Useful Work Transitions in Portugal, 1856-2009.

The use of heat, as a consequence of industrialization, is a recent evolution to the service economy. In contrast to the conventional approach, we perform a useful work accounting, focusing our analysis on the final uses of energy instead of their sources. This enables the assessment of energy-driven activities and capturing of the structure of energy mixes. In addition, we include important energy flows, such as food for humans and feed for working animals, which are usually absent from energy statistics. We consider five different categories of energy uses: heat, mechanical drive, light, other electric uses, and muscle work. We apply this methodology to account for useful work in Portugal from 1856 to 2009. Different transitions in final energy use are identified in this long-term analysis such as the shifts from firewood to coal and from coal to oil and electricity. Useful work shifts from muscle work to mechanical drive uses, and from low to high temperature.