Out of sight, out of mind – but still in lungs
Unlike airliners or motor vehicles, shipping is not seen by most people and levels of pollution from the shipping industry have long been underestimated. Ship engines burn bunker fuel. This petroleum product is basically what is left over after all the cleaner fuels have been extracted from crude oil. It has high sulphur content and its combustion results in excessive levels of SOx (sulphur oxide), NOx (nitrogen oxide) and PM (particulate matter); the last is particularly harmful.
A new International Standard initiated by IEC TC (Technical Committee) 18: Electrical installations of ships and of mobile and fixed offshore units, and its SC (Subcommittee) 18A: Electric cables for ships and mobile and fixed offshore units, has just been published. It aims to cut ships' emissions in ports.
Tighter emission control
The IMO (International Maritime Organization), the UN agency with special responsibility for the safety and security of shipping and the prevention of marine pollution by ships, has introduced international limits to the maximum sulphur content in bunker fuel in Annex VI of its International Convention for the Prevention of Pollution from Ships (MARPOL). This fixes limits on SOx and NOxemissions from ship exhausts. The maximum sulphur content of bunker fuel was set at 3,5% from 1 January 2012 until January 2020, with lower levels to be introduced later.
Some regions (Baltic, North Sea, North America, Caribbean Sea area) have introduced tighter limits in so-called Emission Control Areas (ECAs).
Cutting emission and noise in ports
If ships auxiliary generators used to provide electric power to docked ships do not burn bunker fuel but cleaner fuels, SOx, NOx and PM are still emitted. During a 10-hour stay in port, the diesel engines of a single cruise ship burn around 20 tonnes of fuel, producing some 60 tonnes of CO2.
On average, ships spend 100 days a year in port, using several tonnes of fuel a day to power ancillary systems. Ports are often located in densely populated cities and the environmental impact on the local population may be severe.
Cutting noxious emissions in ports has become a priority worldwide and has led to the introduction of OPS (onshore power supplies), which allow ships to shut down their diesel engines and connect to the land-based grid while they are docked.
Another advantage of HVSC is that it reduces noise and vibration from ships. Crews, dockside workers and nearby residents all benefit from this reduction.
Not new, yet no single standard
Providing electric power from shore to ships at berth is not a recent development; in fact the term commonly used to describe it, "cold ironing", dates back to the time when ships had coal-fired engines that were allowed to go completely cold when in port, as power was supplied from shore.
Navy ships, which on average stay in port much longer than commercial ships, make extensive use of cold ironing. The US Navy, for instance, has been using it for several decades and has developed a unique electrical cable connection system to avoid compatibility issues when calling at different ports.
Generally speaking, first-generation OPS systems operate on low voltages (400-690 V). More recently, high voltage (6-11 kV) has become the standard.
The need for HVSC standards
Currently over 20 ports in North America and Europe implement HVSC but systems across the world are not interoperable, owing to the lack of standardization and differences in system frequency (60 Hz in North America, 50 Hz in Europe and most of Asia), voltage and structural design.
Port Metro Vancouver, one of around two dozen ports in the world to have introduced HVSC, cut its greenhouse gas emissions by 3 000 tonnes in 2010 after installing HVSC for cruise ships.
Voltage levels differ between ports and electrical frequencies and power requirements also vary among vessel categories and sizes. Ocean-going vessels calling at European ports tend to have more 60 Hz electrical systems on board. Peak power demand varies from 1 MW (for container vessels smaller than 140 metres) to 11 MW (cruise ships over 200 metres).
These different systems and the specific local situation determine whether or not frequency converters and/or on-board transformers are needed and may affect the overall cost of an OPS system for port authorities and ship owners.
First International Standard for HVSC published
In 2009, IEC TC 18 issued a PAS (publicly available specification) giving requirements for HVSC systems.
This PAS was prepared in consultation with IEC TC 20: Electric cables, and IEC SC 18A.
It was further developed into an International Standard in cooperation with IEC SC 23H: Industrial plugs and socket-outlets, ISO TC 8: Ships and marine technology, and the IEEE (Institute of Electrical and Electronics Engineers) PCIC (Petroleum and Chemical Industry Committee).
This standard, IEC/ISO/IEEE 80005-1, Utility connections in port – Part 1: High Voltage Shore Connection (HVSC) Systems – General requirements, was published in July 2012.
It describes HVSC systems on board ships and on shore and defines "requirements that support, with the application of suitable operating practices, efficiency and safety of connections by compliant ships to compliant high-voltage shore power supplies through a compatible shore to ship connection".
It is intended to allow different ships "to connect to HVSC at different berths with the benefits of standard, straightforward connection without the need for adaptation and adjustment at different locations that can satisfy the requirement to connect for as long as practicable during stays in port. Ships that do not apply this standard may find it impossible to connect to compliant shore supplies".
To meet these demands IEC/ISO/IEEE 80005-1 addresses:
- HV shore distribution systems
- shore-to-ship connection and interface equipment
- semiconductor/rotating convertors
- ship distribution systems
- control, monitoring, interlocking and power management systems
The standard tackles important safety aspects such as emergency shut downs (ESD), when the ship moves outside the range of permissible motion forward, aft or outward from the dock, and special provisions that are applicable to ESD at LNG (liquefied natural gas) terminals.
The standard also lists additional requirements for RoRo (roll-on/roll-off) cargo and passenger ships, cruise and container ships, tankers and LNG carriers. The relevant IEC, ISO and IEEE committees have approved a new work proposal for a second International Standard for HSVC, to cover the communication interface description.
From an environmental perspective, the use of HSVC is compelling. Compared to low-sulphur marine gas oil used in EU ports, onshore power supply cuts NOx, PM and volatile organic compound emissions by 94%, 89% and 94%, respectively.
Tighter environmental regulations incite more and more ports to put in HVSC systems. In addition to the more than 20 ports in Europe and North America that currently have operational HSVC systems, others are starting or planning to install them. The new IEC/ISO/IEEE International Standard should help drive that wider adoption.