It seems to me people fear solar power...
Yes you can make a robot run on solar power. Like the ones I built sitting on my kitchen table. Check some
BEAM robots out.
No I don't think first will use them. Low power density. Plus, the lights would have to be the correct wavelenght for the cells selected, which would also get expensive. (Different types of cells work better around different wavelengths)
But have faith people.... The energy from the sun at 12:00 noon in Arizona in July can reach 1000 W/m^2. (Here in detroit on a sunny day in the summer it's about 550 W/m^2)
Depending on the type of photovoltaic cell you use, you can get different efficiency. Most crappy terrestial cells give you around 8-12%. But there have been "special" (read: expensive) cells that have gone over 40% efficiency.
by the way... just for fun...
36" by 30" = .70m^2
At 10% eff off of 1000 W/m^2 you would get roughly 70 W.
Of course, everyone would have to wear sunscreen, sun glasses, hats, long pants and sleaves for fear of burning... And we would have to watch the robots for melting...
Oh..... one last thing.... you don't need batteries to store energy. Capacites have come a long way, baby. The Beam bots use regular caps, hybrid electrics can and do use ultra-caps and caps made with aerogels.
Sorry - I've spent some time with my friend, the photovoltaic.