The push to generate more renewable energy from the state’s vast geothermal resources is picking up steam on Hawaii island and Maui.

The potential for geothermal energy generation is enormous. A consultant’s report prepared for the state Department of Business, Economic Development and Tourism estimates that the geothermal resources on Hawaii island and Maui are sufficient to create more than 1,500 megawatts of electrical generating capacity, an amount roughly equivalent to the peak electrical load of the entire state.

Ormat Technologies Inc. operates a 30-megawatt geothermal power plant on Hawaii island already and is preparing to bring another 8 megawatts of generating capacity online at its Puna facility in the next few months. The Nevada-based company also is exploring the possibility of building Maui’s first geothermal plant on the southwestern slopes of Haleakala.

For its part, Hawaiian Electric Co. is soliciting ideas from the public on how best to proceed with the development of future geothermal projects on Hawaii island where alternative energy sources account for 31 percent of the island’s electricity production, the highest share of any island in the state. Ormat’s Puna Geothermal Venture plant alone supplies 17 percent of the island’s total generating capacity, and that will increase to 20 percent after the expansion is completed.

Hawaii Electric Light Co., HECO’s subsidiary that operates on Hawaii island, put out a "request for information" in June and received 20 responses from developers, landowners and others covering a wide range of issues related to geothermal development in Hawaii, including cultural, historical and environmental concerns.

"Geothermal power is already a proven source of firm renewable power that can play an even larger role in Hawaii’s clean energy future," said Jay Ignacio, HELCO president. "This is a first step and with growing interest and discussions around the state we must consider the best approach because developing geothermal is unique," he said.

The state and geothermal developers want to avoid repeating a situation that occurred in the 1980s when a plan to drill geothermal wells in the pristine Wao Kele O Puna rain forest on the slopes of Kilauea drew intense opposition from Native Hawaiians and environmentalists. The project was canceled after a massive demonstration in 1990 in which dozens of protesters were arrested.

Ormat’s Puna facility, the state’s only operational geothermal plant, sits on one of the best geothermal resources in the world. Underground temperatures in the Kilauea East Rift Zone can exceed 650 degrees fahrenheit. The plant captures steam from mile-deep geothermal wells and uses it to turn turbines that in turn run electrical generators. Puna Geothermal Venture has been in operation since 1993.

Although the Kilauea East Rift Zone is the only area in Hawaii where geothermal wells actually have been drilled, DBEDT consultant GeothermEx Inc. used scientific modeling to predict high-temperature resource areas in six other areas on Hawaii island and Maui: Kilauea Southwest Rift Zone, Mauna Loa Northwest Rift Zone, Mauna Loa Southwest Rift Zone, Hualalai, Haleakala East Rift Zone and Haleakala Southwest Rift Zone.

One of the main advantages of geothermal compared with solar- and wind-generated energy is that the steam from the geothermal wells produces firm power similar to that of a traditional oil-fired power plant. Solar power is available only during daylight hours, and even then the electrical output of photovoltaic panels can spike up and down depending on cloud cover. Similarly, the energy produced by a wind turbine can vary depending on wind speed.

Another plus with geothermal is the cost of electricity, which GeothermEx estimates can be produced in Hawaii at a cost of 7 cents to 8 cents per kilowatt hour. That compares with 21.8 cents per kilowatt hour that HECO has agreed to pay developers for solar electricity under the recently enacted feed-in-tariff program.

However, prospecting for geothermal resources in Hawaii can be costly, with the typical project requiring the drilling of one or more test wells through layers of rock to depths of 6,000 feet or more.

"We’re isolated. There are challenges to being on an island," said Mike Kaleikini, plant manager for Puna Geothermal Venture. "The equipment we need is mostly from the mainland. And we don’t have a lot of people who drill geothermal in Hawaii. Right there your costs have escalated by the fact of our location," Kaleikini said.

It typically takes Puna Geothermal Ventures about 90 days to drill a well, he said.

The geological features on Hawaii island make drilling deep wells particularly challenging, said Andrea Gill, renewable energy specialist for the state energy office.

"There are layers of basalt where drill bits have a hard time doing their job and that is an issue," she said. "We certainly have some layers of rock with good integrity."

One of the companies that has responded to HELCO’s request for information regarding geothermal development is Honolulu-based Innovations Development Group, which bills itself as a specialist in socially responsible development.

The company, which operates a geothermal project on Maori trust lands in New Zealand, has held a series of community meetings on Hawaii island and Maui over the past few months. IDG also took part in a recent energy forum in Honolulu and has held various meetings with state legislators and officials regarding its plans for geothermal development in Hawaii.

Robbie Cabral, IDG’s founder and senior adviser, told the West Hawaii Today newspaper that the company has looked at Kealoha Estate land near Pahoa on Hawaii island for development, but added that the company remains open to other sites, preferably those on state or county land.