Plugging into Onshore Power Supply System Innovation: A Review from Standards and Patents to Port Deployment

Abstract

Shore power systems, also known as cold ironing or shore-to-ship (STS) connections, are increasingly recognized as a viable solution to reduce emissions and noise from ships during berthing operations. This paper provides a comprehensive overview of shore power technology, with a focus on typical onboard energy consumption profiles across different types of ship, the main electrical architectures used in shore-side systems, and the compatibility challenges related to frequency, voltage, and control integration. The paper reviews international standards, particularly the ISO/IEC/IEEE 80005 series, that define technical requirements for interoperability and safety. A detailed analysis of recent patents highlights technological innovations in mobility, conversion topologies, and high-voltage integration. In addition, commercially available shore power solutions from major manufacturers are surveyed, with comparative data on power ratings, voltage levels, and converter topologies. Finally, the study discusses current limitations and outlines development directions for Onshore Power Supply systems, including regulatory developments, digital integration, and grid support functionalities. The insights presented aim to support the design, standardization, and deployment of efficient and scalable STS systems in line with global maritime decarbonization goals.

1. Introduction

1.1. Background

The electrification of the maritime sector has emerged as a strategic pillar in the global energy transition, recognized as one of the most promising initiatives to decarbonize maritime transport [1,2,3]. In the face of increasing climate concerns and growing pressure from bodies such as the International Maritime Organization (IMO) to reduce greenhouse gas emissions, the shipping industry is investing heavily in sustainable technologies to promote energy efficiency and reduce its environmental footprint [4,5,6,7].

Against this backdrop, the adoption of Onshore Power Supply (OPS) systems has emerged as a viable and environmentally responsible way to power ships on the berth [8,9,10,11]. Also known in the literature as cold ironing (CI), this concept involves turning off the auxiliary generators of ships during their stay in port and supplying power directly from the shore network [12,13,14]. This measure significantly reduces local air pollutants and noise emissions, thereby improving air quality in port environments and surrounding urban areas [15,16].

However, effective implementation of OPS systems poses significant technical challenges, particularly with respect to the compatibility of the frequency and voltage standards used in land-based networks and onboard ships [13,17,18]. Although most shore-based electrical networks operate at 50 Hz, many ships, particularly those originating from the Americas and Asia, require 60 Hz [17,19,20]. This dissimilarity requires the incorporation of solutions for frequency conversion and voltage adaptation, which are further complicated in port contexts due to the presence of multiple types of ship [8,9,20,21].

The implementation of such systems is often challenged by the heterogeneity of technical interfaces, electrical parameters, and regulatory frameworks between different countries and ports. In response to these challenges, several international standardization efforts have emerged, most notably the IEC/IEEE 80005 series [17,22,23], which aims to harmonize the technical and safety requirements for shore connection systems. Currently, a variety of connection architectures, industrial patents, and commercial solutions have emerged, demonstrating adaptability to diverse operational and geographical contexts [22,24]. These approaches range from centralized solutions to more modular and flexible configurations and are often influenced by factors such as the type of ship, the electrical infrastructure available in the port, and local regulatory requirements.

This paper presents a summary review of OPS systems that addresses the key dimensions that support their development, implementation, and future evolution. The review begins with an overview of OPS systems, followed by a detailed examination of their architectural configurations used to establish the electrical interface between port infrastructure and ships. The technical characteristics of different ship categories are considered, focusing on the specific electrical and operational parameters that influence the design and compatibility of OPS connections. This includes variations in voltage levels, frequency requirements, and shipboard power management systems, which are critical to ensuring seamless integration and safety. The paper then investigates the principal international technical standards that govern OPS systems, with particular attention to those issued by standardization bodies such as the IEC, ISO, and IEEE. These standards provide the regulatory and technical framework necessary for the harmonization and interoperability of OPS technologies, ensuring that ships can seamlessly connect to shore power systems at different ports throughout the world, regardless of the equipment manufacturer or national regulations. The analysis proceeds with a critical evaluation of commercially available OPS solutions, describing their functional characteristics, deployment strategies, and technological maturity of the different implementations currently adopted in various international ports.

1.2. Methodology

This review was conducted following a structured approach adapted to the technological and engineering context of OPS systems. The methodology consisted of four key stages:

• Database Search: A comprehensive literature search was performed using Scopus, complemented by targeted searches in IEEE Xplore, ScienceDirect, and MDPI Journals. Keywords included: “Onshore Power Supply”, “Shore-to-Ship”, “Cold Ironing”, “High Voltage Shore Connection”, and “Maritime Decarbonization”.
• Selection Criteria: Studies were included if they addressed OPS technologies, shore-to-ship architectures, international standards, patents, or commercial deployments. The excluded criteria involved publications with limited technical content.
• Screening and Data Extraction: From an initial pool of studies (2010–2025), articles were selected based on relevance. Data were extracted on system architectures, energy demand estimation methodologies, technical challenges, and case studies in ports. In the case of patents, the time frame was extended to ensure broader coverage.
• Critical Analysis and Synthesis: The selected studies were compared according to their scope, methodological rigor, and contribution to the development of the OPS system. In addition, patents and commercial solutions were analyzed separately to complement academic findings.

A bibliometric analysis, based on an RIS file obtained from the Scopus database, was conducted to guide the structure of the review, as illustrated in Figure 1. The proposed bibliometric visualization for the keywords supplied by the authors was created with the VOS viewer. The figure shows the co-occurrence network of the main keywords, organized into clusters by color, where the size of each node represents the frequency of occurrence and the thickness of the links indicates the strength of their connections. Four main thematic groups can be observed: renewable energy and power generation (red cluster), maritime applications such as cold ironing and ships (green cluster), sustainability and power supply (blue cluster), and economic aspects like costs and electric utilities (yellow cluster). This structure highlights the interdisciplinary nature of the research, connecting technological, environmental, and economic dimensions of the energy transition in port and maritime contexts. In addition to case studies and technical analyses, several works have been published in the form of literature reviews, aiming to synthesize existing knowledge on maritime electrification and, in particular, the adoption of OPS systems. These reviews provide a comprehensive overview of the state of the art, highlighting barriers, technological advances, and regulatory challenges associated with OPS implementation.

Table 1. Summary of literature review studies on OPS and ship electrification.

Author/Year	Scope of Study	Main Contributions	Limitations
Abu Bakar et al. (2023) [3]	Electrification of OPS	Comprehensive overview of cold ironing technologies and port decarbonization strategies	Limited coverage of patents and commercial applications
Deng (2023) [5]	Carbon emissions from shipping	Synthesized global shipping emission trends	Focused on emissions, limited discussion of OPS
Williamsson et al. (2022) [8]	Barriers and drivers of OPS adoption	Identified key barriers (economic, regulatory, technical)	No technical modeling or case validation
Sulligoi et al. (2015) [25]	Shore-to-Ship Power systems	Provided state-of-the-art review of OPS technologies	Outdated regarding recent renewable integration
Mahdi et al. (2023) [26]	Power converters for ship electrification	Classified converter technologies for shipboard systems	Limited focus on ship side
Nuchturee et al. (2020) [27]	Integrated electric propulsion	Analyzed energy efficiency and benefits of integrated propulsion	Limited empirical validation
Yang et al. (2023) [28]	Shore power systems	Discussed key technologies of OPS	High-level discussion, less technical depth
Xu et al. (2022) [29]	DC shipboard microgrids	Reviewed architectures, storage, and converters for ship electrification	Part I only, not OPS-specific
He et al. (2018) [30]	Standards for OPS	Discussed international standards for OPS implementation	Lacked analysis of adoption in practice
Puig et al. (2023) [31]	Regulatory and technological challenges in Europe	Identified barriers in European ports for OPS deployment	Geographically limited to Europe

summarizes the main literature review articles identified in the field, outlining their scope, key contributions, and limitations.

