Cold ironing

Cold ironing, or shore connection, shore-to-ship power (SSP) or alternative maritime power (AMP), is the process of providing shoreside electrical power to a ship at berth while its main and auxiliary engines are turned off. Cold ironing permits emergency equipment, refrigeration, cooling, heating, lighting and other equipment to receive continuous electrical power while the ship loads or unloads its cargo. Shorepower is a general term to describe supply of electric power to ships, small craft, aircraft and road vehicles while stationary.

Cold ironing is a shipping industry term that first came into use when all ships had coal-fired engines. When a ship tied up at port there was no need to continue to feed the fire and the iron engines would literally cool down, eventually going completely cold, hence the term cold ironing.

Shutting down main engines while in port continues as a majority practice. However, auxiliary diesel generators that power cargo handling equipment and other ship's services while in port are the primary source of air emissions from ships in ports today, because the auxiliaries run on heavy fuel oil or bunkers. Cold ironing mitigates harmful emissions from diesel engines by connecting a ship's load to a more environmentally friendly, shore-based source of electrical power. An alternative is to run auxiliary diesels either on gas (LNG or LPG) or extra low sulphur distillate fuels, however if noise pollution is a problem, then cold ironing then becomes the only option.

A ship can cold iron by simply connecting to another ship's power supply. Naval ships have standardized processes and equipment for this procedure. However, this does not change the power source type nor does it eliminate the source of air pollution.

The source for land-based power may be grid power from an electric utility company, but also possibly an external remote generator. These generators may be powered by diesel or renewable energy sources such as wind, water or solar.

Shore power saves consumption of fuel that would otherwise be used to power vessels while in port, and eliminates the air pollution associated with consumption of that fuel. Use of shore power facilitates maintenance of the ship's engines and generators, and reduces noise.

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