Army takes comment on enviro review for 50-MW biofuel project in Hawaii

The U.S. Army has issued a Draft Environmental Impact Statement (DEIS) for the proposed lease of land and granting of easements on Schofield Barracks and Wheeler Army Airfield to Hawaiian Electric Co. for the construction, ownership, operation, and maintenance of a 50-MW, biofuel-capable plant, referred to as the Schofield Generating Station, and associated power poles, high-tension power lines, and related equipment and facilities.

Under the National Environmental Policy Act (NEPA), the DEIS analyzes the environmental impacts associated with construction and operation of the Schofield Generating Station and associated infrastructure. The Army has determined that there are historic properties nearby, but that the undertaking will have no effect upon them. Comment on the draft is being taken for 45 days from publication of a notice in the April 24 Federal Register.

The electricity produced by the project would normally supply power to all Hawaiian Electric customers through the island-wide electrical grid. During outages that meet the criteria specified in the Operating Agreement, plant output would first be provided to Army facilities at Schofield Barracks, Wheeler Army Airfield, and Field Station Kunia up to their peak demand of 32 MW, to meet their missions, and would additionally support the grid up to the station’s full capacity. If there were a full island outage, the power plant could be used to restart other plants on the island.

The Schofield Generating Station would consist of six Wartsila 20V34DF (or similar) multifuel-capable, reciprocating internal combustion engine-generator sets and associated equipment. Each engine would be equipped with selective catalytic reduction (SCR) equipment containing catalysts to reduce nitrogen oxide (NOx) emissions, and an oxidation catalyst to reduce carbon monoxide (CO) emissions. The new facility would provide a total gross generation rating of 50 MW.

Auxiliary equipment would include inlet air filters, gas exhaust silencers and stacks, a closedloop air cooled radiator array, generator step-up and auxiliary transformers, fuel and lubricating oil handling equipment and associated storage tanks, a water purification system, a urea mixing system to supply the SCR emissions control system, a switchyard, and a facility to receive and regasify liquefied natural gas (LNG).

The generator sets would be installed in a single engine hall. Each generator set would generate approximately 8.4 MW gross. Each of the six engine-generator sets is expected to have an overall annual availability (i.e., operability rate) of more than 95%, including scheduled and forced outages. The design of the plant would provide operating flexibility. Each engine is designed to start and be fully operational in 6 minutes or less. Each engine provides various ancillary services, such as ramp up, ramp down, spinning reserve, and voltage and frequency regulation, allowing these units to readily adapt to changing conditions that might arise with large amounts of as-available generation on the grid. The engines can operate at partial load, with a minimum load of 50%. Because each engine can operate independently, this gives the 50 MW plant a minimum load of approximately 4.2 MW.

The reciprocating engines would use a liquid biofuel blend and would also be capable of burning natural gas derived from LNG. If operated at full power all six units combined would require about 450 million British thermal units of fuel per hour, equivalent to around 3,600 gallons of biodiesel blend per hour. The Army and Hawaiian Electric have agreed that at least 50% of the fuel used by the station will be biofuel, and that the station will use a minimum of 3.5 million gallons per year of biofuel. For the remainder of the generating station’s fuel requirements, Hawaiian Electric would have the flexibility to use biofuel, diesel, or LNG, if and when LNG becomes available on the island, in any combination that it deems most efficient and cost-effective.

Biodiesel would be delivered to the site in fuel trucks with approximate capacities of 5,800 gallons and diesel delivered in fuel trucks with approximate 9,000-gallon capacities. These trucks would enter the site through the Schofield Barracks Lyman Gate. The expected truck traffic load would depend on plant usage, and could vary from one to nine trucks per day when in normal operations or islanded mode. In the extreme case of continuous operation at a rated capacity of 100% biodiesel, the traffic load would be 15 trucks per day.

To store liquid fuel, the generating station would include two 32-foot-diameter by 40-foot-high above-ground fuel storage tanks. Two tanks are planned to provide redundancy and reserve capacity during planned tank maintenance. Each tank would have a maximum net capacity of 210,000 gallons. Combined, these tanks would have the capability of storing up to 420,000 gallons of fuel. The facility would include secondary containment for 110% of one tank, in accordance with industry and Army regulations for above-ground storage tanks. When LNG becomes available as a fuel source, it would be delivered to the site in International Standards Organization (ISO) container trucks holding about 10,000 gallons.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.