Microgrid
ProjectsSubmit a project

Home / Directory / Coconut Island DC Microgrid (Moku o lo’e)

Oceania & Pacific / Island & remote community

Coconut Island DC Microgrid (Moku o lo’e)

Current status, energy mix, organizations, suppliers, equipment, controls, reported specifications, and project updates—with source-level citations.

CoverageDetailed public record
Named organizations9
System facts23
Sources reviewed8
Evidence reviewed2026-07-20

The built Coconut Island (Moku o Loʻe) DC microgrid is a University of Hawaiʻi Natural Energy Institute research testbed serving selected critical loads in two Hawaiʻi Institute of Marine Biology buildings. The installed system is 6.2 kW of rooftop PV with an 8 kW/8 kWh lithium-ion BESS, DC loads, a custom OPTO22/Node-RED controller, and an AC-grid interface to the island's aging undersea service. It also supported an electric car and a 24-foot solar-electric boat. Earlier 500 kW-class planning references were proposals; HNEI's current reports establish the much smaller configuration that was actually installed and commissioned.

Research status
Installed, commissioned, and performance-tested by 2024-2025. HNEI's December 2025 annual report says the testbed demonstrated islanded critical-load operation, 3.3% better air-conditioner efficiency and 5% lower lighting power in DC mode, but also says the research project was terminated after loss of APRISES funding in May 2025. The hardware was not reported decommissioned, yet no post-November-2025 operating program is documented.
Historical classification
DC
Reported capacity
500 kW
Coordinates
21.43394, -157.78805
Evidence note: “Every company” cannot be proven from public material alone. This page lists every organization found in the recovered record and reviewed sources, preserves unknown roles, and explicitly marks undisclosed controller or equipment details.
Report missing evidenceResearch methodology

Project delivery

Who was involved in Coconut Island DC Microgrid (Moku o lo’e)?

9 publicly identified organizations. Where a recovered source named a participant without explaining its work, the role remains explicitly unspecified.

Organization

Hawaiʻi Institute of Marine Biology

Host institution and beneficiary; the microgrid serves selected loads in its Marine Mammal Research Project building and adjacent Boat House. [4][3]

Organization

Hawaiʻi Natural Energy Institute

Project owner/research lead through its Grid System Technologies Advanced Research Team; designed, integrated, commissioned, controlled, and evaluated the testbed. [3][4][5]

Organization

Office of Naval Research

Principal funding source for the Coconut Island DC microgrid and APRISES research program. [5][3][4]

Organization

Okinawa Institute of Science and Technology

Partner in the prototype solar-electric car, boat, portable emergency source, swappable batteries, and charging station. [5][4]

Organization

PUES Corporation

Industry partner with OIST and HNEI on the original electric-mobility and swappable-battery systems. [5][4]

Organization

Solar City

Publicly named participant; role not specified in the recovered record [1]

Organization

Spiders

Publicly named participant; role not specified in the recovered record [1]

Organization

University of Hawaii

Publicly named participant; role not specified in the recovered record [1]

Organization

University of Indonesia

Research partner that designed and commissioned DCON DC-DC converters raising the 48 V bus to voltages required by DC loads. [3][6]

System evidence

Energy mix, capacity, and specifications

Values can describe different project phases, generation sources, storage systems, or other components. Source citations are attached to each figure so discrepancies remain visible.

KW Solar
200 [1]
KW Gas/Diesel
440 [1]
Installed rooftop solar
6.2 kW DC on the Marine Mammal Research Project building [3][4]
Stationary battery storage
8 kW / 8 kWh lithium-ion BESS on a 48 V DC bus [5][3][6]
DC distribution voltages
48 V source/battery bus converted to approximately 200-350 V DC for building loads [3][6]
Electric-boat energy system after upgrade
1.98 kWp roof PV and 18.2 kWh fixed batteries arranged as four independently managed 48 V packs [4][3]
Earlier directory proposal
A 2019 state energy directory listed a 500 kW Coconut Island microgrid as proposed/under development; current HNEI build records document 6.2 kW PV and 8 kWh stationary storage instead [7][3]

Controls and hardware

Equipment and controller details

Manufacturer and model are shown only when a source names them. Generic descriptions are not converted into guessed product assignments.

