Microtunneling Meets Mother Nature

by Ronald M. Fedrick, President; Nova Group, Inc., Napa, CA,

Serial Information: Civil Engineering—ASCE, 1995, Vol. 65, Issue 12, Pg. 36-39

Document Type: Feature article

Abstract: The world's first ocean thermal energy plant is getting a double. Microtunneling the second ocean intake 80 ft under the Pacific Ocean is proving challenging, partly due to unexpected seabed geology, and partly to unexpected wave action. The design and construction challenge was to bore parallel pipelines to tap energy from the cold ocean waters deep off Hawaii's shores. Microtunneling turned out to be the best way to drive the twin 1,040 ft suction intake pipelines, but the seabed geology has treacherous lava holes, and, at the surface, wave action nearly shut the site down. Nova Group, Napa, Calif., solved the problems and learned some lessons from the first two landward drives. The ocean drives are under way now. The first Ocean Thermal Energy Project has been operating at the state of Hawaii's Natural Energy Laboratory in Kona since 1982, netting about 50 kW of usable electric power from a gross generation of 210 kW. In 1993, Makai Ocean Engineering, Honolulu, designed a second plant for the lab to draw 39F water from 3,000 ft below sea level. The goal is a gross output of 1 MW with a net 500 kW of usable power.

Subject Headings: Geology | Microtunneling | Sea floor | Underwater pipelines | Water intakes | Wave action |

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