2. OPS Systems Architecture

Various terms are used in the literature to describe technologies that supply the energy demand of ships while its auxiliary engines (AEs) are shut down. The most commonly adopted term is cold ironing, which originates from the historical practice of allowing steam engines to cool, hence, “iron turning cold” while ships were berthed in port [14,32]. Over time, other terms such as Shore-Side Electricity (SSE), Onshore Power Supply, Alternative Maritime Power (AMP), and, more recently, High-Voltage Shore Connection (HVSC), have emerged to describe similar systems. These are often used interchangeably with expressions such as Shore-to-Ship Power, Shore-to-Ship Electrification and Shore-to-Ship Connection [21,25,33,34,35,36].

STS power supply involves the transfer of electrical energy from the local utility grid to the electrical systems onboard the ship via a cable interface while the ship is berthed. This setup allows internal systems on the ship, such as cargo handling equipment, lighting, ventilation, and other auxiliary loads (hotelling load) [37] to remain fully operational without relying on fossil fuel generators onboard. To ensure compatibility, power on the shore is converted in both voltage and frequency according to the electrical requirements of the ship [19]. Regulatory pressures, financial incentives, and the emergence of international standards for STS technologies [35] are key drivers that support their increasing adoption in maritime sectors around the world.

The implementation of STS represents a promising and effective strategy to reduce greenhouse gas (GHG) emissions and other environmental pollutants such as nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter (PM), as well as to mitigate noise and vibration pollution in port areas [21,34,36,38]. An analysis by Corbett and Comer estimated the potential emissions reductions from shore power for at-berth cruise vessels at the Port of Charleston, SC. They found that shore power would greatly reduce air pollution from these ships, as shown in

Table 2. Greenhouse gas estimated emissions reductions from using shore power over auxiliary engines at the Port of Charleston [39].

Pollutant	Percent Reduction Using Shore Power
Carbon Monoxide (CO)	92%
Nitrogen Oxides (NOx)	98%
$\mathrm{P}{\mathrm{M}}_{10}$	59%
$\mathrm{P}{\mathrm{M}}_{2.5}$	66%
Sulfur Dioxide (SO2)	73%
Carbon Dioxide (CO2)	26%

[39]. In addition, several emission calculators are available to estimate the environmental impact at each port, providing support for decision-making and monitoring. Examples include the Shore Power Emissions Calculator by Atlas EV Hub [40], the ASEA Power Systems calculator [41], and the EPA Tools developed by the U.S. Environmental Protection Agency [39,42], among other internationally recognized platforms that allow the evaluation of emissions from ships, cargo handling equipment, and port operations.

A complete STS system typically comprises three core components: the shore-side power supply infrastructure, the cable connection interface, and the shipboard reception system. Two main configurations are widely used: Low-Voltage Shore Connection (LVSC) and High-Voltage Shore Connection (HVSC). The former, ranging between 380 and 690 V, was common in early implementations but requires multiple parallel cables due to limited transmission capacity. In contrast, HVSC systems, typically operating between 6.6 and 11 kV, have gained prominence due to their operational simplicity and efficiency, often requiring only one or two cables. Furthermore, HVSC enables the flexible supply of power to ships with different onboard voltage requirements, including those originally designed for low-voltage reception. However, onboard transformers are required to step down the high voltage to appropriate levels. Due to the complexity and weight of high-voltage cables required for power transfer, a dedicated cable management system (CMS), such as a crane-based deployment mechanism is typically used to ensure safe, efficient, and reliable connection between the ship and the shore power supply [3].

In Figure 2 a generic configuration of these systems is shown.

2.1. Typology and Ship Requirements

There exists a wide range of ship types based on their specific operational functions, such as cruise ships, liquefied natural gas (LNG) carriers, container ships, and roll-on/roll-off (Ro/Ro) ships. These ship categories can be further classified according to their respective power requirements on both the onboard and shore-side systems during port stays. Currently, most ships operate with low-voltage systems, typically within the range of 380–460 V, although a limited number of ships use higher voltage levels [3]. Currently, approximately 75% of the ships are designed to operate at a frequency of 60 Hz, while the remaining 25% use a supply frequency of 50 Hz [3]. As illustrated in Figure 3, most large cruise ships, along with a small subset of large container ships, employ high-voltage onboard systems, whereas the vast majority of other types of ships continue to operate with low-voltage configurations.

Table 3. Power demand, voltage and frequency occurrence of different ships [3,21].

Ship Type	Average Power Demand [kW]	Peak Power Demand [kW]	Peak Power Demand for 95% Ships [kW]	Frequency
				50 Hz	60 Hz
Container ships ($d<140$ m)	170	1000	800	63%	37%
Container ships ($d>140$ m)	1200	8000	5000	6%	94%
Container ships (total)	800	2000	4000	26%	74%
RoRo and vehicle ships	1500	2000	1800	30%	70%
Oil and product tankers	1400	2700	2500	20%	80%
Cruise ships ($d<200$ m)	4100	7300	6700	36%	64%
Cruise ships ($d>200$ m)	7500	11,000	9500	–	100%

summarizes the voltage levels and corresponding power requirements for various types of ships at the shore-side interface, according to the HVSC standard [24]. The table also presents the proportion of categorized ships operating at 50 Hz or 60 Hz. The power values presented in Table 3 correspond to the power needed by the AE while the ship is docked. Subsequently, these values are used to determine the energy demand that the OPS system needs to supply [43].

2.2. Shore-to-Ship Architectures

STS systems can be implemented using different architectures, as shown in Figure 4, each with specific architectural characteristics, operational requirements, and technical constraints [12,21,44]. Centralized AC, presented in Figure 4a, is based on a centralized high-power converter capable of supplying multiple berths simultaneously. This converter is housed in a main station, which, due to its large physical footprint, is typically located away from the quay. It feeds matching transformers placed at the main distribution station. The rated power of the frequency converter and transformers generally ranges from a few megawatts up to 10 MW, depending on the port capacity and demand. Although this centralized solution has been implemented in European ports [45], operational problems have been reported, specifically failures originating from a single connected ship that occasionally led to complete system shutdown, resulting in blackouts on other ships. Such occurrences highlight the critical importance of providing uninterrupted power for maritime safety. To mitigate the risk of total system failure, redundancy strategies should be considered. These may include the integration of local backup systems to ensure continuity of supply during critical failures.

