Wind, solar, and biomass energy are modeled explicitly in the FeliX model. Investment in and development of these energy sources is calibrated to the results of IIASA's Global Energy Assessment (2012) for RCP 6.0. As shown below, future development of renewable energies--especially solar & biomass--shows strong dependence on population growth. In the case of biomass, this dependence has important consequences for land use change: specifically, forest degradation.
Seen above, total annual energy demand is predicted to grow nearly 90% by the end of the century. During this period, fossil fuels lose market share due to the expansion of renewables, with absolute production levels of oil and gas peaking around 2050 and 2060, respectively.
Each of the seven fuels integrated into the FeliX model is modeled independently, according to anticipated prices and return on investment (fossil fuels discussed here and renewables here). This information is used to calculate emissions from energy generation.