| 1. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- 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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| 3. |
- Sousa, Tânia, et al.
(författare)
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Improving the robustness of societal exergy accounting : from primary energy to energy services
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Results of useful exergy accounting at the societal (i.e. national or global) level are potentially important for policy purposes, such as the development of energy or GHG emission scenarios, and the determination of the major energy inefficiencies (and thus improvement potentials) within a country. However, useful exergy societal studies commonly differ in their accounting methodology, which affect the results. Such differences include the starting point (primary or final energy), the method used to compute primary exergy, the classes of useful exergy categories considered, the definition of second law efficiencies, the inclusion (or not) of exergy inputs related with non-energy uses, and the inclusion or not of muscle (and human) work. To help bring a more consistent approach to useful exergy accounting at the societal level, we review the methodologies of past studies, highlighting the differences and discussing their advantages and disadvantages in each case. Based on this, we select our preferred options, leading to a proposed common methodology that can be used to build national and international series of useful exergy.
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| 4. |
- Sousa, Tânia, et al.
(författare)
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The need for robust, consistent methods in societal exergy accounting
- 2017
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Ingår i: Ecological Economics. - : Elsevier BV. - 0921-8009. ; 141, s. 11-21
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Tidskriftsartikel (refereegranskat)abstract
- Studies of societal exergy use have the common aim of tracing the flow of exergy along society, and are used to gain insights into the efficiency of energy use and linkages to economic growth. However, their methodological approaches vary greatly, with significant impacts on results. Therefore, we make a review of past studies to identify, synthesize and discuss methodological differences, to contribute to a more consistent and robust approach to societal exergy accounting. Issues that should be taken into account when making methodological options are discussed and key insights are presented: (1) For mapping of primary inputs and useful exergy categories, the inclusion of all natural resources is more consistent but it has the cost of not being able to distinguish the various energy end-uses in the production of materials. (2) To estimate primary electricity, none of the methods currently used is able to capture simultaneously the efficiency of the renewable energy sector, the environmental impact and the efficiency of energy use in society. (3) To estimate final-to-useful exergy conversion efficiencies, standard thermodynamic definitions should be used because the use of proxies fails to distinguish between increases in exergy efficiency and increases in the efficiency of providing energy services.
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| 5. |
- 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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