A Roadmap for Clean Energy on Kwajalein Atoll

By Paul Ryckbost, P.E., PMP, M.SAME, Derek Miller, and Josh Bakin

A recent effort led by U.S. Army Space & Missile Defense Command to meet the Army Climate Strategy for operations on Kwajalein Atoll studied potential courses of action that would help the remote installation reach 100 percent carbon-pollution free electricity by 2030.

Located in the Republic of the Marshall Islands, U.S. Army Garrison – Kwajalein Atoll is a tremendously remote yet uniquely important and dynamic installation. Situated 2,100-nautical-mi southwest of Honolulu, Hawaii; 3,200-mi north of New Zealand; and 700-mi north of the equator, the base is home to about 1,000 soldiers, government civilians, contractor employees, and host nation personnel and their families.

The garrison has operations on multiple islands across the atoll, with its headquarters on Kwajalein Island. It is responsible for supporting multiple combatant command relationships (U.S. Northern Command, U.S. Strategic Command, and U.S. Space Command) as well as around-the-clock space operations missions that critically rely on power and cooling.

Kwajalein is uniquely strategic, but its geography also means it is positioned at the forefront of impacts from rising sea levels.

To achieve the 100 percent carbon-free electricity laid out in the Army Climate Strategy, U.S. Army Garrison – Kwajalein Atoll studied six potential courses of action, considering the unique geographic location and assets of the remote installation.
Future Outlook

Published in 2022, the Army Climate Strategy adopts aggressive end-state goals to make the service a “resilient and sustainable land force able to operate in all domains with effective mitigation and adaptation measures against the key effects of climate change, consistent with Army modernization efforts.” The document also explicitly states that “the Army is committed to 100 percent carbon-pollution free electricity to meet the needs of its installations by 2030.”

Realizing both the desire to achieve 100 percent carbon-free electricity by 2030 and Kwajalein Atoll’s own desire to provide clean, resilient power to critical assets, Army Space & Missile Defense Command, the installation’s host unit, embarked on a study to identify the most appropriate energy alternatives for the future. The resulting findings were accepted in May 2023 and addressed options for providing energy to the vital missions at the atoll and meeting the end-state goals of the Army Climate Strategy.

Courses of Action

Kwajalein Atoll’s location in the Pacific Ocean actually makes it well-positioned to consider a variety of pathways for meeting or exceeding the Army’s climate goals. Its proximity to the equator makes solar power a high-performing asset, and its placement atop an atoll with adjacent deepwater canyons provides opportunities for the use of ocean water that are rarely available to other defense installations.

A total of six known, available, carbon-free alternatives were considered in the roadmap for Kwajalein, with three technologies selected for further development as potential courses of action: solar photovoltaic with battery energy storage system; hydrogen fuel cells with on-site hydrogen production via photovoltaics, and ocean thermal energy conversion. The other three considerations were dismissed for varying reasons. Wind power was eliminated due to seasonal doldrums that mean multiple months of no wind. Micro-nuclear was eliminated out of respect to host nation concerns. Geothermal was eliminated due to lack of a viable resource.

Research on studying aspects of the technology conducted over the last 30 years denotes that commercial-scale ocean thermal energy conversion is more feasible now, thanks to significant advances in material availability, especially large-diameter pipes and titanium heat exchangers

Modeling Outcomes. The courses of action for Kwajalein Island were derived using an operational scenario model developed to simulate operating modes over a full year using actual load data. The model calculated the amount of fuel and electricity generation required by the existing power plants to meet the projected demands and compared it against each alternative.

For the hydrogen fuel cells and ocean thermal energy conversion options, the existing power plants would only need to be used in emergency and testing mode. Conversely, for the solar option, the plants would need to run to meet peaking requirements. The solar option requires that the current power plants operate approximately 13 percent of the time—consuming over 1-million-gal of diesel fuel at the current electricity consumption rate. Provided there is not a prolonged storm event, the photovoltaic array can produce the hydrogen necessary to assure 100 percent carbon-free electricity using fuel cells.

Each of these three courses of action have risks associated with implementation and operation. Although photovoltaics and battery storage are well-developed technologies, the lack of land space on the installation at Kwajalein requires that the majority of the solar panels (61.5-MW) will be in a floating array located in the lagoon. In addition, battery storage can only provide limited electricity back-up capability due to capacity constraints and high costs.

