|During the last few decades, environmental impact of the petroleum- based transportation infrastructure has led to the wide use of electric vehicles. In contrast to fossil fuel-powered vehicles, the electricity consumed by electric vehicles can be generated from a wide range of sources, including nuclear power and renewable sources such as tidal power, solar power, and wind power. Electric vehicles have drawn much attention from the research world and the auto manufacturing industry. Electric vehicles are also extensively used in many cities in the world.
One type of electric vehicles use batteries as the rechargeable on board electrical storage medium. These batteries have to be switched at battery swap stations when the electricity is to be used up. A new, fully charged battery will be stored on the electric vehicle to provide electricity. The time for switching batteries is much shorter than the charging time by direct connection to generation plants. However, due to the low energy density of batteries compared to the fuel of internal combustion engined vehicles, batteries in electric vehicles must be frequently switched, normally three to four times a day for an electric taxi. Therefore, the availability of battery swap stations are vital to the operations of electric vehicle. For instance, the routing of one or a few vehicles to transport given cargo at minimum cost, may need to incorporate the sojourn points for switching batteries.