ICETEC

Although the principle of OTEC is not at all absurd, it is still beset by a number of troubles, not the least of which is its questionable economics, in turn tied to its energetic efficiency of a mere 2.5%.

One of the reasons for this minuscule efficiency (which would be considered indecent if the "fuel" did not come for free) is the large amount of energy that must be wasted in pumping the cold water from depths of 1,000 to 2,000 ft.; this is used to cool the condenser, which is not very hot anyway the ammonia vapor is only some 20 degreesC warmer. (In a conventional power plant, the steam going into the turbine is up to 500 degreesC hotter than the cooling water, and it is this difference which determines the energetic efficiency.)

But suppose there were some ice around: It could be used as a heat sink. Not only would its temperature be an extra 4 degreesC lower than that of the cold water from the deep, but since it would float on the surface of the ocean, the energy needed to pump the cold water through 1,000 feet or more to the surface would be saved, and the efficiency would increase to 7.5% still not very respectable as efficiencies go, but the 3 fold increase might well swing the economics from the red into the black.

Only one problem left: How do you get ice to float in tropical oceans?

Answer: You tow in an iceberg from the Antarctic. (Icebergs from the Arctic are not sufficiently big, flat, stable or accessible).

That was one of the more noteworthy proposals at the First International Conference on Iceberg Utilization held at Iowa State University in Ames last October. Specifically, the idea summarized above was discussed by R.T. Heizer of Kaiser Engineers, Inc., Oakland, Calif., "Energy and Fresh Water Production from Icebergs."

It would take more than a year for an iceberg to be towed from the Antarctic to the Northern Hemisphere, and there are other difficulties it must be wrapped in a plastic sheet to prevent the warm water melting it (the sun would melt only little in comparison). But would not the energy consumed in towing be greater than whatever energy could be gained from it?

Opinions on this point were divided. A team from the Naval Postgraduate School in Monterey, Calif., suggested that an ammonia engine or even an ICETEC electric generator could be used, making the iceberg truly self propelled under its own energy. But that, of course, would also make it melt away quicker.

Most participants seemed to think that towing icebergs to Australia or other parts of the Southern Hemisphere might make sense; but Saudi Arabia (interested in fresh water) or California seemed highly dubious.

Glaciologist W. Weeks of the US Army Cold Regions Research Lab, a man who ought to know, said that in either case "you would end up with nothing but a towline."