## 4 Fuzzy Control Structure for Supervisory Ejector Cycle and Multi-Solar Collector Systems
### Layer 2: Supervisory Fuzzy Control of Ejector Cooling Cycle  
Layer 2 is a supervisory controller, which will be controlled according to the different modes of operation implemented. This layer will be subject to the temperature variable of the solar collectors \(T_{col}\), which will be a function of the disturbances of solar radiation \(G\). Depending on \(T_{col}\) and \(G\), a reference in the generator mass flow \(\dot{m}_{g}\) and the evaporator mass flow \(\dot{m}_{e}\) are given. The temperature reference \(T_{ref}\) Layer 2 is connected to Layer 1. A supervisory or governor controller uses Servo-Pumps (SP) and Servo-Electronic-Valves (SEEV) as actuators for the evaporator and generator flow. The operating  
Figure 4: Input fuzzy set membership function for Layer 1: (**a**) input for collector temperature; (**b**) input for derivative temperature in the storage tank; (**c**) input error (reference -current temperature) for the storage tank. L, Large; M, Medium; H, High; NH, High Negative; PH, High Positive. Figure 5: Output fuzzy set membership function for the flow reference in each collector. P, Positive; G, Good. modes are defined as an input to the system, according to the conditions of use that the operator or end user requires. The operating modes are defined continuously from 0-5. Mode 0 represents the highest energy consumption savings, and Mode 5 has the highest power consumption, but higher cooling power. The operator or end user according to his or her needs defines the mode of operation; however, the supervisory or optimization layer, based on additional operating conditions such as disturbances and climatic conditions, defines optimal references for a longer time of use of solar air-conditioning. The supervisory controller treats a set of information to optimize the operating conditions of the complete cooling cycle. The temperature in solar collectors, temperature variation in solar collectors and temperature in tank storage and operation modes are the inputs to the multiple input and multiple output plant. Temperature and its variation in solar collectors give the solar energy currently available. The controller outputs are the reference temperature for the tank (reference for Layer 1), mass flow references for the servo-pump controlling the flow of the generator and the servo-valve controlling the flow of the evaporator, to make the eject operate at a critical or noncritical double-choking condition obtain better performance or effective time of use of the air-conditioning system. For the control simulations, the temperature conditions set \(T_{g}\) was 10 \({}^{\circ}\)C higher than the coolant outlet temperature [24], \(T_{R_{out}}=T_{g}-10\)\({}^{\circ}\)C; the coolant inlet temperature \(T_{R_{in}}\)= 30.7 \({}^{\circ}\)C, the condenser temperature \(T_{c}\) = 30 \({}^{\circ}\)C and the evaporator temperature \(T_{c}\) = 10 \({}^{\circ}\)C. For the present investigation, the temperature range of the generator is defined as 55-90 \({}^{\circ}\)C, in relation to Table 1, to determine the operating points of the ejector. Figure 6 shows the entrainment ratio with respect to the different temperatures of the generator, where, at 75 \({}^{\circ}\)C, the optimum operating point is located, according to our objective to optimize the air-conditioning use time; 65 \({}^{\circ}\)C is defined as the minimum temperature of the generator at which the ejector can operate, considering there is a loss of 10 \({}^{\circ}\)C. The behavior of the entrainment ratio at different condenser temperatures is presented in Figure 7; it can be appreciated that the condenser temperature must be maintained at 30 \({}^{\circ}\)C, due to the generator's minimum temperature of 65 \({}^{\circ}\)C, which depends on an entrainment ratio of 0.54654, according to Figure 6.  
Equation (5) determines the thermal load (\(Q_{R}\)) required for the cooling area.