The influx of solar energy, under the best conditions, amounts to only about 1 kW per square meter. Large-scale conversion of solar energy therefore requires large collecting areas - a permanent limitation of solar power.
But the earth's oceans are already collecting solar energy, which is heating up their surface layers. The temperature difference, small though it is (40°F), can be harnessed by a thermal electric power plant whose turbines are propelled by the vapor of a lowboiling-point liquid (ammonia) rather than steam (AtE Dec.73). Nevertheless, the small temperature difference pushes the system to the very edges of engineering know-how; it is something like building a hydroelectric plant with a dam only a few feet high.
But last May, Earl J. Beck of the Navy's Civil Engineering Lab at Port Hueneme, Calif., applied for a patent based on a different idea. To see how it works, consider first a bubble pump, which pumps water from a reservoir through a vertical tube immersed in it; air is injected into the open end at the bottom, and as the air bubbles rise, they lift the water in the tube far above the free water level¾in theory, with sufficiently powerful air injection, to a maximum of several hundred feet.
Now imagine a bubble pump bringing brine from the deep of the sea high above the sea level, to drop down again through a hydraulic (not steam) turbine that powers an electric generator. In this form, the system would serve only as a monument to the incompetence of its designer, for the electric power consumed in running the air pumps would be much greater than the power produced by the generator.
However, Beck proposes to power the bubble pump by the heat of the sea: Warm surface water is introduced to the lower end of a vertical pipe via a constriction; as it exits from the constriction, some of it is flashed into water vapor (cold steam) whose bubbles will lift the water in the pipe above the ocean's free surface, whence it flows through a hydraulic turbine back into the open sea. The energy to run the bubble pump is gained from the warm sea water which gives up heat on being vaporized.
Beck's concept has already been improved on by C. Zener and J. Fetkovich of the Carnegie-Mellon Univ. in Pittsburgh, and we hope to return to their system in a future issue.
[More: Science, 7/25/75, pp.293-295.]
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Vol. 3, No. 2
Newsletter: Access to Energy Newsletter Archive Volume: Volume 3 Issue/No.: Vol. 3, No. 2 Date: October 01, 1975 10:31 AM Title: Oil and Paper
Copyright © 2004 - Access to Energy Newsletter Archive
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