Try
this YouTube video for a look at one approach to a solar-powered hybrid robotic lawn mower. It appears to have a docking station to re-charge the on-board battery, but also a solar PV panel on the mower. Also take a look at
this Google results page.
Not all designs need a sensor wire embedded an inch or so below ground to define the mowing area, but that does seem to be the most cost-effective approach... unless you are mowing a golf course.
A video camera, some image processing software, and perhaps a GPS navigation system might be better adapted to mowing large or irregular areas. You, as a mowing contractor (how else are you going to afford such a system?), could also "train" a "smart" video-based system to remember where to mow each customer's lawn. Your robot mower could probably mow ten or twenty average-sized lawns a day, seven day a week, all summer long. Might earn enough in one season to afford to buy a second mower for the second season, a third mower for the third season... and so on until you make your first million bux and go on to something even more profitable... like maybe building rocket ships to carry tourists back and forth to Moon vacation resorts.
Here in southern Florida grass grows very fast (especially if irrigated) so there is a booming business in lawn maintenance services. A team of three or four, with one or two zero turning-radius riding lawn mowers, takes less than thirty minutes to cut, trim with a weed-eater, and blow away grass clippings on the average sized lot. Not saying these folks are getting feeelthy rich, but it does appear they are making a comfortable living.
