Waste heat operated hybrid (MEDAD) desalination plant: An experimental investigation

This paper presents an advanced desalination cycle called "MEDAD" desalination which is a hybrid of the traditional multi-effect distillation (MED) and the newly-patented adsorption cycle (AD). The combined cycles break the operating regime of conventional MED system and allow some stages to operate below ambient temperature, as low as 5°C in contrast to the conventional MED: The MEDAD cycle results in a quantum increase of distillate production at the same top-brine condition. Being lower than the ambient temperature for the bottom stages of hybrid, ambient energy can now be scavenged by the MED processes whilst the AD cycle is powered by low temperature waste heat from exhaust or renewable sources. In this paper, we present the experiments of a 3-stage MED and MEDAD plants that were fabricated and installed in the air-conditioning laboratory of the National University of Singapore. These plants have been tested at assorted heat source temperatures from 15°C to 70°C. All system states are monitored including the stages temperature and distillate production. It is observed that the synergetic matching of MEDAD cycle led to a quantum increase in distillate production, up to 2.5 to 3 folds vis-a-vis to a conventional MED of the same rating.