The calls to limit ship’s power have suffered a setback in the tortuous week on shipping’s decarbonisation path at the headquarters of the International Maritime Organization (IMO), reports Ship & Bunker.
Limit ship’s engine power
In another tortuous week on shipping’s decarbonisation path at the headquarters of the International Maritime Organization (IMO) one key takeaway from the intercessional discussions on short-term measures to cut greenhouse gas emissions is that the calls to limit ship’s power have suffered a setback.
On the table for discussion this week were proposals to limit ship power, fuel consumption and ship speeds – all with strong and vocal backers.
Proposals from Japan and BIMCO, backed by the likes of Maersk and Union Greek Shipowners, suggested limiting vessel power rather than limiting vessel speed.
Factors that affect vessel speed
Advocates for power limits say many factors affect vessel speed that are totally unrelated to the resulting emission. The factors sited are:
- Ship design
- Hull fouling
- Weather conditions.
They added saying that, as such vessel speed limits could actually penalize more energy efficient vessels.
Study on engine power limitations
The International Council on Clean Transportation (ICCT) has carried out a large study on engine power limitations as a CO2-cutting measure. The preliminary findings created quite a stir at IMO when the study results were revealed.
Using the latest 2018 data on ship’s current engine power loads, in bulkers, tankers, and containerships, the analysis showed that the 20%-30% power limitation of the type discussed by Japan would have zero or negligible CO2 reduction, because the ships are already operating at low load factors.
- The average load factor for engines on oil tankers in the 80,000 dwt to 120,000 dwt range last year was 40% normal continuous rating (NCR).
- For 3,000 to 5,000 teu containerships the annual average load factor last year was 30% NCR meaning these ships would need to get to 50% limitation to get low single digit CO2 reduction.
- Bulk carriers ranging in size from 60,000 dwt to 100,000 dwt only achieve low single digit savings at 40% engine power limitation, the ICCT study showed.
Engine power and CO2 cut
Delegates were told that if engineers ramp up the limitation on main engine power much further to 60%, then it does cut CO2 by 6% to 17% for these ships, but this risked taking nominal engine power below minimum safe propulsion power requirements.
One country delegate attending the IMO talks this week said, “Even engine power limitation’s most ardent supporters had no substantive objections to make to analysis, which showed it simply doesn’t work very well at cutting CO2. Mandatory operational standards are the only way forward now, on either real-world efficiency or real-world speed, take your pick.”
The full and final results from the ICCT study will be published at next year’s Marine Environment Protection Committee (MEPC) gathering at IMO.
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Source: Ship&Bunker
