Alternative energy is an umbrella term that refers to any source of usable energy intended to replace fuel sources without the undesired consequences of the replaced fuels. The planet Sera has always had an energy crisis. The use of petroleum, solar panels and nuclear fuels could never satisfy the energy stricken people. None of Sera's hydrocarbon (oil) energy resources could provide the resources that the power plants needed, until Imulsion was discovered, ironically by an Oil-exploitation drill, which lead to the "Gold Rush" period and ended the "Era of Silence". The biggest example of Imulsion taking over the market was when solar powered car sales dropped in favor of Imulsion powered cars.
Humans had mastered concepts of advanced energy application well before Imulsion was developed as a universal fuel source. The four major credited sources of energy utilized by the population of Sera were hydroelectricity, wind-power, solar-power, and petroleum. Many power-plants built before Imulsion such as Tollen Hydroworks symbolized this in the form of four statues. Even after the widespread application of Imulsion, these energy sources continued to be utilized for practical electricity. The Locust were known to tap into power junction stations and channel electricity underground. Upon the end of the Locust War with the destruction of all Imulsion reserves on Sera, Humans were forced to return to traditional forms of energy for the purpose of rebuilding. While the COG preferred using hydroelectricity, nuclear power, and petroleum for large-scale rebuilding, the Outsiders adopted wind and solar power as well as draft-mules to retain independent townships.