Is there a practical cycle for desalination that operates at specific energy consumption close to the thermodynamic limit? If yes, by how much higher would the specific energy consumption be?

 

The conventional desalination processes such as the MSF, the MED, the ROs, etc., have energy consumption levels that far exceed the thermodynamic limit (typically at 0.78 kWh/m³) by as much as 3.5 to 8 times. It has been reported that the present challenge in energy efficiency for the desalination industry is to have a specific energy consumption of 1.5 kWh/m³. In this presentation, the author shares an efficient adsorption (AD) cycle that is capable of extracting low temperature waste heat typically at 55^o to 85^oC and converting the recovered energy into two useful effects, namely high grade water and cooling. Such a low temperature waste heat is available in abundance, either from the renewable sources such as solar/geothermal sources or exhaust of industrial processes, for which if not recovered is usually purged into the ambient. The low temperature waste energy sources are usually deemed as a free energy source which is non-payable.

 

The performances of a prototype AD plant of NUS are presented for assorted heat source, cooling and chilled water temperatures, and the measured results are reported in terms of the specific daily water production (SDWP) and the specific cooling capacity (SCP). Besides being environmental-friendly, the advanced AD cycle consumes only 1.38 kWh/m³;– the lowest specific energy consumption ever reported for desalination. Another advantage of the AD cycle is the low maintenance cost as there is almost no major moving part. Using a life-cycle prediction, the unit cost of water production by a large-scale AD cycle is US$0.6/ m³ and this cost is the lowest when compared to the other conventional methods. The author also presents the hybridization of the AD cycle to other desalination and cooling methods so as to improve their energy efficiency.

 

 

 

 

 

 

Dr. Cyrille Schwob

Chief Technical Officer

Aerospace Malaysia Innovation Centre,

Malaysia