| China’s inherent resource endowment of coal-rich,oil-poor and gas-poor has led to a long-term coal-based energy consumption trend.However,the environmental concerns originating from the large-scale mining and power generation of coal,as a high-carbon energy source,are increasingly spotlighting,such as climate warming and environmental damage.In order to ensure energy security and cope with climate change,it is necessary to make more efforts to promote energy saving and emission reduction of coal-fired power generation.Clean coal power generation technology is a realistic choice to ensure the security of energy supply,and plays an important supporting role in building a clean,low-carbon,safe and efficient modern energy system.Underground gasification combined cycle(UGCC)is a process in which the coal is in situ burnt controlly to produce combustible gas through a series of physical and chemical effects,and the produced gas is used for power generation.It is a new type of coal clean power generation technology that integrates coal underground gasification and combined cycle power generation technology,which can make full use of difficult or uneconomic coal seam resources and reduce the environmental pollution in the traditional coal mining.In addition,as an important technology component to achieve China’s carbon neutral target,carbon capture and storage(CCS)technology separates carbon dioxide from carbon emission sources and transports it to specific locations for storage,which can effectively reduce carbon emissions from coal-fired plants.Therefore,the integration of UGCC and CCS technologies is of strategic importance to ensure national energy security,mitigate climate change and reduce environmental pollution.Although UGCC-CCS has been proven to be technically feasible,it has not yet been applied for a large scale.Due to various factors such as energy efficiency,environment,economy and investment feasibility,there are still many uncertainties in the commercialization and application of this combined technology.To solve a series of problems facing the large-scale commercial deployment of UGCC-CCS projects,this thesis is oriented to the major strategic needs of the country to cope with the energy crisis and climate change,and integrates scientific methods such as bibliometrics,life cycle assessment,comparative case analysis,scenario analysis,and a combination of qualitative and quantitative methods to conduct a comprehensive evaluation of UGCCCCS projects in energy,environment and economy from a life cycle perspective,and compares the results with those of IGCC power plants to identify the main influencing factors and make suggestions for improvement.Meanwhile,based on real options theory,the investment decision model under the influence of uncertainties was established to provide a scientific reference basis for future investment in commercial application of the project.The main innovative work is summarized as follows:(1)Based on the extended framework of exergy analysis,the exergetic life cycle assessment models for UGCC power plants were established to comprehensively evaluate the indicators affecting the sustainability and thermodynamic performance of UGCC power plants.The results showed that the resource utilization efficiency and environmental sustainability index of UGCC power plants are 19.39% and 18.29%,respectively,and the comprehensive sustainability of the plant is improved after the addition of CCS.Compared with IGCC power plants,UGCC power plants are more advantageous in terms of resource utilization efficiency,but relatively weaker for environmental sustainability.In-depth analysis reveals that the unit of underground coal gasification is the main unit that affects the exergy efficiency of the plant.When the oxygen-coal ratio is 0.6 and the water-coal ratio is 0.1,the exergy efficiency of UGCCCCS plant can increase from 34.27% to 37.56%,which can effectively improve the overall sustainability.(2)Based on the input-output inventory of the whole process of the power plants,the life cycle environmental impact assessment models of the UGCC plant were developed,and the mid-point and end-point environmental impacts were evaluated in detail.The global warming potential and ozone layer depletion potential of UGCC power plants were 16.9% and 74% higher than those of IGCC power plants,while the remaining impacts were lower than those of IGCC power plants.The application of CCS reduced the impact of global warming potential and human health at UGCC power plants by 71% and 46%,respectively,but exacerbated the deterioration of other environmental problems.(3)The life cycle cost models were constructed,which not only included the fuel cost of the plants as well as the internal cost,but also considered the external cost that might be caused by the environmental problems from the perspective of the government and society,and the sensitivity analysis was conducted on the main factors affecting the costs.The results showed that the life cycle costs of UGCC plants were 48.91$/MWh and 61.80$/MWh under two cases of near and long-distance transportation of syngas,respectively,and the external costs accounted for 16.35% and 13.90%,respectively,and the addition of CCS increases the life cycle costs of UGCC plants by 23.78% and18.96%,respectively.Compared with IGCC plants,the total life cycle cost is still competitive,despite slightly higher external cost.(4)A trinomial tree real option model was adopted,and the investment returns of UGCC-CCS projects were evaluated by integrating various uncertainties such as carbon price,technological progress and policy incentives,specifying the critical conditions and the best time for investment,and making constructive suggestions for the selection of the operation mode and the location of UGCC-CCS plants.The results showed that there was no investment possibility for UGCC-CCS plants if the carbon market is not considered.By considering the carbon trading,the critical carbon prices for UGCCCCS plants investment were 518.49RMB/t and 527.93RMB/t under the two operation modes responsible for carbon capture and full processes,respectively,and the best time to invest were 2032 for both.It is necessary to promote early investment in plants by means of government subsidies.When the feed-in tariff subsidy is 0.5RMB/k Wh or the R&D subsidy is 3 billion RMB,the best time to invest in plants can be advanced to2027 and 2028,respectively. |
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