Ready to soak up some more solar energy? Last week we looked at Sandia Labs’ 8-acre heliostat field, in which hundreds of huge mirrors bounce the desert light onto a single tower. Their cumulative reflected light adds up to 400 suns’ worth of radiation, enough to produce 1 megawatt of electricity via an industrial thermal generator. Whew!

Today we’re shifting scales from the massive to the subatomic: instead of measuring energy in suns, we’ll measure it in photons. This is the level on which photovoltaic cells operate, one photon at a time energizing one electron at a time. How do solar panels convert rays of sunlight into a usable electrical current?