Abstract
• 50,000 noon reports from 88 tankers analysed to assess speed-power relationship • Data-driven model combining principles from naval architecture and econometrics • Speed-power exponent is significantly lower than 3 at speeds below the design speed • Environmental effect of slow steaming is overestimated • Imparts attention to speed optimization and not reduction for reducing CO 2 emissions This study investigates the speed-power relationship of ships, and is based on a combined econometric and naval architectural data-driven model fed with operational data from more than 50,000 noon reports obtained from 88 tankers. It is shown that the speed-power exponent is significantly lower than 3 at speed intervals below the design speed. This finding, including the study itself, affects the environmental discussions related to slow steaming, since it implies that slow steaming will not be as good as often stated. As such, the study imparts attention to speed optimisation, rather than reduction, in the political and environmental debate focused on the reduction of carbon emissions from shipping.
Highlights
This study investigates the speed-power relationship of ships, and is based on a combined econometric and naval architectural data-driven model fed with operational data from more than 50,000 noon reports obtained from 88 tankers
As there is a simple linear relationship between fuel consumption and emissions as well as a nonlinear relationship between power and fuel consumption through the specific fuel oil consumption (SFOC) curve, there is a direct relationship between power and emissions; that is, reduced power leads to reduced emissions
This paper has studied the relationship between attained speed and used power by ships sailing at sea
Summary
One of them is slow steaming; in simple terms achieved by reducing the speed of the vessel, leading to a reduction of the main engine demand, even down to 10–20% maximum continuous rating (MCR) according to MAN Energy Solutions (2012) and Psaraftis and Kontovas (2014). The relationship between power P and speed V is often described with P ≈ Vc where c is a constant exponent with a value of at least 3 (MAN Energy Solutions, 2018), noticing that the relationship generally is applicable to relative high speed intervals around the design speed (Psaraftis and Kontovas, 2014). It has been argued that at lower speed intervals, the relationship will underestimate the power and fuel consumption, which means that the effect of slow steaming is overestimated, as reported by Adland et al (2020), Taskar and Andersen (2020), Tillig et al (2018) among others
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