Recent applications of heat pump systems

Heat pump systems offer economical alternatives of recovering heat from different sources for use in various industrial,commercial and residential applications. As the cost of energy continues to rise, it becomes imperative to save energy and improve overall energy efficiency. In this light, the heat pump becomes a key component in an energy recoverysystem with great potential for energy saving. Improving heat pump performance, reliability, and its environmentalimpact has been an ongoing concern. Recent progresses in heat pump systems have centred upon advanced cycledesigns for both heat-and work-actuated systems, improved cycle components (including choice of working fluid), and exploiting utilisation in a wider range of applications. For the heat pump to be an economical proposition, continuousefforts need to be devoted to improving its performance and reliability while discovering novel applications. Some recentresearch efforts have markedly improved the energy efficiency of heat pump. For example, the incorporation of a heatdrivenejector to the heat pump has improved system efficiency by more than 20%. Additionally, the development ofbetter compressor technology has the potential to reduce energy consumption of heat pump systems by as much as 80%. The evolution of new hybrid systems has also enabled the heat pump to perform efficiently with wider applications.For example, incorporating a desiccant to a heat pump cycle allowed better humidity and temperature controls withachievable COP as high as 6. This review paper provides an update on recent developments in heat pump systems,and is intended to be a ‘‘one-stop archive of known practical heat pump solutions. The paper, broadly divided into threemain sections, begins with a review of the various methods of enhancing the performance of heat pumps. This is followed by a review of the major hybrid heat pump systems suitable for application with various heat sources. Lastly,the paper presents novel applications of heat pump systems.