Distributed AC, presented in Figure 4b, addresses the reliability concerns of the first topology by deploying multiple lower-power frequency converters, typically around 1 MW each in the main distribution station [3,46,47]. As illustrated in the configuration, the system includes three or more independent converters, which can operate individually or in parallel (via power management) to meet the demands of ships with higher power requirements. This architecture improves fault tolerance significantly; failures in one converter do not compromise the entire system, thereby enhancing operational reliability. The main drawback of this configuration lies in the increased space requirement to accommodate multiple converters and transformers. To overcome this limitation, a scalable implementation using containerized systems has been proposed. These containers integrate complete conversion paths (converter and transformer), enabling easy future expansion of the STS infrastructure. Scalable systems allow the development of power blocks ranging from several hundred kVA to more than 10 MVA and can be arranged in standard racks or cabinets. This redundant and containerized architecture supports continuous operation even in the event of module failure, with only light performance degradation, offering what is termed advanced redundancy [44,45].

Distributed DC, presented in Figure 4c, introduces a high-voltage direct current (HVDC) based architecture, where the primary advantage lies in the ability to interface power systems operating at different frequencies. In this configuration, the alternating current is rectified at the main distribution station and transmitted in DC form to local inverters on the quay, which then reconvert it into AC to power the ship. The use of HVDC offers several well-established benefits: reduced transmission losses (by approximately 33%), distance-independent power delivery, no need for reactive power compensation, and the ability to interconnect asynchronous grids [45]. In addition, HVDC enables dynamic and precise control over the magnitude and direction of power flow. However, this architecture suffers from a key limitation: the dependence on a single AC/DC converter at the central station, whose failure would lead to a complete system outage. To mitigate this issue, the design can be modernized by integrating several smaller AC/DC converters that operate independently connected to the DC bus, as shown in Figure 4d. This configuration is referred to as the multi-distributed architecture, which enhances system reliability by avoiding a single point of failure. This architecture, referred to here as multi-distributed, draws inspiration from similar designs in the literature, such as multi-string photovoltaic inverters [48], multi-terminal HVDC systems [49], and multi-converter DC microgrids [50]. These examples highlight the well-recognized benefits of modular redundancy, fault tolerance, and operational flexibility, which are likewise achieved in the proposed architecture. Moreover, DC distribution provides the flexibility to integrate with energy storage systems (ESSs) and renewable energy sources (RESs) such as photovoltaics (PV) [3]. In particular, in Centralized and Distributed AC, no conversion equipment is installed directly on the quay, as the physical presence of large power electronic devices could disrupt port operations and infrastructure. A viable solution to this constraint involves using mobile platforms equipped with frequency converters and matching transformers, which can be flexibly deployed at different berths [44,45].

Figure 4. Shore-to-ship architectures. (a) Centralized AC; (b) Distributed AC; (c) Distributed DC; (d) Multi-distributed [3,44,45,51].

Figure 4. Shore-to-ship architectures. (a) Centralized AC; (b) Distributed AC; (c) Distributed DC; (d) Multi-distributed [3,44,45,51].

To support practical orientation-making, the choice of the most appropriate OPS architecture should be guided by port-specific characteristics. A useful framework considers three key dimensions: port size and power demand, ship diversity, and infrastructure constraints. For small to medium ports with relatively homogeneous fleets, a Centralized AC architecture may provide a cost-effective solution, despite its lower redundancy. For medium to large ports serving diverse ship profiles, Distributed AC offers higher reliability and modular scalability, particularly when implemented with containerized systems. Distributed DC becomes attractive for ports that seek to improve efficiency in long-distance power delivery and facilitate integration with renewable energy and storage systems, although careful attention to single-point failure risks is required. Finally, Multi-distributed DC represents the most advanced configuration, suitable for large international hubs where redundancy, scalability, and operational resilience are critical [45]. Therefore, a comparative assessment of the various available STS configurations is essential to determine the most suitable solution for each application.

Table 4. Comparison of the architectures of the STS system [3,44,45].

Architecture	Advantages	Disadvantages
Centralized AC (One central conversion station supplies all terminals via AC lines)	Small footprint of the central station, installed at a distance from the quays. Slightly lower installation cost compared to distributed topologies.	Low power quality (high THD), requires harmonic filters. No inverter-based synchronization with onboard systems. Limited availability of specialized services for large power converters.
Distributed AC (Multiple local AC conversion units near or on the quays)	High system reliability (failure affects only one terminal). Good voltage quality due to local inverter use. Possible containerized installations for flexible expansion. Inverter-based synchronization with ship systems.	Higher installation cost due to multiple conversion units. Occupies physical space near the quay. Potentially higher operational and maintenance costs.
Distributed DC (A central AC/DC station feeds DC lines; local DC/AC converters are located at each berth)	Compact central station footprint. High efficiency due to reduced losses in DC transmission. Good flexibility for future terminal expansions.	DC/AC inverters at quays may interfere with port operations. Failure in the central AC/DC converter affects the entire system.
Multi-distributed (Multiple AC/DC converters feed a common DC bus supplying several terminals; local DC/AC converters are located at each berth)	Increased system redundancy (failure of one AC/DC unit does not disable the system). Shared DC bus allows flexible power distribution to different terminals. High transmission efficiency due to DC architecture. Scalable (supports future power demand increases).	Higher system complexity in terms of protection, control, and coordination. Requires careful design of DC bus and power balancing mechanisms. Slightly higher capital expenditure due to multiple AC/DC units.

provides a comparative overview of the STS architectures described, highlighting their key technical features, advantages, and limitations.

3. Shore-to-Ship Standardization, Incentives and Recommendations

The establishment of international standards for STS power systems is essential to ensure global interoperability, technical reliability, and operational safety [30,52]. Standardization prevents market fragmentation and strengthens stakeholder confidence by providing universally recognized technical guidelines. Joint efforts by international bodies such as the International Electrotechnical Commission (IEC), International Organization for Standardization (ISO), and the Institute of Electrical and Electronics Engineers (IEEE) have resulted in a comprehensive framework that addresses the electrical, mechanical, and safety requirements of STS systems. This framework encompasses the design and installation of low- and high-voltage shore power distribution networks, standardized interface and connection devices, specifications for plugs and sockets, and systems for control, monitoring, and protection.

The Oil Companies International Marine Forum (OCIMF) [53], for example, has emphasized the need for harmonized best practices in the use of shore power, focusing on safety, compatibility, and regulatory alignment. In addition, organizations such as the International Association of Ports and Harbors (IAPH) [54], the World Ports Climate Action Program (WPCAP) [55], and the European Sea Ports Organization (ESPO) [56] have been instrumental in promoting the deployment of shore power as a strategic climate action, offering policy guidance, technical roadmaps, and implementation toolkits.

These coordinated efforts are crucial to overcome interoperability barriers, reduce investment risk, and ensure that port authorities and shipping lines align under a common regulatory and technical framework for decarbonized port operations.

Table 5. Reference International Standards.

