# New Developments and Progress in Absorption Chillers for Solar Cooling Applications
## 3 Newly Developed Commercial Absorption Chillers
### Efficient and Compact Absorption Heat Pump: Cooling and Heating  
A new generation of water/LiBr absorption heat pumps, new-AHP, driven by low-temperature heat, was designed and developed by the Technical University of Berlin (TU Berlin) in collaboration with Vattenfall Europe and ZAE Bayern [13; 14; 24; 25]. The development of this type of new-AHP technology started in 2008 with the optimization of various aspects (including thermodynamic design, cost effectiveness, and manufacturing process) and case studies which were followed by various field tests carried out between 2012 and 2017. Commercial product versions of this chiller technology have been launched since 2014: the model \"Bee\" (50 kW) [26]; the model \"Bumblebee\" (160 kW) [27]; and the model \"Hornet\" (500 kW) [28] which recently came on the market [24]. This technology was developed to address the need for high energy efficiency (thermal COP > 0.75 in cooling mode), a low-temperature driving heat limit (<60 \({}^{\circ}\)C), high heat rejection temperatures (>45 \({}^{\circ}\)C), high energy density, and size compactness [25]. The new AHP divided the whole machine into two main individual modules (as shown in Figure 3 for the model \"Bee\"): a high-pressure vessel (containing the condenser and desorber) and a low-pressure vessel (containing the absorber, evaporator, solution heat exchanger, and solution pump) with base frame. Figure 3: The single-effect water/LiBr absorption heat pump machine with a 50 kW cooling capacity, model “Bee”, from W. Baelz & Sohn GmbH & Co. Adapted from Reference [26]. Note: ABS = absorber; BF = base frame; CON = condenser; DES = desorber; EVA = evaporator; SHX = solution heat exchanger; SP = solution pump. Under the nominal operating condition, the new AHP provides chilled water at supply/return temperatures of 16/21 \({}^{\circ}\)C with a thermal COP of \(\sim\)0.8. The driving hot water and cooling water inlet/outlet temperatures are 90/72 \({}^{\circ}\)C (i.e., temperature glide of 18 K) and 30/37 \({}^{\circ}\)C (for model \"Bee\") or 30/38 \({}^{\circ}\)C (for model \"Bumblebee\"), respectively. The innovative heat exchanger layout of the new-AHP machine (i.e., U-shaped bent tubes) with stable avoidance of thermal bridges on the process side enables the machine to extend its temperature limit for heat rejection up to 50 \({}^{\circ}\)C (which is approximately 35-40 \({}^{\circ}\)C in conventional absorption chillers) with good thermal performance (excellent COP in these operating conditions). Moreover, the new AHP has a more compact design (0.052 m\({}^{3}\)/kW\({}_{\text{cold}}\) for the model \"Bee\" and 0.026 m\({}^{3}\)/kW\({}_{\text{cold}}\) for \"Bumblebee\") and weighs less (15 kg/kW\({}_{\text{cold}}\) for \"Bee\" and 10.94 kg/kW\({}_{\text{cold}}\) for \"Bumblebee\") than other commercially available absorption chillers. Besides, the new AHP design reduced the time required to reach full loading (or attain load changes) by \(\sim\)50% compared to typical absorption chillers which need approximately 30 min. Dead spaces were avoided by optimizing the heat exchanger and housing it as a single component not individual ones. Therefore, these machines reduced the water/LiBr volumes (i.e., refrigerant and solution volumes) by approximately 33.3%, which reduced the machine's working weight as well as the CAPEX and OPEX. The components of the new AHP machine are U-shaped bent tube heat exchangers arranged face-to-face (absorber (ABS) and evaporator (EVA)) or cross-shaped parallel (desorber (DES) and condenser (CON)) (a split CON arrangement was applied, right and left of the DES) [14]. The new-AHP machines (\"Bee\" and \"Bumblebee\") were installed and field-tested in four pilot projects for solar space cooling applications in Jordan [24; 29]. These installations demonstrated the new AHP machine's use as a chiller in extreme conditions with dry cooling towers in a hot climate (illustrated in Figure 4).