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The Kumejima Model
The Kumejima Model
An Island's Future Born from the Sea
The Kumejima Model has attracted international attention as an advanced real-world example of integrated GX (Green Transformation) development in island regions. It has evolved through the long-standing, community-driven efforts of the Town of Kumejima, local industries, residents, and stakeholders, in collaboration with national and local governments, academic and research institutions, and partners from both domestic and international industries.
A defining feature of the model is the strategic utilization of deep ocean water as a local resource, enabling the gradual development of an integrated GX system that connects energy, water, food, environmental, and industrial sectors. This process has been shaped by sustained local initiative, combined with continuous cooperation and knowledge exchange with external partners.
Through these efforts, Kumejima has emerged as a valuable demonstration field where academic research and real-world implementation evolve together. It now serves as an important site for exploring GX pathways that enhance energy resilience, support sustainable economic activities, and promote harmony with the natural environment in island settings.
The Kumejima Model is not intended as a prescriptive solution, but rather as a reference case that offers insights and practical experience for researchers, policymakers, and practitioners working to develop GX strategies suited to the diverse conditions of island regions.
Building on strong local leadership and continued international collaboration, the Kumejima Model is expected to contribute to ongoing global efforts to co-create sustainable and resilient futures for island communities.
The Core Engine of the Kumejima Model :
Ocean Thermal Energy Conversion (OTEC)
One of the core enabling technologies of the Kumejima Model is Ocean Thermal Energy Conversion (OTEC). OTEC is internationally recognized as a transformative renewable energy technology that enables sustainable and self-reliant energy systems in island regions.
Principle of Power Generation
OTEC generates electricity by utilizing the natural temperature difference between warm surface seawater and cold deep ocean water drawn from depths of several hundred meters. This thermal gradient is used to vaporize and condense a working fluid, which drives a turbine to produce continuous and reliable electricity.
Strategic Significance for Island Regions
A key advantage of OTEC is its ability to provide stable, continuous baseload power 24 hours a day, independent of weather conditions, unlike solar and wind energy. This reliability makes OTEC a critical enabling technology for enhancing energy security and supporting sustainable Green Transformation (GX) in island environments.
In addition, deep ocean water utilized in OTEC systems serves as a valuable natural resource that supports integrated applications across multiple sectors, including freshwater production, food systems, environmental sustainability, and industrial development—forming the foundation of a resilient circular island economy.
Integrated Cascaded Utilization of
Deep Ocean Water
One of the defining features of the Kumejima Model is its integrated cascaded utilization system, in which deep ocean water used in Ocean Thermal Energy Conversion (OTEC) is not discarded after a single use, but instead strategically reused across multiple sectors by leveraging its unique physical and chemical properties.
Even after its use in OTEC, deep ocean water retains its low temperature (approximately 10–15°C), exceptional purity, rich nutrient content, and stable composition. These characteristics enable its application beyond energy production, creating sustainable value across aquaculture, agriculture, environmental systems, health, and industry.
Aquaculture:
Enabling High-Value and Sustainable Production
The low temperature and high purity of deep ocean water provide a stable and low-pathogen environment, supporting the sustainable cultivation of high-value marine products such as sea grapes, kuruma shrimp, and oysters.
Agriculture:
Advancing Climate-Controlled Food Production
The cooling properties of deep ocean water can be utilized for soil and environmental temperature regulation, enabling the cultivation of temperature-sensitive crops even in subtropical climates. This expands agricultural potential beyond conventional climatic limitations.
Health and Industrial Applications:
High-Value Resource Utilization
Due to its mineral richness and exceptional purity, deep ocean water serves as a valuable resource for high-value industries, including functional foods, cosmetics, and health-related products.
The Expanding Global Influence
of the Kumejima Model
The integrated GX (Green Transformation) practices and knowledge developed in Kumejima are attracting growing attention among island nations and island regions across the Pacific, Caribbean, and Indian Ocean regions. The Kumejima Model is increasingly recognized as one of the practical reference cases for developing sustainable energy, water, and economic systems adapted to island environments, including applications in countries such as Palau and Nauru.
Furthermore, the Kumejima Model has been introduced by international organizations including the United Nations Industrial Development Organization (UNIDO), the Climate Technology Centre and Network (CTCN), the International Energy Agency (IEA), and the International Renewable Energy Agency (IRENA) as a promising practical example of sustainable GX systems for island regions. It continues to attract attention in international research and policy dialogue on energy transition, climate resilience, and sustainable development.
Environmentally Harmonized Sustainable Energy Systems
The Kumejima Model is based on the utilization of sustainable energy resources in harmony with the natural environment. This approach supports the reduction of dependence on imported fossil fuels while strengthening energy resilience and self-reliance in island communities.
Integrated Energy and Water Systems:
Application to Desalination
Demonstration research on seawater desalination utilizing electricity generated by Ocean Thermal Energy Conversion (OTEC) is actively being conducted in Kumejima. This integrated approach offers a promising pathway toward sustainable freshwater supply solutions for island regions facing water resource constraints.
Creation of Sustainable Local Industries
The Kumejima Model promotes the creation of new industries based on locally available natural resources, contributing to economic diversification and employment opportunities. These efforts are expected to strengthen the long-term socio-economic resilience of island communities.