The cost of an oil tanker is (very roughly) proportional to its surface area; the revenue is proportional to the oil it carries. Since the surface varies as the second power of the linear dimensions, and the volume as the third, the advantage increases with size. (Doubling the linear dimension will quadruple the area, but will increase the volume eightfold.) As any housewife instinctively knows when she buys oranges by the pound, the bigger oranges will give her more orange and less peel. That's what is known as economy of size.
Oil tanker owners are no less smart than housewives, and that is why the size of oil tankers has grown so large. Only a decade ago, a 50,000-ton tanker was considered large; today's VLCC's (very large crude carriers) displace as much as 300,000 tons. But as the price of oil soars, further economies are necessary, and the traditional steam turbine is now being replaced by diesel engines.
Both burn oil, of course, but the heat content of the oil is released in the cylinders of a diesel engine directly, whereas an appreciable amount of it is uselessly lost in the boiler, condenser, and piping of the water/steam cycle. As much as 40 percent fuel savings are possible.
Mobil led the way last year by spending $6,500,000 to convert its 280,000 ton tanker Mobil Hawk to diesel engines, saving 60 tonnes of oil or $8,640 a day, so that they should break even in less than 3 years and reap the profits thereafter. (Isn't it amazing how they practice energy conservation without coercion by DoE bureaucrats?) Almost everybody else's fleet is now being converted, so that the price of conversion has been driven up to some $10 million per VLCC, but it still pays, even when higher maintenance costs for diesel engines are factored in. Japan's government intends to convert 74 of the Japanese tanker fleet in the 220 to 270,000 tonne range, which will save $2,500,000 per ship per year in fuel costs.
And there are other ways to keep fuel consumption down. A ship's "streamlined" shape makes the water glide past it in laminar (layered) flow with minimum friction; a protrusion or roughened surface will cause the flow to become turbulent and waste the energy fed into the water eddies. Shipowners are therefore keeping their hulls clean from seaweed and shells¾saving 15 tonnes in extra fuel over a typical VLCC voyage, plus a $250,000 clean-up bill in drydock every other year. (Imagine! All without EPAcrats forcing them!)
[More: Economist, London, 21 July 1979.]
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Vol. 7, No. 2
Newsletter: Access to Energy Newsletter Archive Volume: Volume 7 Issue/No.: Vol. 7, No. 2 Date: October 01, 1979 02:47 PM Title: More fundamental than energy
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