Theoretical And Experimental Investigation On Thermochemical Hybrid Utilization Of Solar Energy And Clean Fuel

Solar energy,as one kind of promising renewable energy,is available worldwide and environmental friendly.The utilization of solar energy is of great significance for energy conservation and emission reduction,as one of efficient approach to solve the fossil fuel shortage and reduce CO2 and pollutant emission.However,due to the low density,intermittent and unstable of solar energy,solar energy utilization is facing the challenge of low electrical efficiency,instability and high energy storage cost,which restricts the development of solar energy utilization.Supported by the National Natural Science Foundation of China and the National Key R&D Program of China,this paper investigates solar-fuel hybrid utilization,aiming to improve the utilization efficiency and reliability of solar energy.In this work,the hybridation mechanism of solar energy and fuel,multiphysics coupling modelling of solar thermochemical process,system integration and optimization,and experimental integration are investigated.Based on the thermodynamics and thermochemical reaction kinetics,the energy-level coupling mechanism of solar energy and fuel through solar thermochemical conversion is studied.The irreversible loss and exergy enhancement potential of solar thermochemistry process are illustrated under varying solar irradiations,methanol space velocities and concentration ratios to clarify the energy-level enhancements and synergistic mechanism,and the theoretical net solar-to-electric efficiency of solar solar-fuel hybrid thermochemistry system is obtained.For the mid-and-low temperature solar thermochemistry process,the multi-field model coupling sunlight concentrating,heat and mass transfer and thermochemical reaction is investigated,to illustrate the performance of the solar thermochemistry process.With the built model,temperature and reaction distributions of the catalyst bed are illustrated,and performances of the solar thermochemical reaction are investigated under various solar irradiations,methanol space speeds,structure parameters and tracking errors of the concentrator.The structure and operation optimizations of solar thermochemical receivers/reactors are investigated.With the foundation of solar-fuel hybrid mechanisms and multiphysics coupling model,a novel solar-fuel hybrid distributed energy system integrating solar thermochemistry and chemical recuperation processes are investigated.In the proposed system,solar energy and exhaust heat are upgraded into high quality chemical energy via thermochemical conversion,achieving the efficient utilization of solar energy and exhaust heat.The operation strategy of the system under varying user's load demands and solar irradiations are investigated,as well as the operation performances under off-design conditions.With system energy ratio,CO2 emission and economic performances as the optimization obj ects,the multi-objective optimization of system power capacity,solar energy share and storage capacity are employed.Under the system optimal configuration,the annual energy ratio and solar energy share reach 70.22%and 10.39%,respectively.The proposed system shows obvious energy saving,emission reduction and economic advantages,has fuel saving,CO2 emission and cost saving rate of 3 1.49%,39.1 8%and 6.09%,respectively,compared with the separated energy systems.For the solar-fuel thermochemical hybrid utilization,the first 100 kW solar-fuel hybrid power generation pilot plant is designed,constructed and tested.The solar thermochemical process,power generation and system off-design operation are experimentally investigated via the developed experimental system.The performances of solar thermochemical process are experimentally tested with varying solar irradiations and input methanol mass rate,and an Lambert target energy density measured equipment is designed to measure the heat flux distribution of the solar receivers.On a typical operation condition,the average methanol decomposition rate reaches 82.72%,and the solar-to-chemical energy efficiency reaches 40%.The solar-fuel hybrid power generation system with mid-and-low temperature solar thermochemistry and power generation runs successfully for the first time,and the off-design performances of the internal combustion engine and hybrid system are tested.