By using fossil fuels such as wood, coal, oil and gas, it was possible forhumanity to set up civilization in colder climates. Due to the increasingdemands of comfort, a higher mobility and a larger world population, energyexhaustion of these fuels is foreseeable in the midterm.1.1consumption rose tremendously over the last 150 years (see Figure 1.1) andIntroductionWorld..