Membrane distillation (MD) is a thermally driven distillation
process. In this process, hot feed stream is passed along one side of a
hydrophobic membrane, which is only permeable for water vapor and retains
liquid water, whereas the other side is kept at a lower (cooler) temperature.
Due to temperature difference across the membrane, water evaporates at the
feed-membrane interface and the induced partial vapor pressure difference
drives only water vapor through the membrane where it condenses on the other
side of the membrane, called the permeate side.
MD
requires low-grade heat, which can be harvested from solar thermal energy, and
other renewable or waste heat sources. Also, unlike the well-known reverse
osmosis, MD operates at a lower water pressure, which in turns reduces the
capital and operational costs. All these advantages make MD ideal for remote
area desalination plants installations with minimal infrastructure and less
demanding membrane characteristics. However,
MD is faced with challenges that are yet to be addressed in order for this
technology to be competitive with conventional desalination techniques. In
recent years, MD has been coupled with renewable energy sources, such as solar
thermal collectors and photovoltaic (PV) panels, to capitalize on the
attractive features of MD. However, the unsteady nature of renewable energy
sources imposes a challenge on solar powered membrane distillation (SPMD) that
requires special attention on process modeling and system control. Moreover, over
time, membrane permeability changes due to scaling and fouling. All these
factors have to be taken into consideration when modeling MD.
In
this project, the student will design an optimal control strategy to control
the productivity of the combined solar-MD system under different constraints. He will also design monitoring strategies for
fouling detection using estimation methods. Experimental validation will be
performed in collaboration with Water desalination and Reuse center at KAUST.