Cold Ironing Takes Hold: Ports Achieve Cleaner Air by Electrifying Ship Berths

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Last Updated on: 18th May 2025, 01:44 pm

Decarbonizing maritime operations presents one of the more challenging—but also most impactful—frontiers in global sustainability efforts. As we enter the third phase of our comprehensive strategy for zero-emission ports, the focus shifts squarely toward addressing one of the most significant sources of port emissions: auxiliary engines from vessels at berth. Known in industry parlance as cold ironing, shore-side electrification provides vessels with clean electrical power directly from the port’s grid, allowing them to fully shut down diesel auxiliary engines while docked. Successfully implemented, this phase of electrification substantially reduces local air pollution, dramatically lowers greenhouse gas emissions, and strengthens the long-term competitiveness of ports.

This logical progression builds upon the successful groundwork established in the initial five years, where ground vehicles were electrified, and the focus of the second five years, electrifying port vessels, inland shipping and short sea shipping. 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.

Currently, vessels docked in ports typically rely on onboard diesel generators to provide power for critical systems, including lighting, refrigeration, crew accommodations, and operational equipment. These generators are among the largest contributors to air pollution within port boundaries, directly affecting the health and well-being of surrounding communities and port workers. At a representative mid-sized European port, auxiliary generators from visiting ships collectively burn roughly 2,500 tonnes of diesel fuel annually, equivalent to approximately 10 gigawatt-hours of clean electrical power when replaced by shore-side infrastructure. The environmental implications are considerable, with these engines generating substantial local emissions of carbon dioxide, nitrogen oxides, sulfur oxides, particulate matter, and significant noise pollution.

Implementing comprehensive shore power infrastructure requires significant investments in port electrical systems, notably high-voltage shore connection (HVSC) equipment. Meeting international IEC/ISO standards, HVSC installations typically involve specialized high-voltage connections—often in the 6.6 kV or 11 kV range—at berths serving larger vessels, such as container ships, bulk carriers, tankers, and cruise ships. Smaller vessels and inland barges are equipped with lower-voltage shore power connections, appropriate to their scale and power needs. Each berth or group of berths is supported by dedicated shore power stations, complete with frequency converters capable of delivering either 50 Hz or 60 Hz power, depending on vessel requirements, and transformers that ensure stable voltage levels. By the mid-2030s, progressive European ports such as Hamburg plan to have fully electrified all major berths, demonstrating both the urgency and feasibility of broad shore-side electrification within this timeframe.

Ensuring effective adoption of shore-side electrification demands regulatory and policy measures alongside technical infrastructure investments. Ports must coordinate closely with shipowners and operators to ensure vessels are equipped with onboard shore-power connection systems. European regulatory frameworks, notably the Fit for 55 initiative and FuelEU Maritime directive, are significantly accelerating this transition by mandating or strongly incentivizing shore-side electrification at major European ports. By proactively aligning port operations with these frameworks, ports not only improve their environmental performance but also significantly enhance their competitive positioning. Early adopters of shore power infrastructure experience tangible market advantages, including increased attractiveness to shipping operators who are themselves under pressure to demonstrate clear sustainability credentials to their customers.

Total energy requirements for the port have plummeted because rejected energy has plummeted. In the baseline, pre-electrified port, rejected energy was 39 GWh, and it’s dropped to a tenth of that.

Implementing comprehensive shore power infrastructure naturally results in significantly increased electricity demand. For our representative port, replacing approximately 2,500 tonnes of diesel annually with grid-supplied electricity translates to an additional electricity load of roughly 10 gigawatt-hours per year. This represents a substantial increase over earlier electrification phases, bringing total annual port electricity consumption to approximately 45 gigawatt-hours by the end of Phase 3. Peak demand management emerges as a critical operational challenge, with large container vessels individually drawing 1–2 megawatts of continuous power while docked. During periods when multiple large vessels are simultaneously in port, the combined load could easily reach 10–20 megawatts, emphasizing the necessity for robust, well-managed electrical infrastructure capable of reliably meeting substantial, variable power demands.

