What The Heck Does GM Have Plugged Into This Birmingham Building?

We know it's part of GM's Woodward Dream Cruise hoopla as it's at the Birmingham "triangle" next to the 555 building, and we're assuming it's got something to do with the Chevy Volt — but we're not sure what exactly the plug's for. Anyone have any thoughts? A close-up shot after the jump.

What The Heck Does GM Have Plugged Into This Birmingham Building?