Assessment and Optimization of Energy Efficiency

Dear Colleagues,

In order to pursue the energy goals defined for 2030 and 2050, a strong effort regarding the assessment and optimization of energy efficiency is required by researchers, engineers and practitioners. The rational use of resources represents a key point: all resource categories must be accurately managed so as to smartly conduct energy transition. Energy efficiency assessments represent the foundation on which to create, build, design and implement optimization strategies. Examples of drivers in this field are represented by data selection, data acquisition, data storage, data analysis, Industry 4.0, digital twins and Key Performance Indicator (KPI) concepts. Both energy efficiency assessment and optimization represent multidisciplinary challenges where each area can contribute through its distinctive and specific tools. The high specificity and uniqueness of each discipline can make a difference in building a better future.

Prof. Dr. Silvia Maria Zanoli
Dr. Crescenzo Pepe
Guest Editors

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• engineering
• applied mathematics
• industrial processes
• non-industrial processes
• decarbonisation
• hard-to-abate sectors
• rational use of resources
• decision support systems
• expert systems

Energy and the Steady-State Economy

Georgios Karakatsanis ^1,2*, Nikos Mamassis ¹, Christos Makropoulos ¹ and Demetrios Koutsoyiannis <sup>1

1</sup> Department of Water Resources and Environmental Engineering, School of Civil Engineering, National Technical University of Athens (NTUA), 9 Heroon Polytechneiou St., 15870 Zografou, Greece; nikos@itia.ntua.gr (N.M.); cmakro@mail.ntua.gr (C.M.); dk@itia.ntua.gr (D.K.)
² Department of Research, EVOTROPIA Ecological Finance Architectures Private Company (P.C.), 190 Syngrou Avenue, 17671 Kallithea, Greece
* Correspondence: georgios@hydro.ntua.gr; Tel.: +30-69-4555-2243

Abstract: The foundation of the historical course of human civilizations is their energy paradigm, defined as the dominant pattern of energy harvesting from the natural environment. Since the early 19th century, humanity experiences the industrial civilization as its third energy paradigm based on fossil fuels (the preceding ones being the agrarian civilization and hunter-gatherer societies). As the 2nd Law of Thermodynamics dictates that the efficiency of energy transformation processes is limited below 100%, our work formulates theoretically and tests empirically the benchmark conditions of a steady-state fossil fueled (coal, petroleum and natural gas) global economy. At each time step, the steady-state is measured as the level of the maximum useful work introduced to the economy as the normalization of the confirmed nominal fuel reserve by the energy efficiency level. Specifically, our analysis consists in three pillars: (a) The formulation of a model that depicts the life-cycle pattern of the fossil-fuels’ energy paradigm and its empirical testing on data of global primary energy use for the period 1800-2023; (b) The postulation of the methodology of isotechnical curves that depict the economy’s steady-state at each time step and their empirical depiction for the period 1800-2023 for (i) an unconstrained CO₂ emissions and (ii) a constrained CO₂ emissions scenario to highlight the emergence of the energy paradigm’s limiting factor; and (c) The theoretical background of the Jevons’ Effect and its econometric testing for the period 1800-2023 for two variables: (i) energy efficiency increases and their impact on (ii) the future cumulative primary energy use that crowds them out. Based on our findings we further discuss the environmental, economic and technological implications of the ongoing global energy policies.

Keywords: energy paradigm; industrial civilization; fossil fuels; 2nd Law of Thermodynamics; efficiency; steady-state; useful work; nominal reserve; isotechnical; limiting factor; Jevons’ Effect