Economic feasibility of a solar still desalination system with enhanced productivity George M. Ayoub a , Lilian Malaeb b, ⁎ a Civil and Environmental Engineering, Faculty of Engineering and Architecture, American University of Beirut, Bliss Street, Beirut, Lebanon b Water Desalination and Reuse Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia HIGHLIGHTS • Rotating cylinder increases solar still yield by 200–300%. • Calculated cost is comparable to that of renewable desalination methods. • Comparison with fuel-based desalination requires adjustment for externalities. • Environmental degradation and carbon-trading schemes are included. • Justified economic feasibility especially for seawater desalination abstract article info Article history: Received 21 October 2013 Received in revised form 8 December 2013 Accepted 12 December 2013 Available online 3 January 2014 Keywords: Cost analysis Cylinder Desalination Environmental degradation Water productivity Solar still Solar still desalination systems offer sustainable tools for fresh water production. However, their widespread ap- plication is often hindered by their relatively low production rates compared to other desalination methods. In this study, a simple amendment, in the form of a slowly-rotating hollow cylinder, was introduced within the solar still, significantly increasing the evaporative surface area. This new modified still was analyzed in terms of both operation and economic feasibility. The introduced cylinder resulted in a 200–300% increase in water out- put relative to a control, which did not include the cylinder. The resulting percent improvement far exceeds that obtained by other modifications. Unit production cost estimates varied between 6 and 60 $/m 3 depending on discount rates, productivity, service lifetime and initial capital costs. These projections are well within reported cost ranges for renewable-based technologies. In order to evaluate the system's feasibility in real market value, different scenarios that introduce carbon-trading schemes and environmental degradation costs for fuel-based desalination, were performed. Reported costs for fuel-based brackish water and seawater desalination were thus adjusted to include unaccounted-for costs related to environmental damage. This analysis yielded results that further justify the economic feasibility of the new modified solar still, particularly for seawater desalination. © 2013 Elsevier B.V. All rights reserved. 1. Introduction With the advent of climate change issues, the economic importance of environmental degradation has increased. Renewable-energy-based de- salination technologies offer a promising solution to both water shortage and environmental pollution problems. Their relatively lower productivi- ty compared with fuel-based desalination, however, attributes to their higher costs and the need for larger installation areas [1]. On the other hand, acknowledging the environmental damage costs associated with fuel/gas energy sources, the market access of desalination based on re- newable energy becomes justified [2]. The economical viability of renewable-based systems is even higher in countries with the greatest water needs and where the cost of other alternatives such as the pipe work to supply an arid area with water or the cost of fuels is high [3–5]. Today, the world economy steadily shifts from a hydrocarbon basis to one that is based on more sustainable energy forms [6]. In the field of solar desalination, an interest in solar still systems re- vives to develop these devices into a more efficient technology for sus- tainable water production. Solar stills have been used for many decades to produce potable water particularly in remote arid areas. In their sim- plest form, they comprise a transparently-roofed basin containing the sea-, waste- or brackish water to be evaporated. This water is heated under solar radiation, evaporates and condenses as it hits the cooler cover and trickles down into a channel as distillate. Increasing the pro- ductivity of solar stills has been the focus of intensive research. Some studies add heat absorbers such as gravel [7,8], sponge cubes [9–11], rubber [12], glass balls [13], charcoal [14,15], floating absorber alumi- num sheets [16], dyes and inks [12,17,18] among others [19]. Solar stills coupled to reflectors [20–24], flat-plate-collectors [25–27] or separate condensers [28–33] as well as multiple-effect stills [34–41], wicks Desalination 335 (2014) 27–32 ⁎ Corresponding author at: Mail Box 3555 KAUST P.O. Box 4700, Thuwal Jeddah Zip Code 23955-6900, Saudi Arabia. Tel.: +966 5 42349605. E-mail address: Lilian.Malaeb@kaust.edu.sa (L. Malaeb). 0011-9164/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.desal.2013.12.010 Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal