Attention has been paid to the air quality and climate benefit strategy of China's "power transmission from west to east" strategy.

In response to China's strategy of "power transmission from west to east", Environmental Research KuaiBao (Environmental Research Letters) published an article entitled "Air quality and Climate benefits of long-distance Transmission in China" (Air Quality and Climate Benefits of Long-Distance Electricity Transmission in China) on June 13, 2017, studying the deployment strategies to solve the two major problems of air pollution and carbon emissions. It is proposed that long-distance transmission planning with the introduction of renewable energy is very important to maximize air quality and global climate benefits. This paper collates the core viewpoints of this study for reference.

one

Research scheme

Of the current 12 channel construction plans in China, nine will only carry electricity generated by coal, and two will carry hybrid power from wind power and coal power, while one third of the electricity transmitted in South China will come entirely from hydropower. According to the realistic choice of decision makers, researchers from Princeton University, Harvard University, North China Electric Power University of China and Nanjing University designed a basic scenario (BASE) and three hypothetical scenarios. Based on regional atmospheric chemical models and epidemiological data, the potential effects of long-distance power transmission on air quality, health and climate in China were quantitatively evaluated.

The basic scenario uses actual power generation and emission data from 2010. The three hypothetical scenarios are: 1 "CbR" scenario, which refers to using larger and more efficient coal-fired power plants to replace smaller and inefficient coal-fired power plants in the eastern provinces (that is, transporting rich coal from the west as the main fuel to the rich and populous east, and then burning to generate electricity) 2 "CbW" scenario means that 12 channels fully transmit electricity generated by coal-fired power generation; 3 "Hybrid" scenario means that 60% of the electricity transmitted by long-distance transmission lines comes from renewable energy (wind and hydropower) and 40% from coal-fired power generation.

two

Main conclusion

Through a comprehensive assessment, it is found that the CbW scenario is more effective in reducing the impact of air pollution than the CbR scenario, and the two scenarios are roughly the same in reducing carbon emissions, while the Hybrid scenario can minimize the impact of air pollution and carbon emissions. Compared with the CbW scenario, the number of air pollution-related deaths is reduced by 16%, and carbon emissions are reduced by three times.

(1) emissions of air pollutants. In the CbR scenario, sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions from coal-importing provinces in the east fell by only 6 per cent and 11 per cent, respectively. In the power transmission of energy generation (that is, the CbW and Hybrid scenarios), SO2 and NOx emissions in the eastern region decreased by 15 per cent and 16 per cent, respectively, but increased due to the increase in coal power generation in power export areas. Since renewable energy generation does not generate emissions, the increase in SO2 and NOx emissions in power export areas under the Hybrid scenario (4 per cent and 3 per cent, respectively) is smaller than that in the CbW scenario (10 per cent and 8 per cent, respectively). Overall, in the Hybrid scenario, total SO2 and NOx emissions fell by 6 per cent and 9 per cent in all regions importing and exporting electricity, respectively; in the CbW scenario, total SO2 and NOx emissions decreased by 3 per cent and 7 per cent in all regions importing and exporting electricity, respectively.

(2) PM2.5 concentration level. In the basic scenario, the PM2.5 concentration is higher in eastern and southern China, as well as in autumn and winter, which is largely affected by seasonal meteorological conditions. Power transmission through energy generation reduces the average annual PM2.5 concentration in the eastern provinces by 23.3 μ g/m3 (or 2% 7%), which is greater than the reduction in the CbR scenario. Compared with the CbW scenario, although the Hybrid scenario can not further improve the air quality in the east, zero-emission renewable energy generation can avoid the increase of PM2.5 concentration in some power export areas in the north. The downwind areas of the eastern power import provinces can also benefit from the improvement in air quality, and even in the CbW scenario, the PM2.5 concentration in the northeast exit region is slightly lower than in the base scenario. Because the southern and central regions of China are mostly in the downwind of the eastern provinces, the PM2.5 concentration decreases in all three scenarios.

(3) the number of air pollution related deaths. The study estimates that in the base scenario, the annual death toll associated with outdoor PM2.5 exposure in China is 850000 (similar to the 860000 in the global burden of disease study). Compared with the basic scenario, all three scenarios could reduce the number of premature deaths related to air pollution, and the number of premature deaths avoided by the Hybrid scenario was 16% more than that of the CbW scenario. Most of the extra deaths avoided occur in export areas because PM2.5 concentrations drop slightly as more electricity generated by renewable energy is used for transmission. The scale of avoiding deaths in CbW and CbR scenarios is similar (CbW scenarios are slightly higher than 6%). Therefore, at the national level, CbW scenarios have greater health-related air quality benefits than CbR scenarios.

(4) carbon emissions. Under the Hybrid scenario, national carbon dioxide emissions could be reduced by 340 million tons a year, equivalent to a 4 per cent reduction in total carbon emissions. In contrast, CbW and CbR scenarios have little impact on carbon emissions, and their emission reductions are very small (the emission reductions of the two scenarios are basically the same), mainly due to the emission reduction brought about by the efficiency improvement of new coal-fired power plants. The emission reduction of the Hybrid scenario is more than 3 times that of the CbW scenario, indicating that the hybrid power transmission using renewable energy and coal power generation has greater global climate benefits.

three

Policy revelation

The research shows that in China's strategy of "power transmission from west to east", the transmission planning through the deployment of renewable energy has the greatest synergistic benefit of air quality and climate change. The northern and western regions of China are rich in wind and solar energy resources, and the population centers in the east are seriously polluted. The use of power transmission to connect renewable energy production areas with densely populated and polluted areas can make better use of renewable energy in remote areas and reduce carbon emissions while maximizing air quality and health benefits. Therefore, power grid planners should strengthen the deployment of renewable energy in long-distance transmission in order to minimize air pollution and carbon emissions.

The study focuses on the air quality and climate impact of "power transmission from west to east", but long-distance transmission may have other environmental impacts on power export areas. For example, the transfer of coal power to the arid western region could exacerbate water shortages, and the widespread deployment of hydroelectric power could have a significant impact on local ecosystems. Therefore, power grid planners need to comprehensively consider the environmental impact of long-distance transmission on regional, national and even global scales.

Source: "Climate change Science dynamic Monitoring KuaiBao", No. 13, 2017, Lanzhou Literature and Information Center, Chinese Academy of Sciences. Please indicate the source.