
Bio-electronic device can produce electricity using nothing but humidity - wizardforhire
https://arstechnica.com/science/2020/02/bacterial-proteins-plus-ambient-humidity-renewable-power/
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yread
400W/m^2 would be awesome. Unfortunately, as szielins points out in the
comments it's quite a bit less:

"The devices produce a sustained voltage of around 0.5 volts across a
7-micrometre-thick film, with a current density of around 17 microamperes per
square centimetre." From P = IV, that's .5 V * 17 x 10^-6 A / cm^2, or 8.5
microwatts per square centimeter, or .085 watts per square meter--much more
reasonable.

