Exergy efficiency and optimum operation of solar collectors

First and second law analyses of a typical solar air dryer system: a case study

“…It is to be noted that there is fluctuation in both the efficiencies which may be due to the fact that the solar radiation also fluctuates with time as shown in Figure 2. It can be seen from these figures that both efficiencies enhance as time increases up to a certain extent then decrease as the time increases, which is found to be in good agreement with the results obtained by earlier authors (Fuziwara 1983, Kar 1985 Kar 1989, Kar and Shaahid 1989, Duffie and Beckman 1991, Singh and Kaushik 1993, Mishra 1996, Bakos et al 2001, Kaushik et al 2001, Torres-Reyes et al 2003, Kurtbas and Durmus 2004, Luminosua and Farab 2005, Tyagi et al 2007). However, there are some fluctuations observed in both the efficiencies as can be seen from Figures 3-7, which are due to the fact that there are also fluctuations in the solar radiation, as can be seen from Figure efficiency is found to be more, while it is the reverse in the case of second law of efficiency; this can also be seen in Table 2, where a sample calculation has been given for clarity.…”

“…Besides, the major part of the quality of energy (exergy) is lost from the surface of the collector and hence a small part is being transmitted and absorbed by the working fluid (air) circulating within the collector tube. This fact is also in good agreement with the results obtained by others and available in the literature (Fuziwara 1983, Kar 1985, Kotas 1985, Saltiel and Sokolov 1985, Suzuki et al 1986, Kar 1989, Kar and Shaahid 1989, Duffie and Beckman 1991, Singh and Kaushik 1993, Mishra 1996, Bakos et al 2001, Kaushik et al 2001, Torres-Reyes et al 2003, Kurtbas and Durmus 2004, Luminosua and Farab 2005, Tyagi et al 2007. It is important to note that the major part of high quality energy is lost by the collector tubes and only a small part of energy transmitted by it is absorbed by the receiver tubes in which the working fluid (air) is flowing.…”

“…However, it is to be noted that the first law of efficiency is much higher than the second law of efficiency, which can be explained in terms of exergy losses. In other words, exergy, which is a quality of energy, is not conserved unlike energy and hence, due to irreversibility within the collector, a significant part of it (exergy) is lost and cannot be recovered (Fuziwara 1983, Kar 1985, Kotas 1985, Saltiel and Sokolov 1985, Suzuki et al 1986, Kar 1989, Kar and Shaahid 1989, Duffie and Beckman 1991, Singh and Kaushik 1993, Mishra 1996, Bakos et al 2001, Kaushik et al 2001, Torres-Reyes et al 2003, Kurtbas and Durmus 2004, Luminosua and Farab 2005, Tyagi et al 2007). Besides, the major part of the quality of energy (exergy) is lost from the surface of the collector and hence a small part is being transmitted and absorbed by the working fluid (air) circulating within the collector tube.…”

Exergy analysis and parametric study of concentrating type solar collectors

“…At the other limit low flow rates result in high fluid outlet temperatures with high specific work potential but the energy losses increase due to the temperature differences, therefore, the optimum mass flow rate is required. [1][2][3][4][5][6][7][8][9][10][11][12]. Kovarik and Lesse [1] studied the optimal flow for low temperature solar heat collector while Farries et al [2] studied the energy conservation by adaptive control for a solar heated building.…”

An assessment of solar-powered organic Rankine cycle systems for combined heating and power in UK domestic applications

“…Beyond accounting for the useful work lost in the various components of the whole CSHP system, exergy analysis may also be used to evaluate the theoretical maximum power that could be delivered by a solar collector operating at its optimum temperature for a given set of climatic conditions. This approach provides a useful basis for the control of collector operation through the adjustment of the mass flow-rate, and is the subject of numerous studies in the literature including [17,40,41]. It also enables the comparison of a range of collector designs and will be used here to compare the maximum power deliverable under UK climate conditions from the concentrating and non-concentrating collectors presented in Table 1.…”