I worked on a software design project a year or two ago that was exploring the user interface and incentive mechanisms for the consumer side of such a scheme.

I worked on a software design project a year or two ago that was exploring the user interface and incentive mechanisms for the consumer side of such a scheme. This was for one of the big-3 German automakers and the company running a significant portion of Europe's energy grid. It's still a while off, but it is a serious project with the intend to get to market. I'm no expert on the grid side, but if I'm not mistaken, the need just isn't quite there yet because the grid have been able to accommodate current renewable production levels.