Wärtsilä 32 Methanol Engine: A Familiar Four-Stroke Takes On Future Fuel

Credits: Tim Mossholder/ Unsplash
  • The well-proven four-stroke engine platform, introduced in the 1980s, is reimagined as a flexible-fuel prime mover with the ability to burn green methanol.
  • Wärtsilä has also developed retrofit solutions that will allow those engines to burn methanol, leveraging its past experience with Stena Germanica. 
  • Global production of methanol stands at about 100M tonnes, of which about one-third is traded globally.

Over the next few years, shipowners will have a widening array of available two- and four-stroke, dual-fuel engines capable of burning methanol, underpinning the alternative fuel’s uptake in the marine sector.

Four-stroke take on Future fuel

One of those choices will be the four-stroke Wärtsilä 32 Methanol dual-fuel engine, available in 2023. If the Wärtsilä 32 Methanol sounds familiar to you, it should; it is based on the popular Wärtsilä 32 (W32) engine platform which was first introduced in the 1980s, and has been a popular choice for ferries, offshore support vessels, drillships, icebreakers, tugs, dredgers and fishing vessels, either as a prime mover or marine genset. There have been more than 5,300 W32s sold to the marine market, according to the enginebuilder.

Testing blue methanol

This well-proven platform is being combined with years of experience gained in the operation of the ropax ferry Stena Germanica, the first vessel to be retrofitted to operate on methanol. Stena Germanica’s Wärtsilä Z40 engines have been operating on methanol since 2015. 

This includes a milestone testing of blue methanol, produced with CO2 emissions captured from the steel industry, under an EU-funded FReSMe project in 2021.

Flexible fuel engine

Calling the W32 Methanol platform “dual fuel” might be a misnomer because this flexible fuel engine is capable of operating on methanol, light fuel oil, liquid biofuels and heavy fuel oil. 

The cylinder bore will be 320 mm, with a piston stroke of 400 mm, mean effective pressure of 29 bar and an output of 580 kw per cylinder at 750 rpm. 

Available in six, seven, eight, nine, 12 and 16 cylinders, the W32 Methanol engine is IMO Tier III compliant, with a selective catalytic converter (SCR). 

Fuel injection will be handled by common rail injection in methanol mode and jerk pump in diesel mode.

Methanol reducing emissions

Speaking during the Wärtsilä 32 Methanol launch webinar last year, Fredric Sunabacka, product manager for Wärtsilä 32 and 34 engines, pointed out some of the benefits of choosing a methanol as a fuel pathway to decarbonizing international shipping. “Methanol significantly reduces emissions compared to LFO,” said Mr Sunabacka. 

“The Wärtsilä 32 Methanol engine provides a 92% reduction in CO2 with green methanol and a 50% reduction in NOx from the IMO Tier II level. There is also no SOx or particulate matter from methanol combustion.”

Methanol Institute chief operating officer Chris Chatterton noted these favourable environmental benefits of burning methanol are leading to global intergovernmental agency, International Renewable Energy Association (IRENA), forecasting a large uptake in the production of biomethanol and later e-methanol.

Global methanol production

“We’re now looking at projections of over 3M tonnes of forecasted production of both blue and green methanol by 2024,” said Mr Chatterton. 

“Methanol is fairly competitive on an energy content basis with conventional fuels, as well as LNG. We expect that with the scale-up of low-carbon and carbon-neutral methanol, we’ll see prices begin to fall,” he said. 

Global production of methanol stands at about 100M tonnes, of which about one-third is traded globally. Global production of methanol is expected to increase five-fold to 500M tonnes by 2050, close to 80% of which will either be biomethanol or e-methanol.

Green methanol-fueled newbuilds

In some of the first applications of methanol dual-fuel variable-speed main engines, four new heavy-lift newbuilds under construction at Wuhu Shipyard will be equipped with Wärtsilä 32 Methanol main engines in hybrid-battery applications.

Being built for German special project cargo specialist SAL Heavy Lift GmbH, the 149.9 m, 14,600-dwt heavy-lift vessels are scheduled for delivery in 2025, for use in supporting offshore wind farm installations.

SAL Heavy Lift chief executive Dr. Martin Harren said when the ships are delivered, “they will feature outstanding environmental performance and help guide shipping towards a greener future.”

Each of the ships will have a hybrid-battery system with Energy Storage, a power take-off/power take-in (PTO/PTI) generator and motor, multidrive converter, and Wärtsilä Energy Management System for controlling and optimizing the hybrid operations. 

The Energy Storage system will be based on Lithium-Titanium-Oxide (LTO) batteries, which can handle higher amounts of deep cycles than normal Lithium-Ion-based systems, says Wärtsilä. 

It is anticipated that the ESS will significantly reduce fuel consumption and minimize engine load fluctuations through peak shaving during operations in heavy seas.

Increase in global production

At a service speed of 15 knots, Sal Heavy Light anticipates these Orca-class vessels will consume significantly less than 20 tonnes of fuel oil per day – similar to far smaller-sized and geared MPP vessels. 

Alternatively, the company says, the heavy-lift vessels will be able to trade at a slow, ultra-efficient speed of 10 knots, consuming just six tonnes of fuel oil per day, with the capability of reaching a maximum speed of 18.5 knots for urgent deliveries.

If green methanol produced with renewable energy becomes available towards the end of 2030, the Jumbo-SAL-Alliance will be able to offer its customers carbon-neutral transport solutions

Retrofit possibilities

Mindful of the number of legacy four-stroke W32 and Z40 engines still operating, Wärtsilä has also developed retrofit solutions that will allow those engines to burn methanol, leveraging its past experience with Stena Germanica. 

The Finnish engine builder estimates about 2,000 W32 engines can be converted to burn methanol. 

Conversion technology is already available for the W32 and Z40S, with W20 units coming in 2024 and W46F/FDF platforms in 2025.

The scope of such retrofits would cover engineering, including the concept design of vessel integration, system design, detailed design of the engine conversion, conversion of the engines, methanol fuel handling and supply system components, control and sealing oil unit, the engine automation system, installation of the engines, commissioning, testing and project management.

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Source: Riviera


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