The main grid plays as the main power source of land-based maritime grids since the very beginning, such as the seaports and some coastal industries. This type of maritime grids usually operates in a harbor territory and can receive electricity from the harbor city. Some equipment in those maritime grids is driven by electricity and the others may be driven by fossil fuel. Table 8.1 shows the power sources of a terminal port.From Table 8.1, electricity, diesel, petrol and natural gas are four main power sources for a terminal port, especially the electricity and diesel, serving for most of the port-side equipment. When a seaport is less-electrified, the portion from diesel is generally higher. In recent years, the extensive electrification of seaport becomes an irreversible trend, then the electricity now has become the primary power source of a seaport. Diesel now serves for some flexible operating equipment, such as trucks and other carriers. Similar phenomena also happen in other land-based maritime grids, such as coastal factories, since when fully electrified, electricity will serve as the main energy carrier and the main grid will be the main power source.
Main EnginesMost types of maritime grids cannot always receive power from the main grid. They mostly operate as islanded microgrids, such as island microgrids, shipboard microgrids, and various working platforms. For the island microgrids, if they cover a wide area, a small-scale or even medium-scale power plant is possible to construct,