Standard	Description	Implementation
IEC/IEEE 80005-1:2019 [24]	General requirements: high voltage shore side.	Shore
IEC/IEEE 80005-2:2016 [57]	Data communication for monitoring and control.	Shore/Ship
IEC/IEEE 80005-3:2014 [58]	General requirements: low voltage shore side.	Shore
IEC/IEEE 80005-4:2023 [59]	General requirements Direct Current shore connection.	Shore
IEC 62613-2:2016 [60]	Dimensional compatibility and interchangeability requirements for accessories to be used by various types of ships.	Connection
IEC 60309-5:2017 [61]	Dimensional compatibility and interchangeability requirements for plugs, socket outlets, ship connectors and ship inlets for LVSC systems.	Connection
IEC 60092-201:2019 [62]	General system design for electrical installations in ships.	Ship
IEC 60092-503:2021 [63]	AC supply systems with voltages in the range of above 1 kV up to and including 36 kV.	Ship
IEC 60146-1-1:2024 [64]	Specification of basic requirements for semiconductor power converters.	Converter
IEEE 1662-2023 [65]	Onshore and offshore electrical power systems.	Shore/Ship
IEEE 1709-2018 [66]	DC power distribution on ships.	Ship
IEEE 45.1-2023 [67]	Design of shipboard electrical generation and propulsion.	Ship

shows the main standards for STS systems.

3.1. Main Standards for STS Systems

The IEC/ISO/IEEE 80005 series, titled Utility Connections in Port, consolidates technical requirements for low-voltage and high-voltage shore power systems [24,35,57,58,59]. The HVSC standard [24,68] addresses key technical challenges in shore power systems, standardizing connection voltages to 6.6 kV and 11 kV. It defines acceptable voltage deviation ranges for steady-state and transient conditions and establishes thresholds for total harmonic distortion (THD) [24,35,69]. It also specifies requirements for short-circuit current contributions from both shore and ship [70]. The IEC/ISO/IEEE 80005-3 complements this framework by focusing on low-voltage shore connection (LVSC) systems, providing guidelines for smaller vessels such as ferries and inland ships, where typical connection voltages are below 1 kV [58]. According to IEC/IEEE 80005-1:2019 [24], ships with higher power demand should be connected at nominal voltages of 6.6 kV and/or 11 kV. Onboard, the standard nominal voltage is typically 400/440 V AC, although some ships may also operate at 6.6 kV or 11 kV AC. In such cases, a voltage transformer may be required to ensure compatibility with the electrical systems of ships.

Table 6. Summary of key operational tolerances and power quality requirements for STS standards [24,58,71].

Parameter	High-voltage shore connection (IEC/IEEE 80005-1)	Low-voltage shore connection (IEC/IEEE 80005-3)
Nominal Voltage	6.6 kV 11 kV	400 V 440 V 690 V 230 V also possible for less demanding consumption < 50 kW
Voltage Tolerances	No-Load Conditions: 6% of nominal voltage increase Load Conditions: 3.5% max voltage drop
Nominal Frequency	50/60 Hz DC for fast DC charging systems
Frequency Tolerances	Continuous tolerance: ±5%
Transient Response	Voltage: −15% < dV < 20% (1.5 s) Frequency: ±10% (5 s)
Harmonic Distortion	For no-load conditions, voltage harmonic distortion limits: <3% (single harmonics) <5% (total harmonic distortion)
Voltage variations for DC supply	Voltage tolerance (continuous): ±10% Voltage cyclic variation deviation: 5% Voltage ripple (RMS over steady DC voltage): 10%
Voltage variations for battery systems	Components connected to the battery during charging: +30%, −25% Components not connected to the battery during charging: +20%, −25%

summarizes the key operational tolerances and power quality requirements for STS standards.

Other relevant standards include IEC 60092 for shipboard electrical installations; IEC 60146 for semiconductor converters; IEC 61000 for electromagnetic compatibility; and IEEE standards such as IEEE 1662, IEEE 1709, IEEE 1826, and IEEE 45, which collectively define the design and operational guidelines for power distribution on ships and in port environments [62,63,64,65,66,67]. Furthermore, the IEC 62613 series, comprising IEC 62613-1:2018 and IEC 62613-2:2018, specifies the design and dimensional requirements for plugs, socket outlets and ship couplers used in HVSC, ensuring interchangeability between different ship types. These standards also address the mechanical and safety characteristics required for effective and secure connections [60]. The connector design, the switchgear ratings, and the maximum number of power cables per ship are also standardized [46]. Compatibility with rotary or static frequency converters is required to accommodate ships with different electrical frequencies onboard [12]. The shore-side electrical system shall ensure that each connected ship is galvanically isolated from other ships and consumers. For this purpose, a transformer installed on the shore side must provide galvanic isolation and voltage conversion, typically from 20 to 100 kV down to 6.6 or 11 kV, and must include star-connected secondary windings with a neutral earthing resistor. When frequency conversion is required, an earthing transformer must be used [35,71].

Although the IEC/ISO/IEEE 80005 [24,57,58,59] series provides a strong foundation for OPS standardization, several gaps and conflicts remain that hinder full interoperability. One critical issue concerns the lack of harmonization in connector types and cable management systems between manufacturers, which often results in incompatibility between different port and ship installations. Furthermore, while the standards acknowledge both static and rotary frequency converters, they do not provide clear guidance on preferred implementation practices, leading to variations in synchronization performance. Another gap lies in the limited coverage of DC-based OPS systems, with IEC/IEEE 80005-4 [59] still in its early stages, leaving uncertainties regarding voltage levels, protection schemes, and integration with renewable and storage systems. In addition, regional differences in voltage tolerances, earthing arrangements, and galvanic isolation requirements create challenges for manufacturers looking to provide universal plug-and-play solutions. Addressing these gaps is essential to ensure true interoperability and seamless deployment of OPS in various ports and ship types worldwide [71].

3.2. Directives and Recommendations

Due to the considerable environmental benefits and broad applicability of STS systems across ship types, various economic instruments have been introduced to accelerate their deployment. These include direct subsidies for infrastructure development, preferential electricity tariffs, tax exemptions, and environmental penalties for non-compliance. The structure of these incentives depends on the policy objectives of the national governments and the participation of key stakeholders, including port authorities and shipping operators. As highlighted in [52], shifting part of the investment risk to public authorities has proven effective in increasing the adoption rate of shore power systems.

Several European ports have already implemented HVSC systems with substantial financial support from European Union funding programs, which significantly reduce capital costs [72]. Furthermore, the Implementation Decision 2011/384/EU of the Council authorizes Sweden to apply reduced energy tax rates for electricity supplied directly to berthed ships, as permitted by Article 19 of Directive 2003/96/EC [73].

Table 7. Directives and Recommendations.

Directive/Recommendation	Description	Implementation
EU Directive 2003/96/EC [73]	Taxation framework for energy products and electricity.	Shore
EU Directive 2006/339/EC [72]	Promotion of shore-side electricity to reduce emissions.	Shore
EU Directive 2012/33/EC [74]	Limitation of sulphur content in marine fuels.	Ship
EU Directive 2014/94/EU [75]	Deployment of alternative fuels infrastructure.	Shore
EU Directive 2016/802/EU [76]	Reduction in sulphur content of liquid fuels.	Ship
IMO MARPOL Annex VI [77]	Air pollution prevention regulations for ships.	Ship

shows the directives and recommendations for shore power.

Currently, a limited number of ports in several coastal EU Member States are equipped with STS energy facilities, with the majority of the available capacity dedicated to serving container ships, passenger ships, and cruise ships [78]. It is estimated that the EU must triple or even quadruple its capacity by 2030 to meet its current environmental targets. Existing regulations are projected to achieve only a 24% reduction in annual CO₂ emissions within EU ports, which is approximately 4.37 Mt [78]. To maximize the benefits of CO₂ reduction and achieve complete emission neutrality in port operations, a series of directives and recommendations must be adopted.

