Liqun Peng

Clean hydrogen has the potential to serve as an energy carrier and feedstock in decarbonizing energy systems, especially in “hard-to-abate” sectors. Although many countries have implemented policies to promote electrolytic hydrogen development, the impact of these measures on costs of production and greenhouse gas emissions remains unclear. Our study conducts an integrated analysis of provincial levelized costs and life cycle greenhouse gas emissions for all hydrogen production types in China. We find that subsidies are critical to accelerate low carbon electrolytic hydrogen development. Subsidies on renewable-based hydrogen provide cost-effective carbon dioxide equivalent (CO2e) emission reductions. However, subsidies on grid-based hydrogen increase CO2e emissions even compared with coal-based hydrogen because grid electricity in China still relies heavily on coal power and likely will beyond 2030. In fact, CO2e emissions from grid-based hydrogen may increase further if China continues to approve new coal power plants. The levelized costs of renewable energy-based electrolytic hydrogen vary among provinces. Transporting renewable-based hydrogen through pipelines from low- to high-cost production regions reduces the national average levelized cost of renewables-based hydrogen but may increase the risk of hydrogen leakage and the resulting indirect warming effects. Our findings emphasize that policy and economic support for nonfossil electrolytic hydrogen is critical to avoid an increase in CO2e emissions as hydrogen use rises during a clean energy transition.

Battery storage is critical for integrating variable renewable generation, yet how the location, scale, and timing of storage deployment affect system costs and carbon dioxide (CO2) emissions is uncertain. We improve a power system model, SWITCH-China, to examine three nationally uniform battery deployment strategies (Renewable-connected, Grid-connected, and Demand-side) and a heterogeneous battery deployment strategy where each province is allowed to utilize any of the three battery strategies. Here, we find that the heterogeneous strategy always provides the lowest system costs among all four strategies, where provinces with abundant renewable resources dominantly adopt Renewable-connected batteries while those with limited renewables dominantly adopt Demand-side batteries. However, which strategy achieves the lowest CO2 emissions depends on carbon prices. The Renewable-connected strategy achieves the lowest CO2 emissions when carbon prices are relatively low, and the heterogeneous strategy results in the lowest CO2 emissions only at extremely high carbon prices.

China is the world’s largest carbon emitter and suffers from severe air pollution, which results in approximately one million premature deaths/year. Alternative energy vehicles (AEVs) (electric, hydrogen fuel cell, and natural gas vehicles) can reduce carbon emissions and improve air quality. However, climate, air quality, and health benefits of AEVs powered with deeply decarbonized power generation are poorly quantified. Here, we quantitatively estimate the air quality, health, carbon emission, and economic benefits of replacing internal combustion engine vehicles with various AEVs. We find co-benefits increase dramatically as the electricity grid decarbonizes and hydrogen is produced from non-fossil fuels. Relative to 2015, a conversion to AEVs using largely non-fossil power can reduce air pollution and associated premature mortalities and years of life lost by ∼329,000 persons/year and ∼1,611,000 life years/year. Thus, maximizing climate, air quality, and health benefits of AEV deployment in China requires rapid decarbonization of the power system.

Solid fuel consumption and associated emissions from residential use are highly uncertain due to a lack of reliable statistics. In this study, we estimate solid fuel consumption and emissions from the rural residential sector in China by using data collected from a new nationwide field survey. We conducted a field survey in 2010 which covered ∼17,000 rural residential households in 183 counties in China, to obtain data for solid fuel consumption and use patterns. We then developed a Generalized Additive Model (GAM) to establish the relationship between solid fuel consumption and heating degree days (HDD), income, coal production, coal price, and vegetation coverage, respectively. The GAM was used to estimate solid fuel consumption in rural households in China at the county level. We estimated that, in 2010, 179.8Tg of coal were consumed in Chinese rural households for heating and cooking, which is 62% higher than that reported in official energy statistics. We found that large quantities of rural residential coal consumption in the North China Plain were underreported in energy statistics. For instance, estimated coal consumption in rural households in Hebei (one of most polluted provinces in China) was 20.8Tg in 2010, which is twice as high as government statistics indicate. In contrast, modeled national total consumption of crop residues (used as fuels) we found to be ∼50% lower than reported data. Combining the underlying data from the survey, the GAM and emission factors from literature, we estimate emissions from China’s rural residential sector in 2010 to be: 3.3Tg PM2.5, 0.6Tg BC, 1.2Tg OC, 2.1Tg VOC, 2.3Tg SO2, 0.4Tg NOx, 43.6Tg CO and 727.2Tg CO2, contributing to 29%, 35%, 38% and 26% of national total PM2.5, BC, OC, and CO emissions respectively. This work reveals that current emission inventories in China likely underestimate emissions from coal combustion in rural residential households due to missing coal consumption in official statistics, especially for the heavily polluted North China Plain (NCP) region. Per capita income appears to be the driving factor that results in the difference between surveyed data and official data. Residents with high income prefer commercial energy and have a higher per capita fuel consumption than lower income residents. Therefore, rural residential coal combustion may contribute even more to regional air pollution than the large contributions previously identified.