Thermodynamic and Economic Analysis of an Integrated Solar Combined Cycle System
Integrating solar thermal energy into the conventional Combined Cycle Power Plant (CCPP) has been proved to be an efficient way to use solar energy and improve the generation efficiency of CCPP. In this paper, the energy, exergy, and economic (3E) methods were applied to the models of the Integrated Solar Combined Cycle System (ISCCS). The performances of the proposed system were not only assessed by energy and exergy efficiency, as well as exergy destruction, but also through varied thermodynamic parameters such as DNI and Ta. Besides, to better understand the real potentials for improving the components, exergy destruction was split into endogenous/exogenous and avoidable/unavoidable parts. Results indicate that the combustion chamber of the gas turbine has the largest endogenous and unavoidable exergy destruction values of 202.23 MW and 197.63 MW, and the values of the parabolic trough solar collector are 51.77 MW and 50.01 MW. For the overall power plant, the exogenous and avoidable exergy destruction rates resulted in 17.61% and 17.78%, respectively. In addition, the proposed system can save a fuel cost of 1.86 $/MW·h per year accompanied by reducing CO2 emissions of about 88.40 kg/MW·h, further highlighting the great potential of ISCCS.
A polygeneration system for the methanol production and the power generation with the solar–biomass thermal gasification☆
Abstract A polygeneration system of generating methanol and power with the solar thermal gasification of the biomass is proposed in this work. The endothermic reactions of the biomass gasification are driven by the concentrated solar thermal energy in a range of 1000–1500 K. The syngas from the biomass gasification is used to produce the methanol via a synthesis reactor. The un-reacted gas is used for the power generation via a combined cycle power unit. The thermodynamic and economic performances of the polygeneration system are investigated. A portion of the concentrated solar thermal energy can be chemically stored into the syngas, and thus the energy level of the solar thermal energy is improved. Numerical simulations are implemented to evaluate the thermal performances of the proposed polygeneration system. The results indicate that H2/CO molar ratio of the syngas reaches 1.43–1.89, which satisfies the requirements of the methanol synthesis. The highest energy efficiency and the exergy efficiency of the polygeneration system approximately are 56.09% and 54.86%, respectively. The proposed polygeneration system can achieve the stable utilization of the solar energy and the mitigation of CO2 emission, and thus a promising approach is introduced for the efficient utilization of the abundant solar and biomass resources in the Western China.
Use of Low/Mid-Temperature Solar Heat for Thermochemical Upgrading of Energy, Part II: A Novel Zero-Emissions Design (ZE-SOLRGT) of the Solar Chemically-Recuperated Gas-Turbine Power Generation System (SOLRGT) guided by its Exergy Analysis
This paper adds an exergy analysis of the novel SOLRGT solar-assisted power generation system proposed and described in detail in Part I of this study (Zhang and Lior, 2012, "Use of Low/Mid-Temperature Solar Heat for Thermochemical Upgrading of Energy, Part I: Application to a Novel Chemically-Recuperated Gas-Turbine Power Generation (SOLRGT) System," ASME J. Eng. Gas Turbines Power, Accepted. SOLRGT is an intercooled chemically recuperated gas turbine cycle, in which solar thermal energy collected at about 220 degrees C is first transformed into the latent heat of water vapor supplied to a reformer, and then via the reforming reactions to the produced syngas chemical exergy. This integration of this concept of indirect thermochemical upgrading of low/mid temperature solar heat has resulted in a high efficiency novel hybrid power generation system. In Part I it was shown that the solar-driven steam production helps improve both the chemical and thermal recuperation in the system, with both processes contributing to the overall efficiency improvement of about 5.6%-points above that of a comparable intercooled CRGT system without solar assist, and nearly 20% reduction of CO2 emissions. An economic analysis of SOLRGT predicted that the generated electricity cost by the system is about 0.06 $/kWh, and the payback period about 10.7 years (including two years of construction). The exergy analysis of SOLRGT in this (Part II) paper identified that the main potentials for efficiency improvement is in the combustion, the turbine and compressors, and in the flue gas due to its large water vapor content. Guided by this, an improved solar-assisted zero-emissions power generation system configuration with oxy-fuel combustion and CO2 capture, ZE-SOLRGT, is hereby proposed, in which the exergy losses associated with combustion and heat dumping to the environment are reduced significantly. The analysis predicts that this novel system with an 18% solar heat input share has a thermal efficiency of 50.7% and exergy efficiency of 53%, with similar to 100% CO2 capture. [DOI: 10.1115/1.4006086]