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How Do We Improve Fuel Efficiency For Global Shipping?

image credit: Container ships are a prime candidate for fuel efficiency measures
Ron Miller's picture
Principal Reliant Energy Solutions LLC

Ron Miller is an energy industry expert creating value by analyzing assets, markets, and power usage to identify, monetize, and implement profitable energy and emission reduction projects. He is...

  • Member since 2020
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  • Jul 8, 2020

Hull drag is the largest ocean-going ship energy loss, increasing dramatically with hull fouling thus lowering the fuel efficiency of the high sulfur fuel oil (HSFO) used for propulsion. While hull fouling increases barnacle build-up, it also lowers fuel efficiency and increases maintenance time in dry dock.

In tandem with these fuel efficiency problems, the International Maritime Organization (IMO) 2020 rules have dictated a drastic reduction in the sulfur content of fuel to 0.5% or lower from the 2019 level of 3.5%.

KPMG Global says 15 of the biggest ships emit more sulfur dioxide and nitrogen dioxide than all of the world’s cars combined, and one million cars emit as much particulate matter as one cruise ship produces. There are currently 1,500 ships at least 183 meters in length and with a design dead weight of 37,000 tonnes operating in the world.


  1. Use ultra-low sulfur fuel oil (ULSFO) Price for ULSFO is at a premium to HSFO of up to 20%, and world-wide refineries have been gearing to this new product spec
  2. Install scrubbers that remove sulfur from exhaust gas emitted by bunkers. Scrubbers cost as much as USD 5 million per ship and a month at port for the scrubber to be installed
  3. Reduce ship speed Lower consumption in fuel per kilometer, but unfortunately, unless the world can do with a reduction in goods shipped around the globe, this will require more ships to move the current volumes
  4. Evaluate drag reducing strategies Lower drag forces and accompanying fuel demand by injecting micro-bubbles along the ship’s hull

Size Of Problem:

The world-wide shipping industry consumes 350 million metric tons of bunker fuel a year of high sulphur fuel oil (HSFO). Ocean-going ships transport around 80% of the world's goods by volume, but they are responsible for 3% of the global total of warming gases. As of May 2019, about 67% of the shipping industry was not compliant and 65% of refiners are not ready for the new fuel oil. This fuel consumption generates about 1.12 billion tonnes of CO2 every year.

Drag Reducing Strategies - how does the Gas Injected Liquid Lubrication System (GILLS) technology work?

  1. GILLS reduces the drag of a ship’s hull using small micro-bubbles and turbulence modulation (~1.0 mm)
  2. Atmospheric air is compressed to match the hydrostatic pressure along the hull at the bow at different depths below the water surface
  3. Compression costs to match the hydrostatic pressure on the hull are minor compared to the accomplished savings
  4. Air is released via angled hydrofoils with air introducers
  5. As the ship moves forward, it generates negative pressure to induce atmospheric air into the water creating micro-bubbles
  6. The ship glides on an air cushion of bubbles, much like an underwater hydrofoil

Value Proposition:

Assuming the industry adopts ULSFO which is priced at a premium to the current HSFO, a 10% CO2 saving in ULSFO consumption due to GILLS would save about 109 million tonnes of CO2 per year. At the 2 July 2020 Singapore ULSFO price of USD 333.50 per tonne, a 10% fuel savings would be 35 million tonnes pa, or USD 11.67 billion per year.

GILLS technology to inject micro air bubbles at the bow can reduce drag and barnacle build up by lowering drag forces, which costs the ship owner in the form of lower fuel efficiency, and longer maintenance time to remove barnacles in dry dock every five years.

Figure 1 shows the water flow through the hydrofoil which is installed on the hull at the bow to create micro-bubbles.

Figure 1 – Water flow on ship hull creating micro-bubbles


Figure 2 shows the bubble generation and spacing required for the hydrofoil.

Figure 2 – Wave breaking & bubble generation


There have been numerous tests of the GILLS technology, namely the 85 meter Filia Ariea and the 68 meter Ferry Misaki shown in Figures 3 and 4. The tests have shown a 9-10% reduction in fuel consumption from the GILLS technology.

Figure 3 – GILLS on Filia Ariea (85 meters)

Test results for the Filia Ariea yielded a 10% fuel savings from GILLS. Source:

Figure 4 – GILLS on Ferry Misaki (68 meters)


Test results for the Ferry Misaki Filia Ariea yielded a 9% fuel savings from GILLS. Source:

The 9-10% reduction in fuel consumption can be enhanced if we address fuel quality and oxygenation during combustion, realizing an incremental 5% reduction in fuel demand. Improving those factors with a two-track strategy on 1) hull drag reduction and 2) improved combustion together can lower overall fuel use by 15%, potentially saving up to USD 17.5 billion per year globally. More information about fuel savings during combustion can be found in my Society of Mining Metallurgy and Exploration (SME) February 2017 conference paper titled, “Improving Diesel Quality Reduces Cost and Emissions”, Preprint 17-073.


The challenge facing the world-wide shipping industry to reduce the approximate 1.12 billion tonnes of CO2 every year is huge, with potential solutions that are expensive to implement, both from a retrofitting capital perspective as well as dry-dock/non-productive time and higher operating expenses with cleaner fuels.

The GILLS technology in tandem with technologies to improve oxygenation of fuel during the combustion stage, addresses both the hull drag forces that cause increased fuel consumption while lowering fuel use. These two technologies could be the answer to lower CO2 by over 100 million tonnes and saving the shipping industry over USD 17 billion per year.

Copyright © July 2020 Ronald L. Miller All Rights Reserved

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