Development of Offshore Wind–Solar Hybrid Energy System for Sustainable Energy Generation

The increasing demand for electricity, coupled with the need to reduce greenhouse gas emissions and enhance energy security, has intensified interest in hybrid renewable energy systems. This study developed and evaluated an offshore wind–solar hybrid energy system for sustainable electricity generation in the Kimbiji coastal area of Dar es Salaam, Tanzania. A quantitative modelling approach was employed using five years (2019–2024) of wind and solar resource data obtained from coastal meteorological stations and the NASA POWER database. Wind resources were assessed through wind speed extrapolation, Weibull distribution analysis, and wind power density estimation, while solar resources were evaluated using Global Horizontal Irradiance (GHI), Direct Normal Irradiance (DNI), Diffuse Horizontal Irradiance (DHI), clearness index, and ambient temperature. A synthetic hourly load profile representing an average daily electricity demand of 3,000 kWh was developed in HOMER Pro. The hybrid system, comprising photovoltaic modules, offshore wind turbines, battery energy storage, a bidirectional converter, and a diesel generator for benchmarking, was optimised using HOMER Pro's Combined Dispatch strategy. The study found that the site has an annual average wind speed of 6.58 m/s at 100 m hub height, a wind power density of 362.7 W/m², and an annual average GHI of 5.23 kWh/m²/day, confirming the technical suitability of the area for offshore hybrid renewable energy development. The analysis further demonstrated that wind and solar resources exhibit complementary temporal characteristics, significantly reducing the mismatch between renewable energy generation and electricity demand compared with stand-alone systems. However, residual energy deficits during evening peak demand highlight the necessity of integrating battery energy storage to enhance system reliability. Overall, the findings indicate that offshore wind–solar hybrid systems provide a technically feasible and sustainable solution for improving electricity access in Tanzania's coastal communities while reducing dependence on fossil fuels and supporting the transition toward low-carbon energy systems.