Abstract
The impact of energy use on the planet is continuously increasing and stands as an unsolved problem. Energy efficiency remains as the main mitigation factor to curb the growth of energy consumption and related CO2 emissions, arguably the major responsible for climate change. Understanding the driving forces behind efficiency change is therefore crucial for defining energy policies and examining sustainable development pathways. To this aim, we propose a pyramidal approach to progressively analyse and decompose energy intensity, the main global efficiency indicator, using the LMDI method. First, the effects related to supply and demand sides of the energy system are separated. Then, the supply side is further decomposed to reveal structural effects associated with transformation processes and fuel types. The approach is applied to developed (OECD) and developing (non-OECD) regions to provide meaningful analysis and comparison of past trends, which could shed light to future effective environmental actions. The results show that a significant decrease in the energy intensity of both regions has been driven mainly by widespread improvements in demand-side efficiency. Despite huge differences in 1990, rapid globalisation of enhanced conversion devices and passive systems across borders suggests future convergence between developed and developing regions. Regarding the supply side, unfavourable structural changes due to electrification have only been offset by transformation efficiency gains in developed countries. Consequently, emerging economies have worsened their energy sector efficiency as they thrive. Hopefully, they could take OECD’s achievements as a roadmap to decouple development trajectories from an inefficient electrification as soon as possible. Key strategies should address changes in fuel mixes, as they have generally contributed to energy intensity reductions mainly due to shifts from coal and nuclear power towards gas and renewable plants. The proposed methodology could help stakeholders to effectively analyse the energy system and to develop policies to reduce its environmental impact.

Biography
María González-Torres, PhD student in Energy, Chemical and Environmental Engineering at University of Seville – Spain. She is an Industrial Technologies Engineer, with a MSc in Industrial Engineering and an expert in HVAC systems. She is currently working as a researcher in the Department of Energy Engineering at the University of Seville, in cooperation with the University of Cadiz within the Thermal Engineering Research Group. Her research focuses on identifying and quantifying the driving forces that make energy consumption and CO2 emissions change, considering the socio-economic factors leading to their growth and how efficiency and decarbonisation could counteract their effects.

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