The necessity to standardise primary energy quality in achieving a meaningful quantification of related indicators

Systemwide energy return on investment in a sustainable transition towards net zero power systems

“…Additional issues correspond to setting appropriate boundary conditions for all involved technologies and estimating all primary energy at the same energy quality. This study overcomes related issues by applying a newly constructed LUT-EROI model, which estimates all types of CED data following LCA rules as detailed in Methods and the Supplementary Information while also maintaining the same primary energy quality as recommended in Solomon et al 29 . The model applies a mathematical algorithm that allows capturing the change in operation rules of each technology implemented in the LUT Energy System Transition Model (LUT-ESTM) 30 , 31 .…”

“…Low-carbon pathways generated by IAMs differ from cost-optimisation energy modelling in terms of methodology, and conceptualisation of the scenarios, and could yield different EROI outcomes. Together with the divergence of our EROI methodology, developed by Solomon et al 27 , 29 , a careful comparison is necessary. The typical results of our study are consistent with the findings of King et al 19 that applied IAMs to investigate EROI and indicated a decrease in net energy for society.…”

“…Still, the uncertainty of estimating primary energy at the same energy quality remains a fundamental problem of CED and EROI studies. This issue was solved by applying energy conversion factors to estimate primary energy at the level of electricity quality as recommended in Solomon et al 29 . The ecoinvent database provides CED values by separating them into eight sub-categories (renewables: biomass, geothermal, solar, potential-barrage water, kinetic-wind, and non-renewables: fossil, nuclear, and primary forest) according to the energy resource type as MJ-equivalents 54 .…”

“…EROI analysis for such a long process, disparities in features of technologies (efficiency, process types, lifetime) and the product utilisation purpose are indisputable main issues. Ensuring energy quality consistency 29 and continuity through all energy supply chain processes is the priority of a systemwide EROI analysis. Thus, the traditional approaches usually do not fit highly complex energy systems.…”

“…Hereby, this study expands the newly developed Excel-based LUT-EROI model (LUT stands for Lappeenranta-Lahti University of Technology) to study global systemwide EROI using the nine global transition scenarios presented in Aghahosseini et al 6 , to evaluate the sustainability risk of these transition scenarios from the perspective of physical EROI. The overall modelling framework improved on the existing shortcomings of corresponding EROI studies and enhances the representativeness of the estimated physical EROI values by implementing a holistic approach for estimating primary energy quality at electricity level 29 , creating a broader cumulative energy demand (CED) database for technologies based on life cycle assessment (LCA) databases 28 , and integrating EROI estimation with energy system model output 27 . Notably, the potential impacts of the electricity generation mix on EROI and significant factors contributing to these impacts are deeply analysed.…”