Riding the success of Otto-cycle, lean-burn technology, Winterthur Gas & Diesel has gained a strong foothold in the LNG newbuilding market
It would be hard to argue with the success of WinGD’s X-DF engines, particularly in the LNG shipping sector. Unveiled in 2013 by the Swiss-headquartered engine developer, the X-DF dual-fuel engine series has progressively gained market share in LNG newbuilds, climbing from 50% in 2016 to almost 100% in 2020, according to WinGD director of global sales Volkmar Galke.
“X-DF engines have become the standard solution for the LNG carrier – a ‘no brainer’ for the shipowners and shipyards,” Mr Galke tells Marine Propulsion.
The success of the X-DF has coincided with the rise in orders for newbuildings to meet the future global demand for natural gas. Mr Galke says 233 X-DF engines are on order, with another 50 X-DF engines in operation in LNG carriers.
“It was essential to offer a solution for reducing methane slip which didn’t compromise efficiency”
One shipowner betting on X-DF propulsion in its newbuilds to drive cash flow growth is Gaslog Ltd. This year, it has added three X-DF LNG carriers, Gaslog Windsor, Gaslog Wales and Gaslog Westminster, each with a capacity of 180,000 m3. Gaslog Windsor and Gaslog Westminster are both under long-term charter to Centrica until 2027, while Gaslog Wales is under charter to JERA until 2032. Those ships will be joined by four others, with deliveries through to Q3 2021. All four of those LNG carriers are under log-term charter to Cheniere. Gaslog expects the seven LNG carriers to deliver annual EBITDA of US$145M. Five other Gaslog X-DF propulsion LNG carriers are under long-term charter to Shell, Total and Endesa. Gaslog told investors in September that once fully delivered, its dozen X-DF ships would account for a US$2.5Bn contracted backlog and US$265M EBITDA.
“The main reasons behind the X-DF’s market success in the LNG carrier segment,” says Mr Galke, “are the benefits of the low-pressure gas solution: low capex, low emissions (best solution for preserving air quality) and low energy demand of the auxiliaries.”
Of course, X-DF engines have found success outside the LNG carrier sector; CMA CGM’s recently delivered 23,000-TEU container ship CMA CGM Jacques Saade and its eight sister vessels are each fitted a WinGD 12X92DF main engine.
Based on the lean-burn Otto-cycle combustion principle, in which fuel and air are premixed and burned at a relatively high air-to-fuel ratio, the two-stroke X-DF engines can operate on low loads of gas and are IMO Tier III compliant out of the box, emitting low NOx emissions and virtually no sulphur oxides or particulate matter.
One of the bugbears cited by critics of Otto-cycle low-pressure technology is methane slip. Methane – a potent greenhouse gas – is some 28 times more powerful than CO2 on a 100-year timescale. Researchers at Winterthur Gas & Diesel have been hard at work coming up with a solution to mitigate the engine’s methane slip. At a virtual press conference in June, WinGD unveiled exhaust recycling technology, which it anticipates will reduce methane slip by half while also incrementally improving fuel consumption.
Introduced with its second-generation X-DF 2.0 engine, WinGD’s Intelligent Control Exhaust Recycling (iCER) technology captures the unburnt fuel (methane) before it is ejected through the exhaust, providing the engine a second chance to combust it.
As a result, WinGD is confident its X-DF 2.0 engines will have methane slip levels of about 1.0-1.2 g/kwh, as compared to 2.0-2.5 g/kWh in its first-generation engines. Fuel consumption is also improved by 3% in gas mode and 5% in diesel mode.
“We have reached a level in terms of engine performance and emission that was unthinkable only five years ago,” says Mr Galke. “It was essential to us to offer shipowners a solution for reducing methane slip which didn’t compromise efficiency.”
“With the X-DF 2.0, we have reduced the methane slip by about 50% compared with the previous version,” says Mr Galke. iCER recycles the exhaust gas to reintroduce it into the combustion chamber. “Such gas recirculation then acts as an ‘inert’ gas that slows the combustion, making it more efficient,” he says.
Since the first X-DF engine came into service in 2016, WinGD has gained considerable insight to enable improvements to the engine design. “We pioneered the lean engine combustion applied to low-speed engines,” says Mr Galke. “Today, we can say that we have a solid knowledge of the thermodynamic and the cause-effect of the several parameters that influence the Otto process applied to a low-speed engine.
“The engine performance has been regularly improved until reaching the efficiency of 52%, which is very close to the traditional diesel low-speed engine,” he adds.
Besides capex, when it comes to engines, reliability and lifecycle maintenance are hot-button issues for shipowners. WinGD has made several design improvements to the engine, especially the piston running aspects, to make its reliability comparable to a diesel engine.
Results from the overhaul of the first X-DF-engines in operation have been encouraging.
“The benefits of the low-pressure gas solution: low capex, low emissions”
CSSC Marine Service (CMS), a subsidiary of China State Shipbuilding Corp (CSSC), completed the first major overhaul on two 6X62DF engines on LNG carrier SK Audace while at anchor in Sabine Pass, Texas.
Owned and operated by South Korea’s SK Shipping Co, SK Audace was the first-ever X-DF-powered vessel in operation. Since SK Audace’s delivery in 2017, its X-DF engines have reached 18,000 operating hours, more than 99% of which was in gas operation. The LNG carrier operated on diesel less than 1% during manoeuvring.
During the overhauls, carried out over nine days, no abnormalities were found. The CMS Korea team also observed that the 6X62DF engine parts were in excellent condition compared to engines historically overhauled by CMS that operate on heavy fuel oil (HFO).
Preparing for X-fuels
As shipping transitions towards decarbonisation in the decades ahead, HFO and even fossil LNG will become fuels of the past. Existing LNG-fuelled vessels will need to transition to burning lower carbon-intensive ‘drop-in’ fuels, such as bioLNG or biomethane.
But WinGD does not see these future fuels as a problem for the X-DF technology. “We do not expect any technical or operational issues,” says Mr Galke. “There are already some customers that successfully use biomethane in their X-DF engine without any relevant performance difference compared with fossil methane.”
Adds Mr Galke: “Actually, the use of bioLNG (and synthetic methane from renewable energy) is a scenario that we believe to be one of the most sustainable from an environmental, technical and economical point of view.”
Researchers at WinGD have been conducting testing to validate the application of several alternative fuels – so called ‘X-Fuels’ – examining their injection behaviour and combustibility. “That is then followed with a pilot application to prove the reliability of the fuel before considering introducing it to our engine portfolio,” explains Mr Galke.
Thinking about the future fuel landscape, Mr Galke says: “As an industry, we are still a long way from identifying which fuel or fuel combination will follow or compliment LNG to further pave the way to decarbonisation.”
He concludes: “Our job is not to determine which will be the fuel of the future, but to provide the technology required to ‘digest’ the fuel of choice. That remains our core competence in Winterthur.”