Integrating marine renewable energy (MRE) with conventional energy sources and logically constructing island energy systems is crucial for alleviating island energy supply challenges and helping coastal energy systems achieve a sustainable, low-carbon transition. In this study, the status of marine energy utilisation technologies is reviewed, with a focus on advancements in energy conversion equipment, grid integration, and energy storage. The economic feasibility and environmental sustainability of marine energy systems are comparatively analysed to enhance the development and utilisation of marine energy technology while reducing the economic cost of power generation. Suitable equipment is highlighted for islands, with efficient energy generation strategies proposed to achieve cleaner, localised, and cost-effective island integrated energy system (IIES) design. Island energy facilities vary, and integrated development is crucial for building new energy systems. Based on the types and resources of island energy, IIESs are constructed for hierarchical energy utilisation and multi-energy coupling, coordinating resources to achieve source–grid–load–storage integration. The optimisation of IIESs is reviewed, with a focus on modelling methods, intelligent algorithm development, and system simulation. This study differs from previous research as it considers the integration of marine energy into existing systems to achieve comprehensive integration of multiple energy sources. Additionally, optimisation and solution methods for IIES models are summarised. To integrate complex, multivariable energy systems and create stable and predictable outputs, marine energy and load forecasting methods are explored. Overall, this study supports the advancement of marine energy utilisation, focusing on its progressive integration into island energy systems as the efficiency of marine energy improves. This work aims to inspire the development of new functions and modules based on existing system optimisation and forecasting techniques.

Liquefied Natural Gas (LNG), as a vital form of natural gas resources, has exhibited a steadily increasing trend in global production and trade volumes. LNG terminals are facing the challenge of how to recover and utilise cold energy in a safe and efficient regasification process, while coordinating with the natural gas pipeline network transport scheduling. This study proposes an integrated regulation and collaborative optimisation approach for natural gas pipeline networks and LNG cold energy cascade utilisation systems. For natural gas pipeline network systems, P-Graph develops multi-period gas-electric interconnected supply chain network to optimise resource allocation. For the LNG cold energy cascade utilisation system, a dual Organic Rankine Cycle (ORC) framework for both power generation and refrigeration is developed, as well as thermodynamic analysis and heat integration techniques are applied to optimise system efficiency. Using a coastal LNG terminal in Zhejiang, China, as a case study, when the LNG regasification flow rate is 62.46 t/h, cold energy generates electricity of 2,335.94 kW and air-conditioning cooling load of 1,651.5 kW, system efficiency reaches 44.75 %. The peak regulation and gas storage effect of LNG is significant, which helps to alleviate that energy shortage in the region, and the coupled system of LNG and natural gas pipeline network improves energy utilisation efficiency and economic benefits for LNG industry chain.