Combination of passive and active enhancement methods for higher efficiency of waste-fired plants; flue gas and solar thermal processing

Abstract

This article presents a novel and applied solution for increasing the efficiency and cost-effectiveness of waste-fired power plants and comprehensively analyzes the proposal from thermodynamic, economic, and environmental aspects. The idea is centered around the simultaneous use of passive (flue gas condensation) and active (solar thermal heaters comprising evacuated tube collectors and parabolic trough collectors) for feedwater preheating. In this way, the extracted heat from the turbines for this purpose could be used directly for power generation, and thus, higher waste-to-power efficiency of the cycle. The proposed configuration and the base-case power plant are both simulated in TRNSYS software for dynamic modeling and comparison of the results over an entire year of operation of the power plants. For making the results more reliable for real-life operation conditions, the simulations are run for a real case study in Qassim city, Saudi Arabia. The results of exergy analysis show that the waste incinerator with the annual exergy destruction of 128.3 GWh is the main source of irreversibility in both models. The results further indicate that the proposed novel system is the more suitable option with 11.36 GWh and 68.18 GWh more annual produced electricity and heat, respectively. With these numbers, although the unit product cost of the proposed novel system is 2.2 $/MWh higher than the conventional plant due to the high cost of solar systems, the new system results in a 205.08 ton/GWh lower CO2 emission index which is extremely important and even of high economic value preventing large emission taxes.