Economic Analysis of Membrane Distillation

The application of membrane distillation (MD) technology is increasing, but is still not adopted commercially. One of the key needs to demonstrate the practical viability of MD in a diverse set of applications is to provide convincing estimations of its cost. This chapter reviews publicly available literature which have presented methods for costing MD. Water production cost (WPC) is commonly used, incorporating both the captical and operating costs normalised to the volume of fresh water produced. 28 publications presenting original MD costing were found, dating back to 1987. Renewable energy desalination is the most common, and has persisted in interest since 1987 to the present day. Water production as its own application (utilising original or waste thermal) has been costed to a lesser extent, and has not led to recent publications. Niche industrial applications represents a smaller proportion, but interestingly has emerged recently to be a significant focus where authors have found favourable economics. The final category of costing papers was optimisation studies which present economically optimal working conditions and cost sensitivities. For the WPC findings, solar driven MD costs ‘as published’ have remained within the range of $10-18/m3, but when considering inflation, the 1987 upper range was $34/m3, indicating solar MD is becoming more affordable. As WPC is very sensitive to energy cost, sourcing thermal energy from geothermal or ocean temperature gradients, or by offsetting the solar panel energy costs (e.g., by electricity cogeneration) can reduce the WPC by an order of magnitude, falling in the typical range of conventional water production MD driven by low cost energy (e.g., waste heat), $0.70- $0.80/m3 or by fuel derived thermal energy in the order of $1.50/m3. WPC for niche industry applications varies widely as expected for the widely varying contexts. WPC generated by performance optimsation studies where about double the costs estimated from the dedicated water production studies. In conclusion, there appears to be sufficient knowledge to confidently cost MD technology for a range of applications. Interest to explore MD economics is maintained for renewable energy desalination but recently emerging in niche industrial applications, indicating a likely commercial direction particularly if the trend continues to for MD equipment to become more affordable.status: publishe