PhD Student Position Water Harvesting from Air (4.4)


The earth’s atmosphere contains about 4% of the earth’s total fresh water. Harvesting humidity is therefore an interesting technology to supply to the ever increasing demand for fresh water. The technology is most promising for arid locations without connection to the centralized power grid.   Cooling humid air makes the vapor condensate, which then can be collected. However, energy-wise there is a better option. Prior to cooling, the relatively small amount of water vapor is separated from the high background of other components in the air, particularly nitrogen. This way only the water vapor needs to be cooled down, saving more than half of the energy. PDMS or SPEEK-coated membranes are impermeable for water in the liquid state but show a high selectivity for water vapor over nitrogen gas. The driving force for water vapor permeation across the membrane is the difference in partial water vapor pressure between the feed and permeate side. At the permeate side the vapor pressure can be reduced by (a combination of) low total pressure (‘vacuum’), a condenser and a (dry) sweeping gas. Coupling the system to either a wind turbine or solar energy generator creates a stand-alone device.                                

Research challenge
A previous PhD student on this topic investigated the feasibility of this technology by performing simulations. In this way the effect of several parameters has been studied theoretically but these results still await the translation of this knowledge into a functional prototype. The aim of this current project is to explore different configurations, for example, in respect to membrane and condenser (e.g., direct contact, air gap or sweep gas) and design a working prototype. In addition, the membrane itself can be part of the focus (e.g., inside-out spiral, outside-in spiral or planar). Even the investigation of entirely new membrane material belongs to the options. 

The ideal candidate has an MSc degree and is a creative (mechanical) engineer with solid knowledge of thermodynamics and mass transport phenomena. Knowledge on membrane technology is an advantage. 

Our offer
Doing a PhD in the Netherlands takes 4 year.
You earn a salary to make a living.
In year 1 the salary is €30.674, in year 4 €39.214 before tax.
The amount of paid holiday days is 35/year. 

The research project is part of the Wetsus research theme Dehydration
The following companies are part of this research theme: Avebe, Feyecon, (Dutch Rainmaker)

Promotor: Not yet decided
For more information contact dr. Henk Miedema of Wetsus ( or dr. ir. Antoine Kemperman of University Twente ( 

Wetsus, Leeuwarden, The Netherlands

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