Abstract
The solar stills were developed to fulfil the freshwater need of the growing population. The paper presents the recent modifications made in still to improve their productivity like the application of phase change materials (PCM), connecting flat-plate collector (FPC), use of nanoparticles, stepped solar still, and attaching separate condenser in the still. