Offshore virtual power plant features battery and compressed air energy storage
A Maltese and Chinese research group has conceived an offshore mooring and power platform (OMPP) which could be run by solar and wind power, plus energy storage, in Malta’s national waters.
The proposed VPP would feature a P2S setup to electrify anchored and bunkering ships – vessels which are being refueled – at the OMPP, with surplus electricity fed to the Maltese grid. Numerical calculations and site selection methodologies were used to size the system and test its feasibility.
“A key technology to sustainable practices in the maritime industries is shore-to-ship (S2S), which allows ships to turn off these diesel engines by drawing power from the shore’s electricity grid,” said the academics. “Very large floating structures (VLFS) platforms, with their stability and load-bearing capacity in open waters, are particularly well-suited to host S2S systems, resulting in P2S capabilities that offer a sustainable energy solution for vessels at sea, including hybrid and electric ships.”
The academics said Malta’s strategic position in the Mediterranean as a key maritime hub makes it an ideal location for their OMPP. Based on the country’s National Policy for the Deployment of Offshore Renewable Energy, the academics identified “Area 3” as suitable for offshore solar, wind and energy storage, as it has relatively shallow offshore characteristics and is one of six designated bunkering areas off Malta.
“The OMPP connects to the offshore VPP via a medium voltage direct-current (MVDC) link, approximately 20 km long,” stated the research group. “The platform, with estimated dimensions of 1,200 m by 300 m, is designed to accommodate up to four ships, each up to 200 m long. It features a 24 MVA P2S facility with four berths, each providing up to 6 MVA. The platform dimensions are based on a 20 m buffer zone on each side of the ships, allowing four ships to dock comfortably with a safety margin for operational flexibility.”
Following the numerical simulation, and using weather data, the scientists concluded their system would require a 200 MW floating wind farm and a 300 MW floating solar site to supply ship demand and export energy to Malta’s grid. They posited the use of Maxeon’s 3 SPR-MAX3-430 modules, with 430 W of power and 22.7% efficiency, installed with a horizontal orientation. The simulation proposed the SG 8.0–167 DD wind turbine, with 6.04 GWh/km2.
“A detailed sizing analysis of the offshore battery energy storage system and subsea compressed air energy storage was conducted to optimize the energy storage capacity and ensure seamless power supply,” said the group. “The analysis revealed that a battery energy storage systems (BESS) capacity of 390 MWh is necessary to meet the short-term demands while the compressed air energy storage (CAES) system, with a capacity of 1,260 MWh, provides additional energy security during prolonged periods of low renewable [energy] generation.”
The team said the proposed system would ensure that OMPP could maintain reliable power supply to the berths under varying conditions. “The simulation-based assessments confirmed the technical viability of the OMPP, though the study also identified several economic and technical challenges that still need to be addressed,” stated the academics. “Future work should focus on optimizing the cost structure, possibly through modular designs or alternative financing models, to enhance the economic attractiveness of such systems.”
The system was presented in the paper “Renewable energy systems in offshore platforms for sustainable maritime operations,” published in Ocean Engineering. The study was conducted by researchers from the University of Malta and China’s Tiangong University.
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