The hydrogen fuel cell solution utilizes solar power to generate the hydrogen that can be stored and provide sufficient back-up capability to assure 100 percent carbon-free electricity. Hydrogen storage requires high-pressure (3,000-psi or greater) to deliver the hydrogen to the fuel cell and for effective storage. Both hydrogen generation and storage have inherent safety concerns due to its explosive nature and high-pressure conditions.

Ocean thermal energy conversion is a demonstrated technology, but it has not been built at full commercial scale. However, an operational 250-kW system located at the Natural Energy Laboratory Hawaii Authority on Hawaii Island has proven that the power cycle works as designed and is being used as a research and development facility to evaluate heat exchanger technology. Research on studying aspects of the technology conducted over the last 30 years denotes that commercial-scale ocean thermal energy conversion is more feasible now, thanks to significant advances in material availability, especially large-diameter pipes and titanium heat exchangers.

Importantly, all three potential technological solutions have a political risk in that the permission of the Republic of the Marshall Islands is required to utilize the lagoon, either for floating solar arrays or for a floating ocean thermal energy conversion platform.

The ocean thermal energy conversion solution would result in a 100 percent carbon-free electricity solution for Kwajalein Atoll as well as provide clean water for the remote island.
Substantial Savings

Ocean thermal energy conversion was selected as the best overall alternative to meet the Army’s goals on Kwajalein Island. The proposed facility, combined with a central electric chiller and chilled water distribution system, offered the best economic solution when compared to solar and hydrogen fuel cell alternatives. Ocean thermal energy conversion provides dispatchable power that can be constructed with off-the-shelf components to produce sufficient electricity for the foreseeable future for Kwajalein Island. Excess power is available to deliver to nearby Ebeye Island.

For this process, generators create power through a simple closed Rankine power cycle in which the warm surface water is utilized to evaporate a working fluid (such as ammonia), which expands through a turbine-generator system to produce electricity. The fluid is subsequently condensed in a heat exchanger utilizing cold seawater drawn from the depths of the ocean (more than 3,000-ft down). The system also includes an embedded reverse osmosis plant capable of producing 500,000-gal/day of fresh clean water from the deep ocean source.

Financing Arrangement. Procurement of the preferred ocean thermal energy conversion plant would occur through a power purchase agreement or military construction funding. In the power purchase agreement, the Army would contract for a third party to construct, own, operate, and maintain the plant and sell electricity and water to the government under a 25-year contract.

A lifecycle cost analysis of all three options was conducted using the conventional net present value methodology, bringing all future costs back to mid-2023 using approved discount and inflation rates of the Office of Management & Budget. Capital costs were developed using the standard military construction programming method, incorporating non-binding budgetary quotes where possible for equipment line items. All capital costs were inflated to the anticipated mid-point of construction (2027), assuming that projects are initiated in time to have facilities operational by 2030.

The lifecycle cost analysis indicated that the power purchase agreement would provide substantial savings for the Army as compared to a continued reliance on diesel generation—identifying a savings potential of nearly $463 million over the 25-year contract. This represents a 14.3 percent savings. Estimates for costs were derived using a “mock PPA” approach that developed a pro forma incorporating industry standard expectations for return-on-equity and conventional project financing methods.

Toward Clean Electricity

The ocean thermal energy conversion solution reduces long-term energy costs for the island, provides ample clean freshwater to meet the needs of Kwajalein and Ebeye, and offers a 100 percent carbon-free electricity solution. The photovoltaic and battery alternative is approximately the same lifecycle cost over the 25-year period of analysis. But it would require significant use of the existing power plants and a roughly 150-acre floating solar array, as opposed to a two-acre to three-acre ocean thermal energy conversion facility.

For the outer islands of the garrison (Roi-Namur, Meck, Illeginni, Gagan, and Legan), which would be too far from the plant, the proposed alternative is photovoltaic production with battery storage. The current approach is to utilize floating solar panels to augment or supplant ground-based photovoltaic systems for each island. Recommended systems at each of the islands are sized to meet the current and projected electricity demands and utilize conventional battery (lithium-ion) storage.

As of early 2024, the Army is actively exploring next steps to begin implementation of all preferred alternatives.

Paul Ryckbost, P.E., PMP, M.SAME, is Vice President, Project Manager, Energy & Utility Solutions, Guernsey; paul.ryckbost@guernsey.us.

Derek Miller is Lead Engineer, USAKA Infrastructure Team, U.S. Army Space & Missile Defense Command; derek.d.miller14.civ@army.mil.

Josh Bakin is Environmental Compliance Manager and Climate Change Specialist, U.S. Army Space & Missile Defense Command, joshua.d.bakin.ctr@army.mil.

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