| It is urgent to reform the world energy structure for mitigating the serious energy and environmental problems.The energy production and consumption according to local conditions,vigorous development and efficient utilization of renewable energies,and the optimization and upgrading of multi-energy complementary technologies and distributed energy systems are the key directions.There are rich biomass and solar energy resources in china because of flourishing agriculture,which have great utilization potential.Based on the energy properties of solar energy and biomass,the solar thermochemical is deeded as an efficient method for improving the utilization efficiency of solar energy and biomass.It is means that concentrating solar energy is used to provide the heat in biomass gasification for rich-hydrogen fuel production.This method leads to the boost in level of solar energy,realizing the indirect cascade release of biomass chemical energy.Therefore,studies on the thermochemistry complementary utilization of solar energy and biomass were conducted in the work,which achieves the financial support provided by the National Natural Science Foundation of China.The research contents contain the mechanism,calculation method and system integration.The main contents and results of the paper are summarized as follows:(1)Based on the energy attributes of solar energy and biomass,the energy conversion mechanism for the complementary use of concentrated solar energy and biomass fuel was explored,and the mathematical models were established and experimentally verified.First,the energy grade equations were established using the first law and the second law of thermodynamics,and the energy conversion and release rules were studied.It shows that the thermochemical complementary method increases solar energy level and realizes the cascade of fuel chemical energy.The irreversible loss mechanism in the energy conversion process was revealed by an Energy-utilization diagram(EUD).Secondly,two mathematical models of the complementary method were established according to thermodynamic equilibrium and reaction kinetics,and the comparative analysis between them was conducted.Finally,a high-temperature biomass gasification experimental rig was developed to verify the energy conversion mechanism and calculation models.(2)A small-scale thermochemical reactor driven by solar energy and biomass was designed based on the complementary utilization mechanism and calculation method,and the multiphysics simulation was carried out to study the distribution of speed,temperature and substance concentration in the reactor.The dish-concentrating solar energy was used to drive biomass gasification,which realizes the conversion from solar energy to chemical energy.The multiphysics model fully considered the energy transfer equations of geometric optics,heat transfer,CFD,material diffusion,and chemical reactions.The results show that the conversion rate of biomass is 98.45%,the share of CO and H2 in products is 27.45%and 51.34%,respectively,and the conversion efficiency from solar energy to chemical energy is 21.57%.The effects of solar radiation intensity and the ratio of water vapor to biomass components on the reactor performance were also studied.(3)A multi-generation system driven by solar energy and biomass for synthetic natural gas(SNG)and power was proposed based on the principle of stage conversion and cascade utilization of energy,and the thermodynamic performances and the impacts of key parameters(gasification temperature and converted synthetic gas share)on system performance were studied.In the system the unreacted syngas is directly burned in the combined cycle for power production,which reduces the irreversible loss of the synthesis reaction and promotes the improvement of the system performance.The results show that the SNG production capacity of the system is 0.306 m3.SNG/kg-bio,and the primary energy efficiency is 47.88%.Compared with the traditional gasification method,the energy saving rate of the system is 15.29%.The system achieves the best performance when the gasification temperature and the converted syngas share are1000°C and 0.55,respectively.The research results provide a new way to response the shortage of natural gas resources in China.(4)To explore the integration rule of the thermochemical complementary utilization method and the distributed energy system,a distributed energy system integrated with a solar hybrid biomass gasification was proposed,and the design and off-design thermodynamic performance of the system were conducted,as well as the economy evaluation.The hybrid gasification method addresses the restrictions of time-varying solar energy on the system performance.Compared with the reference system that combines a solar/Stirling power generation system and a traditional biomass gasification distributed energy system,the investment payback period of the new system is reduced by 3.94 years.Finally,based on the building load demand,the optimization and matched analysis with supply and demand for the proposed system were studied,and genetic algorithm was used to evaluate the application potential of the system in different climate regions in China.The results show that the new system has obvious advantages in energy saving,environment,and economic performance compared to the separated systems,and the overall system performance has been improved by about32.7%?62.4%.The performance advantages of the system are prominent in severe cold or cold areas,mainly because of abundant solar energy resources and stable heat load demand of the building.The annual operating strategies are given and the impacts of economic volatility on system benefits are also investigated. |
PDF Full Text Request