A comprehensive analysis of a thermal energy storage concept based on low-rank coal pre-drying for reducing the minimum load of coal-fired power plants. (25th June 2019)

• Record Type: Journal Article
• Authors: Sun, Yang; Xu, Cheng; Xin, Tuantuan; Xu, Gang; Yang, Yongping
• Is Part Of: Applied thermal engineering. Volume 156(2019)
• Page Start: 77
• Page End: 90
• Publication Date: 2019-06-25
• Subjects: Coal-fired power plant -- Low-rank coal pre-drying -- Operational flexibility -- Minimum load -- Thermal energy storage -- Thermodynamic analysis; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2019.04.049
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: A thermal energy storage concept based on low-rank coal pre-drying (LD-TES). Minimum load of coal-fired power plants is significantly reduced by LD-TES. Electric power is stored equivalently with high round-trip efficiency (92.8%). CO2 emission of the power plant is significantly reduced by the adoption of LD-TES. Abstract: In the context of renewables penetration, coal-fired power plants are required to operate at the minimum load in low-demand periods of the grid. However, combustion in the boiler will become unstable in low load conditions, which constrains the load reduction of coal-fired power plants, especially the plants fueled by low-rank coal (LRC). This work proposed a thermal energy storage (TES) concept based on LRC-drying (LD-TES) to reduce the minimum load of LRC-fired power plants (LCPPs). A simple experiment was employed to verify the feasibility of energy storage through LRC drying. The advantage of LD-TES compared with traditional low-temperature TES was revealed based on the thermodynamic analysis. Moreover, an LCPP system integrated with LD-TES was proposed, and the minimum load reduction attributed by LD-TES and the energy/environmental performance of the integrated system is determined quantitatively. To achieve this goal, a thermodynamic model is employed for system simulation and evaluation, and the TES scheme based on hot water tank (HWT-TES) using the same heat source as LD-TES is chosen for comparison. The results show that, pre-drying and storage of LRC is feasible for hourly thermal energy storage, and LD-TES can equivalently store electric power in megawatt magnitude (11.1–25.0 MW) with high round-trip efficiency (92.8%). Besides, LD-TES can also significantly reduce the CO2 emission of LCPP systems.