To reliably supply the increased electrical load, significant expansion of renewable energy capacity—particularly offshore wind—is essential. Ports would ideally secure approximately 50 megawatts of offshore wind capacity by the late 2030s, a level of generation capable of producing roughly 175 gigawatt-hours annually given typical offshore capacity factors of around 40%. This comfortably exceeds the projected port demand, ensuring surplus renewable electricity is consistently available. Strategically locating wind farms offshore, with dedicated cable connections directly into port substations, enhances operational reliability and reduces transmission losses.

In addition to offshore wind, continued expansion of solar installations—an additional 5 to 10 megawatts, likely a small portion of offshore platform-based solar as China’s major port cities are building—further bolsters renewable energy supply. Enhanced grid interconnections, potentially at high voltages of 110 kV or 150 kV, facilitate efficient and flexible power exchange, ensuring ports can effectively manage periods of surplus generation by exporting excess electricity to regional grids or storing it for later use.

Large-scale battery energy storage systems become critical at this stage, effectively balancing renewable variability and managing intense peak loads created by simultaneous vessel charging. Ports would deploy battery storage capacities in the range of 50–100 megawatt-hours, sufficiently large to provide significant peak shaving capabilities—delivering sustained power bursts during times of peak demand—and smoothing the intermittent nature of renewable generation. A 100 megawatt-hour battery installation, for example, would have the capacity to supply continuous power of approximately 10 megawatts for ten hours, effectively managing intensive demand periods and ensuring grid stability. Additionally, such storage systems provide crucial short-duration backup power in case of grid outages, enhancing port resilience and operational reliability.

Financially, Phase 3 of electrification represents a substantial but strategically justified investment, on the order of €150 million. Capital expenditures would include approximately €30 million dedicated to equipping around twenty berths with HVSC systems—comprising cable reels, substations, frequency converters, and transformers. An additional €10–15 million would support central infrastructure, such as main substations and frequency conversion facilities. Offshore wind energy development would entail investment commitments of approximately €80 million from the port, depending on partnership structures or power purchase agreements. Battery storage systems, at expected future prices around €300 per kilowatt-hour, would add another €30 million for a 100 megawatt-hour installation. Necessary grid upgrades and interconnection enhancements might account for an additional €20 million, bringing the total projected investment to approximately €150 million. Although substantial, this investment yields significant long-term economic benefits through sharply reduced fuel and maintenance costs, enhanced regulatory compliance, and strengthened competitive positioning.

Operationally and environmentally, comprehensive shore power electrification delivers transformative benefits. Eliminating in-port vessel auxiliary engine emissions virtually eradicates localized air pollutants—carbon dioxide, nitrogen oxides, sulfur oxides, particulate matter—and significantly reduces ambient noise pollution, resulting in immediate and tangible public health improvements. Economically, vessel operators gain substantial cost savings through reduced fuel expenditures and decreased onboard generator maintenance, reinforcing the attractiveness and financial viability of ports offering comprehensive shore-side electricity.

From a strategic perspective, ports implementing comprehensive shore power early establish themselves as forward-looking leaders in maritime sustainability, gaining substantial competitive advantages. Aligning early with regulatory requirements positions these ports as preferred hubs for shipping operators increasingly pressured to demonstrate verifiable sustainability efforts. Industry analyses from leaders like APM Terminals consistently illustrate significant reductions in total cost of ownership through electrification as battery costs plummet, further reinforcing the strategic business case underpinning comprehensive shore-side electrification.

Ultimately, Phase 3 shore-side electrification serves not only as an essential environmental and economic improvement but as a critical foundation for subsequent, deeper maritime decarbonization measures, including full vessel electrification and zero-emission propulsion strategies. Ports that proactively embrace comprehensive shore power infrastructure today lay the critical groundwork for long-term market leadership, operational resilience, and sustained competitive advantage in a rapidly evolving global shipping landscape.