The regulatory scope should be broadened to include all ships with a gross tonnage (GT) of 400 or more, mandating their connection to shore power in all EU ports. This expansion should extend beyond the current ports of the trans-European transport network (TEN-T), which currently cover less than 70% of the energy demand of ships in port [79]. Extending obligations to ports outside the TEN-T network could quadruple infrastructure deployment needs, significantly increasing the potential for emission reductions. Boilers onboard ships, which currently account for 44% of CO₂ emissions in EU ports, must be integrated into shore power requirements. Boilers are responsible for up to 70% of the port energy consumption in tankers and between 26% and 34% in container and passenger ships. Electrification or connection of boilers to shore power systems would increase infrastructure demand by approximately 15% to 26%, nearly doubling the potential CO₂ savings [78].

Clear targets for the share of renewable energy in port electricity supplies should be established to minimize the environmental footprint of shore power. Incentivizing local clean energy generation in ports will further enhance sustainability and reduce greenhouse gas emissions. The economic viability of shore power deployment depends on developing attractive business models and economic incentives. High capital and operational costs currently hinder adoption, which requires the review of tax policies and electricity tariffs to incentivize shore power usage [8]. Mechanisms such as preferential tariffs, subsidies, and environmental penalties for non-compliance should be employed. Including externalities such as public health benefits in financial assessments will increase the attractiveness of shore power investments. Furthermore, integrating the maritime sector into the EU Emissions Trading System (EU ETS) will strengthen the economic rationale for shore power by increasing the cost of carbon emissions [8,78].

Effective stakeholder collaboration is imperative. Cooperation among ship operators, port authorities, policymakers, research institutions, grid operators, electricity suppliers, cargo owners, and equipment manufacturers is needed to coordinate investments and promote adoption along key shipping routes. Strengthening the capacity of port authorities to handle increasing energy demands and fostering strong partnerships with local authorities and grid operators will be crucial to the successful implementation of shore power systems Economic instruments have played a vital role in the acceleration of shore power deployment. Direct subsidies for infrastructure, preferential electricity tariffs, tax exemptions, and penalties for non-compliance have proven effective. Public authorities that share part of the investment risks have notably increased adoption rates [52]. Several European ports have benefited from substantial EU funding programs that reduce capital costs to implement HVSC systems [80]. Furthermore, the Council Implementation Decision 2011/384/EU authorizes Sweden to apply reduced energy tax rates for electricity supplied directly to berthed ships, as allowed by Directive 2003/96/EC [73].

In addition to the established directives, recent developments have further strengthened the regulatory framework for the deployment of OPS. The International Association of Classification Societies (IACS) introduced new Unified Requirements that specifically address OPS retrofits, providing guidelines on the safe integration of shore connection systems into existing ships [81]. These recommendations cover electrical protection, interface compatibility, and operational procedures, thereby supporting fleet-wide adaptation. At the European level, the FuelEU Maritime Regulation (EU 2023/1805) mandates that container and passenger ships connect to OPS when at berth in major EU ports from 2030 onward, setting a binding requirement for operators [78,82]. Complementing this, the Alternative Fuels Infrastructure Regulation (AFIR, EU 2023/1804) requires all TEN-T core and comprehensive network ports to deploy OPS infrastructure by 2030, ensuring wide availability across Europe. Together, these initiatives provide a robust and forward-looking regulatory framework that accelerates OPS adoption and directly supports EU decarbonization goals [78].

3.3. European Incentives and Research Agendas

The policy frameworks of the European Union have increasingly emphasized the deployment of shore-side electricity as a key strategy for port decarbonization and improvements in air quality in coastal urban centers [83]. Since the adoption of Directive 2014/94/EU on the deployment of Alternative Fuels Infrastructure [75], STS has been explicitly identified as a priority infrastructure for TEN-T core network ports, with mandatory installation by 31 December 2025, unless a cost–benefit analysis demonstrates disproportionate investment relative to environmental advantages. Member states may also apply reduced taxation on electricity supplied to shore-side systems and ships at berth under the Energy Taxation Directive, a derogation already adopted by countries such as Denmark, Germany, Spain, Sweden, France and Italy [84].

Incentive design research shows that a combination of installation subsidies (for infrastructure deployment) and utilization subsidies (rewarding actual use by ships) can optimize environmental outcomes and financial effectiveness. However, economic modeling suggests that the installation of infrastructure without sufficient uptake of ships may not produce net emission reductions unless the deployment and regulatory incentives are properly aligned [85]. To support implementation, EU financial instruments such as the TEN-T program and the Connecting Europe Facility (CEF) have co-funded numerous OPS infrastructure projects. At the national level, governments in Germany, France, Italy, Norway, Sweden, and Denmark have implemented support schemes that grant financial aid, tax reductions, or direct subsidies to offset the high capital and operational costs of shore power installations. In Norway, entities such as Enova SF and the NOx Fund have invested hundreds of millions of NOK in OPS in Norwegian ports [85]. Notable examples include

• A joint EUR 18.8 million CEF funded project involving Bremerhaven, Gothenburg, Aarhus, and Stockholm to enable shore power for container ships by 2030 [86].
• A EUR 3.2 million grant under the Alternative Fuels Infrastructure Facility (AFIF) awarded to the Port of Antwerp Bruges (Zeebrugge) to install cruise ship OPS starting in 2026 [83].
• European Commission approval of a EUR 570 million Italian national scheme providing up to 100% reduction in general system charges (network fees) for electricity used in shore power systems, valid until 2033 [87].

Beyond infrastructure funding, there are cornerstone initiatives such as the Zero Emission Waterborne Transport (ZEWT) partnership, established to accelerate the transition of inland and maritime waterborne transport to zero emissions by 2030 [53,88]. ZEWT fosters public–private collaboration and guides strategic investment priorities for research in electrification, alternative fuels, and enabling infrastructure such as OPS. It also contributes to the development of a Strategic Research and Innovation Agenda (SRIA), which outlines key milestones for technological, regulatory, and operational deployment in the direction of decarbonized shipping [53]. The European Research and Innovation Agenda, particularly under the Horizon Europe program, has increasingly supported pilot and R&D projects involving OPS. Horizon Europe Cluster 5: Climate, Energy and Mobility define priorities in clean transport and port electrification, directly funding innovation in cold ironing, smart energy systems, and grid integration [80]. Earlier Horizon 2020 initiatives also played a critical role in advancing the digitalization and integration of renewables in maritime contexts [89]. The long-term direction of the EU research landscape is described in the Horizon Europe Strategic Plan 2025–2027, which identifies port electrification and resilient, climate-neutral infrastructure as the foundational pillars of the wider Horizon 2030 vision [88]. In conclusion, these cascade funding mechanisms enable ports to access targeted grants for innovation.

3.4. Economic Perspective on OPS Deployment

Beyond regulatory and technological aspects, the deployment of OPS systems also has important socio-economic impacts. The installation and operation of the OPS infrastructure generates direct employment opportunities in engineering design, construction, and maintenance, while also creating indirect jobs in related sectors such as manufacturing of electrical equipment, cabling, and converter technologies. For ports, the deployment of OPS is increasingly related to the concept of “green ports” [90], increasing their competitiveness in attracting environmentally conscious shipping companies and improving their public image among local communities. In addition, OPS contributes to healthcare cost reductions by reducing air pollutants emissions in densely populated coastal cities, which has been identified as a significant external economic benefit in cost–benefit analyses of shore power projects. These socio-economic dimensions reinforce the broader value proposition of OPS adoption, extending beyond emission reductions into regional development and public welfare gains [46,78].

