Evaluation and enhancement of solar powered membrane distillation

  • Rasha B. Saffarini

Student thesis: Master's Thesis

Abstract

Potable water for some regions of the world is difficult or even impossible to find. By removing salt from a supply of seawater, desalination has emerged as an important source of fresh water in many parts of the world. However, desalination is inextricably linked to energy, which itself is a critical resource. To solve the emerging crisis of energy and water, renewable energy technologies for desalination is the key. Membrane distillation (MD) is a relatively new desalination process, that is being investigated as a low cost and energy saving alternative to conventional desalination processes. Membrane distillation separation process can be accomplished at atmospheric pressure and temperatures lower than the boiling point of the salt water. This makes it suitable to be coupled with cost-effective and reliable solar technologies, such as conventional static flat plate, and evacuated tubes collectors. As a result of many system limitations, the development of membrane distillation has not yet come to the commercial scale, but it has become a promising technology of the future as indicated by the past decade of research and development. This thesis provides a techno-economic assessment of established solar powered membrane distillation (SP-MD). The study focuses mainly on SP-MD systems that had been tested under field conditions for at least several days. The SP-MD systems are reviewed in terms of their physical properties and operating conditions, and evaluated in terms of several performance indicators, such as membrane flux achieved, energy consumption, gained output ratio , performance ratio, and the energy recovery scheme applied. Besides the design and technical limitations, the relatively high energy costs of the system could also stand in the way of MD being commercialized. Therefore, an economic evaluation was carried out to understand the main contributors to water production cost in SP-MD systems, and to determine the most economical configuration. To facilitate this latter research, UAE was chosen as a hypothetical location for the analyzed SP-MD plant. On this basis, an economic model was constructed to predict the cost of different MD configurations. When operational problems of MD were investigated, the most common problem was found to be pore wetting of membranes. Therefore, an experimental study was conducted to probe the effect of membrane morphology change under operating temperatures of the MD process on the pore wetting of the MD membranes. An array of characterization tools was methodologically utilized to understand this unforeseen effect.
Date of Award2012
Original languageAmerican English
SupervisorHassan Arafat (Supervisor)

Keywords

  • Distillation
  • Solar pumps

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