Why Make Tugs Electric?

Tugboats are critical to the maritime industry and can be found in ports and coastal areas worldwide. A key role for tugs is guiding larger vessels safely to or from a berth by pulling on strong ropes attached to the ship or pushing against the ship’s hull. Larger tugs escort tankers from the open ocean into the port to provide an extra layer of safety in case the ship loses power, or its rudder fails. These tasks require tugs to be powerful and maneuverable.¹

Despite the relatively small size of tugboats, their powerful propulsion systems allow them to exert enormous force. Traditionally, tugboats have relied on diesel engines due to their high power and reliability. However, these engines release significant amounts of greenhouse gases (GHGs) and other air pollutants detrimental to the environment. With an increased focus on reducing air pollution and decarbonizing shipping, there has been a growing interest in electrification.² HaiSea Marine and SAAM Towage are two Canadian tug operators leading the way.

Two types of electrified tugboats are currently available: fully electric and hybrid electric. In fully electric tugboats, power comes from a battery that is recharged by plugging in at a dock like an electric car. Fully electric tugs are often equipped with a small onboard generator that can be used in an emergency. Limitations in the battery life mean that fully electric tugs are optimal for short distances, such as port and harbour operations.³ For tugs that need longer range, hybrid tugboats combine engines with battery-electric propulsion allowing them to access either form of energy, increasing their range while reducing overall fuel consumption.³ Their use is not limited by battery range to harbours or near-port areas.³

Electric tugboats help reduce the maritime industry’s carbon footprint, contributing to global efforts against climate change, while providing co-benefits in noise reduction and reduced fuel consumption.

Case Study: HaiSea’s First All-Electric Tugboat

A partnership at the forefront of maritime innovation, HaiSea Marine is a joint venture majority owned by the Haisla Nation in partnership with Seaspan ULC.⁶ The organization made headlines with its introduction of all-electric tugboats in April 2023.⁷  This initiative not only highlights technological progress but also underscores the organization’s commitment to Indigenous reconciliation and ecological consciousness.

Demonstrating its commitment to environmental responsibility, HaiSea Marine now has three ElectRA 2800 electric harbour tugs and two larger RAstar 4000-DF escort tugs that will burn either Liquefied Natural Gas (LNG) or diesel fuel. The ElectRA 2800 can exert approximately 70 tonnes bollard pull, while the RAstar 4000-DF escort tugs have 100 tonnes bollard pull and the ability to generate up to 200 tonnes of force, making them among the most powerful tugs on Canada’s West Coast.⁸

These tugboats will play a crucial role in safeguarding the transit of cargo vessels through vulnerable marine ecosystems. The three smaller electric tugs will help LNG carriers get safely to and from berth at the LNG Canada terminal. The two larger escort tugs will accompany LNG carriers from Triple Island near Prince Rupert all the way through Douglas Channel to the terminal and back again.

Advantages of Electric Tugboats

Electric tugboats reduce air pollution, fuel consumption, and noise. Although HaiSea Marine was the first in Canada to bring in electric tugs, SAAM Towage has also acquired two of the same tug design, created by Canadian naval architect Robert Allan Limited, for use in the Vancouver harbour.

Electrification reduces GHG emissions and air pollutants, ensuring compliance with global standards. Hybrid tugs reduce emissions by 30-60% compared to conventional tugboats.⁹ Fully electric tugboats produce zero emissions during voyages, so if the electricity used to charge their batteries comes from fully renewable sources (such as the BC Hydro electric grid), they can be a true zero-emission solution.

For example, the ElectRA 2800 series tugs used by HaiSea and SAAM are equipped with a 5,288 kWh battery, ten times the size of the battery in an electric car. The batteries were developed by Corvus Energy at their Vancouver, BC facility. They are sized to allow the tug to perform regular operations using 100% battery-electric power. Doing so prevents the production of particulate matter, sulphur oxide and nitrogen oxide emissions. Each tug reduces carbon dioxide equivalent emissions by an amount comparable to nearly 1,000 gasoline cars annually.¹⁰

Beyond emissions reduction, electric tugboats contribute to marine conservation objectives by operating more quietly, without the engine vibrations produced by conventional tugs. The constant noise emanating from marine operations impacts marine species’ ability to communicate, find food, and reproduce.¹¹ Electrifying tugboats also reduces noise for the benefit of the crew.

These advantages demonstrate how electrifying tugboats is reducing the marine industry’s environmental impact.

Limitations of Current Electric Tugboats

The emergence of electric tugboats offers a promising shift in maritime technology, but the transition is not the easiest.

The most conspicuous hurdle is the initial investment required for electric tugboats. These vessels are generally more expensive – 50% more – than their traditional counterparts due to the high cost of electric propulsion systems.¹³ These costs include not only the vessel itself but also the infrastructure needed for charging and maintenance. Furthermore, the lack of widespread adoption means there are few economies of scale to bring down costs. Operators must weigh these initial costs against long-term benefits, such as energy savings and reduced fuel costs.

Additionally, the physical size and weight of batteries present design challenges. Batteries must be accommodated without compromising the tugboat’s functionality, including space for crew and necessary equipment. Designers must find a balance to accommodate the electric propulsion system without affecting the tugboat’s versatility and operational efficiency.

Fires caused by lithium-ion batteries in consumer devices raise concerns about their safety. Lithium-ion batteries store a large amount of energy in a small space, providing high energy density. However, this also means that if a battery cell is damaged or improperly charged, it can lead to a significant release of energy in an uncontrolled manner, commonly known as thermal runaway, where the cell’s internal components break down and release gases that can ignite if exposed to oxygen. In the confined space on board a ship, this could be catastrophic.

Fortunately, the battery’s designers use a system called passive single-cell thermal runaway protection which means that even if one of the cells in the battery goes into thermal runaway, the damage will not spread to other cells. Other measures to ensure safety include teaching staff how to safely handle batteries and identify and remove damaged lithium-ion batteries.¹⁴ Operators are committed to safe operations and conduct regular system review to identify and respond to any risks.

Future Directions

The prioritization of several key initiatives will support the production of more electric tugboats.

First, accessible charging infrastructure is vital. As the number of electric vessels increases, ports must be equipped with high-capacity charging stations for quick turnarounds and minimal disruption to operations. Governments and port authorities can provide incentives for the installation of charging stations.¹⁵ An example is the funding provided by the Government of Canada to support the installation of shore-power technology for cruise and container ships at Canadian ports.¹⁶

Further, innovations in battery technology could lead to higher energy density solutions, which would reduce the size and weight of batteries and increase the number of vessels in which fully electric propulsion systems would be possible. Continuous technological advancements will play a crucial role in addressing the current limitations of electric tugboats to make electrifying all tugboats a more viable option in the maritime market.

Conclusion

Electric tugboats represent a shift towards a more sustainable maritime industry. Despite the challenges associated with their adoption, the long-term benefits to the environment, operational costs, and crew wellbeing make them a worthwhile investment. The investment by HaiSea and SAAM Towage in battery-electric tugboats provides a case study for the application of these technologies. As technology evolves and regulatory frameworks adapt, electric tugboats are likely to become an increasingly common sight in ports around the world.

About the Author

Yu Han (Veronica) Guo is a Grade 11 student at York House School. She completed a three-month research internship at Clear Seas working on the Pathways to Zero-Impact Shipping project in spring 2024. Veronica is passionate about engineering innovations that improve the sustainability of our world. 

References

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