The world’s most efficient engine becomes a colossal generator of clean energy

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

This Finnish company is famous for making the world’s largest combustion engines, notably the 27-metre-high, 44-metre-long, 110,000-hp RTA96-C. The Wärtsilä 31 engine is slightly smaller, measuring just 4.7 metres high and 8.7 metres long. It runs on fossil fuels and can generate up to 13,142 hp (9,800 kW).

The cylinder bore and stroke (31 x 43 cm) sound enormous if you come from a car or motorcycle background, but compared to some of the company’s larger engines, with cylinders big enough to fit a person in, they are relatively compact.

Converted into a generator, the 31SG-H2 version can run on natural gas, or a mixture of natural gas and 25% hydrogen, or 100% hydrogen, making it the world’s largest hydrogen generatorA second flex-fuel 31H2 will run on all hydrogen, a blend of hydrogen and natural gas, or natural gas alone.

It is designed for supporting clean energy sources intermittent power sources such as solar and wind, with no minimum uptime or downtime and the ability to ramp up and synchronise with the grid in just 30 seconds, at the push of a button. By using hydrogen, Wärtsilä can generate 100% carbon-free electricity.

Anders Lindberg, President of Wärtsilä Energy, said: “We need to be realistic that natural gas will play a role in our energy systems for years to come. Our flex-fuel engines can use natural gas today to provide flexibility and balance, allowing renewable energy to thrive. They can then be converted to run on hydrogen when it becomes available, paving the way for the journey to net zero.”

Wärtsilä’s power plant concept has been granted Phase 1 certification by TÜV SÜD, ensuring regulatory compliance. It must pass two more certifications before production can begin. Hydrogen-ready engines are expected to be delivered in 2026. It remains to be seen how efficiently this huge machine could operate and how it might compare in terms of long-term economics on an industrial scale to a large fuel cell, which could convert hydrogen back into electricity and water.

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