On-Site Power

Schofield Generating Station Highlights Value of Reciprocating Engines

Hawaii plays a critical role in America’s self-defense and military readiness, and the island of O’ahu houses installations for the Army, Air Force, Navy, Marine Corps, and Coast Guard.

BY KIERAN MCINERNEY, PE, CEM

Hawaii plays a critical role in America’s self-defense and military readiness, and the island of O’ahu houses installations for the Army, Air Force, Navy, Marine Corps, and Coast Guard. Nestled between two mountain ranges, O’ahu’s central valley provides natural cover and centralized locality for the U.S. Army Garrison-Hawaii, whose mission includes “enabling readiness for a globally-responsive Army.” Military readiness requires a stable electricity grid, and Hawaii’s isolated location in the Pacific Ocean presents unique fuel supply and grid vulnerability challenges. In addition, Hawaii and the Department of Defense (DOD) are each pursuing ambitious renewable energy goals, so new generation projects on the island must support renewable energy targets alongside reliability, security, and economic drivers.

Located on the Schofield Barracks Army installation, the Schofield Generating Station is a collaboration between the U.S. Army and Hawaiian Electric Company. Photo courtesy: Burns & McDonnell

The Schofield Generating Station is a perfect example. Located on the Schofield Barracks Army installation, the 50-megawatt (MW) multi-fuel reciprocating engine plant is a collaboration between the Army and Hawaiian Electric Company. Upon completion in Spring 2018, the facility will enhance the flexibility, reliability, and security of the electric grid while advancing each party’s renewable energy goals through the use of biodiesel. The new generating station’s flexible technology also enhances the utility’s ability to integrate wind and PV onto the grid, thus serving as a renewable energy force multiplier.

The DOD is one of the largest energy consumers in the world, and the military installations in Hawaii are collectively the largest customers served by Hawaiian Electric. So when the Army Garrison requested improved energy security and increased renewable energy production on its installations, the utility desired a solution to satisfy its largest customer while also benefitting the rest of O’ahu. “Our primary goal was to provide reliable, renewable, and resilient power to the Army and all of our customers,” said Jack Shriver, Manager of Generation Project Development, “but there were several variables that impacted the design. We needed a location away from our vulnerable coastline, operational flexibility, fuel flexibility, black start capability, and obviously the permitting and economics had to work. It was an interesting challenge.”

The task for Hawaiian Electric involved developing a facility that addressed a diverse set of drivers:

  • Energy Reliability. All existing generating stations on O’ahu are located on or near the coast, which means they may be vulnerable to coastal effects such as hurricanes and tsunami. Hawaiian Electric was seeking an inland location to mitigate those risks. Fuel flexibility was also a concern because O’ahu imports all of its fuel except for biofuel. It was important to build a facility that could switch fuels when necessary due to availability or cost.
  • Energy Security. In addition to the inland location, the team desired a site within the boundaries of an Army installation to maximize physical security. The lease for the site required that the generating station provide power directly to the Army under certain mission critical conditions. Finally, it was decided that the new facility should not only be black start capable itself, but that it should serve as a source of black start power to other generating stations in the event of an island-wide outage.
  • Renewable Energy Integration. The parties required a plant that could burn biodiesel fuel while exhibiting the operational flexibility to support a dynamically evolving grid. Hawaii’s best local energy resources are its sunshine and trade winds, and Hawaiian Electric plans to supply 100 percent of its electricity from renewable sources by 2045. Because these sources are intermittent, a new generating station must be able to support fluctuations in renewable supply through fast start and high ramp rate capabilities.

The Schofield Generating Station meets these goals and more. The plant will be owned and operated by Hawaiian Electric, connecting to the existing Wahiawa substation via a 46 kV transmission line included in the project scope. The plant is located on eight acres of land leased from the Army at Schofield Barracks, an installation that provides housing and services to the U.S. Army Garrison-Hawaii. Because the site is within the Army boundary approximately eight miles from the coast, it is invulnerable to coastal events and maximizes physical security.

During an emergency, the plant can provide a dedicated feed up to 32 MW to support critical facilities at Schofield Barracks, Wahiawa General Hospital, and Wheeler Army Airfield. The remainder of the generating station’s capacity can be used to restore critical infrastructure in the local community or to black start other units.

The plant includes six Wärtsilä 20V34DF reciprocating internal combustion engine (RICE) generators for a total net output of approximately 50 MW. These heavy-duty, medium speed engines can operate on natural gas or liquid fuels. The plant is designed and permitted to operate on both biodiesel and ultra-low sulfur diesel, but design considerations were included to accommodate potential installation of liquefied natural gas (LNG) infrastructure in the future. “We first looked for any technology that could solve the reliability equation. Then we looked at the technical details like start time, ramp rate, and fuel flexibility,” Shriver said. “Finally, when we factored in the heat rate and multi-shaft reliability, these engines were by far the best option for this application.”

The plant is expected to operate as a peaking unit that can quickly respond to changes in load or renewable energy supply. RICE generators can achieve start times under ten minutes to reach full power, with optimal heat rates and ramp rates when compared to other peaking technologies. Plus, the output and heat rate curves are essentially flat over the expected ambient temperature range, so the effects of hot, humid weather are negligible.

The plant will advance multiple renewable goals both directly and indirectly. First, the plant will run on at least 50 percent biofuel. Biodiesel operation directly enables Hawaiian Electric’s pursuit of 100 percent renewable energy by 2045, and Hawaiian Electric is already experienced with sourcing the fuel for other generators. The use of biodiesel also supports the Army’s goal to generate 1 gigawatt (GW) of renewable energy on its installations by 2025.

These same renewable energy goals are also indirectly supported by the Schofield plant because the fast start and flexible operation characteristics will allow for a higher penetration of renewables on the existing grid. Due to the impacts of high solar penetration and cost-effective energy efficiency projects, Hawaii’s load curve looks significantly different today than it did 10 years ago. The peak demand is lower and occurs later, when the sun sets and solar power gives way to traditional firm power generators. “In aggregate, rooftop PV is by far our largest generator on O’ahu during daylight hours,” says Shriver. The RICE technology at Schofield is better suited than the island’s existing generators to accommodate the high ramp rates required to compensate for wind and PV fluctuations. This flexibility will enable continued expansion of renewable technologies.

Upon completion, this plant will be an important energy source for the customers of Hawaiian Electric, and uniquely beneficial for its largest customer, the DOD. “The Army came to us with a specific request, but we worked together to make sure the solution was sustainable in the long term and supported all of our customers,” Shriver said. Hawaii and DOD are consistent early adopters of innovative energy technologies, leading American efforts to provide renewable energy solutions. To keep pace with renewable energy integration, the sustainability of O’ahu’s electric grid demands flexibility, reliability and security. Constructing the Schofield Generating Station is further proof that Hawaiian Electric can meet these needs now and in the future.

Author

Kieran McInerney is a development engineer in Burns & McDonnell’s Energy Division.

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