An economic evaluation of renewable energy-powered membrane distillation for desalination of brackish water

Membrane Distillation (MD) is an emerging technology that, on a technical level, has been demonstrated to be a promising technique in regard to enabling the provision of potable water in remote areas and arid regions. Though extensive studies have invested their efforts in optimizing the operating parameters of MD, few have focused on investigating its economic feasibility; a real-world constraint that limits even the most effective of inventions. This study provides a systematic evaluation of the economics involved in using an MD system to produce potable water from brackish water. This study takes into consideration both the direct and indirect effects of identified key parameters (plant size, use of waste heat, membrane permeability). Results indicate that individually, utilizing solar energy, waste heat recovery, and reducing the plant size significantly impact the final cost of water purified, ergo water price (WP). Likewise, combining solar-thermal sources with waste heat to power MD processes can in turn result in a greatly lowered water price. For instance, a MD system relying on waste heat and solar thermal (providing 40% and 60% of its energy requirements respectively), can lower water price from $6.80/m3 (the price of operating a standalone MD solely powered by grid electricity) to a mere $1.6/m3. Finally, a sensitivity analysis was performed to optimize the cost savings that can be realized via the MD process. It was shown that increasing membrane permeability and contribution of renewable energy (i.e. solar-thermal and waste heat) used in operating the process, while reducing the desalination plant capacity, would likely result in a significant decrease in the water production cost of MD, leading to a more competitive, sustainable, and economically-feasible desalination process for small-scale and remote applications.