One of the questions that is often put to the crew on a cruise ship is - how does the
ship get electricity?
The answer is… really long extension cords...
So, there you have it.
And thanks for watching…
Okay, not really.
Today we’ll look at how ships generate power and how that power is used!
Hi I’m Chris Frame…
I’m a maritime history author and lecturer I write maritime history books and speak at
maritime museums and aboard cruise ships around the world.
If you're interested in cruise ships, cruising or maritime history I think you’re going to like it
here so hopefully you’ll subscribe at the end of the video?
In the 1980s it was estimated that an ocean liner the size of the 70,000 gross ton QE2
generated enough electricity every day to power the City of Southampton!
That’s a lot of power.
And even though battery storage tech is improving at a great rate, you’d currently still struggle
to find a battery that could hold enough power to propel a large ship on a long distance
voyage, while still providing power for the services needed to keep a city at sea running.
A cruise ship’s power plant also needs to fit on the ship, with space left over for
all of the passenger facilities, crew areas and storage spaces that are needed on board…
And while some cruise ships these days can run on shoreside power when docked, storing
the power from shoreside sources for use at sea, isn’t currently a mainstream option,
not yet anyway.
Instead, cruise ships generate their own electricity, and have done since the 19th century.
The shipboard electricity is used to run things such as: hotel services - like lights and air-conditioning,
lifts (or elevators for my American friends) as well as safety and security systems, like
the fire alarms, navigational systems and even things you’re less likely to think
about, such as cold storage refrigerators, desalination plants and; of course – the propulsion system!
All these systems are power hungry.
And they take up a fair amount of space onboard.
On most ships, propulsion systems, giant refrigerators and desalination plants are located below
the waterline of the ship in giant mechanical areas … if you’re interested in learning
more about what is beneath the waterline, check out my recent video about it!
So we know ships generate their own electricity.
But how do they do this?
Well the most common power-plant on cruise ships at the moment are diesel-electric systems.
In these systems, diesel engines are used to produce electricity which then powers the
different services on board.
.
These systems are a form of indirect drive.
The engines are not directly attached to the propellers that move the ship.
Rather, a large chunk of the electricity is used to power the propulsion motors that drive
the propellers, or power the pods on many modern ships.
This contrasts with the direct drive systems of old.
Compound and reciprocating engines, and even the first steam turbines were all forms of
direct drive propulsion.
This meant that the engines were attached directly to the propeller shaft, or paddle
wheel in the oldest ships.
As the pistons turned, this turned the propeller or paddle wheel shaft.
On reciprocating systems, such as those found aboard the Olympic and Titanic, the main engines
created the propulsion while steam was bled off the main plant and fed into dynamos which
generated electricity to power the ships hotel services.
This is one of the reasons why Titanic’s lights could stay lit up long after the main
engines were turned off.
Direct drive engines are the simplest way of powering a ship, but they aren’t the
most effective.
It was discovered in some of the earlier steam turbine ships, that the speed at which the
propeller was most efficient and the speed at which the turbine was most efficient, were
different.
This led to serious vibration issues when the ship was run at speed.
Indirect drive engines attempted to overcome this problem, though they are a little more
complex and require more machinery.
Indirect systems convert the electricity produced by an engine to allow it to run the ship.
These engines are more efficient overall, and they allow both the engines and the propulsion
system to run at their own most efficient speed, by separating the process of creating power
from the act of using that power.
This brings us back to the diesel-electric plants, used to produce electricity.
From the 1980s this became the most common way to power a cruise ship, and between 1980
and now, nearly all cruise ships were built with this system.
But there were some ships that bucked this trend.
A less common but important alternative system is a turbo-electric plant.
These systems use steam turbines or on modern ships, gas turbines, to produce electricity.
Gas turbines had a boost in popularity during the 2000s, with several cruise ships built
using these plants.
These included the Island and Coral Princess, Royal Caribbean’s
Radiance Class, and Celebrity’s Millennium class all using these engines.
Their fuel costs a lot more than diesel, but they are significantly cleaner burning and
thus considered better for the environment.
Some passenger ships employ hybrid systems that make use of more than one power generation
source.
A great example of this is the Queen Mary 2, which employs both desired electric and
gas turbines during its cruises and crossings.
The base load power for hotel services and slower cruising can be achieved by the cheaper-to-run
diesel electric plant, but when QM2 needs a boost of extra energy the gas turbine plant
is activated.
As the shipping industry attempts to transition to greener fuel sources we are starting to
see a shift in the propulsion of new ships.
Many new builds are being completed with LNG powerplants.
These power plants are indirect drive systems, so can quite easily be adapted to work with
existing propulsion technology, and bring with them a reduced carbon footprint when
compared with their diesel predecessors.
So now we know some of the main ways that electricity is produced aboard cruise ships.
But what about some less known or carbon-neutral systems?
Well it may surprise you to know that there have been a few novel passenger ships built
over the years with one being notable for being a nuclear powered ship.
The Savannah entered service in 1962 for States Marine Lines and utilised Babcock and Wilson
Nuclear Reactor.
This nuclear plant did the same job as a diesel or gas plant – generating electricity.
The electricity is then used to power the ship.
The ship’s propulsion system was virtually carbon neutral, but the public’s concern
relating to nuclear power meant this tech never caught on for cruising.
Today, research is being done into hydrogen as a future fuel source and there have been
some successful battery powered cargo ships that are capable of operating over short distances.
Another interesting green solution is being explored by both Hurtigruten and Ponant.
Both lines are investing in sail powered ships.
This is an interesting innovation, precisely because it isn’t really an innovation at
all.
Sail powered ships existed long before steam powered ships, but over time were abandoned
in favour of the certainty provided by steam power at being able to guarantee the duration
of a voyage.
Where Hurtigruten and Ponant are looking to push the boundaries is by using wind technologies
to create a reliable power source – something the sailing ships of old could never really
do.
With all of the advances in technology that we have had over the past two hundred years,
it will be exciting to see how these new ships perform.
So there you have it.
A ship gets its electricity by making it itself.
For the most part, this is by burning fossil fuels, and works much the same as a non-renewable
land-based power plant.
Cruise lines are making steps to source greener fuels, but more needs to be done, and quicker,
to meet the urgency needed to fight climate change.
One last point - when a ship is in port, it requires much less power than when it is underway.
Generally, when a ship is in port some of the engines are taken offline, with the ship
only producing as much energy as it needs to keep the hotel services up and running.
And it is here that we find a proven greener solution - when both port and ship are equipped
with cold ironing capabilities.
Cold ironing allows a ship to run off shoreside power when it is in port.
This has benefits for air quality, and if shoreside power comes from renewable sources
then it has a real overall benefit to the environment.
So the next time you hear someone ask, where does the ship get its electricity, you’ll
know the answer.
It makes it itself.
But if the ship is in port and using cold ironing?
Well then it uses really long extension cords.
Thanks so much for watching. And I hope you found the video interesting?
If you did, please don't forget to give it a like and subscribe for future cruise and maritime history content. Thanks once again
for watching and until next time, I hope to 'sea' you on board.
[OUTTAKES]