Instead of stepped gears like a conventional transmission, it has a fixed planetary gear, and changes engine speed by adjusting the generator electric load.
Babcock builds smaller nuclear units of 100 megawatts, which can also be aggregated together to supply as much power as a base-load nuclear generator, or 1, 000 megawatts.
Neither solar nor wind are powerful enough to carry the heavy load that a backup generator must provide to a facility such as a hospital or a school or a county prison.