A robust evaluation of the adoption of OPS requires not only a regulatory review but also an economic perspective. Several cost–benefit assessments indicate that while capital expenditure (CAPEX) for OPS infrastructure is high, long-term benefits from fuel savings, emission reductions, and avoided health costs often outweigh these investments. For example, the U.S. Environmental Protection Agency estimated that shore power fuel costs, which are generally higher than equivalent marine fuel costs, are largely offset by significant social benefits stemming from improved local air quality and reduced carbon emissions, suggesting that the cost–benefit ratio is approximately neutral [39]. Similarly, the European Union analyses within the Alternative Fuels Infrastructure Facility (AFIF) framework report that OPS projects achieve a positive net present value under preferential electricity tariffs or tax exemptions [91]. From a shipowner’s perspective, OPS reduces fuel consumption costs and potential penalties under emission trading schemes, although uptake is closely related to tariff design and port incentives.

4. Patent Landscape

To support the advancement of sustainable and efficient STS power supply systems, a significant number of patents have emerged globally, reflecting the diversity and maturity of technological approaches in this field. These contributions encompass solutions that address both operational and infrastructural challenges, highlighting trends in mobility, power conversion, and grid integration. This analysis examines 23 selected patents, grouped into three core thematic areas: Mobility and Connectivity Interfaces, Power Conversion Topologies and Control, and High-Voltage Integration and Grid Interfacing. Each category corresponds to a critical aspect of delivering stable, compatible, and safe electrical power to docked ships, offering insight into how innovation is shaping the future of shore power systems.

Table 8. Distribution of the analyzed patents by region, publication period, and main technological focus.

Region	Publication Period	Number of Patents	Main Technological Focus
China (CN)	2012–2019	12	AC-DC-AC conversion, intelligent control, HV integration.
Europe (EP/DE)	2011–2020	3	Mobile/universal interfaces, MV connection, redundant systems.
United States (US)	1999–2018	5	Automatic connection, scalable topologies.
Others (International WO)	2006–2013	3	Standardized connectors, infrastructure universality.
Total	1999–2020	23	Interfaces, conversion, grid integration.

summarizes the distribution of the analyzed patents by region, publication period, and technological focus, highlighting geographical trends and the progressive maturation of shore power system innovations.

4.1. Mobility and Connectivity Interfaces

Several patents focus on physical systems that facilitate an adaptable and simplified connection between the shore and the ship. For example, EP2458724A1 (2011) [92] focuses on the development of a mobile shore power supply unit, emphasizing portability and ease of deployment. It employs a 12-pulse rectifier–inverter topology operating at 10 kV input and providing 720 V at 50 Hz. Similarly, CN107732900A (2018) [93] describes a method and a system for shore connection aimed at improving operational convenience and safety. WO2013175061A1 (2013) [94] addresses the STS electrical interface by proposing a standardized connection module to ease the deployment between ports. WO2007060189A1 (2007) [95] introduces a universal connection system compatible with varying shore infrastructures, and US7646114B2 (2010) [96] presents a solution for automatic ship connection to shore power, reducing manual intervention. Other patents, such as US8482164B2 (2013) [97], propose buoyant harbor power supplies, while CN202455277U (2012) [98] and CN108321791A (2018) [99] suggest shore power systems tailored for different voltage levels and specific berthing conditions. Despite the variety of solutions, most of these patents address hardware-level or infrastructural aspects, often without providing an integrated approach that considers system-level optimization, automation, or adaptability to evolving power grid constraints and ship energy demands. Therefore, a gap remains in the development of a flexible, intelligent, and scalable shore power interface that ensures operational efficiency, grid compatibility, and compliance with international standards, particularly for ports with diverse ship traffic and infrastructure heterogeneity. These patents emphasize the development of adaptable, standardized, and in some cases automated connection systems. These inventions reflect a growing demand for flexible shore-side infrastructures that can accommodate a variety of ship configurations while minimizing human intervention. Mobile units, buoyant power modules, and universal connectors highlight a design philosophy centered on improving safety, ease of use, and operational speed during the docking process.

4.2. Power Conversion Topologies and Control

The technical heart of shore power systems lies in their ability to convert and regulate voltage and frequency. DE202014103274U1 (2014) [100] and CN105305449B (2018) [101] both propose AC-DC-AC topologies with adjustable output parameters, converting from a 10 kV source to a 6.6 kV output. Similarly, CN108306521A (2018) [102] integrates a sixpulse diode rectifier and a cascaded H-bridge inverter to achieve frequency and voltage adaptation from 6.6/10 kV at 50 Hz to 6.6 kV/60 Hz. In CN106628096A (2017) [103], an integrated shore–grid converter is proposed, improving bidirectional flow and reactive power control. CN108110753A (2018) [104] refines this concept with a frequency conversion unit that adapts to different maritime zones. US8610308B2 (2013) [105] and US10153581B2 (2018) [106] present scalable and modular approaches to convert shore-side AC power into formats suitable for marine applications. Meanwhile, CN105633957A (2016) [107] introduces a variable frequency power supply, adaptable to ship requirements through feedback-based regulation. Patents such as CN101917004B (2013) [108] and CN203434629U (2014) [109] bring intelligent control to the spotlight, emphasizing automatic regulation, energy savings, and environmentally friendly operation. US5920467A (1999) [110], one of the earliest in the domain, establishes a base for the conversion of AC shore power through a robust inverter-based system.

In terms of power conversion topologies and control, the analyzed patents reveal a clear trend toward advanced AC-DC-AC architectures (distributed DC), modular inverter configurations, and intelligent control systems. These technologies are crucial to ensure compatibility with ships operating on different electrical standards, particularly with respect to voltage levels and frequencies. Several inventions propose solutions that allow for bidirectional power flow, real-time regulation, and enhanced power quality, underscoring the importance of adaptability and energy efficiency in modern STS systems.

4.3. High-Voltage Integration and Grid Interfacing

As ports increasingly draw power from high-voltage distribution networks, patents have emerged to address safe and efficient integration. CN110061527A (2019) [111] details a control method that ensures synchronization between the shore grid and the ship systems, minimizing transient disturbances. Patent EP3229334B1 (2020) [112] proposes a flexible electric power system that supports high-capacity and redundant operation through segmented converters. WO2006079636A1 (2006) [113] introduces a distribution voltage connection mechanism for direct medium-voltage interfacing, reducing transformation stages. CN110143144A (2019) [114] explores wireless charging for electric ships, suggesting an evolution toward non-contact power delivery in specific docking scenarios.

These innovations demonstrate how shore power supply systems are increasingly being designed to connect directly to medium- and high-voltage distribution networks. Innovations in this area target the synchronization of ship and shore systems, fault-tolerant designs, and even non-contact wireless power transfer. These developments indicate a shift toward higher power capacities and more seamless integration with port electrical grids, aligning with global trends in port electrification and decarbonization. Patent analysis reflects a dynamic innovation ecosystem that supports the deployment of shore power technologies. The continuous development of flexible connection systems, advanced power conversion methods, and high-voltage grid integration solutions signals a concerted global effort to reduce ship emissions in ports, comply with environmental regulations, and advance sustainable maritime operations.

