Abstract
In China, the electricity load is concentrated in the east, but low-rank coal resources are concentrated in the west. To solve this contradiction, in this study, three cases for energy transmission about power system with and without solar energy were studied by life cycle assessment (LCA). Case 1 directly combusts low-rank coal to generate electricity in western China and transmits it to eastern China by grid. Cases 2 and 3 upgrade low-rank coal and transport it to eastern China for power generation. With the evaluating indicators and various stages of LCA, the impact of each case on the environment was compared clearly. The results show that over 90% of the pollutant emission comes from coal combustion throughout the life cycle. The pollutant emission of upgraded coal transportation is less than 5%. With low-rank coal upgrading then combusting, the total emission is less than that of direct combustion. In particular, with solar energy added, the emission of combustion can be further reduced. On the bases of LCA, analytic hierarchy process (AHP) was used to establish the connection of these four evaluation indicators to comprehensively evaluate the performance of the three cases through the objective function of AHP, which provided guidance for the energy transmission and utilization in the eastern and western China. Finally, sensitive analysis shows the main major factors affecting system performance on the system. The results show that the Case 3, which integrates with solar energy, performs best in the whole life scale.
Highlights
In China, western regions have abundant coal resources, while eastern demand for electricity is great, which creates an imbalance in energy supply and demand
The goal and scope of the life cycle assessment (LCA) analysis is shown in Figure 5 with the aim of calculating the primary energy consumption and the emissions of greenhouse gases such as CO2, CO, and CH4 ; acid gases such as SO2 and NOx ; and particulate matter (PM) 2.5 of Cases 1–3
For solar energy generation processes, traditional analytical methods usually only calculate the energy conversion rate without considering the pollution emissions and primary energy consumption (PEC) in the preparation process to use the energy [29], but the results of LCA indicates that the process of creating conditions for utilizing solar energy has emissions and PEC
Summary
In China, western regions have abundant coal resources, while eastern demand for electricity is great, which creates an imbalance in energy supply and demand. If the electric power generated in the west China can be transferred to the eastern via the electric gird, the problem of imbalance between energy supply and demand can be partly solved. More than half of the coal reserves in the western China are low-rank coals [1], suffering from high moisture content and relative low power generation efficiency, leading to a uneconomic pattern to directly transferring electric power from the west China to the east China [2]. In addition to electric power transmission, directly transportation of coal from the western China to the east where it is demand is a pattern for energy transfer. It is significant to pay attention to the improvement of local power generation efficiency in Xinjiang while ensuring efficient power transmission
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