At first glance, it looks like a storage refrigerator you might see in somebody’s garage — and it runs just as quietly. But the GenCell G5rx is a hydrogen fuel cell generator that is part of a compact system using the latest technology to help companies like San Diego Gas & Electric reduce disruptions during power outages. “When the grid is off, this is on,” said Gil Shavit, chairman of GenCell, the company that has contracted to deliver more than two dozen G5rx systems to SDG&E.