Given these results and using the commonly accepted 100-year global warming potential factor for methane, WinGD’s X-DF engines show a 15% improvement in total GHG emissions (including methane) compared to corresponding Diesel engines running on marine diesel oil. Combined with local pollution reductions – around 40% for particulate matter, 99% for sulphur oxides and 90% for nitric oxides (without aftertreatment, unlike high-pressure engines) – the environmental credentials of X-DF engines are apparent.
The GHG emissions reduction of fossil LNG is not of a magnitude to satisfy upcoming marine regulations, notably IMO’s ambition of reducing emissions by at least 50% by 2050 (compared to 2008 levels). But the eventual use of renewable, non-fossil LNG will make this step possible. In the meantime, X-DF technology makes vessels ready to take that step. And the latest X-DF engine technologies are already closing the gap.
In June, WinGD introduced the first second-generation technology for X-DF engines. Intelligent Control by Exhaust Recycling (iCER) technology allows the percentage of inert gas in the combustion chamber to be increased, delivering enhanced combustion control. The technology, available for all new X-DF engines, is based on a low-pressure exhaust recycling path, including an efficient cascade exhaust gas cooler (CEC), with negligible contamination of cooling water due to clean gas fuel and combustion. This not only reduces the reactivity of gas/air-mixture by replacing oxygen in suction air with carbon dioxide but also improves thermodynamic behaviour of the X-DF engines in terms of brake specific gas consumption, firing pressure fluctuations, emissions and allows an increase of power density.
The result is a reduction in methane slip emissions of up to 50% when using LNG and a significant reduction of fuel consumption, of 3% in gas mode and 5% in diesel mode. The combination of these two factors represents a leap in GHG emissions performance for X-DF technology, explains Dr Weisser.
“What is really impressive about this technology is that at the same time as reducing methane slip we’re also reducing gas consumption quite considerably,” he says. The new technology does not simply reduce methane slip by cutting gas consumption. Rather the gas fuel reduction is compounded with improved methane slip performance.