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where the biomass is used by a combined heat and power generating station, $\genfrac{}{}{0.1ex}{}{E}{{\eta }_{el}}\left(\genfrac{}{}{0.1ex}{}{{\eta }_{el}}{{\eta }_{el}+C_h\times {\eta }_h}\right)$;

in any other case, $\genfrac{}{}{0.1ex}{}{E}{{\eta }_{el}}$.