查看更多>>摘要：Water use efficiency(WUE)is a critical evaluation indicator of ecosystem responses to climate change and its extremes.However,the influence of the timing of extreme drought on the variation of ecosystem WUE under severe water stress has not been studied extensively.In particular,the modulation of drought impacts on WUE under regional hydro-climatic conditions and biome types is poorly understood.Considering observation-based ecosystem flux and drought index datasets,this study examined the impact of extreme seasonal drought on WUE in China and attempted to reveal the underlying drivers of seasonal variations in drought impacts.Results showed that the direction and magnitude of drought impacts on WUE depend on the occurrence time of extreme drought and the seasonal dynamics of regional ecological and climatic conditions.Across the vegetated regions in China,the most widespread reduction in WUE under extreme drought conditions was observed in summer,whereas approximately 60％of the study area showed positive changes in WUE under extreme drought conditions in spring.Furthermore,the co-regulation of drought characteristics and background environmental conditions in determining the impacts of extreme seasonal drought on ecosystem WUE is highlighted.Classification and regression tree analysis results illustrate that leaf area index(LAI)and drought timing dominated ecosystem WUE variation in response to extreme drought in China.Regions with lower LAI experienced more serious reductions in WUE under extreme drought.These findings indicate the importance of accounting for the interaction between drought seasonality and biome features in assessing drought impacts,thus contributing to improving the modelling of terrestrial ecosystem responses to climate extremes under global warming.
查看更多>>摘要：The role of hydrogen in the transition to carbon-neutral energy systems will be influenced by key factors such as carbon neutrality pathways,hydrogen production technology costs,and hydrogen transportation costs.Existing studies have not comprehensively analyzed and compared the impact of these key factors on the development of hydrogen supply and demand under China's carbon neutrality pathways.This study uses the Global Change Assessment Model(GCAM)with an upgraded hydrogen module to evaluate the development potential of China's hydrogen industry,considering various carbon neutrality pathways as well as hydrogen production and transportation costs.The findings indicate that,by 2050,hydrogen could account for 8％-14％of final energy,averting 1.0-1.7 Bt of carbon emissions annually at an average mitigation cost of 85-183 USD t-1CO2.The total hydrogen production is projected to reach 75-135 Mt,with 34％-56％from renewable energy electrolysis and about 15％-29％from fossil fuel-based CCS.On a sectoral level,by 2050,the hydrogen demand in the industrial and transportation sectors is expected to reach 37-63 Mt and 30-42 Mt,with a potential reduction of about 0.6-0.9 BtCO2 and 0.5-0.6 BtCO2.The share of hydrogen in the final energy of the steel and chemical sectors is estimated to be 9％-19％and 17％-25％,collectively accounting for 36％-42％of total hydrogen demand and 46％-50％of total emission reduction potential.Realizing hydrogen's emission reduction potential relies on the rapid development of hydrogen production,transportation,and utilization technologies.Firstly,the development of on-site electrolysis for hydrogen production and early deployment of industrial hydrogen applications should be prioritized to stimulate overall growth of hydrogen industry and cost reduction.Secondly,vigorous development of renewable energy electrolysis and hydrogen end-use technologies like fuel cells should be pursued,along with the demonstration and promotion of hydrogen transportation technologies.Lastly,further advancement of carbon market mechanisms is essential to support the widespread adoption of hydrogen technologies.
查看更多>>摘要：Hydrogen and electricity are crucial and interdependent energy carriers in China's pursuit of carbon neutrality,suggesting the necessity of utilizing cost-effective low-carbon technologies that facilitate their integrated development.The cost-optimal,provincial level,deployment of low-carbon technologies under this long-term goal remains to be determined.This study employs the REPO model to identify the cost-optimal,low-carbon hydrogen production mixes and the evolution of the integrated power system of China from 2020 to 2050.The integrated planning and operation of hydrogen supply and power systems are explored at the provincial level.The role of high-temperature gas-cooled reactors in this integrated energy system is also analyzed.The results reveal that electrolytic hydrogen would dominate China's hydrogen supply after 2040,with alkaline,proton exchange membrane,and solid oxide electrolyzers produce over 1 Mt of hydrogen in the short term,by 2035,and in 2050.Leveraging the low-carbon heat production of high-temperature gas-cooled reactors in addition to its electricity generation to meet the thermal requirements of solid oxide electrolyzers could boost the output to 4.2 Mt in 2050 and reducing the total system CO2 emissions and costs by 2.28％and 0.05％,respectively.By 2050,the integration of hydrogen supply and power systems also generates up to 2194 TW h of flexible electricity demand by electrolyzers,which raised the renewable energy penetration by 4 percentage points while decreasing the need of flexible natural gas power generations and energy storages.This study is valuable for proposing the analytical framework and performing the provincial-level study of decarbonization of China's integrated hydrogen supply and power system.
