New boat engine is environmentally-friendly

A new type of boat propulsion system that reduces emissions, removes the need for oil, has no propeller and reduces noise pollution, means that boating could become a little more environmentally-friendly.

The system, being developed by Hertfordshire-based firm Pursuit Dynamics, works by injecting steam into an elongated funnel-shaped unit under the boat and filled with seawater. The temperature difference between the seawater and the steam cause the steam to condense, resulting in an implosion that draws in water and air through the funnel. This produces a reactive thrust, propelling the boat through the water.

The new system requires no gearbox, which means that it does not need oil, so removing the potential environmental hazard posed by both oil use and disposal. Fewer working parts also mean less noise. There is nothing more than a very low muted sound coming from the steam generator and the pump used to circulate water, Pursuit Dynamics CEO John Heathcote explained to edie.

Heathcote also notes that concern has been expressed about the ecological impact of injecting steam into the water. But he dismisses this. The temperature difference between Pursuit Dynamics’ system and the surrounding water is only 3-5ºC as the volume of steam is very low in comparison to the surrounding water, compared to 800ºC for a turbo diesel engine, he explains. The fact that there is no propeller to damage marine wildlife is also an environmental advantage.

Emissions are also less of a problem with the new engine, Heathcote says. Not only does the system produce fewer emissions, but they are also emitted to the air rather than directly into the water as with more traditional boat engines, he says. However, the system does use fossil fuels to generate the steam, but it could use biofuels, and in the future could be combined with a fuel cell.

“The environmental benefits are greater than anything we can see out there,” he told edie.

Traditional two-stroke boat engines emit 25% of their fuel and oil directly into the water or air. This means that in the US alone marine two-stroke engines spill 15 times more oil and fuel every year into waterways than did the Exxon Valdez, according to the US Environmental Protection Agency. The California Air Resources Board has also found that a seven-hour ride in a recreational boat powered by a two-stroke engine produces the same amount of smog-causing emissions as over 100,000 miles in a passenger car.

Currently, the new Pursuit Dynamics system is being marketed at recreational boats, for both inboard and outboard motors, from 40 horsepower upwards, but it has greater possibilities. “We don’t think there is a size limitation,” said Heathcote.

The system is moving towards commercial realisation. Its latest prototype has recently been verified by the University of Hertfordshire as being capable of running at the same efficiency level as a two-stroke outboard engine. The company is expecting further efficiency improvements in the near future.

“Hitting the two-stroke efficiency level is an important milestone for us as it clearly demonstrates that our technology has the potential to be commercially viable,” said Heathcote. “The ability to reach this efficiency level has been the highest risk associated with this project to date.”

The company’s last challenge before bringing the engine onto the market is to find a suitable lightweight and efficient steam generator. To that end, a number of options are currently being investigated.

And finally, when the propulsion system is released onto the market it will cost less to manufacture and maintain than the equivalent traditional boat engine, says Pursuit Dynamics.

Action inspires action. Stay ahead of the curve with sustainability and energy newsletters from edie