## 3 Results  
Figure 5 represents the average energy delivered per day to the absorption chiller as a function of the specific collector surface along the summer season (June-September) obtained using the TRNSYS model (Figure 1) and the climatic data corresponding to Madrid. As expected, the energy delivered per day increases with the collector field surface. Figure 5 also shows that the lower the driving temperature (75 \({}^{\circ}\)C, continuous line) the higher the energy delivered. This result is logical since the lower the temperature of the fluid that circulates through the solar collectors the greater their efficiency. This trend also agrees with the one registered at the Miguel Hernandez University facility (Table 1). It can also be seen how the storage volume has a greater effect at low specific collector surfaces. As the collecting surface increases, the effect of the storage volume is weaker. For the driving temperature of 75 \({}^{\circ}\)C and a specific surface area of 2.5 m\({}^{2}\)/kW\({}_{\text{cool}}\) the difference between the energies delivered corresponding to the specific storage volumes of 15 and 50 L/m\({}^{2}\) is 26 kWh/day (208-182), while for the surface area of 4 m\({}^{2}\)/kW\({}_{\text{cool}}\) and the same specific storage volumes, the difference is 7 kWh/day (278-271). The evolution of the temperature in the storage tank for the driving temperature of 75 \({}^{\circ}\)C is represented in Figure 6 to study the effect of the specific collector surface and storage volume on the energy delivered to the absorption chiller. The hot water temperature and energy delivered to the absorption chiller are represented in Figure 6a for the specific collector surface of 2.5 m\({}^{2}\)/kW and storage volumes of 15 and 50 L/m\({}^{2}\). In Figure 6b the same variables are represented for the specific storage volume of 15 L/m\({}^{2}\) and collector surfaces of 2.5 and 4 m\({}^{2}\)/kW. The two days represented in Figure 6 correspond to 8 and 9 July (4512 to 4560 ho of the year). Figure 6a explains the difference between the left ends of the curves corresponding to 75 \({}^{\circ}\)C in Figure 5. In both cases when the hot water temperature reaches 77.5 \({}^{\circ}\)C, 50 kW are withdrawn from the storage tank. This extraction of energy is shorter in the case of the specific storage volume of 50 L/m\({}^{2}\) (continuous line) since it takes longer to bring the 4375 L to 77.5 \({}^{\circ}\)C with the energy provided by the 87.5 m\({}^{2}\) of solar collectors. The extraction of energy when the temperature of the tank reaches the set-point (77.5 \({}^{\circ}\)C), implies a decrease in the temperature of the tank with this collector surface until producing a stop and a second withdrawal in the case of the specific storage volume of 15 L/m\({}^{2}\) (discontinuous line). Figure 6b shows that for the specific storage volume of 15 L/m\({}^{2}\), the collector surface of 4 m\({}^{2}\)/kW (140 m\({}^{2}\)) is sufficient  
Figure 5: Energy delivered per day to the absorption chiller as a function of the specific collector surface. to achieve an increase in the temperature of the water in the storage tank simultaneously with the removal of energy for driving the absorption machine. This combination yields the highest energy delivered per day. It was somewhat expected that the storage volume more favorable was the minimum analyzed since there is temporary coincidence between cooling demand and solar radiation supply. In view of the results shown in Figure 5, it is worth asking whether it is convenient to reduce the accumulation volume below the 15 L/m\({}^{2}\). Lower storage volumes were analyzed and represented in Figure 7.  
This figure shows a transition zone between 10-15 (depending on the driving temperature) and 30 L/m\({}^{2}\). The increase in accumulation above 30 L/m\({}^{2}\) has a negligible effect on the range studied. An additional reduction below 10-15 L/m\({}^{2}\) also does not seem to have a positive effect and generates transients that should be analyzed from an experimental point of view.