The Wärtsilä 31 engine is in the Guinness Book of World Records for being the most efficient 4-stroke marine engine ever made in its class. It also boasts the highest power per cylinder in engines of equivalent bore size. It can be configured in 8 to 16 cylinders and with a power output ranging from 4.6 MW to 10.4 MW at 720 and 750 rpm.

This Finnish company is best known for making the world's largest combustion engines – notably the 89 ft (27 m) tall, 44 ft (13 m) long, 110,000 horsepower RTA96-C. The Wärtsilä 31 engine is a fair bit smaller, maxing out at 15.4 ft (4.7 m) high and 28.8 ft (8.7 m) long, and running on fossil fuel, it can crank out up to 13,142 horsepower (9,800 kW).

The cylinder bore and stroke (12.2 x 16.9 inches, or 31 x 43 cm) sound enormous if you're coming from the auto/moto world, but compared to some of the company's bigger engines, which have cylinders big enough to walk into, they're relatively compact.

Converted to a generator, the hydrogen-ready 31SG-H2 version can run on natural gas, or a blend of natural gas and 25% hydrogen – or it can be upgraded to run on 100% hydrogen. There's also a flexible-fuel 31H2 designed to run natively on full hydrogen, but also accepting natural gas or blended fuels.

Both promise to be the world's largest hydrogen-powered generators when rolled out – assuming there's enough hydrogen available to run them.

The hydrogen power station is designed for firming up a renewables-based grid, quickly ramping up or down to support intermittent clean energy sources such as solar and wind, with no minimum up or downtime and the ability to ramp up and synchronize with the power grid in as little as 30 seconds with the push of a button. By using hydrogen, Wärtsilä can generate electricity 100% carbon-free.