System principles and applications of hybrid sorption-compression heat pump - A review

Heat pumps are widely used in energy conversion and management. To take full advantage of vapor compression and sorption principles, hybrid sorption-compression heat pumps were proposed for practical needs. The hybrids have a number of advantages, such as flexible operating range, large temperature lift and high energy efficiency. A comprehensive review is performed on system principles and applications of hybrid sorption-compression heat pump including absorption-compression (ABC) and solid sorption-compression (SSC), particularly taking cycle features as the main thread. Characteristics of different hybrid cycles are summarized and analyzed. There are mainly four types of ABC cycles, featuring with the compressor placed at different positions in terms of practical need. Among them, the ABC cycle with compressor between absorber and generator is an efficient approach to upgrading industrial waste heat to a high temperature of above 100 degrees C. For SSC cycles, there are two main types. Ammonia or hydrogen is chosen as refrigerant. Large chemical reaction heat can considerably improve cycle efficiency. The review indicates that most researches of hybrid cycles focused on theoretical and experimental performance analysis, selection of working pairs and development of novel cycles. Few applications are found because appropriate compressors for hybrid cycles are not commercially available. In future, compressors of high efficiency and reasonable price should be specially designed and manufactured. Additionally, new working pairs for industrial waste heat recovery are expected. Moreover, energy efficiency improvement of hybrid cycles in applications is urgently needed. Finally, for SSC, some novel cycles can be developed for high thermal energy storage. (C) 2019 Elsevier Ltd and IIR. All rights reserved.