The Sonnenschiff solar city in Freiburg, Germany is very much energy positive. The self-sustaining city accomplishes this feat through smart solar design and lots and lots of photovoltaic panels pointed in the right direction.
It seems like a simple strategy -- but designers often incorporate solar installations as an afterthought, or worse, as a label. Designer Rolf Disch, emphasize power production from the start by smartly incorporating a series of large rooftop solar arrays that double as sun shades. The buildings are also built to passive house standards, which allows the project to produce four times the amount of energy it consumes!