| Solar thermochemical process hybrid with fossil fuels is more likely to be used for producing clean fuels.The research on the solar thermochemical process is an important frontier in the utilization of the renewable energy in the current.The low density solar energy can be converted into high-density chemical energy of the solar fuels by using the solar thermochemical process.The solar energy is stored in the solar fuels and can be further used for producing liquid fuels.Thus,the utilization of solar energy can be achieved by using the solar thermochemical process.According to the "Revolution and Innovation Plan in Energy Technology(from 2016 to 2030)" published by China,to accelerate the investigations on the solar fuels production is important.It not only meets the impending demand in energy technology breakthrough,but also has an important strategic significance for the sustainable developing and utilizing the solar energy in China.Here in this dissertation,the research work of energy storage by solar solid fuel that produced from solar driven chemical-looping process from three aspects:the energy conversion mechanism in the solar thermochemical process hybrid with fossil fuels,the method of the energy storage by using the solar solid fuel and the experimental validation of the key process in the solar fuel production.The current energy conversion mechanism for the solar thermochemical process is based on the process driven by solar only.For the solar thermochemical process driven by multi-energy,both the complementation in quantity and the coupling in quality for the solar energy and the fossil fuel are involved.Thus,the existing energy conversion mechanism is not fit for recognizing the thermochemical process driven by multi-energy.The conversion characteristics and behaviors for the energy with different quality should be studied in further.Based on the principle of cascade utilization of the chemical energy in the fossil fuel,from the viewpoint of solar concentration and fossil fuel conversion,this study focus on the level changing of the Gibbs energy in the solar hybridization thermochemical process.Using the high temperature solar driven natural gas reforming,mid-temperature solar driven chemical-looping combustion and low temperature solar driven methanol decomposition,the complementary coefficient in quantity and the coupling coefficient in quality between the solar energy and chemical energy of the fossil fuel are quantificationally given.The interaction between these two coefficients is discussed,and the role of this interaction on reducing the irreversible loss of the solar thermochemical process is explored.Additionally,the function of the energy match in level in improving the net solar-to-electricity efficiency is investigated.The study in this dissertation provides an important basis for developing the energy conversion mechanism in the energy systems that driven by multi-energy.Facing the problem that the oppressive re-radiation loss and the low conversion of the fuels in the high temperature solar thermochemical process,this study propose a new method that storing solar energy in solar solid fuel by using the mid-temperature solar driven chemical-looping combustion,and further integrated a power generation system by using this new energy storage method.In this power generation system,the chemical-looping combustion of dimethyl ether(DME)and CoO driven by the solar heat at 350 °C is adopted.The annual performance of the proposed system is given and the performance of the system with and without energy storage in the four typical seasonal days are compared.The results show that,the energy storage density of the Co is 570 kWh/m3,it is 5 and 8 times higher than that in the sensible heat storage and phase change heat storage at the same temperature.The annual net solar-to-electricity efficiency in the proposed system is 22.4%,10 percentage higher than that in the power generation system driven by solar only.The above study expands the chemical-looping combustion into concentrating solar power field,provides a new method to develop the energy conservation and storage in the energy systems that driven by multi-energy.Chemical-looping combustion is the key process in the energy storage by using solar solid fuel that proposed in this dissertation.Based on the aforementioned energy conversion mechanism and energy storage method,this study originally develops a 10 kW prototype of the porous honeycomb chemical-looping combustor.In this honeycomb reactor,the integration of the chamber and the oxygen carrier is obtained.From the geometric model,the energy conversion model,the gas-solid reaction model,the design method for the honeycomb reactor is given.By using CH4 and syngas as the fuel,using NiO/NiA12O4,CoO/CoAl2O4,CoO-NiO/A12O3,Fe2O3/Al2O3;as the oxygen carriers,the relevant validation experiment have been performed in the 10 kW honeycomb CLC reactor.Experimental results show that,the huge temperature fluctuations in the traditional fixed-bed is avoided by using honeycomb CLC reactor.Besides,the gas-solid reaction rate in the honeycomb CLC reactor is 3-4 times higher than that in the traditional fixed-bed,leading to the complete conversion of CH4 more than 90%by converting into CO2.In the 150 hours continuous operation by using the honeycomb CLC reactor,the reactivity of the oxygen carriers keeps nearly no change.Moreover,the influences of the micro-channel shape in the honeycomb CLC reactor are studied by using syngas as fuel gas and the Fe2O3/A12O3 as oxygen carrier.The results show that the honeycomb CLC reactor with triangle micro-channel has the maximum gas-solid contact area and the highest oxygen transfer rate.The above research lays the foundation for the further development of a solar direct chemical looping combustion reactor with high reactant conversion and stability. |
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