Geothermal power has a prominent position in the Hawaii island energy portfolio, and has the potential to make the county energy self-sufficient. But before Hawaii County moves toward that bright future, it is imperative to know the full story on the costs as well as the benefits of any expansion of geothermal development.

So it makes perfect sense that Mayor Billy Kenoi’s office is advancing a plan to study the health risks of geothermal power generation on residents of Puna.

Energy figures show geothermal occupying only a 2 percent sliver of the Hawaii’s energy portfolio, but in 2013 the generation by Puna Geothermal Venture (PGV), the state’s only geothermal plant, in operation since 1993, represented nearly a quarter of Hawaii island’s energy production.

That proportion can only increase, given Hawaii island’s optimal conditions for geothermal energy generation in the zone with the most volcanic activity. The lava in the Kilauea East Rift Zone, specifically, produces steam from water that seeps through the permeable rock strata, energy that can be conveyed to the surface through a geothermal well.

The residual volcanic elements in that steam, however, present the primary concern about health risks, one that was evident in the wake of Tropical Storm Iselle. Transmission lines that ordinarily transfer power to the grid were downed by fallen trees, tripping off the plant. To relieve pressure, the plant released a plume of geothermal fluid containing high concentrations of hydrogen sulfide.

More than 100 people living nearby reported with discomfort, complaints including severe lethargy, nausea, red eyes, burning eyes and respiratory problems.

Hawaii needs to know more about these health effects than anecdotal reporting can provide. The Geothermal Asset Fund, a source built through $50,000 annual contributions from PGV, is being tapped for the $750,000 needed to underwrite the study.

Preliminary plans for the study put the focus on assessing the effects of geothermal on the central nervous and respiratory systems and on anxiety disorders. But it’s heartening to see that the county’s Windward Planning Commission also has required consultation with the federal Centers for Disease Control and Environmental Protection Agency in defining the scope of the study before proposals are accepted.

Besides bolstering the case for the health study, the geothermal accident also underscored the need for better safeguards in the operation of the system, especially under the duress of a major storm. One of the release valves that was supposed to keep pressure from building had become stuck, leading to the release of high concentrations of gas.

Such unanticipated problems show the need for oversight of operations, and the prudence of the request by Hawaii County Civil Defense: PGV must cut back its operations in advance of future wind events and have power backup to maintain its monitoring system.

PGV has the capacity to produce up to 38 megawatts of power, but the island offers the possibility for significant expansion. A 2008 report prepared for the state also identifies two other sites with geothermal development potential: Hualalai, northeast of Kailua-Kona, and the Mauna Loa Southwest Rift Zone near South Point.

Geothermal energy is what utilities call "firm power," the most reliable source for electrical generation, competing well with fossil fuels and having the added advantage of being renewable. Hawaii island is uniquely equipped to tap this resource for the benefit of its residents.

But any energy source has its demerits as well, and before geothermal advances further, Hawaii needs to view the landscape from all angles.