In order to model the entire global energy system and its possible future development in ETM (EUROfusion TIMES Model) a reference energy system (RES) has been identified, which covers all available energy conversion technologies in the model. In a bottom-up approach all relevant commodities and processes have been identified and classified, that are relevant within the global energy system.

The reference energy system of a region in the ETM model is outlined above. The numbers of considered technologies are shown in brackets within each sectoral box. There are more than 1400 individual technologies considered in the model. The relevant commodities are indicated along the links of the RES. Each generic commodity name stands for a number of fuels. For instance, the generic name COM*** stands for the set of fuels considered in the commercial sector (COMELC, COMOIL, COMNGA, etc.).

The total number of distinct commodities exceeds 100. In each region, 42 demand segments cover five end-use sectors: residential (11 segments), commercial (8 segments), agriculture (1 segment), industry (8 segments) and transportation (15 segments). Each demand segment is serviced by end-use technologies, whose number varies depending on the segment, as indicated by the figures within brackets in each box. These figures indicate the number of existing and future technologies available in each sub-sector. 

Based on the assumption of a perfect forecast a projection of the global energy system up to 2100 is carried out. Main socio-economic drivers are assumed to be population and GDP.