moving. Planes have already been fantastically optimized, and there is no
prospect of significant improvements in plane efficiency.
For a time, I thought that the way to solve the long-distance-transport
problem was to revert to the way it was done before planes: ocean liners.
Then I looked at the numbers. The sad truth is that ocean liners use more
energy per passenger-km than jumbo jets. The QE2 uses four times as
much energy per passenger-km as a jumbo. OK, it’s a luxury vessel; can
we do better with slower tourist-class liners? From 1952 to 1968, the eco-
nomical way to cross the Atlantic was in two Dutch-built liners known as
“The Economy Twins,” the Maasdam and the RijnsdamE. These travelled
at 16.5 knots (30.5 km/h), so the crossing from Britain to New York took
eight days. Their energy consumption, if they carried a full load of 893
passengers, was 103 kWh per 100 p-km. At a typical 85% occupancy, the
energy consumption was 121 kWh per 100 pkm – more than twice that of
the jumbo jet. To be fair to the boats, they are not only providing trans-
portation: they also provide the passengers and crew with hot air, hot
water, light, and entertainment for several days; but the energy saved back
home from being cooped up on the boat is dwarfed by the boat’s energy
consumption, which, in the case of the QE2, is about 3000 kWh per day per
So, sadly, I don’t think boats are going to beat planes in energy con-
sumption. If eventually we want a way of travelling large distances without
fossil fuels, perhaps nuclear-powered ships are an interesting option
(figures 20.31 & 20.32).
International shipping is a surprisingly efficient user of fossil fuels; so get-
ting road transport off fossil fuels is a higher priority than getting ships
off fossil fuels. But fossil fuels are a finite resource, and eventually ships
must be powered by something else. Biofuels may work out. Another option
will be nuclear power. The first nuclear-powered ship for carrying
cargo and passengers was the NS Savannah, launched in 1962 as part of
President Dwight D. Eisenhower’s Atoms for Peace initiative (figure 20.31).
Powered by one 74-MW nuclear reactor driving a 15-MW motor, the Sa-
vannah had a service speed of 21 knots (39 km/h) and could carry 60 pas-
sengers and 14000 t of cargo. That’s a cargo transport cost of 0.14 kWh per
ton-km. She could travel 500 000 km without refuelling. There are already
many nuclear-powered ships, both military and civilian. Russia has ten
nuclear-powered ice-breakers, for example, of which seven are still active.
Figure 20.32 shows the nuclear ice-breaker Yamal, which has two 171-MW
reactors, and motors that can deliver 55 MW.