A critical evaluation of the surveyed patents reveals that AC-DC-AC topologies dominate the OPS innovation landscape. This prevalence can be attributed to their technical maturity, ability to adapt voltage and frequency to heterogeneous ship standards, and the flexibility to implement scalable configurations. Furthermore, AC-DC-AC converters enable advanced control strategies, including bidirectional power flow, harmonic mitigation, and real-time regulation, which are essential to ensure compatibility with modern grids and diverse ship requirements. From an intellectual property perspective, regional and institutional ownership trends reflect enterprise competitiveness in OPS development. The most recent patents originate from China, driven by strong governmental incentives for port electrification and contributions from both state-owned enterprises and academic institutions. European patents emphasize modular and redundant systems, often linked to industrial leaders in power electronics and port infrastructure. In contrast, US patents, while earlier in time, tend to focus on automatic connection mechanisms and scalable architectures, suggesting a priority on operational convenience and interface standardization. This distribution indicates a shift in global competitiveness. While the US played a pioneering role, China is leading the innovation race, aligning OPS technology with broader energy transition and decarbonization policies. Such patterns mirror competitiveness analyses in ship power system patents, where leadership is increasingly associated with regions investing in large-scale deployment of sustainable maritime infrastructures.

5. Ports with Shore Power and Commercial Solutions

During the past two decades, the implementation of shore power systems has gained significant momentum in ports across North America, Europe, and parts of Asia. As shown in

Table 9. Examples of ports implementing shore power systems [3,115,116,117].

Year	Port Name	Country	Capacity [MW]	Voltage [kV]	Frequency [Hz]	Ship Types
2010	San Diego	U.S.A.	16	6.6 & 11	60	Cruise
2010	San Francisco	U.S.A.	16	6.6 & 11	60	Cruise
2010	Karlskrona	Sweden	2.5	11	50	ROPAX
2011	Long Beach	U.S.A.	16	6.6 & 11	60	Cruise
2011	Oslo	Norway	4.5	11	50	Cruise
2011	Prince Rupert	Canada	7.5	6.6	60	Cruise
2012	Rotterdam	Netherlands	2.8	11	60	ROPAX
2012	Ystad	Sweden	6.25–10	11	50 & 60	Cruise
2013	Trelleborg	Sweden	3.5–4.6	11	50	ROPAX
2015	Hamburg	Germany	12	6.6 & 11	50 & 60	Cruise
2019–2023	Kiel	Germany	4.5–16	6.6 & 11	50 & 60	Ferry & Cruise
2024	Stockholm	Sweden	Not specified	0.4 & 0.69 & 6.6 & 11	50 & 60	Cruise

, a wide range of ports have installed shore-side electricity infrastructure to support the decarbonization of maritime operations, particularly in high-traffic regions and for ship types with prolonged port stays, such as cruise ships, ROPAX ships, and container carriers [3].

Pioneering implementations date back to the early 2000s, with ports like Gothenburg, Zeebrugge, and Juneau leading the transition by offering medium-voltage shore connections between 6.6 kV and 11 kV. These early systems typically provided capacities ranging from 1 MW to 10 MW, sufficient for power demands during berthing. Over time, port infrastructure has evolved to support higher capacities, with examples such as the Port of Los Angeles reaching up to 60 MW and major cruise terminals in Vancouver and Hamburg operating with capacities exceeding 12 MW.

Shore power has been increasingly deployed in North America and Asia, driven by both environmental regulations and port-level initiatives. In the United States, the Environmental Protection Agency (EPA) published a national Shore Power Technology Assessment, highlighting the potential of OPS to reduce emissions in ports with high container and cruise traffic [39]. Complementing this, the California Air Resources Board (CARB) has enforced the At-Berth Regulation, which requires a progressive share of container, reefer, and cruise ships to connect to OPS at major Californian ports such as Los Angeles, Long Beach, and Oakland. Enforcement data show that compliance rates have increased significantly, supported by both infrastructure investment and penalty mechanisms [42]. The International Council on Clean Transportation (ICCT) has also performed a national screening of U.S. ports to prioritize OPS deployment, identifying locations where shore power would deliver the highest public health and climate benefits [118]. Key findings highlight the importance of targeting container and cruise terminals with long berthing times. In Asia, Shanghai has emerged as the leading case for implementing large-scale OPS facilities supported by municipal and national incentives. The city’s port authority has mandated OPS readiness for new terminals and provided subsidies to retrofit existing berths, resulting in one of the world’s largest OPS deployment programs [119].

A key technical challenge in shore power implementations is the frequency mismatch between the shore-side electrical grid and shipboard systems. For example, while the European grid typically operates at 50 Hz, many ships require a 60 Hz supply. This discrepancy requires the use of frequency converters, which play a critical role in ensuring compatibility and safe energy transfer between shore infrastructure and onboard systems.

In addition to port infrastructure developments, the market for commercial power conversion solutions has expanded significantly [26].

Table 10. Commercial converters and shore power supply solutions and their technical features.

Product	Manufacturer	Power [MVA]	Voltage [V]	Efficiency	Key Features
SINAMICS SM120 [120] (frequency converter)	Siemens	4–13.3	3300–7200	98.5%	Scalable design, liquid-cooled, high efficiency, suitable for phased port expansions.
SFC Shore Power [121] (frequency converter)	Greencisco	0.06–0.4	HV: 6600 LV: 440	≥95%	Compact footprint, suitable for small- to medium-scale installations, transformer-integrated.
MV7000 [122] (frequency converter)	GE Vernova	4–48	3300–13,800	99%	Water or air cooled, suitable for high power applications, compatible with hybridization and storage, low harmonics output.
ShoreCONNECT [123]	Wabtec	6.5–20	HV: 6600–11,000 LV: Individual cable handling	NA	Available in fixed, mobile, crane-integrated, and fully autonomous configurations; robotic cable handling.
PowerFit HV [124]	Cavotec	HV: Up to 7.5 LV: Up to 3.6	HV: 6600 LV: 380–450	NA	Wall- or skid-mounted, compact, integrated safety interlocks, ideal for RoRo terminals and ferries.
PowerMove [124]	Cavotec	Up to 20	6600–11,000	NA	Containerized and flexible deployment, weatherproof enclosure.
PowerAMPReel [124]	Cavotec	4–8	HV: Up to 6600 LV: Up to 1000	NA	Cable management system for OPS, integrated shore power module, designed for harsh marine environments.
SIHARBOR [125]	Siemens	2–16	6600–11,000	NA	Containerized system, plug-and-play operation, air-cooled, integrated power conversion.

lists a representative set of commercially available shore-side frequency converters specifically designed for shore power supply applications. These include systems from manufacturers such as ABB, Siemens, Greencisco, Cavotec and others, with solutions that support a wide range of voltage and power levels.

