CCS Coupled Energy Storage Technology In Coal Fired Power Plants For Peak Shaving:System Development And Performance Study

The large amount of CO₂ emissions has caused many environmental problems such as global warming.As a country with the largest carbon emission,China is facing enormous pressure on CO₂ emission reduction.The discontinuity and instability of renewable energy make it unconvienient for peak shaving.In addition,to gurantee the renewable energy power,more and more traditional coal-fired power stations cannot operate at full load at most times.This seriously affects the health level and economic performance of the unit.Therefore,traditional coal-fired power plants ought to explore safer and more economical peak-shaving methods while controlling their pollutant emissions.In the context of the country’s vigorous development of energy storage technology,coupling it with Carbon Capture and Storage（CCS）technology is a piece of new thought to achieve peak shaving and improve the stability of the power grid.Currently,there are few reports about the carbon capture process for simultaneous CO₂ capture and peak shaving in a coal-fired power plant,and no relevant research has considered the impact of boiler load variation on system efficiency.In order to achieve the balance between the supply and demand of power system and ensure the peaking operation of the power station,the philosophy of this concept is that:the boiler always operates at boiler rated load to ensure the highest boiler efficiency.A 1000MW_e ultra-supercritical coal-fired power plant is selected as the reference unit.Three systems are proposed for peak shaving in a coal-fired power plant by using different CCS technologies coupled energy storage.The energy utilization form of the traditional carbon capture coal-fired power plant is optimized,and the peak shaving capacity is improved.The traditional oxy-combustion system and the new concept of oxy-combustion system with energy storage are firstly simulated in Aspen Plus^?.The result shows that the conversion of coal-fired power plant into oxy-combustion units will make the net electric efficiency decreasing from 9.35%¹0.92%.As the load decreases,the net electric efficiency decreases more.The new concept of oxy-combustion system coupled with cryogenic O₂ storage will further make the average daily net electric efficiency of the system decrease 0.58%¹.16%.Moreover,the average daily net electric efficiency of the new concept of oxy-combustion system will decrease with the increase of energy storage capacity.The new concept of oxy-combustion system can greatly improve the peak shaving capacity of the system and enhance the operational flexibility of the system.The peak-shaving coefficient can reach 2.30,and it can be higher while the minimum net power output reduce during off-peak times.The traditional calcium looping（CaL）combustion system and the new concept of CaL system with energy storage are then investigated.The result shows that the net electric efficiency of the new concept of CaL system without cryogenic O₂ storage system is 35.52%,while that of the conventional CaL system is 34.54%.The proposed CaL process can reduce the CO₂ abatement penalty.Including the cryogenic O₂ storage system,the peaking capability of the proposed system can range from 512.1MW to 1041.0MW.Correspondingly,the net electric efficiency can be improved from 18.19%to 36.97%.Increasing the rate of oxygen production can reduce the minimum net power output to lower than 512.1MW.The peaking capability can be regulated by the rate of oxygen production where excess oxygen serves as a byproduct.The traditional monoethanolamine（MEA）-based CO₂ capture system and the new concept of MEA-based CO₂ capture system with energy storage are finally studied.The result shows that when the 1000MW coal-fired power plant retrofitted to a MEA-based CO₂ capture system will make the net electric efficiency of the system reduce 10.28%¹0.96%.As the load decreases,the net electric efficiency decreases more.The new concept of MEA-based CO₂capture system coupled with lean and rich solvent storage will further make the average daily net electric efficiency of the system increase 1.76%².08%.However,its growth rate will decrease with the increase of energy storage capacity.The new concept of MEA-based CO₂capture system can greatly improve the peak shaving capacity of the system.The peak-shaving coefficient can reach 2.34.It can be higher while the minimum net power output reduce during off-peak times.Meanwhile,it will also reduce the economic performance of the system.In the three proposed systems of the paper,the new concept of MEA-based CO₂ capture system has the best thermal performance,and the new concept of CaL system has the best peak shaving capability.This paper provides some new references for improving the peak shaving capacity of power grid systems and provides a new route for the retrofitted of coal-fired power plants in the future.