Energies 2019 , 12 , 247
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• Prior to the use of SECs from other studies, it is recommended that the factors affecting the production of the products, calculations and assumptions on which these calculations were based should be scrutinized critically to ensure the reliability of the comparisons. • SEC is a convenient and easy-to-use energy efficiency indicator with the potential for use in various benchmarking applications, provided that it is calculated with adequate assumptions and calculations to ensure its reliability. • Further quantitative analyses are recommended on SEC from various studies for studying the underlying tendencies and relationships among the factors affecting SEC, e.g., the time trends, extent of studies, levels of benchmarking, etc. • We recommend to be clear about the assumptions and calculations when calculating SEC and applying SEC from other studies for enabling evaluation whether the possible difference in SEC is not just caused by the differences in the underlying assumptions when calculating SEC alone. Specifically, it is recommended to consider: Origin, availability and quality of information and data that was used for calculating SEC. That system boundaries are as precise as possible, e.g., energy used by the main equipment and/or auxiliary equipment used in production and/or parts of it. The conversion of non-primary energy carriers to primary energy carriers, e.g., the PEFused. The calculation of energy use and the number of products for individual products in cases when partitioning of products is present. Whether sold products or produced products used for the calculations. Other factors that may influence SEC such as specifications of equipment, e.g., age of equipment, specifications of production, e.g., production rate, and environmental conditions.
Figure2. Examples of factors affecting the numbers for energy used and products, and therefore SEC.
Author Contributions: All the parts of the manuscript were discussed among all the authors. A.L. was the main author and wrote all the parts except the one about SEC in international energy management systems, which was mainly written by M.A. Funding: This research was funded by the Swedish Energy Agency, research project number 40537-1, the Swedish Environmental Protection Agency, Carbonstruct research project, project number 802-0082-17, and the Division of Energy Systems at the Department of Management and Engineering, Linköping University. Acknowledgments: Authors thank the anonymous reviewers for the comments. Conflicts of Interest: The authors declare no conflict of interest.
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