01

Microgrid controller

Opto 22 — OPTO22 industrial controller

Custom HNEI control system using Node-RED and JavaScript/Node.js for scheduling and transitions among AC, DC, and hybrid operating modes, with Groov View dashboard monitoring. [4][3]

02

Grid-interactive inverter

Schneider Electric — XW Pro

Bidirectional inverter used primarily to convert AC utility supply to the 48 V DC bus, paired with two MPPT charge controllers; HNEI's reviewed report does not state its nameplate rating. [4]

03

DC-DC converters

University of Indonesia — DCON

Three research converters described at 3 kW each, raising the 48 V PV/BESS bus to 200-350 V for lighting, cooling, refrigeration, and other loads. [3][6][8]

04

DC end-use equipment

Model not publicly disclosed

AC/DC-capable air conditioner, AC/DC LED lighting, refrigeration, critical plug-load inverter, multipoint metering, contactors, breakers, and data-collection equipment installed across two buildings. [4][3]

05

Electric-boat batteries

Model not publicly disclosed

The original 11.2 kWh swappable packs were replaced by four fixed 48 V packs totaling 18.2 kWh, each with its own BMS, plus modern charge controllers and fault-tolerant switching. [4][3]

Technical record

Architecture, performance, and project updates

Concise technical facts, milestones, operating results, and later developments. Dated notes distinguish historical design claims from current evidence.

  • Management

    Advanced Communications and Microgrid Control [1]

  • Generation

    Small-scale wind turbines [1]

  • Generation

    Distributed Solar PV [1]

  • Generation

    2 Diesel Generators to backup critical loads [1]

  • Architecture

    Coconut Island remains connected to Oʻahu through an aging undersea electrical service, while the DC testbed can isolate selected critical loads. The stationary PV/BESS supplies a 48 V bus, DCON converters feed higher-voltage DC loads, and the Schneider inverter links to AC service. [4][3]

  • Measured efficiency result

    Periodic AC/DC switching found an average 3.3% air-conditioner efficiency improvement and approximately 5% lower LED-lighting power in DC mode. Plug loads were excluded because they remained AC-only. [4][3]

  • Control-system reliability fix

    One-second Modbus polling overloaded the controller and caused freezes. HNEI reduced active connections, changed polling to five-second intervals, and shrank an oversized dashboard icon, eliminating observed freezes and stabilizing monitoring. [4]

  • Mobility-system lifecycle

    The original swappable-battery station suffered BMS/charger conflicts, poor cell balancing, and rising end-of-life failures. It was decommissioned during APRISES19 and the electric car and boat received fixed batteries; this does not mean the building microgrid was decommissioned. [4]

  • Electric-boat integration

    The upgraded 24-foot boat demonstrated initial bidirectional energy flow in laboratory trials. Engineering for a permanent shore connection and full vehicle-to-grid integration began, but the May 2025 funding stop halted that next phase. [4][3]

  • Project outcome

    HNEI validated islanded critical-load operation and DC efficiency/control benchmarks, then reported project termination following loss of APRISES funding. The latest report does not say the installed testbed was removed, nor does it establish continued routine operation after November 2025. [3][4]

  • Capacity correction

    Historical 500 kW-class planning listings and secondary 200 kW solar/440 kW diesel summaries do not match HNEI's as-built record. The verified installed building testbed is 6.2 kW PV with 8 kW/8 kWh stationary storage; island-wide diesel assets are not part of that testbed rating. [7][3][4]

Provenance

8 sources

Primary owner, government, university, supplier, and engineering sources are preferred. Archived references preserve claims whose original pages moved or disappeared.

  1. [1]
    Recovered Microgrid Projects record

    Internet Archive · Archived source · captured 2021-04-20

  2. [2]
    Moku o Lo’e DC Microgrid

    hnei.hawaii.edu · Archived source · captured 2021-04-20

  3. [3]
    HNEI Annual Report to the 2026 Legislature: Coconut Island DC Microgrid

    Hawaiʻi Natural Energy Institute · Primary source

  4. [4]
    APRISES 22 Final Technical Report

    Hawaiʻi Natural Energy Institute / Office of Naval Research · Primary source

  5. [5]
    HNEI Report to the 2021 Legislature: Coconut Island DC Microgrid

    Hawaiʻi Natural Energy Institute · Primary source

  6. [6]
    Asia Pacific Regional Energy System Assessment Final Technical Report

    Hawaiʻi Natural Energy Institute · Primary source

  7. [7]
    Hawaii Energy Facts & Figures, July 2019

    Hawaii State Energy Office · Primary source

  8. [8]

Continue exploring

Related projects in Oceania & Pacific