Efficiency-Driven Iterative Model for Underwater Compressed Air Energy Storage (UW-CAES)

The competitiveness of large-scale offshore wind parks is influenced by the intermittent power generation of wind turbines, which impacts network service costs such as reserve requirements, capacity credit, and system inertia. Buffer power plants smooth the peaks in power generation, distribute electric power when the wind is absent or insufficient, and improve the capacity factor of wind parks and their profitability. By substituting the variable pressure storage with an underwater variable volume air reservoir and reducing the wastage of compression heat using liquid Thermal Energy Storage (TES), which eliminates the combustor, the plant design allows overcoming the most common drawbacks of CAES plants. Underwater Compressed Air Energy Storage (UW-CAES) plants are investigated with a thermodynamic model to drive the power plant design toward efficiency maximization. Functional maps, constrained on the plant pressure ratio and the number of compressor/turbine phases with inter-refrigerated/inter-heating phases, are drawn by solving the model iteratively for the heat exchangers' effectiveness to meet the target turbine discharge temperature, selected in advance to avoid unfeasible mathematical solutions.