The Portuguese energy sector changed substantially during the period 1995–2010, with the introduction of natural gas and a larger renewable energy production. During the same period, the country also continued the shift to a service economy. By 2005, these two transitions led to a large increase in primary energy use (PEU), followed by a significant decline until 2010. The goal of this paper is to identify the main driving factors of changes in the Portuguese PEU through structural decomposition analysis. To do so we build a novel hybrid model with a detailed description of the energy sector in physical units, and a coarser description of the rest of the economy in monetary units. The results show that the main drivers were final demand (increasing PEU) and the direct energy intensity (decreasing PEU); while the energy and economic transitions also contributed to decrease PEU, although to a lesser extent.

The analysis of useful exergy (UE), which is the minimum amount of work required to produce a given end-use, provides insights on the relationships between structural changes and energy transitions because it focuses on what energy is used for, i.e., energy services, rather than where it comes from, i.e., energy carriers. In this paper, UE was accounted for Mexico in 1971–2009. It was found that UE experienced a six-fold growth, led by the increasing share of mechanical drive and electric energy uses. Structural changes such as industrialization and complete electrification mainly drove UE transitions. Technological progress, mainly driven by the industrial sector, and electricity availability caused an improvement in the aggregate final-to-useful efficiency of the economy. In addition, the trend of increasing UE economic intensity shows that Mexico became more dependent on UE per unit of economic output during industrialization. The results suggest that UE trends were more influenced by structural transitions while final exergy trends were more influenced by economic fluctuations. It is concluded that energy policy design in developing countries undergoing or starting the process of industrialization should focus on: (1) improvements in final-to-useful efficiency, especially of the transportation sector and (2) growth of the productivity of UE.