Review on the energy and economic efficiencies of passive and active solar distillation systems G.N. Tiwari a , Lovedeep Sahota b, ⁎ a Bag Energy Research Society (BERS), SODHA BERS COMPLEX, Plot No. 51, Mahamana Nagar, Karaundi Varanasi, UP 221005, India b Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India HIGHLIGHTS • Performance of different solar stills (passive/active) has been studied theroretically and experimently. • Passive double slope solar stills perform better than passive single slope solar stills on the basis of productivity. • Active single slope solar still (N PVT-FPC/N-PVT-CPC) performs better than the active double slope solar still (N PVT-FPC/N-PVT-CPC) above critical water depth on the basis of productivity and vice versa. At critical water depth, yield is approximately same. • Use of water based nanofluids having better thermo-physical and optical properties improve the solar still productivity. abstract article info Article history: Received 6 April 2016 Received in revised form 25 August 2016 Accepted 29 August 2016 Available online 5 September 2016 Water is one of the prime elements responsible for life on the Earth. The demand of potable water is growing con- tinuously due to its rapid use in agriculture, industry, and population. To overcome the challenge of water short- age, it is essential to minimize the gap among the demand and supply of potable water by developing alternative technologies of water purification. It is becoming a challenge to avail of low cost potable water to mankind. Solar distillation is one of the most promising, simple, and economic methodology for salt and brackish water purifica- tion by utilizing solar energy (renewable energy source). Worldwide, various researchers experimentally ana- lyzed the performance of different types of solar stills and numerous research works has also been performed to develop the theoretical models based on energy balances. In present paper, experimentally and theoretically detailed work done in recent past on passive and active solar stills has been highlighted. System performance; exergoeconomic and enviroeconomic analysis; different solar still designs; and recent techniques in solar stills have been discussed in detail. Furthermore, a discussion on future scope of the work on solar stills for sustainable potable water production is given with some recommendations. © 2016 Elsevier B.V. All rights reserved. Keywords: Active solar still Passive solar still Nanofluids 1. Introduction Potable water is essential for all living organisms to survive on the Earth. The availability of potable water from the natural water resources is shrinking day by day due to rapid growth of population, poor water management and water pollution. Due to geography, climate, engineer- ing, regulation, and competition for resources, most regions face drought of potable water supply. The inflation of water crisis would be controlled if we can effectively conserve, manage, and carefully distrib- ute the available fresh water. Today, it is the main challenge to fulfill the gap between demand and supply of potable water to make it available for all the creatures on the planet earth. Contaminated water usually contains bacteria, viruses, parasitical organisms, dissolved and undisclosed materials, chemical and physical contaminants which causes serious damage of health on consumption. Consequently, it is essential to find an alternate methods or techniques to purify the contaminated or filthy water (rain water, boring wells, rivers, lakes, oceans etc.) to avail low cost potable/fresh water. There are various high and medium technologies available for water purification viz. Multiple Effect Distillation (MED), Multi Stage Flash (MSF) desalination, Thermal Vapor Compression (TVC), Mechan- ical Vapor Compression (MVC), Reverse Osmosis (RO) and others. All these technologies depend on conventional source of energy (electrici- ty) and require high-tech parts i.e. batteries, filters or membranes etc. On the other hand, solar distillation is the simplest, cost effective, and environment friendly technology for water purification. The classifica- tion of solar desalination methods has been illustrated in Fig. 1(a). Solar desalination is one of the popular treatment solutions through- out the world. Solar distiller or simply solar stills produce pure water by Desalination 401 (2017) 151–179 ⁎ Corresponding author. E-mail address: gntcesiitd@gmail.com (L. Sahota). http://dx.doi.org/10.1016/j.desal.2016.08.023 0011-9164/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal