Powering Ports: Electrifying Harbor Craft & Ferries For Lower Costs & Emissions

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The path toward decarbonization in the maritime industry requires practical, phased strategies that deliver clear operational, environmental, and economic benefits. In this third installment of our detailed exploration into achieving zero-emission port operations, we shift our focus from electrifying ground equipment to the critical next phase—electrifying port vessels such as harbor tugs, service boats, and local ferries.

This logical progression builds upon the successful groundwork established in the initial five years, moving ports deeper into maritime decarbonization and establishing critical infrastructure for even more ambitious steps to come. The baseline energy demand was established in the introductory article. This particular order is simplified to allow a particular part of port energy demands to be assessed. In reality, ground vehicles, port, inland and short sea vessels and shore power will be electrifying with fits and starts somewhat in parallel, with ground vehicles ahead, and vessels and shore power likely occurring in parallel.

Harbor vessels, despite their relatively modest number compared to land-based equipment, disproportionately contribute to emissions within port areas. Typically, a mid-sized European port operates around three diesel harbor tugs, each burning approximately 150 tonnes of marine diesel per year. Alongside these, smaller service boats, pilot craft, and ferries contribute substantially to local air pollution, noise, and greenhouse gas emissions. Transitioning these vessels to battery-electric or hybrid-electric solutions presents a highly attractive and immediately impactful opportunity, given their predictable operating patterns, localized area of operation, and relatively straightforward charging infrastructure needs.

Electrifying harbor tugs serves as the cornerstone of this second decarbonization phase. Proven electric tug designs, such as the Damen RSD-E Tug 2513, have emerged in recent years, equipped with substantial battery capacities in the 2.5 to 3 megawatt-hour range. This battery capacity comfortably allows multiple assist operations between recharging intervals. For example, an electric tug can complete a full day of harbor maneuvering tasks, returning periodically to dedicated high-power charging stations at its berth for rapid recharging sessions lasting one to two hours. The installation of these high-power shore-side charging stations—capable of delivering up to 1.4 megawatts per tug—ensures minimal operational disruption and high availability. This level of performance has been demonstrated successfully in trials at leading European ports, validating both technical feasibility and the substantial economic savings associated with electrification.

Once again, the total primary energy required drops due to the greater efficiencies of electric drive trains being powered by renewable electricity, hence the diminishing rejected energy. As a reminder from previous articles, we aren’t including bunker fuel for ships in these Sankey diagrams simply because that dwarfs the energy required for port operations. We’ll deal with that in a later five year increment.

The benefits of electrifying harbor vessels extend significantly beyond reduced emissions alone. Operational economics are particularly compelling. Electric vessels exhibit far lower total cost of ownership compared to diesel-powered counterparts. Maintenance costs are substantially reduced, given fewer moving parts and lower wear and tear on electric drivetrains compared to complex diesel engines. Fuel costs, often volatile and subject to geopolitical risk, give way to far more stable and predictable electricity prices. Damen Shipyards has documented that operating costs for electric tugs fall below one-third of equivalent diesel vessels, making the economic rationale for electrification not just viable, but overwhelmingly attractive.

In parallel, the port’s local ferry operations offer another powerful electrification opportunity. Ferries typically run predictable, short-distance routes ideal for battery-electric operation. Electric ferries have already been widely deployed with great success across Northern Europe, particularly in Norway and Denmark, showcasing proven reliability, passenger acceptance, and dramatic emissions reductions. Transitioning ferry routes to battery-hybrid or fully electric operation involves equipping ferry terminals with high-capacity charging infrastructure capable of delivering rapid charges during short turnaround times—often around ten minutes per charge at power levels of two to three megawatts. Implementing these changes virtually eliminates diesel use on ferry routes, greatly improving local air quality and significantly reducing operational expenses.

