arises from vibrations in the device’s atomic lattice, which occur due to entropy.