This paper describes the development of a solar-assisted multi-stage vacuum membrane distillation (SMVMD) system.
The proposed system employs heat recovery unit (HRU) for the energy recovery from the permeate
vapor to the feed seawater.
Temperature modulating (TM) scheme is also implemented for the attenuation
of temperature fluctuations of the feed seawater.
A commercial shell-and-tube capillary membrane module
consisting of an array of polypropylene hydrophobic fibers has been adopted for the system design and
mathematical model development. The SMVMD system is studied for the different numbers of HRUs using a
mathematical model. For a solar-assisted VMD system with 24-stage, the total water production of SMVMD
system with 10 HRUs is found to be 3.37 m3/day, which is about 34% higher as compared to the system with a
single HRU. For a VMD system without solar-thermal unit, the overall specific thermal energy consumption
(OSTEC) decreases by 20% with an increase in the number of HRUs from 1 to 10. For the different numbers of
HRUs in the range of 1–10, the system OSTECs with solar-thermal system having 150 m2 of evacuated-tube
collectors and 16 m3 seawater storage tanks are 28%–36% lower compared to those without the solar thermal
system.