Comparative Energetic and Exergetic Analysis of Conventional and Sloped Solar Chimney Power Plants

Comparative Energetic and Exergetic Analysis of Conventional and Sloped Solar Chimney Power Plants

Hela Atia (Applied Thermodynamic Research Unit (UR1), National Engineering School of Gabes, University of Gabes, Tunisia), Adrian Ilinca (Wind Energy Research Laboratory, University of Quebec at Rimouski, Canada), Ali Snoussi (Applied Thermodynamic Research Unit (UR1), National Engineering School of Gabes, University of Gabes, Tunisia), Rachid Boukchina (Arid Regions Institute, Tunisia) and Ammar Ben Brahim (Applied Thermodynamic Research Unit (UR1), National Engineering School of Gabes, University of Gabes, Tunisia)
Copyright: © 2020 |Pages: 17
DOI: 10.4018/IJEOE.2020100104

Abstract

A CFD analysis using ANSYS Fluent software was conducted to study the effects of collector slope on solar chimney's performances. Three solar chimney configurations, named A, B, and C, which correspond, respectively, to an inclination angle of the collector roof of 0°, 2.5°, and 5°, were investigated. The results show that the thermodynamic performances of the solar chimney were improved by increasing the inclination angle of the collector roof. In fact, the power extracted from the sloped solar chimney power plants increases with increasing the inclination angle and the solar radiation intensity, while it achieves a maximum at 800 W/m2 for configuration A. The energetic and the exergetic analysis show that configure B has the best performance in terms of conventional, effective, and total efficiencies of the collector and in terms of exergy destruction ratios in both the collector and the transition section. Whereas, configuration C has the highest amount of power extracted and the best overall energetic efficiency.
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Introduction

Solar chimney power plant (SCPP) is a promising process for large scale renewable electricity production due to its simplicity and ease of maintenance. This concept was proposed by professor Schlaich in the 1970s (Schlaich, Bergmann, Schiel, & Weinrebe, 2005). It consists of three components, namely, a solar collector, a chimney and a turbine generator. The collector is used to heat incoming air by green-house effect. The heated air flows into the chimney. The pressure difference between the chimney base and the outlet represents the system driving force which leads to driving the turbine installed at the collector center. Ground under the collector could be used for greenhouse farming and the system doesn’t require water for efficient operation. These advantages make the SCPP suitable for use in arid regions.

Many researchers have been interested to the study of the SCPP (Amirkhani, Nasirivatan, Kasaeian, & Hajinezhad, 2015; Dehghani & Mohammadi, 2014; Ghalamchi, Kasaeian, & Ghalamchi, 2015; Koonsrisuk & Chitsomboon, 2013; Lebbi, Chergui, Boualit, & Boutina, 2014; Li, Guo, & Wang, 2012; Nasirivatan, Kasaeian, Ghalamchi, & Ghalamchi, 2015; Patel, Prasad, & Ahmed, 2014; Xinping Zhou, Wang, & Ochieng, 2010). For a best understanding of this process, many analytical models were developed and numerical simulations using computational fluid dynamic codes were carried out. Pasumarthi & Sherif (1998) developed a mathematical model of the collector and studied the profiles of temperature and velocity across it. Results obtained from simplified models were compared to numerical calculations using Fluent in the studies of Pasthor et al. (Pastohr, Kornadt, & Gurlebeck, 2004) and Sangi et al. (Sangi, Amidpour, & Hosseinizadeh, 2011). The basis of those resarch works was the prototype of Manzanares, and, calculations showed a convergence of both methods with experimental results. Many works (Bilgen & Rheault, 2005; dos S. Bernardes, Voß, & Weinrebe, 2003) showed that the chimney height, the pressure ratio, the collector diameter and the optical properties of the collector roofs are important parameters for solar chimney design. In addition, the study of Cao et al. (Cao, Li, Zhao, Bao, & Guo, 2013) using a program based on TRNSYS demonstrates that design parameters and techno-economic cost of a solar chimney power plant depend on climate conditions and location of each country. This confirms the results of Schlaich (Schlaich et al., 2005) who considered that there is no optimal geometry. In fact, design parameters depend on material availability and their costs for each country. Fasel, Meng, Shams, and Gross (2013) investigated the scaling effect on solar chimney using ANSYS Fluent and an in-house developed CFD code. The analytical scaling laws applied were verified. Many researchers (Gholamalizadeh & Kim, 2014; Guo, Li, Wang, & Liu, 2013) applied a discrete ordinate model for modeling solar radiation in the collector. Other works (Cao, Zhao, & Guo, 2011; Cao, Zhao, Li, & Guo, 2013) compared the performances of a conventional and sloped solar chimney. In the study of Koonsrisuk et al. (Koonsrisuk & Chitsomboon, 2013), the effects of the area changes due to collector slope and chimney outlet divergence were studied. It is found that the power is hundred times higher than that in the conventional solar chimney. Bilgen and Rheault (2005) proved that a solar chimney built at suitable mountain hills produces 85% as much as a SCPP with horizontal collector. In addition, many researches were interested to model the heat transfer phenomena occurring in the collector and develop heat coefficient correlations (Aurélio dos Santos Bernardes, Von Backström, & Kröger, 2009; Bernardes et al., 2003; Pretorius & Kröger, 2006; Xinping Zhou, Yang, Xiao, & Hou, 2007).

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