Characterizing of water-energy-emission nexus of coal-fired power industry using entropy weighting method
The coupled relationships among water, energy, and emission, i.e., water-energy-emission nexus (WEEN), are found to be spatial-temporally characterized. This research is aimed at evaluating the spatial-temporal characteristics of the WEEN of the selected 227 coal-fired power plants in China from 2012 to 2014 by employing the entropy weighting method. Firstly, the WEEN performances (the sub-indicators, i.e., the emissions, water for cooling, water for pollutant removal, energy for electricity generation, and energy for pollutant removal) of the plants are computed. Then, each sub-indicator of the WEEN performances is compared at plant level. Finally, the entropy weighting factor is introduced to evaluate the overall performances of WEEN (defined as the WEEN indicator). The results show that NOx and SO2 removal sub-indicators were with the highest entropy weights. Overall, the WEEN indicator improves significantly from 0.21 (2012) to 0.37 (2014), which means the increases of pollutant removal were more significant than the changes in water and energy inputs. The power plants located in Northern China and Central China grids show more significant improvement. This is mainly contributed by the improvement of the three emission sub-indicators and the larger amount of removed pollutants. By evaluating the improvement of WEEN indicators, the overall performances of WEEN with the simultaneous consideration of water, energy and emission are quantitatively addressed, which reflect the technology improvement and the strict policies and regulations behind it. This research provides a quantifiable and integrated way to evaluate and compare the various aspects of WEEN at the plant level.