Systems integrator and equipment maker Rolls-Royce has quietly been adding hybridizing energy-storage packages to a diverse list of vessels. Yet, so, too, has one of its clients — Louisiana-based SEACOR Marine, as it reacts early to tightened emissions and energy-management standards, or EMS, for vessels plying Europe and North America. Fuel savings and energy-company clients seeking green credentials are, it turns out, just part of the upside driving battery retrofits.The fuel savings to be had for keeping thrusters on battery power are a powerful selling point, to be sure.