The islands usually face challenges in their energy supply due to their specific location. On islands that are distant from the land, power is typically provided by diesel generators. Therefore, oil tankers must regularly refuel the island in order to supply the necessary fuel for diesel generators. As a result, if the fueling procedure is not completed for whatever reason, the island will not receive the necessary energy, which will result in an unavoidable loss of load. Due to their strategic location, some of these islands are used as military islands to protect the nations and waterways. Given the vital role that these military islands play for nations, a delay in supplying the island with energy can seriously harm security, the economy, and other factors. Transferring fuel to these islands is typically difficult, and in some cases impossible, under certain circumstances, such as war. Therefore, reducing the island's reliance on fossil fuels as much as feasible is vital to ensure the energy security of these specific islands. Diesel generators provide electricity to Larak Island, which is situated in the Strait of Hormuz. Larak Island serves as a military island due to its geopolitical location, hence it is crucial to consistently provide Larak with electricity. Therefore, in this paper, a combination of distributed generations and system storage is used to supply the Larak island. The photovoltaic, wind and tidal plants are considered the main power plants, and fuel cells with electrolyzers and hydrogen tanks have also been used as storage systems. In addition, the diesel generator is considered the system backup. The considered objective functions to design and manage Larak island's power supply system are reducing diesel generators fuel consumption, reducing electricity cost, and reducing electricity outages and lost power generation of renewable resources.