Figure 3 (left): The 24m EDDY Tug 24, rated 75tonnes bp; Figure 4 (right): the 30m EDDY Tug 30, rated 65tonnes bp


against 2008 levels. Figure 1 demonstrates the striking impact hereof if the world tug fleet continues to use (low-sulphur) MDO and MGO as main fuel sources. Te 2008 emissions benchmark is set as


“100”, which has to be reduced to 60 by 2030 (the horizontal green line). We are already at 156, while, in 2030, this is estimated to be around 224. Te 2030 world tug fleet GHG emissions would thus not need to be reduced by 40% but by a shocking 73% compared to the levels achieved in 2030 when continuing to do ‘business as usual’. To complicate things further, IMO’s


definition refers to emission reductions of the entire world fleet by 2030, and not simply to emission reduction of vessels built aſter 2030. In other words, tugs would need to be 73% cleaner overall by 2030. Considering typical newbuilding rates (around 3% annually) and economical tug life (25+ years), this is only possible if course changes drastically, and fast. A dozen scenarios were analysed to


meet the MEPC 72 2030 target. Te short answer is that it is a very tough target, requiring immediate action. For example,


the scenario of Figure 2 shows that all tugs built after 2020 would need to be ‘near-zero-emission’ , while all existing tugs need to switch to alternative fuels by 2021 (assuming availability and 35% local GHG emission reduction), plus an increased newbuilding (and scrapping) activity of 620 tugs above forecast rate per year worldwide. The likelihood of this happening is


obviously zero, but a five-year delay would require near-zero-emission tug newbuilding (and scrapping) rates to triple.


Hybrid tug developments State-of-the-art tugs are well designed and mature, which makes it difficult to squeeze a few percent of energy savings out of them. Since 70%+ emission reductions thus cannot be expected from current tugs in a cost-effective manner, more drastic change is needed. EDDY Tug anticipated the need for


more energy-efficient tugs and developed low-resistance, diesel-direct/diesel- electric-driven tugs with in-line thrusters (one forward and one aſt). Te diesel-


gre  The m - tg model hh s capable of zero emissions and is rated 90tonnes bp


electric part typically consists of two 500kW electric motors and two 560kW generators (see Figures 3 and 4). The 24m EDDY concept proved


particularly useful for its capability to operate in very restricted spaces (such as locks) but its length is too short to optimise for energy efficiency (nevertheless, it consumes less fuel than ‘normal’ tugs of the same size and power). Te 30m EDDY tug transits at 9knots+ on a single 560kW generator, without generating wake, and consumes 30-50% less fuel, thereby also reducing CO2 emissions equivalently compared to ‘normal’ tugs of the same power and performing the same ship-assist tasks (the longer the transits, the higher the savings). To further reduce fuel consumption and


emissions, a logical next step would be to add batteries. Te EDDY 24 does not have the space, nor displacement reserve, for this but the EDDY 30 can accommodate around 500kWh of battery capacity. Tis allows for up to 45 minutes of emission-free transits. However, with the diesel-electric


component representing roughly a quarter of the total power, the desired 70%+ GHG emission reduction cannot be guaranteed. This is why,


recently, a


next-generation ‘crossover’ EDDY-X tug was developed,which has a fully diesel-electric/ battery hybrid drive-train and further improved energy efficiency (see Figure 5).


nergy effieny Truly improving energy efficiency is key to achieving low emissions in a cost-effective, practical manner. But it is complex to realise, requiring a mindset shift. Incorporating an in-line thruster arrangement is just one aspect, but many more steps need to be taken to achieve 30% lower displacement compared


Ship & Boat International November/December 2018 23


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