A review of unconventional bottoming cycles for waste heat recovery: Part I - Analysis, design, and optimization

In this paper, an extensive overview of unconventional waste heat recovery power cycles is presented. The three-unconventional waste heat recovery bottoming cycles discussed in this paper are the air bottoming cycle, carbon dioxide-based power cycles and Kalina bottoming cycle. The review paper is divided into two parts; first part is about a detailed discussion of energy, exergy, economic analysis, as well as reviewing part load analysis, component design, power augmentation and comparative studies. Whereas, the second part of the review paper demonstrate and thoroughly review the applications of the aforementioned unconventional bottoming cycles, including renewable energy sources. According to the literature, it was found that the air bottoming cycle is not as competitive when compared to the conventional bottoming cycle, such as the steam Rankine cycle. Nevertheless, air bottoming cycle can be economically competitive for low system capacities. Furthermore, CO2 power cycles have shown better performance in terms of energetic and exergetic analyses when compared to the conventional bottoming cycles. The transcritical and supercritical CO2 power cycles excel to recover low and medium grade waste heat, respectively. Finally, Kalina bottoming cycle was found to be competitive to recover the low-grade waste heat when compared to organic Rankine cycle. In addition, optimizing the ammonia-water concentrations at different stages of the cycle has the most notable effect in improving the cycle's performance.