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Asia / Island & remote community

Nushima Island DC Microgrid

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

CoverageDetailed public record
Named organizations13
System facts27
Sources reviewed9
Evidence reviewed2026-07-20

This was a fiscal-2012-to-2014 Japanese Ministry of the Environment demonstration on Nushima Island in Minamiawaji, Hyogo Prefecture. It is not Naoshima in Kagawa, as the recovered catalog's historical location says, and it is unrelated to the Niijima smart-grid project. The experiment linked three small 360 V DC microgrids, 8 kW of photovoltaic generation, 1 kW of wind and a 46 kWh stationary lithium-ion battery, supplemented by the island's AC utility supply. It also tested mobile batteries, ship-to-grid power from a plug-in hybrid boat, direct-DC appliances, visualized dynamic pricing and demand response.

Research status
The funded technology demonstration concluded after fiscal 2014. The reviewed sources document the prototype, conversion performance and behavioral trials, but do not establish that it became an island-wide production microgrid or remained in service after the project. No authoritative operating, replacement or decommissioning update through July 2026 was found. The historic system was grid-assisted and experimental, not a self-sufficient renewable power system for all of Nushima.
Historical classification
DC
Reported capacity
See component specifications
Coordinates
34.46409, 133.97097
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 Nushima Island DC Microgrid?

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

Organization

Fuji Electric Co., Ltd.

Power and controls industry partner [3]

Organization

Hyogo Prefectural Institute of Technology

Project participant and current public source describing the demonstration and its reported conservation result. [6]

Organization

Japanese Ministry of the Environment

Funded the regional distributed-energy technology demonstration during fiscal years 2012-2014. [6]

Organization

Keitsushin Technology Industry Co., Ltd.

Industry partner [3]

Organization

Kobe University

Lead research organization for the Nushima DC microgrid demonstration. [6][7]

Organization

Ministry of the Environment, Japan

Technology-development and demonstration funder [3]

Organization

Nakanishi Metal Works Co., Ltd.

Industry partner [3]

Organization

Osaka City University

Research partner [3]

Organization

Ritsumeikan University

Research partner [3]

Organization

Ritsumeikan University and Osaka City University

Academic collaborators in the multi-institution demonstration program. [6]

Organization

Sansha Electric Manufacturing Co., Ltd.

Power-electronics partner [3]

Organization

Sanyo Electric Co., Ltd.

Industry and equipment-development partner [3]

Organization

Sanyo Electric, Keitsushin, Sansha Electric Manufacturing, Nakanishi Metal Works and Fuji Electric

Industrial collaborators listed by the Hyogo Prefectural Institute for the project; the source does not assign every item of equipment to a specific company. [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
1 [1]
KW Wind
1 [1]
Storage
1 [1]
DC bus
360 VDC [4]
Solar PV
8 kW in the published demonstration description [5]
Wind generation
1 kW [5]
Battery storage
46 kWh in the published demonstration description [5]
Reported outcome
Approximately 30% reduction in electricity consumption using DC conversion and demand-response measures [3]
Photovoltaic capacity
8 kW in the published prototype configuration. [7][9]
Wind capacity
1 kW in the published prototype configuration. [7][9]
Stationary battery
46 kWh lithium-ion battery. A continuous power rating was not established in the reviewed sources. [7][9]
DC bus
360 V DC trunk, with conversion to 19/24 V DC and 100 V rms AC for conventional loads; selected appliances operated directly at 360 V DC. [7]
Utility assist
The demonstration could draw from the local 220 V, three-phase, 60 Hz AC utility network through a bidirectional converter; it was not an exclusively renewable islanded system. [7]
Demand-response trial population
The project presentation describes price/usage displays and demand-response engagement across 76 households, while one system diagram labels a 51-household dynamic-pricing area. These dated presentation values are preserved rather than silently reconciled. [8]

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

DC energy-management controls

Model not publicly disclosed

Controls battery charge/discharge from total power balance and state of charge across a 360 VDC bus; no commercial controller model is identified. [4]

02

Power conversion

Model not publicly disclosed

High-frequency-link DC/DC converters, sinusoidal PWM DC/AC inverter, AC/DC grid interface, and converters for stationary/mobile batteries and ship charging. [4][3]

03

Stationary battery

Model not publicly disclosed

46 kWh lithium-ion storage connected to the 360 V DC architecture. Manufacturer, cell chemistry subtype and model were not identified in the reviewed publications. [7]

04

Power conversion

Model not publicly disclosed

High-frequency DC/DC converters supplied low-voltage DC loads, while a DC/AC inverter supported conventional 100 V rms loads and a bidirectional converter interfaced with the utility network. [7]

05

Mobile energy storage

Model not publicly disclosed

Two forms of transportable battery and a 96 V mobile architecture were tested to move stored energy among the separated DC microgrid sites. [8]

06

Ship-to-grid resource

Model not publicly disclosed

A plug-in hybrid boat was used as a mobile energy resource in the S2G experiment. The project source does not establish a commercial vessel or battery model. [6][8]

07

Direct-DC appliances

Model not publicly disclosed

Prototype loads included equipment designed to accept the 360 V DC bus directly, avoiding an additional conversion stage. [7][8]

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.

  • Location correction

    The site is Nushima Island (沼島), administered by Minamiawaji in Hyogo Prefecture. Naoshima in Kagawa is a different island; the recovered catalog's Naoshima location is erroneous. [6][8]

  • Architecture

    Three separated DC microgrid sites combined local renewables, stationary and mobile storage, an AC-grid interface, direct-DC and conventional AC loads, plus supervisory information exchange. Energy could be moved physically by battery or boat rather than through a continuous island-wide DC cable. [7][8]

  • Conversion performance

    Laboratory/field measurements reported more than 90% conversion efficiency when charging the stationary battery and whole-system conversion efficiency around 80%, with some configurations above 70%. These are component/prototype measurements, not an annual microgrid efficiency or renewable share. [7]

  • Behavior and conservation

    The Hyogo project account reports that combining visualized variable pricing with the distributed-energy trials reduced electricity consumption by about 30%. The source does not provide a long-term normalized baseline or claim that generation alone caused the reduction. [6]

  • Timeline

    The Ministry of the Environment demonstration ran during fiscal years 2012-2014. A 2015 symposium presentation documented the concluded experiment and its mobile-battery, ship-to-grid and dynamic-pricing elements. [6][8]

  • Evidence gap

    No current operator page, later commercial deployment, annual generation record, permanent islanding test or post-demonstration asset disposition was found through July 2026. [6]

Provenance

9 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 2020-07-06

  2. [2]
    http://microgrid-symposiums.org/wp-content/uploads/2015/09/a-Tamaki_20150819.pdf

    microgrid-symposiums.org · Archived source · captured 2020-07-06

  3. [3]
    Nushima stand-alone distributed energy demonstration using DC technology

    Hyogo Prefectural Institute of Technology · Primary source

  4. [4]
  5. [5]
    Common DC bus integration — Nushima Island case

    IET Smart Grid · Secondary research

  6. [6]
    Regional Distributed Energy Technology Demonstration Project on Nushima Island

    Hyogo Prefectural Institute of Technology · Primary source

  7. [7]
  8. [8]
    DC Microgrid Project in Nushima Island

    Kobe University / Microgrid Symposium · Primary source

  9. [9]

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