Ionic liquid-based hybrid absorption cycle for water heating, dehumidification, and cooling

Water heating, dehumidification and space cooling are responsible for significant energy consumption in buildings. A potential energy saving measure is to develop hybrid systems that can utilize the sensible and latent heats removed in space cooling to heat water. In this paper, we present experimental results on a hybrid system that utilizes the latent heat released in the dehumidification process for water heating. This system absorbs water vapor from the air and transfers the heat of phase change into the process water. The absorbed water vapor is then liberated in a desorber and subsequently condensed in a condenser, while its latent heat is transferred to the process water. The condensed water vapor can then be either drained (if dehumidification is desired), or utilized in an evaporative cooling process (if sensible space cooling is desired). In essence, the system can exchange both sensible and latent heats with its ambient. The main innovations implemented in the system are (1) a semi-open absorption system architecture to lower the system cost, (2) a membrane-based absorber to alleviate the liquid entrainment issue encountered in the conventional packed bed absorbers and (3) an ionic liquid that eliminates the crystallization risks and minimizes corrosion issues normally associated with LiBr-based absorption systems. A water heating thermal COP of 1.4 is achieved at 30°C, 70% RH ambient conditions.