An experimental study of floating wick basin type vertical multiple effect diffusion solar still with waste heat recovery A.K. Kaushal a , M.K. Mittal a, ⁎, D. Gangacharyulu b a Mechanical Engineering Department, Thapar University, Patiala, Punjab 147004, India b Chemical Engineering Department, Thapar University, Patiala, Punjab 147004, India HIGHLIGHTS • Multiple float wicks in basin for reducing thermal inertia. • Feed water pre-heating by heat recovery from waste feed water. • FW-BVMED-HR still showed better Cumulative efficiency than conventional basin type VMED still of same glass and basin area. • High convective heat transfer from float wick to first partition plate. • Increased night distillate due to additional heat stored in multiple floating wicks. abstract article info Article history: Received 10 January 2017 Received in revised form 21 February 2017 Accepted 19 March 2017 Available online xxxx In the present study, a floating wick basin type vertical multiple effect diffusion solar still with waste heat recov- ery (FW-BVMED-HR) has been constructed by modifying the conventional design of basin type VMED solar still (reference still). The reference still has been modified by incorporating improvements like multiple floating wicks in the basin and heat exchanger for waste heat recovery in order to determine the cumulative effect of both of these improvements. The performance of the FW-BVMED-HR still was compared with reference still under identical weather and operational conditions by running them side by side simultaneously. Both the stills were made of same dimensions and materials, and consisted of four effects. On a clear sunny day, the distillate productivity of FW-BVMED-HR still was found to be 21% higher than the reference still. High distillate productiv- ity resulted, due to high convective heat transfer by humid basin air from high temperature float wick surface to first partition plate, feed water pre-heating from waste heat recovery, reduced basin bottom and side losses, and high night distillate productivity as a result of additional heat stored in multiple floating wicks. © 2017 Elsevier B.V. All rights reserved. Keywords: Solar distillation Floating wick Vertical multiple effect Diffusion Heat recovery 1. Introduction Human population in many areas of the world do not have access to safe drinking water. This often leads to health hazard from water borne diseases. In India, there are few places, inhabited by humans, which are regarded as desert. In few states, due to excessive use of groundwater for irrigation as for paddy sowing and industrial purposes, the ground- water level goes down considerably. This situation aggravates further in summer season as most of the surface water reservoirs also start dry- ing up. Hence some states in India face acute water shortage in summer season. The summer season is also the peak load season for the electrical power consumption from household and industry sector. Moreover in future, the growing human population may have to move into areas which are presently considered deserts having water scarcity. Almost all the conventional water desalination technologies need energy, either in electrical form or heat form. Under such conditions, at least the need for safe drinking water can be met from solar distillation. Existing tech- nology must be constantly upgraded in terms of efficiency and equip- ment cost in order to reduce the cost of generating per liter of water. The single slope basin type still, although simple in design, has low productivity. Many efforts have been made by researchers to improve the productivity of basin type stills. Some of these improvements are very simple in implementation and low in cost, but lead to significant rise of still efficiency [1–5]. Solar stills with heat storage medium in basin and stills with inclined wick absorbers have shown significant in- crease of productivity over the conventional basin stills [6–13]. Multiple effect diffusion stills have higher productivities than single slope basin type stills, since the latent heat of condensation is recycled several times in the partition plate distillation section. Use of wetted wicks in stills reduces the thermal inertia and increases the rate of Desalination 414 (2017) 35–45 ⁎ Corresponding author. E-mail address: madhup.mittal@thapar.edu (M.K. Mittal). http://dx.doi.org/10.1016/j.desal.2017.03.033 0011-9164/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal