Energies 2019 , 12 , 247
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by Kramer et al. [56]. However, in some references “pulping” is more likely to be used to describe pulp making including all processes that were used to produce pulp, judging by the SEC values. Namely, the SECs for BAT for “chemical pulping” amount to 4.85 GWh/kt and 4.84 GWh/kt in [57], and are in line with SEC values for “chemical pulp total”, 4.47–5.10 GWh/kt, in [7] and “chemical wood pulp”, 4.53 GWh/kt, in [8] (Tables A1 and A2 in Appendix A). Examples of SEC for various paper grades are presented in Table A3 in Appendix A, and SEC for various processes during paper production is presented in Table A4 in Appendix A. SEC for paper grades under the same or similar names, e.g., newsprint, seems to vary more than could be accounted for by using different PEFs. For example, SEC for newsprint varies from 1.44 to 2.55 GWh/kt, making the comparison between SEC from different studies challenging. 5. Analysis and Proposed Improvements When Using SEC Despite the frequent use of SEC when benchmarking and working towards improving energy efficiency, clear and detailed descriptions of the assumptions that the SEC calculations are based on seem to be lacking in both scientific literature and international standards. Therefore, based on the review of scientific publications and standards addressing and using SEC, the following important improvements are proposed to improve the reliability and comparability of SEC: • Define system boundaries. For example, describe whether energy use by auxiliary systems, wastewater treatment facilities, support systems, in situ transport, etc. were included. • Describe all the assumptions and calculations for calculating the amount of energy used. For example, how the PEFs were calculated and what data was used. • Define the products and assumptions for calculating the amounts of products. For example, are the products everything that was produced or only the products that were sold? Present assumptions and calculations for calculating amounts of products when partitioning of products was present. • When comparing with SECs from other studies, beware of the possible effects due to the differences in assumptions, calculations and other relevant issues, e.g., environmental effects. 6. Conclusions The importance of being able to monitor the progress of industrial energy efficiency cannot be understated. With the aim of critically analysing SEC in relation to industrial energy efficiency, some conclusions could be drawn from this study: • SEC is affected by several factors (Figure 2). • SEC is of greater use if longitudinal benchmarking, i.e., the same company, sector or country, over time, is undertaken. • If using SEC for benchmarking between companies, sectors, or countries, extreme caution is required in order to benchmark correctly. • The reviewed standards in this paper provide useful general guidance on the use of SEC as an indicator for energy efficiency, but do not provide a reader with sufficient details of the full range of challenges when using SEC. Hence, more support is needed in this respect, to support both researchers and industry practitioners. Since there is a gap in both research and international standards in the usage and challenges of SEC, a plan for further use of SEC together with monitoring activities is needed. • The difference in the primary energy factor (PEF) can influence SEC calculations significantly. • SEC is a more optimal e-KPI within the same study, when all deployed SECs are calculated in the same way, and with the same underlying assumptions. • We suggest that specific exergy consumption with the abbreviation SEC would be a more correct term than specific energy consumption. Alternatively, specific energy use could be used.
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