Energies 2019 , 12 , 247
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was calculated as the sum of annual electricity production from e.g., hydropower, nuclear power and imported electricity, minus exported electricity, and then divided by the net electricity used by all sectors in the country [6]. Calculations for the Swedish example were conducted using the Swedish Energy Agency’s data [49]. PEF results for Sweden are presented in Table 2, and show that the PEF for Sweden was lower than the fixed PEF in Europe (2.5) over the period from 2002 to 2015, i.e., 1.61–1.95 (Table 2).
Table 2. Primary energy factor (PEF) for Sweden over the period from 2002 to 2015.
Years 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 PEF 1.84 1.84 1.95 1.88 1.79 1.79 1.79 1.61 1.65 1.69 1.78 1.80 1.78 1.78
Hence, PEFs also differ among individual countries, e.g., according to Wilby et al. [47], the PEF is 3.4 for France, 1.4 for Norway and 2.9 for Poland. Differences in SEC between countries contribute to further uncertainties in regard to calculating SEC. If the exact assumptions and calculations are not presented when comparing studies from different countries, SECs need to be recalculated uniformly. Even though it is possible that in some cases energy carriers with PEF of 1 can be used, the knowledge of how PEF affects SEC is important when comparing the SEC with that from studies with PEF of energy carriers not equal to 1. For instance, when evaluating changes in SEC over time that includes time with PEF for not all energy carriers being equal to 1. For example, the average PEF for Sweden over the period 2002–2015 is 1.78, which makes the fixed PEF of 2.5 about 1.4 times higher. When the same data is used to calculate SEC for the total energy, the results show that the fixed PEF of 2.5 gives ~11% higher SEC for total energy for pulp mills and ~15% higher SEC for total energy for paper mills (Table 3).
Table3. Specific individual energy carriers’ use and specific total energy use, calculated using PEF 1.78 and 2.5. Specific individual energy carriers’ use has been calculated from Farahani et al. [50].
Variables
PulpMill
PaperMill
Steam use (GWh/kt) Electricity use (GWh/kt)
4.28 0.85 5.80 6.40
2.33 0.76 3.70 4.20
Total energy, when PEF = 1.78 Total energy, when PEF = 2.5
Difference in SEC for total energy (%)
11.00
15.00
In summary, PEF differs, whereby a difference of 1.4 for one non-primary energy carrier can alone lead to ~11–15% difference in SEC. Therefore, it is recommended to describe what PEF have been used and how the PEF were calculated as well as to scrutinize what PEF in other studies were used for assuring the validity of the comparisons among SEC from different studies and for correctly evaluating sources for variation of SEC. 4.3. SEC in International Standards ISO 50001:2011 (standard on energy management systems—requirements with guidance for use [15]) specifies that an organization should identify the relevant energy performance indicators for monitoring and measuring its own energy performance, and that those indicators should be reviewed and compared to the appropriate energy baseline. Organizations shall establish, implement and maintain energy objectives and targets, as well as appropriate timeframes for their achievement, considering all the legal requirements, significant energy uses and opportunities for improving energy performance as identified in the energy review [15]. ISO 50006:2017 [17] provides instructions on how energy performance indicators (EnPIs) and energy baselines (EnBs) are established, used and maintained in the process of measuring energy
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