| On the background of ’carbon peak and carbon neutral’,the development of renewable energy has been vigorously boosted.However,wind and solar energy have the volatility and intermittent characteristics,which seriously endanger the stability of China’s existing power grid.The continuous and stable power output of renewable energy is significant for building a high proportion of new energy electric power system.Nevertheless,China’s coal-based resource structure has determined that the coal-fired power generation units will still be the main source of power supply in the future.As the solid footing of China’s power supply,ultra-high parameter coal-fired power generation technology can effectively realize the goal of clean and efficient utilization of coal.If unstable solar thermal energy is inputted into efficient coal-fired units,it will not only reduce the coal consumption of coal-fired units,but also continuously and stably output clean electricity generated by solar energy.Therefore,solar-aided ultra-high parameter coal-fired power generation is worth to attract more attention.In this paper,tower solar aided ultra-supercritical double reheat coal-fired power generation technology is studied.The main contents of the paper are as follows:A novel type of tower solar aided coal-fired power generation(TSACPG)system with or without thermal energy storage(TES),which realizes the cascade coupling of tower solar energy and ultra-supercritical double reheat power generation unit.The corresponding simulation model is established to achieve accurate simulation under different loads.In the TSACPG system without TES system,the tower solar energy is used to heat the first reheat extraction steam,and the maximum flow rate of that under different loads is calculated without affecting the normal operation of the original coalfired boiler.In the TSACPG system with TES system,based on the principle of energy cascade utilization,the high temperature solar energy is used to heat the first and the second reheat steam extracted from the boiler and the low-temperature solar energy is used to heat the boiler feed water simultaneously,and the deep coupling of solar energy with boiler and steam turbine is realized.Without affecting the operation of the boiler,combined with various methods of regulating steam temperature,the maximum flow rates of the extracted steam under different loads are obtained.According to the proposed TSACPG system,the thermodynamic performance is explored in the TSACPG system without TES system and the thermodynamic performance,economic performance,and environmental performance of the system under different loads are studied in the TSACPG system with TES system respectively.In the TSACPG system without TES system,introducing solar energy into the first reheat steam can realize the high-grade utilization of solar energy.It can not only reduce the coal consumption of the original coal-fired unit,but also realize the high solar to electricity efficiency.Compared with other schemes in the similar researches,it has significant advantages in boiler exergy efficiency,power generated from solar and solar to electricity efficiency.In the TSACPG system with TES system,the input of solar energy in coal-fired units is further increased.Under different loads,the boiler exergy efficiency is significantly improved,and the reduction of standard coal consumption rate under 100%turbine heat acceptance(THA)condition is 39.85g/kWh.The solar to electricity efficiency,power generated from solar and the proportion of solar power generation can reach 28.62%,120.90MW and 18.32%respectively.In terms of economic performance,the heliostat area and coal saving cost for different typical days and different night TES hour are introduced.With the increase of night TES hour,the system investment and annual coal saving cost are on the rise.In order to avoid the occasionality of a specific typical day,the economic performance differences between different level direct normal irradiance(DNI)regions are also analyzed based on the operation of the typical year.The analysis results indicate that levelized cost of electricity(LCOE)of solar field and the payback year is the lowest in the high level DNI region,which are 43.11(?)/kWh and 10.43 years.And they are the highest in the low level DNI region,which are 74.54(?)/kWh and 18.03 years.In terms of environmental performance,the maximum annual CO2 emission can be reduced 526739.55 tons.Based on the TSACPG system with TES system,a reasonable operation strategy is proposed in this paper to realize the cross-time utilization of solar energy.It can contribute to increase the utilization time of solar energy at night and reduce the waste of solar energy during the day.In different level DNI regions,the annual performance of the system under different solar multiples(SM)and TES hours was explored.The annual electricity output from solar,annual solar to electricity,and LCOE of solar field are quantitatively analyzed.The advantages of the improved strategy show priority in terms of thermodynamic performance and economic performance.Further,after the comprehensive consideration of the thermodynamic and economic performance,the configuration of the solar field of the TSACPG system was synergistically optimized.The compromise results are obtained,which were 14.14 hours/2.64 in high level DNI region,14.22 hours/2.61 in medium level DNI region and 12.15 hours/2.52 in low level DNI region,respectively.In the multi-time scale performance analysis,it is found that the TSACPG system in High level DNI regions can show better thermodynamic performance,reduce investment costs,and reduce more CO2 emissions.Finally,a novel solar contribution evaluation method of the TSACPG system is proposed.It distinguishes the difference between solar exergy and coal exergy.The position where the solar energy input coal-fired units is also considered.When compared with other three evaluation methods,the comprehensiveness and accuracy of this method are demonstrated.The exergy analysis of the TSACPG system also lays the foundation for the follow-up research. |
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