Cold Ironing Explained

Save Money and the Environment in the Long Term

Quantum of the Seas. Royal Caribbean

Cold Ironing is the practice of providing shore power to a ship so the ship may shut down primary and secondary combustion engines while in port. The main benefits are fuel savings and reductions in pollution and noise.

The term came into existence during the time when ships were coal fired. Once the coal fired ship was in port and attached to a shore based power source the engines no longer needed to be stoked by coal and the fires would die down until the large iron engines grew cold.

Hence, cold iron became cold ironing.

Not everyone uses the same terminology. The ports in the United Kingdom use the term shore supply. Recreational vessels commonly use this practice world-wide and refer to it as shore power.

So if recreational boats use this technology and it has been around since the days of coal fired ships why isn’t it used more widely?

The simple answer is cost, but there a few other issues as well.

The first is getting power to the port. This is not very difficult technology to implement but it is expensive. As an example we will use a cruise ship terminal.

The amount of amount of power necessary to meet the demands of a single ship might be fifteen megawatts (MW). If the port can accommodate four ships the capacity needs to be at least sixty MW.

But because the port will not have four ships in port at some times only a portion of the needed capacity is used. Regardless of use the port still must incur the expense of a sixty megawatt transformer substation on site and the feeder line from the utility.

Some ports have solved this problem by growing their cold ironing capacity incrementally but this is a much more expensive solution. A single 60 MW transformer is less expensive and more efficient than four fifteen MW transformers. Utility feeds must also be upgraded as the electrical current increases.

The cable which feeds the ship is also a major expense but only a fraction of the cost of the supply and substation. These are BIG cables and need to be handled by light boom cranes, the process of connecting and disconnecting can take hours.

After expense, standardization is the next big hurdle. These heavy cables vary in size because of different voltages supplied to shore side facilities around the world. Common voltages range from 11,000 to 400 volts of alternating current (AC) with 6600 volts AC being the most common.

If you are wondering why the voltage varies so much it is because of Ohm’s Law. Ohm’s Law tells us that when voltage is increased current is reduced. To understand current think of it like water pressure in a pipe. When there is too much pressure in a water pipe the pipe will burst, in the same way too much current in a cable will destroy the cable in spectacular fashion.

When the voltage is increased from 6600 volts AC (VAC) to 11,000 VAC the size of the cable may be reduced by approximately half its thickness. Making the cable lighter saves money in materials but the value is greater in the savings of labor.

Connecting and disconnecting shore supply may take hours so even a savings of ten or twenty minutes will reduce costs significantly over the lifetime of the system.

This will save ship operators some of the expense of port charges which often reach well into five figures for large vessels.

Cold ironing is expanding because of environmental regulations and public demand. Cruise ship operators are sensitive to the fact that their passengers do not want to breathe heavy fuel oil fumes if they do not want to leave a ship while in port. Some areas like the State of California require ships to burn a cleaner and more expensive fuel while in their waters.

The particulates emitted by ships are a major health concern. While at sea the crew is exposed constantly but only part of the particulate pollution makes it to populated areas on shore. In a situation where the ship is docked with engines at idle the entire exhaust plume is often directed at centers of population and commerce.

Potential future taxes on emissions and fuel cost savings are driving some projects forward, but adoption of this technology is very slow in the private sector. The early adopters of this technology are the Navies of the world.

Naval ships spend a lot of time in port. Much more than the average of one hundred days per year a merchant ship is docked. Systems like heating, cooling, refrigeration, vacuum sanitation, and data must be kept online to avoid damage to the ship and sailors while in port.

Navies have the advantage of having a bureaucracy to guide their hand. No, you didn’t misread that last sentence it did say bureaucracy is an advantage in this case. The entire fleet can use the same standard of voltage, and connection method. Ships may even power each other in some cases.

Renewable power cannot go without mention in this discussion. It is a significant possibility but much more likely to be distributed into the power grid than to exist on the grounds of a port.

Solar photovoltaic panels would take up a vast space which is generally unavailable in a crowed port area. Wind, just like solar is intermittent and would need some backup source of power like a utility feed or generator on site. If you are thinking about a battery bank it would be the size of a twenty story building.

One very specific possibility is hydroelectric power which flows constantly and has a variable capacity by controlling how much water goes into the turbine. If a port was located near an appropriate source this could be the best way to power a ship with little environmental impact. We can only dream.