Why don't we use our own light production at night (I mean home, buildings, streets,..., lighting) to charge photovoltaic panels instead of wasting it?
Answer
Solar panels work with sunlight. The energy per square meter of light from the sun , depending on the geographic area etc is of order of
8 hour summer day, 40 degree latitude 600 Watts per sq. meter
In one hour a photovoltaic cell of one square meter will provide energy of 600 watthours
Take a light bulb of 100 Watthour . To gather all that irradiance one would need to cover all the walls of the room with photovoltaics, which typically are 30% efficient. So one would gather 30 watthour of that "wasted energy" for an enormous cost in photovoltaics. ( disregarding that photovoltaics should be specially developed for low intensity conditions and as pointed out in the comments that a lot of that energy is in the infrared spectrum ).
In analogy will be the economics for other situations, Take a stadium with its large light sources, the power falls as $1/r^2$, where r is the distance between the light source and the panels.
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