Theoretical modeling and performance evaluation of a marine aquavoltaic system in the northern part of Iran

• Gomishan in the Caspian Sea is the ideal location for aquavoltaics due to its temperature, salinity, and chlorophyll. • Aquavoltaic system integrates a 196 kW FPV with Salmo salar aquaculture to increase energy and yield. • The aquavoltaic system achieves a profit of 42.32%, a payback period of 4 years and an IRR of 42.32%, outperforming the alternatives. • Water cooling increases the energy input by 13.55 MWh, reduces heat losses and increases efficiency. This study presents the theoretical modeling and performance evaluation of a marine aquavoltaic system that integrates a 196 kW floating photovoltaic (FPV) installation with Salmo salar cage aquaculture in the Gomishan region of the Iranian Caspian Sea. The objective is to assess the technical feasibility and economic viability of dual-use marine infrastructure for simultaneous food and energy production. Site selection was conducted using MODIS and SMOS satellite datasets processed through SeaDAS to evaluate the sea surface temperature, chlorophyll-a concentration, and salinity across Iranian coastal waters. A techno-biological growth model was applied using the FinFish Aquaculture Tool to simulate fish production, while PV performance was modeled in PVsyst, considering marine cooling effects and thermal losses. Economic evaluation was performed using net present value (NPV), internal rate of return (IRR), payback period (PBP), and benefit-to-cost ratio (BCR) indicators based on RETScreen and Excel cash flow analysis. The results indicated an annual electricity yield of 300.86 MWh and annual fish production of 498.48 kg per cycle. The FPV subsystem achieved a PBP of 5.2 years and an IRR of 24.71%, whereas the aquaculture subsystem exhibited a PBP of 1.4 years and an IRR of 84.24%. The overall BCR confirmed economic feasibility under current tariff conditions. The findings demonstrate that marine-based aquavoltaic deployment using CIGS thin-film technology is technically viable and economically competitive in temperate coastal environments.