Nvidia has put its name behind a fledgling effort to put mini-data centers beside people’s homes in boxes that look like HVAC units. It’s a “power” play, considering that the main bottleneck to building out more data center capacity is not money or chips, but rather retrofitting the electrical grid to supply the power. The idea, put forward by a California smart utility box company called Span, is to put the GPUs where the power has already been…