Advanced Thermodynamic Analysis and Evaluation of a Supercritical Power Plant

Ligang Wang,Yongping Yang,Tatiana Morosuk,George Tsatsaronis

doi:10.3390/en5061850

Ligang Wang, Yongping Yang + Show 2 more

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https://doi.org/10.3390/en5061850

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Abstract

A conventional exergy analysis can highlight the main components having high thermodynamic inefficiencies, but cannot consider the interactions among components or the true potential for the improvement of each component. By splitting the exergy destruction into endogenous/exogenous and avoidable/unavoidable parts, the advanced exergy analysis is capable of providing additional information to conventional exergy analysis for improving the design and operation of energy conversion systems. This paper presents the application of both a conventional and an advanced exergy analysis to a supercritical coal-fired power plant. The results show that the ratio of exogenous exergy destruction differs quite a lot from component to component. In general, almost 90% of the total exergy destruction within turbines comes from their endogenous parts, while that of feedwater preheaters contributes more or less 70% to their total exergy destruction. Moreover, the boiler subsystem is proven to have a large amount of exergy destruction caused by the irreversibilities within the remaining components of the overall system. It is also found that the boiler subsystem still has the largest avoidable exergy destruction; however, the enhancement efforts should focus not only on its inherent irreversibilities but also on the inefficiencies within the remaining components. A large part of the avoidable exergy destruction within feedwater preheaters is exogenous; while that of the remaining components is mostly endogenous indicating that the improvements mainly depend on advances in design and operation of the component itself.

Highlights

45% of global electricity generation is derived from coal, while natural gas and nuclear energy make up about 20% and 15%, respectively [1,2]
Exergy destruction in each component calculated in conventional exergy analysis is split, according to the sources and controllability
Inherent irreversibilities in turbines contribute more or less 90% to their total exergy destruction, while this proportion drops down to 70% when it comes to feedwater preheaters

Summary

Introduction

45% of global electricity generation is derived from coal, while natural gas and nuclear energy make up about 20% and 15%, respectively [1,2]. It has been well known that the supercritical coal-fired power plants are energy systems with high fuel consumption, low efficiency, and relatively large amounts of pollutants and greenhouse gas emissions. Exergy analysis can identify the location, the magnitude, and the sources of thermodynamic inefficiencies in a thermal system [3], and provide information for improving the overall efficiency and the cost effectiveness of a system or for comparing the performance of various systems [4]. Throughout the last decades, this conventional exergy analysis has been discussed and applied to a wide variety of coal-fired power plants, for example, see [5,6,7,8,9]. Conventional exergy analysis is always used to evaluate the performance of an individual component at certain operation conditions, without considering the interactions among components or the actual achievable best behavior of the component under investigation

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