In the context of nanotechnology (specifically MNT/molecular manufacturing as described by Eric Drexler in Engines of Creation) "free energy" could refer to pho

In the context of nanotechnology (specifically MNT/molecular manufacturing as described by Eric Drexler in Engines of Creation) "free energy" could refer to photovoltaic panels that cost essentially $0. That may or may not have been the author's intent. It's what I thought of when I read that sentance