Hawaii island is gearing up to add locally produced hydrogen to its diverse mix of alternative energy resources.

Officials at the state-funded Hawaii Natural Energy Institute are preparing an environmental assessment for a facility that initially would produce hydrogen for use in fuel cell vehicles. Later phases of the project would explore the use of hydrogen as an energy source for electricity generation.

HNEI has an agreement with Puna Geothermal Ventures to build the hydrogen production facility on the grounds of PGV’s plant about 20 miles southeast of Hilo.

The plant will use an electrolyzer to separate water into hydrogen and oxygen. The hydrogen would then be loaded into pressurized cylinders and trucked to Hilo and Hawaii Volcanoes National Park where it will be used to power fuel cell shuttle buses.

The hydrogen produced at the plant will truly be a "clean" fuel because the electricity used to run the electrolyzer will come from a geothermal facility, said James "Mitch" Ewan, institute hydrogen systems program manager.

Puna Geothermal is providing the land free to the institute, and the electricity at a discounted rate. "We’re really leveraging everything we can to make this work," Ewan said.

The electrolysis process is fairly energy intensive. HNEI’s electrolyzer would use about 4 megawatt-hours of electricity per day, the equivalent of powering about 100 homes.

Its goal is to have the environmental assessment completed by January and the hydrogen production plant and fueling stations finished by March, Ewan said.

The Federal Transit Authority is providing two 19-passenger ElDorado shuttle buses to be used at Hawaii Volcanoes National Park. HNEI is providing a third to the Hawaii County Mass Transit Agency.

The ElDorado buses, which come from the manufacturer with gasoline engines, will be retrofitted with fuel cells by the state-funded Hawaii Center for Advanced Transportation Technologies. The cost to buy and convert the buses is about $500,000 each. The state is contributing $1.8 million to the project.

The fuel cells convert hydrogen into electricity that is used to power the vehicle’s electric motor. Fuel cells are more than twice as efficient as internal combustion engines and produce no emissions except water, according to HNEI.

HNEI’s short-term goal is to analyze the performance of the electrolyzer under different operating conditions, according to the environmental assessment. It also will evaluate the feasibility of hydrogen as an energy storage and grid management tool.

Hydrogen generated at the facility could be stored and used to run electrical generators that would help offset the fluctuations in power being generated by wind and solar resources, according to the environmental assessment.