To power the building, Blee and Halligan hooked up two solar panels—though not without difficulty. "The roof faces the wrong way—north—so we couldn't mount the panels on it," Blee says. Instead, they affixed the two 1.5-by-1.5-foot solar arrays to a nearby existing wall and ran cables back to the structure. To increase efficiency by not having to convert the 12-volt power coming from the panels to higher, more appliance-friendly wattage, the architects installed 12-volt light fixtures throughout. "You can't plug a laptop into the wall, but it's a more simple and robust system: just two panels wired into the battery," Blee says.  Photo 1 of 6 in A Couple Restores a Seemingly Hopeless Mill in France