This was my first rover. It features six wheel drive, suspension, and steering, in addition to differential-drive steering. Trouble was, with all that, it was a bit flimsy once carrying the weight of the solar panel. So I started over.
The topmost picture is the second rover. It was plenty sturdy, but I wasn't happy with its turning. So I started over. MOCpage of the latest rover.
For these rovers, I had to design a solar energy system that could power a Mindstorms robot. Among other things, this involved creating the following devices:
A solar panel. Duh. :)
A recharging energy storage system.
Modifications to the Mindstorms brick to give it a "sleep mode" - an ultra low energy-drain mode where everything is turned off to help the Energycan recharge faster, and when the Energycan is charged, turns everything turns back on to use the stored energy.
Some configurations in which these new electric bricks can be used.