# Energy Analysis of Kalina and Kalina Flash Cycles Driven by Renewable Energy
## 3 Results and Discussion
### Performance of Kalina Cycle (KC) and KFC with Optimal Flash Pressures
It is worth noting that the exergy destruction ratio at the power components shows a different behavior against ammonia fraction to the net power production [16]. The effect of flashing in the HRVG is also opposite to those in the power components and throttle vale: the exergy destruction in the HRVG is larger in the KFC than the KC, and vice versa for power components and throttle vale. However the difference between cycles diminishes rapidly with the increase of ammonia fraction. A big difference of the exergy destruction ratio of the throttle valve in two cycles for the low ammonia concentration range is remarkable. Note that the pressure of the working fluid plummets from flash pressure to condensing pressure through the throttle valve. Figure 9 depicts the dependence of the ratios of exergy destroyed at the flash vessel (\(Df\)), lost through coolant exhaust (\(D\)co), and destroyed at mixer (\(D\)m) for \(P_{H}\) = 24, 36 bar in the KC and KFC. In both systems, the exergy destruction at the flash vessel decreases with the increase of ammonia fraction or the decrease of the separator pressure, which is mainly caused by the effect of increase in the dryness factor in the separator and the consequent decrease in the mass flow rate at the flash vessel. Except for very low ammonia fractions and high pressure of \(P_{H}\) = 36 bar, the exergy loss through coolant exhaust increases with the increase of ammonia fraction or decrease of separator pressure mainly because the dryness factor in separator is increased and consequently the fluid temperature at condenser inlet is raised. In the exceptional case of \(P_{H}\) = 36 bar and ammonia fractions below 45%, exergy loss of the coolant exhaust decreases with increasing ammonia fraction, which is mainly caused by the effect of increased exergy input. The exergy destruction of the mixer exhibits a hill shape against the ammonia fraction as a result of competition between the effects of the dryness factor and mass flow rate. The difference of the exergy consumption at the flash vessel and through the coolant exhaust between the KC and KFC is insignificant. Furthermore, both ratios are lower than 4%. Figure 7: Dependence of \(\eta_{\rm ex}\), \(D\)c, and \(Dr\) on ammonia mass fraction for \(P_{H}\) = 24, 36 bar in the KC and KFC. Figures 10 and 11 show the dependence of (a) separate and (b) cumulative ratios of exergy consumption on the ammonia mass fraction (\(x_{b}\)) for separator pressure of 16 bar in the KC and KFC, respectively. As the flash pressure is highly restricted to selection from a narrow range between separator pressure and condensing pressure, the effect of flashing is not expected to be remarkable for this low separator pressure. The results for the KC are very close to those of the KFC and hard to differentiate with the naked eye. Two systems show almost same behavior quantitatively as well as qualitatively. Correspondingly the only additional component of flash vessel in the KFC yields nearly zero exergy destruction (_Df_). The top three exergy consumptions are due to power generation (\(\eta_{ex}\)) and destruction at the condenser (_Dc_) and HRVG (_Ds_) for the considered concentration range. Ratios of exergy destruction of the condenser and HRVG and the exergy loss through coolant exhaust (_Dco_) are increasing function of \(x_{b}\); by contrast, \(\eta_{ex}\) and the ratios of power components (_Dw_) and regenerator (_Dr_) are the decreasing function of \(x_{b}\). The rest of the ratios are lower than 3%. Figure 8: Dependence of _Ds_, _Dw_, and _Dv_ on ammonia mass fraction for \(P_{H}\) = 24, 36 bar in the KC and KFC. Figure 9: Dependence of _Df_, _Dco_, and _Dm_ on ammonia mass fraction for \(P_{H}\) = 24, 36 bar in the KC and KFC. Figures 12 and 13 show the dependence of (a) separate and (b) cumulative ratios of exergy consumption on the basic ammonia mass fraction (\(x_{b}\)) for separator pressure of 48 bar in the KC and KFC, respectively.