Outline

  • Abstract
  • Keywords
  • Nomenclature
  • 1. Introduction
  • 2. System Descriptions
  • 3. Mathematical Modeling
  • 4. Results and Discussion
  • 4.1. Solar Irradiation Intensity Variation Results
  • 4.2. Net Electrical Power Variation Results
  • 4.3. Steam Turbine Inlet Pressure Variation Results
  • 4.4. Detailed Exergy Analysis of System Components Results
  • 5. Conclusions
  • Acknowledgement
  • References

رئوس مطالب

  • چکیده
  • کلیدواژه ها
  • 1. مقدمه
  • 2. توصیفات سیستم
  • 3. مدل سازی ریاضی
  • 4. نتایج و تبادل نظر
  • 4.1 نتایج تغییر پذیری شدت تشعشع خورشیدی
  • 4.2 نتایج تنوع قدرت الکتریکی خالص
  • 4.3 نتایج تنوع فشار درچه توربین بخار
  • 4.4 تحلیل اکسرژی دقیق نتایج اجزای سیستم
  • 5. نتیجه گیری ها

Abstract

In this paper, detailed exergy analysis of selected thermal power systems driven by parabolic trough solar collectors (PTSCs) is presented. The power is produced using either a steam Rankine cycle (SRC) or a combined cycle, in which the SRC is the topping cycle and an organic Rankine cycle (ORC) is the bottoming cycle. Seven refrigerants for the ORC were examined: R134a, R152a, R290, R407c, R600, R600a, and ammonia. Key exergetic parameters were examined: exergetic efficiency, exergy destruction rate, fuel depletion ratio, irreversibility ratio, and improvement potential. For all the cases considered it was revealed that as the solar irradiation increases, the exergetic efficiency increases. Among the combined cycles examined, the R134a combined cycle demonstrates the best exergetic performance with a maximum exergetic efficiency of 26% followed by the R152a combined cycle with an exergetic efficiency of 25%. Alternatively, the R600a combined cycle has the lowest exergetic efficiency, 20–21%. This study reveals that the main source of exergy destruction is the solar collector where more than 50% of inlet exergy is destructed, or in other words more than 70% of the total destructed exergy. In addition, more than 13% of the inlet exergy is destructed in the evaporator which is equivalent to around 19% of the destructed exergy. Finally, this study reveals that there is an exergetic improvement potential of 75% in the systems considered.

4.1. Solar irradiation intensity variation results

Solar irradiation intensity variation effects on the exergetic performance of the system considered is illustrated in Fig. 3–5. Fig. 3 reveals that as the solar irradiation intensity increases, the exergetic efficiencies of the thermal cycles increase. This result can be explained as follows. First, the solar field is designed to work with a specific range of solar collector rows. Second, receiving more solar radiation means better utilization of the available solar collector field, which could result in using fewer numbers of solar collectors. Therefore, as demonstrated in the figure, improvement in the overall exergetic efficiency of the system can be obtained as the thermal irradiation increases. This figure illustrates that the SRC-V has the highest exergetic efficiency while SRC-A has the lowest exegetic efficiency.

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