Rob Mortimer, Managing Director of Dubai-based clean-fuel technology firm Fuelre4m, shared an article with Singapore-based bunkering publication Manifold Times detailing how the measurement of bunker fuel consumption can affect how true efficiency of fuel is measured:
My background is in telecoms, data, and radio communication, where everything from speed to capacity is logical, measurable, and provable. However, venturing into the world of combustion engines and renewable-based hybrid generator sets was an eye-opener. Unlike the precise measurements in telecoms, the shipping industry still measures fuel consumption in liters and gallons, ignoring the crucial fact that fuel is consumed in weight. This disparity affects how we measure the true efficiency of fuel.
In shipping, operators have advanced in measuring vessel performance with technology, yet they still overlook the efficiency of the fuel itself. The industry commonly uses Specific Fuel Oil Consumption (SFOC) to measure fuel usage per unit of energy produced. SFOC is calculated as the mass of fuel consumed per hour divided by the engine’s power output during that period. While this metric has been used for decades, it doesn’t account for the varying quality of fuels.
For instance, a 1% variation in fuel quality, seemingly negligible, can have a significant impact when burning 600 metric tonnes (mt) of fuel per month. Over a year, this 1% difference equates to 72mt of fuel, which, according to the International Maritime Organization (IMO), translates to 226mt of CO2 and greenhouse gas emissions. The assumption that one metric tonne of fuel will always produce the same power, regardless of slight quality differences, is flawed.
The problem is rooted in using SFOC as an average reference for engine performance, not fuel performance. Engine manufacturers provide data based on ideal conditions with a specified fuel quality. These numbers are then normalized and used as averages for future calculations, overlooking the variations in fuel quality from bunker to bunker.
It’s akin to assuming that fuel from different gas stations is identical, when in reality, it can vary significantly due to factors like mixing, contamination, and aging.
The key issue with SFOC is that it doesn't account for the fact that different fuels, even of the same type, have varying energy densities. For example, Heavy Fuel Oil (HFO) has an energy density of 40-42 MJ/kg, while Methanol has only 21-23 MJ/kg. This variance can be as much as 5-6% within the same fuel type, leading to substantial differences in power output and fuel efficiency.
To accurately measure fuel efficiency, we need to consider the mass of fuel in relation to the power it produces. This requires precise measuring equipment, such as torque or shaft power meters. These devices don't directly measure torque but instead gauge minute changes in the propeller shaft as it twists with varying forces. By calibrating these meters to account for the quality of the fuel, we can more accurately assess the energy released and adjust power readings accordingly.
Power cards, another essential tool, allow engineers to evaluate the combustion process and measure cylinder power output. These measurements can then be used to fine-tune the torque meter readings, ensuring that they reflect the true efficiency of the fuel being used. This method moves us beyond relying solely on the engine’s power rating and towards a more scientific approach to evaluating fuel performance.
The recent drive towards alternative fuels, spurred by the global push to reduce fossil fuel consumption, has highlighted the need for a balanced approach. While alternatives like biofuels and LNG have their place, they often come with challenges and trade-offs. For example, biofuels have lower energy densities, requiring more fuel to produce the same power and potentially increasing emissions. Dual-fuel engines, designed to switch between traditional and alternative fuels, can be complex and problematic in operation.
The reality is that fossil fuels will remain a significant part of the energy mix for the foreseeable future. Rather than abandoning them prematurely in favor of less-proven technologies, the focus should be on optimizing the fuels we currently use. By improving the efficiency of fossil fuels through better measurement and treatment, we can achieve significant environmental benefits without the risks associated with untested alternatives.
Fuelre4m is at the forefront of this optimization effort with its Re4mx fuel reformulator technology. This technology conditions fossil fuels pre-combustion, enhancing atomization and energy release while reducing particulate matter and pollutants. Coupled with advanced measuring tools like mass flow meters, torque, and power meters, Fuelre4m offers a comprehensive system for improving fuel efficiency and reporting, helping ships achieve IMO emissions targets without incurring additional costs.
Photo credit: Fuelre4m
Published: 11 September, 2024