The continued advancement and deployment of such commercial technologies, supported by increasingly stringent environmental regulations and international standardization (ISO/IEC/IEEE 80005) [120,121,124], are accelerating the global adoption of Shore Power. These systems not only contribute to substantial emission reductions in port areas, but also provide long-term operational and environmental benefits to shipowners, port operators, and coastal communities

The growing adoption of shore power infrastructure in global ports has been paralleled by notable advances in shipboard conversion technologies. As ships become increasingly dependent on high-capacity electrical systems during berthing, onboard converters have evolved to meet diverse voltage and frequency requirements with greater efficiency and precision. Manufacturers have introduced a variety of topologies, including active front ends, and modular frequency converters, designed to ensure compatibility with various shore power configurations while maintaining power quality and system stability.

These technological advances are further supported by regulatory frameworks and standardization efforts that encourage the integration of shore power solutions. As ports expand their capabilities and more ships are equipped with compliant systems, shore connection is transitioning from a small solution to a mainstream practice. This progress reinforces the larger objectives of maritime electrification, offering a pathway to reduced emissions and improved energy performance in port operations.

Despite the momentum of OPS deployment, significant operational barriers remain. One of the most pressing issues is grid capacity, as the simultaneous connection of multiple large ships can cause voltage dips and require major reinforcement of medium- and high-voltage substations [126]. Another recurring challenge is compatibility and interoperability, particularly with respect to connector types, earthing arrangements, and frequency conversion requirements, which vary between manufacturers and regions. Reliability concerns are also present: in centralized topologies, the failure of a single high-power converter may compromise multiple berths, while cable management procedures add operational complexity at the quay [3,44,45,51]. However, several drivers are accelerating OPS adoption. Mandatory regulations such as CARB’s At-Berth Regulation in California or the EU’s AFIR and FuelEU Maritime mandates create binding requirements that compel both ports and shipowners to invest in OPS [78]. Economic instruments, including preferential tariffs, subsidies, and penalty schemes, further improve the business case for operators. Environmental and societal drivers also play a role: OPS reduces emissions of NOx, SOx, and PM in densely populated port areas, directly improving air quality and public health. Finally, corporate sustainability commitments and international climate goals motivate shipping lines and terminal operators to embrace OPS as part of their decarbonization strategies [74,75,76,82,91].

6. Conclusions and Development Directions

This paper has provided an overview of the current and future state of Shore Power systems, encompassing architectural paradigms, ship requirements, regulatory frameworks, patents, commercial solutions, and global deployment examples. The evidence confirms that STS systems are not merely compliance tools; they are strategic enablers of sustainable maritime operations. A review of patented and commercial solutions shows a clear trend toward modularity, scalability, and higher efficiency. However, technological diversity and heterogeneous ship fleets continue to pose integration challenges. As the urgency of maritime decarbonization intensifies, STS power systems are no longer a peripheral solution. They are becoming central pillars in the transition to cleaner port operations [127,128]. Driven by technological innovation, regulatory momentum, and the growing societal demand for environmental responsibility, these systems are rapidly evolving into more efficient, intelligent, and versatile architectures [27,129].

6.1. Development Directions in OPS

To provide a clearer outlook, development directions are presented in a structured way:

• Transition to DC-based OPS Architectures. Although traditional shore power is highly dependent on transformer-based and static frequency conversion to deliver AC energy at compatible levels, a paradigm shift is underway. The growing presence of DC microgrids onboard ships, often incorporating battery energy storage systems (ESSs), fuel cells, and renewable energy sources (RESs), has accelerated interest in DC-based shore power connections [22,28,29,69]. In particular, multi-distributed architectures provide higher efficiency, fewer conversion losses, and seamless integration with modern onboard systems.
• Advanced Power Electronics and Converter Technologies. Advanced DC-DC converters act as galvanically isolated, voltage-regulating, high-frequency transformers [130]. Future developments must address EMI management and control complexity at high power levels. These technologies will be critical to support hybrid AC/DC operations and integration with renewable energy [26,29,50,131].
• Automation, Digitalization, and AI/ML for Power Management. Automation and digitization are reshaping the way STS systems are operated and maintained. Through smart sensors, condition monitoring, and digital twins, operators can gain real-time insights, allowing predictive maintenance and optimized energy quality [132]. The integration of Artificial Intelligence (AI) and Machine Learning (ML) will enable dynamic power management, fault prediction, and adaptive control of OPS systems, ensuring reliability under varying ship and port demands.
• Wireless Power Transfer (WPT). Another frontier of innovation is the rise of wireless power transfer (WPT), particularly inductive power transfer (IPT), as a safer and more resilient alternative to traditional cabling. For OPS, IPT could eliminate heavy cable handling in large ships, reduce quay congestion, and minimize human error during high-voltage connections. Although prototypes have been tested primarily on ferries and small ships [133,134], scaling up to container ships or cruise ships requires breakthroughs in efficiency and electromagnetic compatibility [93,135,136,137,138,139,140].
• OPS–RES Integration and Hybrid Systems. A dedicated pathway for OPS–RES integration is emerging, where ports combine photovoltaic (PV), wind, and storage systems with OPS infrastructure. Hybrid OPS–RES systems can reduce dependence on the main grid, improve local energy resilience, and contribute to decarbonization [82,141,142]. Optimization strategies include model predictive control, AI-based energy scheduling, and multi-objective optimization for cost and emission reduction.
• Standardization and Interoperability. At the systemic level, standardization is emerging as a key enabler of interoperability and global adoption. Frameworks such as the IEC/IEEE 80005 series [24,57,58,60] support the development of plug-and-play systems that simplify deployment, reduce engineering overhead, and adapt to a wide range of ship types and port layouts. Innovations such as containerized or mobile STS units are also expanding the reach of the technology to smaller or seasonal ports, offering flexibility where it is needed most [22].
• Integration with Smart Grids and Bidirectional Operation. Looking ahead, the convergence of port electrification and smart microgrids is redefining the role of STS systems within the broader energy ecosystem [26]. Ports are beginning to function as active energy hubs, integrating renewable generation, energy storage, and bidirectional grid interaction. In such settings, STS systems can go beyond supplying ships: they can also absorb power from ships equipped with large onboard storage (ship-to-grid, S2G), contributing to local energy resilience [143].

6.2. Multidimensional Integration Challenges

Despite the promising outlook, several engineering challenges must be addressed for the large-scale adoption of OPS. Grid stability under large OPS loads is a primary concern, as the simultaneous connection of multiple ships with multi-MW demand can cause voltage dips, frequency deviations, and harmonic distortion, requiring advanced grid support converters and demand-side management [126]. Additionally, many ports lack sufficient medium- or high-voltage infrastructure, necessitating significant investment in substations, cabling, and quay retrofits [8]. The cybersecurity of digitalized OPS systems also represents a critical challenge; with the integration of digital twins, AI-based control, and IoT devices, OPS becomes increasingly exposed to cyber threats, making secure communication, encryption, and intrusion detection essential [57]. Furthermore, long-term investment strategies must align with evolving international environmental regulations and port-specific economic constraints to ensure cost-effectiveness and regulatory compliance [8]. Addressing these integration challenges will determine the feasibility, scalability, and pace of OPS deployment worldwide. Looking forward, the future of shore power lies at the intersection of standardization, smart grid integration, and adaptation to renewable energy. Its success will depend not only on coordinated regulatory frameworks and international collaboration but also on overcoming these technical and operational challenges to achieve scalable, secure, and intelligent deployment.