Electrification of harbor vessels, including tugs, ferries, and smaller service craft, naturally increases overall electricity demand at the port. By the end of this second phase (around year ten), total electricity consumption is anticipated to rise by approximately five to eight gigawatt-hours annually. Electrifying three diesel harbor tugs alone replaces about five gigawatt-hours of diesel fuel energy annually. Accounting for improved efficiencies of electric motors, this translates to a grid demand increase of roughly three to four gigawatt-hours. Additional charging requirements for local ferries further add one to two gigawatt-hours annually. This cumulative increase brings total port electricity consumption up to roughly 35 gigawatt-hours per year by year ten, even as diesel consumption plummets by approximately half a million liters annually—effectively eliminating the port authority’s direct fossil fuel use.

Meeting this incremental electricity demand strategically necessitates substantial investment in renewable energy capacity, particularly offshore wind. By year ten, the port would ideally deploy or secure around ten to fifteen megawatts of offshore wind capacity, leveraging Northern Europe’s favorable wind resources. Operating at typical offshore capacity factors around 40%, a fifteen-megawatt wind farm can generate roughly fifty gigawatt-hours annually, comfortably covering the additional electrification load while creating surplus energy that can either be exported or utilized for future expansion needs. Complementing offshore wind, expanded on-site solar generation—approximately five to ten additional megawatts installed across rooftops, canopies, and available port land—further enhances renewable capacity, providing daytime energy and improving grid balance. Robust grid interconnections remain essential, both for importing electricity during renewable production shortfalls and exporting surplus energy, ensuring overall system stability and reliability.

Beyond the obvious proof points for offshore wind and port-adjacent solar in Europe, China’s example is instructive. Each coastal city is building platforms offshore with a GW of solar on them, and offshore wind farms up to 30 GW. There’s lots of room offshore, despite limited room in crowded cities and busy ports.

To effectively manage the dynamic charging demands from harbor vessels and ferries, as well as smoothing renewable generation variability, the port invests in an expanded battery energy storage system of approximately twenty megawatt-hours. This battery system serves multiple essential functions: buffering the significant instantaneous power demands during high-power tug and ferry charging events, storing excess renewable energy generated overnight for daytime usage peaks, and ensuring resilience during periods of grid instability. For instance, a twenty-megawatt-hour battery installation provides the flexibility to deliver continuous bursts of five megawatts over four-hour periods, sufficient to accommodate simultaneous charging sessions of multiple harbor vessels without imposing undue stress on the local grid infrastructure.

Financially, this second phase of electrification represents a significant but highly justified investment, on the order of one hundred million euros. Major capital expenditures include approximately thirty million euros extra for three new electric harbor tugs compared to diesel equivalents, five to ten million euros dedicated to electrifying ferries and service vessels, and roughly five million euros for high-power vessel charging infrastructure, including substations and rapid-charging stations. Offshore wind energy development requires around fifty to sixty million euros investment for fifteen megawatts of capacity, while the expanded battery storage system accounts for about ten million euros. While these costs are substantial, they are offset rapidly by considerable operational savings—lower fuel and maintenance expenditures—and enhanced regulatory compliance, competitive positioning, and future market attractiveness.

Strategically, electrifying harbor vessels is not simply an environmental imperative; it represents a critical competitive advantage in a rapidly evolving maritime landscape. Ports adopting early electrification significantly reduce their vulnerability to volatile fuel prices and tightening emissions regulations, enhancing operational resilience and attractiveness to sustainability-driven customers and logistics operators. Proven examples such as APM Terminals’ total cost-of-ownership analyses consistently demonstrate that electrification reduces risk and boosts long-term profitability, solidifying a port’s competitive market position.

The electrification of port vessels during this critical second phase creates tangible environmental benefits, significant financial savings, and strategic competitive advantages. It sets the stage for deeper electrification initiatives, including comprehensive shore power implementation and ultimately, broader vessel propulsion electrification. Ports that embrace this step-by-step transition will emerge as leaders in maritime decarbonization, effectively positioning themselves for success in a zero-emission future.