Wind-solar Energy Coupling For Large-scale Stable Hydrogen Supply To Chemical Process

As the global energy consumption increases and traditional energy supply rates keeps decline,the contradiction between limited fossil resources and unlimited energy demand will intensify.Also,the problem of global warming caused by the using of fossil fuels is becoming more and more serious.To reduce the consumption of fossil fuels and alleviate environmental pressure,one of the effective solutions is focusing on clean,reliable,low-carbon,and renewable energy systems.Wind energy and solar energy are typical clean energy sources.Benefiting from the inherent advantages of geographical location and topography,China has abundant wind and solar energy reserves.In recent years,China’s wind power and solar power industries have developed rapidly.The rapid growth of installed capacity of wind power and photovoltaics has led to a high rate of wind and solar curtailment.The localized use of energy is considered an effective path.However,the randomness and volatility of wind and solar energy hinder their large-scale industrial application.In this dissertation,the basic fluctuation characteristics of wind energy and solar energy are first analyzed.Multi-dimensional wind energy and solar radiation data are obtained through the MERRA-2 database and the NOAA database.Using the method of spectrum analysis,the power data is regarded as a discrete digital signal,and the improved discrete fast Fourier transform model is used to obtain the spectrogram of wind power and solar power.According to the analysis of the spectrogram,it is concluded that solar energy and wind energy have periodic fluctuation characteristics on daily and annual scales.Based on this,the fundamental wave model and core wave model of wind power and solar power periodic fluctuations are established.From the mechanism level,the periodic characteristics of power have been demonstrated,which provides theoretical support for the further analysis and utilization of them.Through the visual processing of wind energy and solar energy reserves,the regional distribution differences and geographic matching of them are analyzed.The four northwestern provinces with abundant wind and solar energy reserves serve as research case sites for wind and solar complementary characteristics.After filtering random fluctuations by establishing a filter model,a phase difference analysis method is proposed to demonstrate the complementary phase difference characteristics of wind energy and solar energy.It is confirmed that the wind and solar energy of four typical energy cities have partial complementary effects,and the regional distribution of the four northwestern provinces of wind and solar complements are further analyzed.Finally,through spectrum analysis and volatility analysis,the effect of wind-solar energy coupling complementation on the improvement of power supply stability is demonstrated,and the scientific nature of the phase difference analysis method is verified.Through the comprehensive analysis of wind and solar energy complementary,it provides theoretical support for the establishment of a large-scale stable hydrogen production system.On the basis of theoretical analysis,a wind-solar coupled power for electrolytic hydrogen production system（WPCt H）is proposed.Each unit model is established,and the suppression characteristics of energy storage equipment to fluctuations are analyzed.To improve the economic performance of hydrogen production,this article further explored the addition of stable and low-cost coal power to eliminate the power intermittent,and established a reasonable allocation model of system capacity.The system selects 9%as a reasonable coal-to-electricity ratio,which reduces the required battery investment while considering the environmental performance of the system.The annual hydrogen production scale of the integrated system can reach 10,000 tons,and the fluctuation rate of the hydrogen supply flow rate is less than 10%.By establishing the technical-economy and life cycle assessment model of the hydrogen production system,the economic performance and environmental performance of the hydrogen production system in four case cities are evaluated.The results show that the CO₂ emission intensity of WPCt H is 1.4～1.7 kg CO₂e/kg H₂,which is much lower than the 20.9～27.5kg CO₂e/kg H₂ of coal-based path.The cost of hydrogen production is 19.76～21.32 CNY/kg H₂,which is slightly higher than the cost of hydrogen production from coal to hydrogen with carbon capture.This paper further proposes a coal-to-ethylene glycol process（WPCt EG）integrated with the WPCt H system.WPCt H is used to provide high-purity hydrogen for the DMO hydrogenation section of the coal-to-ethylene glycol（Ct EG）process.Through process analysis and integration,a framework for system integration and reasonable capacity allocation is established,key units in the system are simulated,and a data interaction module is established to realize the interaction of hydrogen production and coal-to-glycol process data.The key parameters of WPCt EG system are determined by simulation:the reasonable H₂/CO ratio range of EG synthesis process is 1.95～2.05,and the best hydrogen-to-coal mass ratio is 0.069.The system can provide 68.68 t/h of EG product.Under the same coal feed rate,the output of EG in the WPCt EG system is 34.70 t/h higher than that of the Ct EG process.Based on the analysis of carbon element flow in the whole process,the carbon utilization rate of WPCt EG process is42.7%,which is much higher than 21.5%of Ct EG,and the carbon emission intensity is 0.93t CO₂e/t-EG,which is much lower than Ct EG’s 2.58 t CO₂e/t-EG.The efficiency has increased by 7.6%.Based on the carbon element flow analysis of the whole process,the carbon element utilization rate of the WPCt EG process is 20.9%higher than that of Ct EG,and the carbon emission intensity of 0.93 t CO₂e/t-EG is much lower than Ct EG,and the exergy efficiency is increased by 7.6%.Compared with the coal-based process,the total production cost of the new system is reduced from 4750 CNY/t-EG to 4589 CNY/t-EG,and the internal rate of return is15.36%,which is higher than the 13.05%of the Ct EG process.The new process greatly improves the utilization of carbon elements,reduces greenhouse gas emissions,and improves the economic performance of the system.