6. Conclusion

The world "s Primary Energy is 12 billion TOE (Tonnes of Oil Equivalent)/year, i.e. energy close to 140,000 TWh.

But most of this energy is lost in power plants, vehicle engines, wood-burning stoves... The energy actually used (i.e. the real need for energy) is only around 60,000 TWh, of which 50,000 comes from fossil fuels, and 10,000 from nuclear power, hydroelectricity and biomass, with 20,000 TWh used in the form of electricity.

The most common mid-century forecasts are :

• 9 billion inhabitants ;

• production multiplied by 3 or even 4;

• but only a 2-fold increase in energy use, taking into account a major effort to save energy, the average cost per kWh could therefore double without significantly increasing the weight of energy...