| 1. |
- Felício, Laura, et al.
(författare)
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Insights from past trends in exergy efficiency and carbon intensity of electricity : Portugal, 1900–2014
- 2019
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Pinto, Ricardo, et al.
(författare)
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The rise and stall of world electricity efficiency:1900–2017, results and insights for the renewables transition
- 2023
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 269
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Tidskriftsartikel (refereegranskat)abstract
- In the coming renewables-based energy transition, global electricity consumption is expected to double by 2050, entailing widespread end-use electrification, with significant impacts on energy efficiency. We develop a long-run, worldwide societal exergy analysis focused on electricity. Our 1900–2017 electricity world database contains the energy carriers used in electricity production, final end-uses, and efficiencies. We find world primary-to-final exergy (i.e. conversion) efficiency increased rapidly from 1900 (6%) to 1980 (39%), slowing to 43% in 2017 as power station generation technology matured. Next, despite technological evolution, final-to-useful end-use efficiency was surprisingly constant (∼48%), due to “efficiency dilution”, wherein individual end-use efficiency gains are offset by increasing uptake of less efficient end uses. Future electricity efficiency therefore depends on the shares of high efficiency (e.g. electrified transport) and low efficiency (e.g. cooling and low temperature heating) end uses. Our results reveal past conversion efficiency increases (carbon intensity of electricity production reduced from 5.23 kgCO2/kWh in 1900 to 0.49 kgCO2/kWh in 2017) did little to decrease global electricity-based CO2 emissions, which rose 380-fold. The historical slow-pace of transition in generation mix and the need to electrify end-uses suggest that strong incentives are needed to meet climate goals.
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| 3. |
- Tostes, Bernardo, et al.
(författare)
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On the right track? Energy use, carbon emissions, and intensities of world rail transportation, 1840–2020
- 2024
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Ingår i: Applied Energy. - 0306-2619. ; 367
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Tidskriftsartikel (refereegranskat)abstract
- The history of rail transport can offer valuable insights for future energy transitions due to its importance in promoting clean mobility. There is a complex interplay between the evolution of the railway network, fuel consumption, efficiency, energy service, and CO2 emissions that requires further exploration. We developed a dataset that covers energy use in all stages of rail transportation, as well as the length of track, energy service, and CO2 emissions at the world scale. To deal with missing data we utilized machine learning techniques for the first time in a historical energy reconstruction study. Our analysis reveals that for world rail transport (1) the final-to-useful efficiency has increased by 30-fold from 1840 to 2020, mainly due to the replacement of steam trains with diesel and electric ones, (2) the peak in final energy use occurred in the 1940s, while useful energy use and transport service continue to grow, (3) there was a reduction in the energy (carbon) intensity from approximately 20 to 0.2 MJ/tkm (2 to 0.02 kg CO2/tkm) between 1840 and 2010, due not only to the increase in final-to-useful efficiency but also to rising occupancy, better operating conditions, and reduced losses by the passive system.
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