ABSTRACT
Energy use patterns have undergone significant changes since mankind started using energy. Prior to the Industrial Revolution, energy was mostly derived from the natural energy f lows and human and animal power, and energy usage was limited. Since then, two grand transitions have shaped energy systems at all levels. The first transition involved a gradual shift towards coal from traditional energies in the nineteenth century leading to a coal-dominated energy system in the early twentieth century. The second involved a decline of coal and the emergence of petroleum as the dominant fuel in the middle of the last century. The arrival of steam engines powered by coal was the main driver in the first transition and it gained acceptance because of its higher energy density, f lexibility and mobility. For the second transition, the innovations of internal combustion engines and electricity conversion technologies proved crucial. Oil emerged as the dominant energy form by virtue of its ease of use arising from f luidity, versatility, relative cleanliness compared to coal and universal appeal.
