## 4 Results
The theoretical maximum values were obtained at solar noon, when the value of the angle of incidence is zero. In Figure 12, the useful heat flux is affected by the global thermal losses estimated as \((U_{L})\times(A_{r})=13.67\) W/K. However, the negative trend for larger values of the angle of incidence is caused by the incidence angle modifier described by the Equation (3). Figure 5.2 Thermal efficiency, exergy efficiency, and useful heat, 11 December 2017. Figure 5.3 Theoretical and experimental useful heat in the solar collectors’ field. Figures 13-16 show the experimental evaluation of absorption cooling system taking into account the previous results. Figure 13 shows the external generation power as a function of the heating water temperature, for several condensation water temperatures. In the presented curves it is possible to identify two sections: in the first one, the thermal power increases linearly with the increases in the heating water temperature, this behavior is kept to a point where there is no increase in the thermal power, this point gives rise to the second section of the curves, in which the thermal power does not tend to present any change when the generation temperature is increased. The generation temperatures in the initial zone of each curve represent the temperatures of the heating water to which the absorption refrigeration system can begin to operate, however, in this section, there is still potential for heat transfer to the solution, so the operation of the cooling system is recommended at a temperature outside this zone. The fact of operating the absorption system at a generation temperature where the slope of each curve changes, guarantees that the potential for the heat transfer (temperature difference) in the generator has been used effectively. Finally, in the second operation zone, it is observed that when the temperature of the generation water is increased, there is no increase in the thermal power transmitted to the solution. As it can be seen in Figure 13, for the curves corresponding to a condensation water temperature at 26 \({}^{\circ}\)C and 28 \({}^{\circ}\)C, the condition in which the cooling power reaches its maximum is not perceived. This is due, because, for these curves, this point is above the range of generation temperatures considered. Figure 13 is very important to determine at what temperature the hot water is expected to be supplied to the system generator, in order to get an acceptable performance from the absorption cooling system, this temperature depends on the available condensation water temperature. In Figure 14, the external generation power is plotted as a function of the external cooling power. In this figure, it can be seen that for each condensation temperature shown, there is an approximately linear relationship between these variables. This figure shows that, for the range of operating conditions shown (condensation water temperature), a linear function can be found that relates the required generation power to the desired cooling power. Figure 5.4 Generation power as a function of the generation temperature. Figure 15 shows the variation of the external coefficient of performance as a function of the external heating power, for each condensation temperature. From this figure it is observed that for each curve, as the heating power increases, the COP initially presents an increasing trend, after that, it reaches a maximum point and subsequently decreases with the increase in the heating power. It is worth mentioning that since during the tests reported, the solution mass flow rate was maintained constant through the system generator, so the increase in thermal power is due to an increase in the generation water temperature.