Bio-electricity

[kandrathe]

I was merely positing possible ways to harness this energy - with technology still out of reach - without the use of a living host (i.e. animal or human).

We do harness this energy. Such as, Alcohol.

sunlight → plants → sugars + yeasts + water → C2H5OH

C12H22O11 (sucrose) + H2O + invertase → 2 x C6H12O6

C6H12O6 (fructose/glucose) + Zymase → 2 x C2H5OH + 2 x CO2

I think what you are after is a way for machines to metabolize and use energy, and it really doesn't matter what form that energy takes.

Sun → energy → work + potential energy storage (for excess)

For mammals, the potential is stored as lipids, and has an energy density near to coal. Glucose is the active fuel of our cells, and so our bodies regulate a nearly constant supply to keep us running.

Then, when energy levels get low enough another system kicks in;

potential energy → energy → work

In essence then, a simple model would be a solar cell, a battery, a motorized water pump, and a storage tank. When work needs to be done (storage tank is low) a switch turns on the the pump until the tank is filled, meanwhile another system keeps the battery fully charged due to solar power.

I think you are imagining just more complicated versions of that simple closed loop model of energy capture, and energy consumption.