Updated: Dec 19, 2022
Clean fuels for powering ships have been identified, but the widespread adoption of fuels like hydrogen, ammonia, or methanol is still many years away. The good news is that for some types of ships, electrification is available now.
When you watch from shore, ships at sea sometimes appear to glide across the horizon without any effort at all, but if you’ve ever been in the engine room of a large ship, you’ll know it takes a whole lot of power to make that happen. Ships can be fitted with huge engines, some the size of a small house, to provide the power needed to make its journeys. A large car ferry requires over 20,000 horsepower, and a container ship can easily be double or even triple that amount.
Since the transition away from sail power in the 1800s, ships have been powering their engines by burning fossil fuels: first coal, then fuel oils such as bunker and diesel. These fuels are a significant contributor to greenhouse gas emissions. According to estimates from the International Maritime Organization (IMO), the shipping industry alone is responsible for approximately 2.5% of global CO2 emissions every year—roughly the same emissions as the country of Germany. These emissions contribute to climate change, air pollution, and other environmental problems.
In recent years, many shipowners have shifted to Ultra-Low Sulphur Diesel (ULSD), Liquid Natural Gas (LNG), and various bio- and renewable-diesel fuels. These fuels offer some emission reductions, but they are ultimately just a transitional step as each of these fuels still releases greenhouse gases into the atmosphere. Clean sources for powering ships have been identified, but the widespread adoption of fuels like hydrogen, ammonia, or methanol is still many years away. The good news is that for some types of ships, full-electrification is available now.
Marine electrification is the use of electricity as a source of power for ships and other marine vessels. Some or all of the ship’s power requirements come from batteries that can be recharged using on-shore electric hookups. Vessels using this kind of power contribute much less to pollution, and may offer other benefits such as reduced noise and vibration.
In British Columbia, where almost all the electrical power we generate is hydro power, marine electrification has an appealing elegance: energy derived from water is put to use in the water. That is, power generated through spinning turbines at a hydro reservoir is transferred to a ship and is used to spin its propellers through the water.
Of all the different types of marine vessels, ferries are prime candidates for electrification because they typically have short, frequent crossings between land-based terminals. Although electric vehicles on land represent a growing proportion of what we see on the roads, electric vessels over waterways are far less common. This is mainly because electric charging and storage technologies have needed to improve significantly to reach the scale needed for deployment in the marine industry. A large amount of power is required to push a ferry through the water—with these power requirements scaling up exponentially as speed requirements increase—and to run all the systems necessary for the safety and comfort of ferry users, from ventilation to coffee machines. Energy storage requirements for an all-electric ferry can be 10 to 100 times greater than what’s needed for a car. And marine electrification is just as much a shore project as a ship project; electrification often involves custom shore-side solutions to fit the unique site conditions: grid power, dock arrangements, and accommodations for tidal and environmental conditions.
The phrase “electric ferry” is typically used to refer to an entire spectrum of vessels that use various levels of electric-power technologies. Below is a breakdown of the types of ferries in this broad category.
A diesel-electric ferry is fitted with a large diesel generator that produces electricity, and powers an electric motor to propel the ship. This type of propulsion has been used for decades in the marine industry. Like a traditional ferry, all the power needs of the ship are primarily met by burning fuel—but in this case, the power is converted into electricity to achieve propulsion. This type of arrangement can be found on the “Jumbo Mark II” ferries in Washington State, or “Coastal” class ferries in BC.
Diesel-Electric Hybrid, also called Electric-Ready
A diesel-electric hybrid ferry is similar to a diesel-electric ferry, but is also fitted with onboard batteries of sufficient size to provide a short duration of propulsive power if needed. Batteries are charged through the generator, which is powered by fuel, so in essence all the power needs of the ship are primarily met by burning fuel. The new ferry being built for Kootenay Lake is considered electric-ready, as are the “Island Class” ferries, which are also found in BC.
Plug-in Electric Hybrid
A plug-in electric hybrid is a vessel that is configured like a diesel-electric hybrid but also has a high-capacity charger to accept a shore charge. A vessel’s power needs are jointly met by grid power and by burning fuel. Hamburg’s new passenger-only ferries are considered plug-in hybrids, as is the Color Hybrid in Sweden
An all-electric (or fully electric) vessel is one where none of the ferry’s power needs are met by burning fuel on-board. Shore power from the electricity grid is used to charge on-board batteries, which are used for all the vessel’s power requirements. Norway has been a global leader in advancing the technologies to make this possible, starting with MV Ampere in 2015, and currently has a fleet of all-electric short-run car ferries. In Canada, there is currently one such ferry, the Marilyn Bell I, which serves Billy Bishop Airport in Toronto. Building on car ferry experience, Norway has more recently brought into service the world’s first all-electric high-speed passenger-only ferry, MS Medstraum. This award-winning ferry was designed through an EU partnership to leverage the latest marine technologies. It is fitted with Richmond’s Corvus batteries, and charges on shore with the equivalent of six car chargers.
Look carefully at the terminology on electric ferries used in news articles, reports, and other places: often if you dig deeper, you will see that “electric ferry” is used to talk about many types of vessels that still burn fuel as their primary source of power. With limited exceptions, almost every ferry that currently exists in North America operates by burning fuel as a primary power source. And although sometimes a ferry can be refitted to increase its reliance on electric power, not every ferry is a candidate for full electrification. For larger car ferries on longer crossings, full electrification is not practical, nor is the technology ready.
Finally, however, marine technologies have advanced to the point where it’s possible to build a reliable, robust all-electric ferry to make passenger-only trips of well over an hour at 23 knots. Greenline is bringing this technology to British Columbia in the near future, aiming to be the marine company that delivers the province’s first clean all-electric ferry fleet.
Tiago Fioreze, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons