## 1 Introduction
[PERSON] [14] described a residential micro-Combined Cooling, Heating and Power (CCHP) system, including a low-temperature Proton Exchange Membrane Fuel Cell (PEMFC) power unit and a half-effect lithium bromide absorption chiller. The author carried out numerical simulations in order to demonstrate the energetic feasibility and performance of this configuration. According to the author's results, the highest exergy utilization factor (ExUF) value was obtained for the minimum evaporator temperature (4 \({}^{\circ}\)C), minimum condenser temperature (27 \({}^{\circ}\)C), and 67 \({}^{\circ}\)C in both generators (high- and low-temperature) of the absorption chiller. [PERSON] and [PERSON] [13] carried out a comparative theoretical analysis of five configurations of LiBr/water absorption refrigeration systems, included the half-effect configuration. Based on the authors' results, when the evaporator temperature was 4 \({}^{\circ}\)C with condenser temperatures of 33 \({}^{\circ}\)C and 39 \({}^{\circ}\)C, the half-effect system could be operated at lower generator temperatures, around 57 \({}^{\circ}\)C and 67 \({}^{\circ}\)C, respectively. The COP values calculated were approximately 0.40 and 0.42, respectively. This was a significant result because it meant that it was possible to use a heat source at a low thermal level that could be obtained from low-cost solar collectors or waste heat in order to produce air conditioning. [PERSON] et al. [12] analyzed, through mathematical simulations, the performance of five different configurations of absorption cooling systems operating with ammonia/lithium nitrate. The authors concluded that the half-effect system might reach evaporator temperatures around 0 \({}^{\circ}\)C at generator temperatures as low as 50 \({}^{\circ}\)C, with a COP value around 0.3. [PERSON] et al. [15] carried out an exergy analysis for single-, double-, triple-, and half-effect water/lithium bromide absorption cycles. According to the results, the highest exergy destruction rates in the cycle occurred on the two absorbers, followed by the two generators. As the heat source temperature increased, the concentration differences between incoming and leaving solutions in the generators and absorbers increased, which was accompanied by higher exergy destruction rates. [PERSON] [16] carried out a comparative study between single-effect and half-effect absorption cycles with an identical cold output and water/LiBr as a working mixture. The author demonstrated that the calculated COP of the half-effect system was approximately half of the COP of the single-effect system, but the exergy efficiency of the latter was slightly lower. The results of the thermodynamic analysis showed that, when the evaporation temperature was maintained at 4 \({}^{\circ}\)C, condenser and absorber temperatures varied from 28 \({}^{\circ}\)C to 38 \({}^{\circ}\)C; generator temperature varied from 40 \({}^{\circ}\)C to 80 \({}^{\circ}\)C; the maximum COP values for half-effect cooling systems were from 10 \({}^{\circ}\)C to 10 \({}^{\circ}\)C. The results of the experiments were summarized in Table 1.  
Figure 2: Pressure–Temperature diagram for a half-effect absorption cooling system. 0.408 to 0.435; and the maximum exergy efficiency was from 14.7% to 22.6%. Besides, the author concluded that for generator temperatures higher than 78 \({}^{\circ}\)C, a single-effect system must be used, but on the other hand, when generator temperatures are less than 78 \({}^{\circ}\)C, it is recommended to use a half-effect system. [PERSON] et al. [17] described a 1-kW cooling capacity half-effect absorption prototype, which used hydro chlorofluorocarbon (HFC)-based working fluids (R134a as refrigerant and N,N-dimethylacetamide (DMAC) as absorbent). According to the experimental performance evaluation, the evaporator temperature was as low as 7 \({}^{\circ}\)C, with generator temperatures from 55 to 75 \({}^{\circ}\)C. The optimum generator temperature was in the range of 65-70 \({}^{\circ}\)C, for which the coefficient of performance was 0.36.