Dynamic modeling and simulation of solar thermal power storage systems

doi:10.19799/j.cnki.2095-4239.2024.1160

Abstract

Abstract:

In recent years, numerous exemplary solar thermal power stations have been established nationwide. Integrating these stations with efficient thermal energy storage systems is crucial for improving their power generation efficiency and reducing operational costs. This study investigates the operation of thermal energy storage systems by developing a dynamic model of a two-tank indirect thermal energy storage system. Mathematical models for the salt storage tank, oil/salt heat exchanger, and molten salt pump have been constructed, along with a PI control module to automatically control the speed of the molten salt pump. The STAR-90 simulation platform simulates the dynamic charging and discharging processes under typical daily conditions at the CGN Delingha 50 MW trough solar thermal power stations during the vernal and autumnal equinoxes. The results indicate that the performance curve of the molten salt pump model closely matches the actual manufacturer data. Compared to the original thermal energy storage system model, this new model more accurately captures molten salt flow fluctuations resulting from variations in input heat transfer oil temperature and flow rate. During heat storage, fluctuations in the hot oil inlet temperature at the oil/salt heat exchanger considerably influence the cold molten salt flow. The speed of the molten salt pump exhibits a strong nonlinear correlation with the flow rate, while the power consumption of the pump is linearly related to its speed. Under vernal equinox conditions, the average mass flow rate of molten salt is about 800 t/h, with an average pump speed of 154 r/min and a power consumption of 87 kW. During the autumnal equinox, the average mass flow rate increases to 1400 t/h about, with an average pump speed of 265 r/min and power consumption of 115 kW. When the turbine operates at a power output of 28 MW during heat discharge, the flow of hot molten salt is maintained at 2411 t/h owing to the stable flow and temperature of the cold heat transfer oil in the oil/salt heat exchanger. In this situation, the speed and total power consumption of the molten salt pump reach 855 r/min and 205 kW, respectively. The research provides valuable theoretical insights and practical references for optimizing the design and operation of thermal energy storage systems in solar thermal power stations.

Key words: solar thermal power generation, thermal storage system, dynamic modeling, system simulation

CLC Number:

TK 02

Han LI, Gang YU, Ershu XU, Zhirong LIAO, Qiang WANG, Chen CHEN, Yuepeng XING. Dynamic modeling and simulation of solar thermal power storage systems[J]. Energy Storage Science and Technology, 2025, 14(3): 1234-1246.

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温度/℃	密度/(kg/m³)	比热容/[J/(Kg·℃)]	黏度/(mPa· s)	热导率/[W/(m·℃)]
280	1912	1491.2	3.76	0.975
300	1899	1467.6	3.26	1.01
320	1887	1498	2.84	1.05
340	1874	1501.5	2.48	1.09
360	1861	1505	2.19	1.13
380	1848	1508.4	1.96	1.16
400	1836	1512	1.77	1.2

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