Lignite drying with solar energy: Thermodynamic analysis and case study

As a clean, free, and nondepleting source, solar energy has become the focus of increasing attention in the drying industry. A lignite-fired power plant integrated with a solar dryer (LPPS), in which solar energy is used to dry lignite and the predried lignite is used to generate electricity, is analyzed theoretically in this paper. The aim of this study is to evaluate the energy performance of solar drying under different system parameters. Thermodynamic models, with which the second-law efficiency of the LPPS could be maximized, were developed. A reference case with three kinds of lignite as input fuel was analyzed to quantify the system performance. The first-law and second-law efficiencies were obtained. The solar-to-electric conversion efficiency in the LPPS is more than 34%. Therefore, solar drying is a potential technology that should be promoted in lignite-deposited areas. Moreover, the influence of main parameters on the performance of system was analyzed. Dryer efficiency is determined to have significant influence on the solar-to-electric conversion efficiency.