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Power on the Water: Moving People and Delivering Goods with Diesel

    Whether on the high seas, in the harbor, or transiting the North Pole or the vast inland waterways of the US, diesel engines are at work moving people and goods more efficiently, with lower emissions, than ever before

    Remember the container ships backed up off the California coast several months ago? That sight and the news coverage surrounding it provided a closer look at container ships, global shipping, and supply chains like never before. There were many large vessels waiting to dock and unload offshore, which provided one example of the role of diesel technology in global shipping.

    Diesel powers the marine sector. Everything from container ships and cruise lines, to passenger and vehicle ferries. Tugboats maneuvering vessels into docking position or towing grain barges up the mighty Mississippi River; powered by diesel. Harbor fire and rescue boats, many U.S. Coast Guard vessels and the icebreakers of our Great Lakes. The majority of these vessels run on diesel.

    Diesel technology has long been the power of choice for the marine sector, thanks to its efficiency, scalability, reliability, power, and performance. Diesel engines are particularly suited for the demanding work of moving these large vessels at steady speeds for long distances reliably, while using the least amount of fuel possible. And thanks to changes in fuels, engine and emissions control technology, and new propulsion systems, these boats are more efficient and lower in emissions than ever. New workboat engines manufactured since 2015 have 86% fewer nitrogen oxide emissions and 90% fewer emissions of particulate matter. To reduce emissions while in port, many vessels have been outfitted with shore power systems that allow a boat to plug into electrical power during loading and unloading, thereby eliminating the need to run engines to create electricity for the hoteling aspects of the vessel.

    Marine vessels are mostly seen from afar while docked in a port and remain much of a mystery below deck. Most larger vessels – ferries, container ships, tugboats – have several engines, some devoted to propulsion and some devoted to other needs like generating electrical power or to run fire-fighting pumps. A typical ocean-going container ship may have as many as four to six separate diesel engines just for generating electrical power along with one or two larger main slow-speed diesel propulsion engines directly linked to the propeller(s). 

    The size and power of marine engines can be offsetting. Most car engines are around 150-200 hp, but each of the main drive engines on some tugboats can generate in excess of 4,000 hp. That’s a lot of power for vessels that are charged with towing and pushing massive tankers and container ships carefully into the dock. For the slower-moving larger container and cruise ship vessels, these use a use slow-speed diesel engine enabling the vessel to sustain about 20 knots. And the engines aboard container ships are physically large, 80-100 feet in length and height the size of a five-story house. Cruise ships use engines that generate power equivalent to about 50,000 hp.

    Like all other diesel engines and fuels, dramatic improvements have been made over time. In 2020, the International Maritime Organization (IMO) that governs ocean going shipping, implemented a new global 0.5% sulfur cap on marine fuels. If not using scrubbers (pollution control devices), owners of older vessels must use as ship fuels either marine gas oil (MGO), or special fuels while transiting in and around ports and coastlines in Emissions Control Areas (ECA), such as the Port of Los Angeles (CA). Here ECA category approved fuels include low sulfur MGO, new modified fuels and blends, liquefied natural gas (LNG), or electric/battery power. Many newer engines can run on blends of fuels to reduce consumption and cut emissions.

    Innovations in marine vessel propulsion and fuels are happening, largely dependent on the size of the vessel and its operation. Several diesel hybrid electric ferries have been launched, enabling operators to reduce fuel costs while sustaining operations. Increased interest in LNG for some of the largest container vessels is growing, though limited global refueling options are available as compared to diesel. And interest in hydrogen for powering internal combustion engines and fuel cell applications is also being explored. Renewable and biodiesel fuels are also being utilized in harbor craft and workboats, along with commercial fishing and tour vessels. These drop-in replacement fuels offer vessel owners and operators a way to lower their carbon emissions compared to traditional diesel fuel while utilizing their existing fueling and maintenance infrastructure without any changes. Other strategies to reduce emissions include repowering vessels during drydock periods, replacing older generation diesels with new more efficient models.

    Whether on the high seas, in the harbor, or transiting the North Pole or the vast inland waterways of the US, diesel engines are at work moving people and goods more efficiently, with lower emissions, than ever before. Hybrid propulsion systems and some alternative fuels are emerging in some vessel applications, but diesel is expected to continue to dominate the marine sector for decades to come.

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