Mechanism And Methodology Study On Parabolic Trough Concentrating Solar Photovoltaic-Thermochemical Hybrid Utilization

Climate change and sustainable development represent the global challenges for humankind.To satisfy the energy demand of humankind,solar energy as the largest renewable energy is expected to play a dominant role.The solar energy utilizations are mainly categorized as solar thermal utilization and solar photovoltaic utilization.Currently,the solar energy conversion efficiency is lower and unsatisfied.To cascade solar energy utilization,full-spectrum solar energy utilization has drawn widespread attention.Supported by key project of National Natural Science Foundation of China,this academic dissertation focuses on the high-efficiency solar energy utilization from the viewpoint of energy quality.The research works are conducted for cascading solar energy utilization from three aspects: the mechanism of irreversibility in the full-spectrum solar energy conversion,the hybrid approach of photovoltaic and thermochemical processes and experimental validation.From the viewpoint of thermodynamics,the concentrating solar energy involves in the nature of both quantity and quality.To investigate the maximum work ability of full-spectrum concentrating solar energy,a maximum work ability model of solar spectra is preliminarily built.And the maximum work ability and energy level of ultraviolet,visible and infrared spectra is analyzed in the single photovoltaic process and thermochemical process.Meanwhile,the effect of key parameters including wavelength and concentration ratio on the maximum work ability and energy level of different spectra is studied.Moreover,this dissertation explores the irreversibility in the concentrating solar energy conversion,and then gives the expression of irreversible loss.In addition,the characteristics of irreversible loss distribution for spectral energy is also revealed.The study in this dissertation provides an important basis to explore the hybrid approaches for cascading solar energy utilization in energy quality.According to the energy level of ultraviolet,visible and infrared spectra,the concentrating solar photovoltaic/thermochemical hybrid approaches are proposed and studied,which integrate with transparent photovoltaics(PV)and above-/sub-mirrors.In detail,to reduce the loss of full-spectrum work ability in the photovoltaic generation,this dissertation studies a hybrid approach integrating with transparent PV and thermochemical process.A physic model of transparent PV is built,and the corresponding relationship is disclosed between cut-off wavelength and photovoltaic bandgap energy.And the proportion of energy is investigated among photovoltaic electricity,joule heat and transmitted energy,while Silicon and Cadmium Telluride transparent PV are adopted.In addition,the effect of transmissivity of PV on the solar energy conversion is studied in the thermochemical process.Moreover,to reduce the irreversible loss in the concentrating sunlight process,this dissertation explores a method of firstly splitting and then concentrating sunlight.Subsequently,a hybrid approach is studied by using the proposed method of concentrating sunlight.An energy conversion model is built,and the conversion characteristics for the solar energy is described in both photovoltaic generation and thermochemical process.The designed performance and distribution of energy loss are also studied in the hybrid system,while Monocrystalline Silicon M-Si PV and methanol decomposition are adopted.Finally,the influence of key parameters on the processes of concentrating sunlight,photovoltaic generation and methanol decomposition,the study discloses the potential of solar-to-electricity conversion.Based on the aforementioned energy conversion mechanism and hybrid approach,this study explores a design methodology of the spectral splitting parabolic trough concentrator,which first splits and then concentrates sunlight.And the mathematical equations of profile are given in further.Using M-Si and methanol decomposition,this study designs and develops a 2kWe test bench integrating with concentrating solar photovoltaic process and solar thermochemical process.Presently,experimental verifications of cascading solar energy utilization are conducted.