查看更多>>摘要：Previous studies of water use for coal-fired power generation may have overlooked inter-sectoral impacts in the supply chain.Indeed,to devise effective water conservation strategies during the ongoing energy transition,it is of utmost importance to analyze the sectoral water use structures and flows in the supply chain and identify the sources of water scarcity.Therefore,based on the power sector-split environmentally extended input-output(EEIO)model and the life cycle assessment(LCA)idea,we comprehensively analyze the nexus between coal-fired power generation and water use from a sectoral perspective.Our findings reveal a complex and diverse water use structure in coal-fired power generation.The technology of production inherently determines the high intensity of water withdrawal,and the close intersectoral linkages,particularly with agriculture,construction,and some industrial sectors,in the production process result in an intricate web of indirect water withdrawal and blue water footprint(WF).Moreover,the grey WF,primarily sourced from coal mining and indirectly tied to tertiary industries,underscores critical areas for attention in water pollution management.Finally,water use in the coal-fired power sector is projected to remain at elevated levels in the short to medium term under various transition strategies.Following an in-depth exploration of the coal-fired power-water use nexus,the findings can offer new perspectives and specific entry points for sustainable energy development and water resource management.
查看更多>>摘要：The long-term stability of the cast-in-place footings in permafrost regions has received much attention due to its climate sensitivity.The current research lacks long-term data validation,especially in the context of climate change.Based on the 13-year(2011-2023)temperature and deformation monitoring data from the Qinghai-Tibet Power Transmission Line,this study investigates the characteristics of permafrost variation and its impact on the stability of tower footings under the cooling effect from thermosyphons.The results reveal that the thermosyphons effectively reduce the ground temperature around the footings.After the first freeze-thaw cycle,the soil around the tower footings completed refreezing and maintained a frozen state.In the following 13 years,the ground temperature continued to decrease due to the cooling effect of thermosyphons.The duration notably exceeded the previously predicted 5 years.The temperature reduction at the base of the footings cor-responded well with the frost jacking of the tower footings and could be divided into three distinct phases.In phase 1,the ground temperature around the footings rapidly reduced,approaching that of the natural field,while the footings experienced pronounced deformation.In phase 2,the ground temperature decreased at a faster rate,and the deformation rate of the footings slowed down.In phase 3,the frost jacking of the footings gradually retarded with the decrease in base temperature.Additionally,the ground temperature differences of over 1℃ were observed among different tower footings,which may lead to the differential deformation among the tower footings.The ground temperature differen-tiation is attributed to the difference in solar radiation intensity,which is shaded by the tower structure from different directions.This study provides theoretical support and empirical accumulation for the construction and maintenance of tower footings in permafrost regions.
Ling-Yu MENGZhan TIANDong-Li FANFrans H.M.VAN DE VEN...
976-987页
查看更多>>摘要：As the world grapples with the profound impacts of climate change,water scarcity has become a pressing issue.However,there is a shortage of in-depth research on the trade-offs between water resource dependence and the economic,ecological,and social needs of arid and semi-arid regions like Lanzhou,China.Flower cultivation in Lanzhou relies heavily on the Yellow River,often overlooking the potential of natural rainfall.Here we first calibrated a water balance model through artificial precipitation experiments in a Soil and Water Conservation Demonstration Park in Lanzhou.We then developed a multi-objective optimization model to balance the cost-benefit considerations of various plausible measures across economic,ecological,and social dimensions in the searching for solutions that are more adaptable to climate change and local devel-opment needs.Model simulations show that the solutions we designed can effectively manage water-shortage days,significantly reduce Yellow River water extraction,and improve cost-effectiveness,meeting 66％-80％of water needs for flower cultivation in the studied park.The findings highlight the potential of rainwater collection and utilization solutions to mitigate water scarcity in arid and semi-arid cities,thereby enriching water resource management.
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