# New Developments and Progress in Absorption Chillers for Solar Cooling Applications
## 3 Newly Developed Commercial Absorption Chillers
### Single/Double-Effect Absorption Chiller: Solar-Gas Fired
The contribution of driving heat inputs (i.e., from solar energy and gas combustion) for the production of cold is illustrated in Figure 11 at different cooling water inlet temperatures (28-34 \({}^{\circ}\)C) [40]. The inlet temperature of hot water was between 75 \({}^{\circ}\)C and 90 \({}^{\circ}\)C. The inlet temperature of cooling water has a significant effect on the share of the solar energy and gas consumption, e.g., each reached 50% of the cooling capacity at cooling water and hot water inlet temperatures of 28 \({}^{\circ}\)C and \(\sim\)89 \({}^{\circ}\)C, respectively. Also, the minimum hot water inlet temperature was between \(\sim\)59 \({}^{\circ}\)C and 72 \({}^{\circ}\)C, the cooling water inlet temperature was between 28 \({}^{\circ}\)C-34 \({}^{\circ}\)C, and the chilled water was supplied at 7 \({}^{\circ}\)C with a cooling capacity of 239 kW [40]. This hybrid chiller operated at nearly 55% of its nominal capacity using only solar energy to supply chilled water at 7 \({}^{\circ}\)C. Besides, in order to be economically competitive, the solar cooling system has to work with high solar fraction (Equation (3)) and the primary energy rates ratio (Equation (5)) must be higher than one. Therefore, the solar-gas-fired single/double effect water/LiBr absorption chiller was designed and developed to address this cost effectiveness using optimized solar energy use and gas consumption. In parallel, Thermax Ltd. developed and commercialized absorption chillers designed on the basis of the single/double-effect technology to enable maximum use of heat sources at two-temperature levels with a single machine [42]. The chiller is known as a multi-energy driven chiller (2D Series) in which the high-temperature heat source is used in the double-effect desorber, while the low-temperature heat source is used in the single-effect desorber. In this type of chiller, high-temperature steam (3.92 to 9.81 bar), exhaust gas (350 to 600 \({}^{\circ}\)C), and hot water (150 to 180 \({}^{\circ}\)C) are supplied to the high-temperature desorber, whereas steam (up to 2.94 bar) and hot water (80 to 95 \({}^{\circ}\)C) are supplied to the low-temperature desorber. Additionally, it has a backup direct oil/gas-fired system. For instance, in the EJ Series product line (see Figure 12), engine exhaust gas and jacket cooling water are used in high-temperature and low-temperature desorbers, respectively, to drive the absorption chiller. The nominal cooling capacity of the commercially available absorption chiller of this type is between 175 and 12,300 kW, medium- to large-capacity, with chilled water supplied at temperatures up to \(-\)1 \({}^{\circ}\)C and brine supplied up to \(-\)2 \({}^{\circ}\)C. It has a thermal COP between 1.1 and 1.2. The main differences between the Thermax EJ Series and Kawasaki's hybrid chiller are the type of high-temperature desorber (indirectly driven by exhaust gas and directly gas-fired, respectively) and the flow arrangement of the absorber and condenser cooling water connections (see Figures 10a and 12a). The above small-to-large capacity of newly developed water/LiBr chiller technologies with special features suitable for solar space cooling applications are summarized in Table 1.  
Figure 11: Effect of driving hot water inlet temperature for the contribution of solar energy and gas on cooling capacity at a chilled water supply of 7 \({}^{\circ}\)C and several cooling water inlet temperatures [40].