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72 Third IMO GHG Study 2014
engine loads below 25%, which is the lowest load in the E3 cycle. Further, when looking at emissions beyond
NO x , which is required to be tested during engine certification, the number of valid tests available for review
significantly drops off. Similar to EF testing, published SFOC data are limited, particularly over wide engine
load factor ranges (% MCR). There is uncertainty around the effects that engine deterioration has on an
engine’s emissions profile and SFOC.
Boiler usage
Hot steam on board ships is used to provide cargo and fuel oil heating as well as to run cargo operations
with steam-driven pumps. The energy required to run these operations is usually taken from auxiliary boilers
running on fossil fuels, mainly HFO. During voyages, waste heat from the main engine is used to provide the
energy needed for steam generation. However, at low engine loads, the heat provided by the exhaust boiler is
not enough to meet all the heating demand on board. At low engine loads, both the auxiliary boiler and waste
heat recovery provide the heat needed by the vessels. The shift from exhaust to auxiliary boilers happens at
20%–50% engine load range (Myśków & Borkowski, 2012), as illustrated in Figure 52.
Figure 52: General boiler operation profile (Myśków & Borkowski, 2012)
With lower engine loads, the auxiliary boiler is the main source of heat on board a vessel. With sufficiently
high engine loads, waste heat recovery can produce enough steam for the vessel and the auxiliary boiler may
be switched off. The operational profile of the auxiliary boiler of a container carrier is presented in Figure 53.