Geothermal energy pool may expand


By TOM CALLIS

Tribune-Herald staff writer

For anyone who has gazed upon the fiery glow of Kilauea, or relaxed in the steam caves and hot ponds along its East Rift Zone, it’s clear the Big Island hosts one of the most geologically active places on earth.

But underground heat sources may extend far beyond Pele’s reach into areas separated by millennia from the hot spot that created the Hawaiian Islands, at least one scientist believes.

And if accessible, they could expand the use of geothermal energy to dormant parts of the isle as well as possibly Maui and Oahu, said Donald Thomas, director of the University of Hawaii at Hilo’s Center for the Study of Active Volcanoes.

It may seem counterintuitive that islands with volcanoes long extinct could still host a geothermal resource.

Thomas said that may not be too unlikely since old rift zones — zipper-like fractures where magma intrudes away from a volcano’s summit — could host cooling, though still quite hot, magma.

Where there’s heat, there’s the potential for creating geothermal electricity, currently limited to one 38-megawatt power plant, Puna Geothermal Venture, outside Pahoa.

But whether that heat exists where Thomas thinks it does remains mostly theory, he acknowledges, and the volcanologist is leading a 2-3 year effort to find out just how hot Hawaii is under the surface.

“We know geologically speaking where underground heat is likely to exist …,” Thomas said.

“We don’t know how fast it dissipates.”

It’s guessed that magma may stay hot for at least 500,000 years after being disconnected from its source, he said. That heat could potentially even last for millions of years.

To probe for those heat sources, researchers are using a non-invasive technique that relies on the detection of “extremely low-frequency radio waves,” Thomas said.

Sensors are placed on the surface, and depending on how the radio waves act, researchers can tell if it’s passing through magma or even water sources, he said.

They can detect radio waves traveling as deep as 20 kilometers below the surface, though it’s likely that any magma sources would be no more than 5 kilometers underground, Thomas said.

The project is funded so far with a $1 million U.S. Department of Energy grant and about $400,000 from the state Department of Land and Natural Resources, he said.

The effort started 10 months ago, Thomas said, and he estimates he has enough funding to last about another year. He plans to seek additional funding.

So far, research has been limited to the Kilauea summit and its East Rift Zone.

Thomas said researchers are using the volcanically-active area to collect data with which to compare other parts of the islands.

Later, sensors are also planned to be placed on Hualalai and Mauna Kea before moving onto Maui and Oahu.

On Mauna Kea, Thomas said the researchers will look for a rift zone that is believed to cut through land owned by Parker Ranch and the Department of Hawaiian Homelands.

“We’ll make a start in Parker Ranch and see what that tells us,” he said.

Parker Ranch CEO Dutch Kuyper told Pacific Business News last week that he hopes to one day produce geothermal power from the ranch’s extensive landholdings.

Thomas said the university is working with Lawrence Berkeley National Laboratory on the research project.

Email Tom Callis at tcallis@hawaiitribune-herald.com.

 

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