For instance, the DLR in Germany is flying an EC 135 testbed with full "fly by light" system.
Is that not just a fancy way of saying 'solar powered' ?
I guess if it was the blades that had the solar panels on them, in flight the whole area of the disc becomes a large receptor which becomes vastly larger than the 4/5 individual blades themselves.
As shown in the pic below, instead of just the surface area of the 4 blades themselves producing the electricity, you'd have a panel the size of the red area as shown here;
or you could have a rotor system something like this to accomodate the solar panels;
But I guess the size and number of the batteries required would be the limiting factor for practical use, hence it's only on a testbed....for now.
But where do you stop?
Thermal power units that take the heat from the leading edges or maybe even little wind turbines along the leading edges topping up the batteries, the possibilities are endless... !