Reduction of solar photovoltaic resources due to air pollution in China

Solar photovoltaic (PV) electricity generation is expanding rapidly in China, with total capacity projected to be 400 GW by 2030. However, severe aerosol pollution over China reduces solar radiation reaching the surface. We estimate the aerosol impact on solar PV electricity generation at the provincial and regional grid levels in China. Our approach is to examine the 12-year (2003–2014) average reduction in point-of-array irradiance (POAI) caused by aerosols in the atmosphere. We apply satellite-derived surface irradiance data from the NASA Clouds and the Earth’s Radiant Energy System (CERES) with a PV performance model (PVLIB-Python) to calculate the impact of aerosols and clouds on POAI. Our findings reveal that aerosols over northern and eastern China, the most polluted regions, reduce annual average POAI by up to 1.5 kWh/m2 per day relative to pollution-free conditions, a decrease of up to 35%. Annual average reductions of POAI over both northern and eastern China are about 20–25%. We also evaluate the seasonal variability of the impact and find that aerosols in this region are as important as clouds in winter. Furthermore, we find that aerosols decrease electricity output of tracking PV systems more than those with fixed arrays: over eastern China, POAI is reduced by 21% for fixed systems at optimal angle and 34% for two-axis tracking systems. We conclude that PV system performance in northern and eastern China will benefit from improvements in air quality and will facilitate that improvement by providing emission-free electricity

Climate, air quality and human health benefits of various solar photovoltaic deployment scenarios in China in 2030

Solar photovoltaic (PV) electricity generation can greatly reduce both air pollutant and greenhouse gas emissions compared to fossil fuel electricity generation. The Chinese government plans to greatly scale up solar PV installation between now and 2030. However, different PV development pathways will influence the range of air quality and climate benefits. Benefits depend on how much electricity generated from PV is integrated into power grids and the type of power plant displaced. Using a coal-intensive power sector projection as the base case, we estimate the climate, air quality, and related human health benefits of various 2030 PV deployment scenarios. We use the 2030 government goal of 400 GW installed capacity but vary the location of PV installation and the extent of inter-provincial PV electricity transmission. We find that deploying distributed PV in the east with inter-provincial transmission maximizes potential CO2 reductions and air quality-related health benefits (4.2% and 1.2% decrease in national total CO2 emissions and air pollution-related premature deaths compared to the base case, respectively). Deployment in the east with inter-provincial transmission results in the largest benefits because it maximizes displacement of the dirtiest coal-fired power plants and minimizes PV curtailment, which is more likely to occur without inter-provincial transmission. We further find that the maximum co-benefits achieved with deploying PV in the east and enabling inter-provincial transmission are robust under various maximum PV penetration levels in both provincial and regional grids. We find large potential benefits of policies that encourage distributed PV deployment and facilitate inter-provincial PV electricity transmission in China

Air quality, health, and climate implications of China’s synthetic natural gas development

Facing severe air pollution and growing dependence on natural gas imports, the Chinese government plans to increase coal-based synthetic natural gas (SNG) production. Although displacement of coal with SNG benefits air quality, it increases CO2 emissions. Due to variations in air pollutant and CO2 emission factors and energy efficiencies across sectors, coal replacement with SNG results in varying degrees of air quality benefits and climate penalties. We estimate air quality, human health, and climate impacts of SNG substitution strategies in 2020. Using all production of SNG in the residential sector results in an annual decrease of ∼32,000 (20,000 to 41,000) outdoor-air-pollution-associated premature deaths, with ranges determined by the low and high estimates of the health risks. If changes in indoor/household air pollution were also included, the decrease would be far larger. SNG deployment in the residential sector results in nearly 10 and 60 times greater reduction in premature mortality than if it is deployed in the industrial or power sectors, respectively. Due to inefficiencies in current household coal use, utilization of SNG in the residential sector results in only 20 to 30% of the carbon penalty compared with using it in the industrial or power sectors. Even if carbon capture and storage is used in SNG production with today’s technology, SNG emits 22 to 40% more CO2 than the same amount of conventional gas. Among the SNG deployment strategies we evaluate, allocating currently planned SNG to households provides the largest air quality and health benefits with the smallest carbon penaltie

Air Quality-Carbon-Water Synergies and Trade-offs in China’s Natural Gas Industry

Both energy production and consumption can simultaneously affect regional air quality, local water stress, and the global climate. Identifying the air quality-carbon water interactions due to both energy sources and end-uses is important for capturing potential co-benefits while avoiding unintended consequences when designing sustainable energy transition pathways. Here, we examine the air quality carbon-water interdependencies of China’s six major natural gas sources and three end-use gas-for-coal substitution strategies in 2020. We find that replacing coal with gas sources other than coal-based synthetic natural gas (SNG) generally offer national air quality-carbon-water co-benefits. However, SNG achieves air quality benefits while increasing carbon emissions and water demand, particularly in regions already suffering from high per capita carbon emissions and severe water scarcity. Depending on end-uses, non-SNG gas-for-coal substitution results in enormous variations in air quality, carbon, and water improvements, with notable air quality-carbon synergies but air quality-water trade-offs. This indicates that more attention is needed to determine in which end-uses natural gas should be deployed to achieve desired environmental improvements. Assessing air quality carbon-water impacts across local, regional and global administrative levels is 43 crucial for designing and balancing the co-benefits of sustainable energy 44 development and deployment policies at all scales

Environmental Consequences of Potential Strategies for China to Prepare for Natural Gas Import Disruptions

