Optimal Integration Of Solar-assisted Steam Power System

Utility systems consume large amounts of fossil fuels each year to meet the energy requirements of various processes in the process industry.However,with the increasing depletion of fossil energy and the increasing aggravation of environmental problems such as greenhouse effect and air pollution,more and more scholars are committed to the development of clean energy.Among them,solar energy has attracted much attention because of its wide distribution and abundant reserves.In this study,solar energy was introduced into the design of steam power system as a partial substitute for traditional fossil fuels to supply energy for chemical production process.In order to meet the real-time demand of steam and power in the production process,an optimization design method of steam power system coupled with solar thermal technology was proposed.The main contents are as follows:(1)In order to achieve the optimal integration of the solar thermal system and the steam power system,the superstructure of the solar-assisted steam power system is constructed firstly,and the corresponding mixed integer nonlinear programming model is established,with the goal of minimizing the total annual cost and environmental impact at the same time,and the ε-constraint method is adopted to optimize the multi-objective problem to determine the optimal system structure,equipment size and operating strategy.The changes in solar radiation intensity and power load over time is considered,and the changes in the economic performance of the system before and after the introduction of the storage tank is compared.The results of the case show that the method proposed in this chapter can effectively realize the optimal design of the solar-assisted steam power system.In addition,when the environmental impact restrictions are stricter,the molten salt storage tank can significantly improve the economic performance of the system.(2)A two-stage stochastic mixed integer linear programming model that simultaneously minimizes the two goals of annual total cost and environmental impact is established.The model takes the uncertain fluctuations of solar radiation intensity,steam load and electric load in the actual process into account.A clustering method based on k-medoids and a three-point approximation method are used to generate operating scenarios.In the analysis of the case study,by weighing the economic goals and environmental goals,analyzing the distribution of different goals with the scene,discussing the cost composition of the obtained system,and giving some guidance in the system design stage.In addition,the results obtained by the deterministic model and the stochastic programming model are compared.The results show that considering the uncertainty of the parameters will increase the scale of the system and increase the cost to a certain extent,but the resulting system has a higher ability to resist uncertain fluctuations in actual production.(3)Perform thermodynamic analysis on each independent equipment unit in the optimal system structure obtained in the first part,and calculate the energy loss and exergy loss of the unit to obtain the quantitative and qualitative changes in energy and the reasons for the corresponding process.Then put forward specific reform suggestions for the main exergy loss links to improve the rationality of energy use.According to the calculation results,it can be found that most of the exergy loss is due to the energy loss and the unequal temperature heat transfer process in each equipment unit.By adding a heat recovery structure,the exergy loss in the boiler can be effectively reduced,thereby the rationality of energy usage is improved.