Insights from past trends in exergy efficiency and carbon intensity of electricity: Portugal, 1900–2014

Research output: Contribution to journalReview article


We use the societal exergy analysis to identify periods and factors controlling efficiency dilution and carbon deepening of electricity in Portugal from 1900 to 2014. Besides estimating the carbon intensity of electricity production, we propose a new indicator, the carbon intensity of electricity use, which quantifies CO 2 /kWh of electricity derived useful exergy. Results show final to useful efficiency dilution until World War I (50% to 30%) due to a decrease in share of the high-efficiency transport sector and from mid-1940s to 1960 and mid-1990s onwards (58% to 47% and 47% to 40%) due to an increase in share of the low efficiency commercial and residential sector. Decarbonization from 1900 to mid-1960s, with carbon intensities of electricity production and use dropping respectively from 12.8 to 0.2 and from 33.6 to 0.4 kg CO 2 /kWh due to an increase in thermoelectricity efficiencies and an increase in share of hydro. Then, a period of carbon deepening until 1990 with carbon intensities tripling due to a shift in shares from hydro to thermoelectricity and more recently a period of decarbonization with carbon intensities decreasing to 0.35 and 0.9 kg CO 2 /kWh, due to the increase in renewable electricity despite a dilution in final to useful efficiency.


External organisations
  • University of Cambridge
  • University of Lisbon
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Energy Systems


  • Aggregate carbon intensity, Electricity, Exergy efficiency, Societal exergy accounting
Original languageEnglish
Article number534
Issue number3
Publication statusPublished - 2019 Feb 7
Publication categoryResearch