Worldwide efforts to switch away from coal have increased the reliance on natural gas imports for countries with inadequate domestic production. In preparing for potential gas import disruptions, there have been limited attempts to quantify the environmental and human health impacts of different options and incorporate them into decision-making. Here, we analyze the air pollution, human health, carbon emissions, and water consumption impacts under a set of planning strategies to prepare for potentially fully disrupted natural gas imports in China. We find that, with China’s current natural gas storage capacity, compensating for natural gas import disruptions using domestic fossil fuels (with the current average combustion technology) could lead up to 23,300 (95% CI: 22,100–24,500) excess premature deaths from air pollution, along with increased carbon emissions and aggravated water stress. Improving energy efficiency, more progressive electrification and decarbonization, cleaner fossil combustion, and expanding natural gas storage capacity can significantly reduce the number of excess premature deaths and may offer opportunities to reduce negative carbon and water impacts simultaneously. Our results highlight the importance for China to increase the domestic storage capacity in the short term, and more importantly, to promote a clean energy transition to avoid potentially substantial environmental consequences under intensifying geopolitical uncertainties in China. Therefore, mitigating potential negative environmental impacts related to insecure natural gas supply provides additional incentives for China to facilitate a clean and efficient energy system transition

Guidelines for Modeling and Reporting Health Effects of Climate Change Mitigation Actions

Background: Modeling suggests that climate change mitigation actions can have substantial human health benefits that accrue quickly and locally. Documenting the benefits can help drive more ambitious and health-protective climate change mitigation actions; however, documenting the adverse health effects can help to avoid them. Estimating the health effects of mitigation (HEM) actions can help policy makers prioritize investments based not only on mitigation potential but also on expected health benefits. To date, however, the wide range of incompatible approaches taken to developing and reporting HEM estimates has limited their comparability and usefulness to policymakers. Objective: The objective of this effort was to generate guidance for modeling studies on scoping, estimating, and reporting population health effects from climate change mitigation actions. Methods: An expert panel of HEM researchers was recruited to participate in developing guidance for conducting HEM studies. The primary literature and a synthesis of HEM studies were provided to the panel. Panel members then participated in a modified Delphi exercise to identify areas of consensus regarding HEM estimation. Finally, the panel met to review and discuss consensus findings, resolve remaining differences, and generate guidance regarding conducting HEM studies. Results: The panel generated a checklist of recommendations regarding stakeholder engagement: HEM modeling, including model structure, scope and scale, demographics, time horizons, counterfactuals, health response functions, and metrics; parameterization and reporting; approaches to uncertainty and sensitivity analysis; accounting for policy uptake; and discounting. Discussion: This checklist provides guidance for conducting and reporting HEM estimates to make them more comparable and useful for policymakers. Harmonization of HEM estimates has the potential to lead to advances in and improved synthesis of policy-relevant research that can inform evidence-based decision making and practice

Substantial air quality and climate co-benefits achievable now with sectoral mitigation strategies in China

China is the world's top carbon emitter and suffers from severe air pollution. We examine near-term air quality and CO2 co-benefits of various current sector-based policies in China. Using a 2015 base case, we evaluate the potential benefits of four sectoral mitigation strategies. All scenarios include a 20% increase in conventional air pollution controls as well as the following sector-specific fuel switching or technology upgrade strategies. Power sector (POW): 80% replacement of small coal power plants with larger more efficient ones; Industry sector (IND): 10% improvement in energy efficiency; Transport sector (TRA): replacement of high emitters with average vehicle fleet emissions; and Residential sector (RES): replacement of 20% of coal-based stoves with stoves using liquefied petroleum gas (LPG). Conducting an integrated assessment using the regional air pollution model WRF-Chem, we find that the IND scenario reduces national air-pollution-related deaths the most of the four scenarios examined (27,000, 24,000, 13,000 and 23,000 deaths reduced annually in IND, POW, TRA and RES, respectively). In addition, the IND scenario reduces CO2 emissions more than 8 times as much as any other scenario (440, 53, 0 and 52 Mt CO2 reduced in IND, POW, TRA and RES, respectively). We also examine the benefits of an industrial efficiency improvement of just 5%. We find the resulting air quality and health benefits are still among the largest of the sectoral scenarios, while the carbon mitigation benefits remain more than 3 times larger than any other scenario. Our analysis hence highlights the importance of even modest industrial energy efficiency improvements and air pollution control technology upgrades for air quality, health and climate benefits in China

Global methane emissions from pit latrines

Pit latrines are an important form of decentralized wastewater management, providing hygienic and low-cost sanitation for approximately one-quarter of the global population. Latrines are also major sources of the greenhouse gas methane (CH4) from the anaerobic decomposition of organic matter in pits. In this study, we develop a spatially explicit approach to account for local hydrological control over the anaerobic condition of latrines and use this analysis to derive a set of country-specific emissions factors and to estimate global pit latrine CH4 emissions. Between 2000 and 2015 we project global emissions to fall from 5.2 to 3.8 Tg/y, or from 2% to 1% of global anthropogenic CH4 emissions, due largely to urbanization in China. Two and a half billion people still lack improved sanitation services, however, and progress toward universal access to improved sanitation will likely drive future growth in pit latrine emissions. We discuss modeling results in the context of sustainable water, sanitation, and hygiene development and consider appropriate technologies to ensure hygienic sanitation while limiting CH4 emissions. We show that low-CH4 on-site alternatives like composting toilets may be price competitive with other CH4 mitigation measures in organic waste sectors, with marginal abatement costs ranging from 57 to 944 $/ton carbon dioxide equivalents (CO2e) in Africa and 46 to 97$/ton CO2 in Asia