Energies 2023 , 16 , 280
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to play an important role in the future decarbonization of the shipping sector [51]. For instance, since 2016 seven oceangoing vessels have been operating equipped with dual fuel, two-stroke engines, which can run on methanol, heavy fuel oil (HFO), marine diesel oil (MDO), or marine gas oil (MGO) [52]. Brynolf et al. [53] showed that the environmental impact of renewable methanol is relatively lower than HFO and other alternatives such as liquified natural gas (LNG), liquified biogas, and fossil methanol. A transition assessment of DNV-GL shows that the uptake of at least three or four different carbon-neutral fuels in the shipping sector could account for 60–100% of shipping energy use by 2050. The tightening of shipping emission regulations in the next two to three decades could ensure that fleets shift directly to carbon-neutral methanol or ammonia while other low-carbon alternatives such as bio-MGO, e-MGO, bio-LNG, e-LNG function as drop-in fuels for existing ships [54]. Within the P2X concepts, methanol is a hot topic and has the potential to be one of the solutions to use and store large-scale renewable electricity as seen in Figure 6. The requirement of electrolyzers in producing the needed hydrogen in the synthesis of e-methanol opens up opportunities to integrate more renewable generation into the future power sector (i.e., matching time of generation to time of load). Therefore, the interactions between the renewable power and methanol (e-methanol) sector could lead to higher shares of intermittent renewable energy resources in a net zero emission world within the next three decades. Last but not least, methanol can play a significant role as a green hydrogen energy carrier. Similar to the case of ammonia, the energy density of methanol is very interesting for transporting green hydrogen from one region to another for example from Australia to Asia. This is feasible as the supply infrastructure for transporting methanol is already in place due to the existing supply of huge quantities of methanol around the world annually. Figure 9 shows the key roles green ammonia and methanol can play in tomorrow’s carbon-neutral world.
Figure9. Role of green ammonia and methanol in a carbon-neutral future.
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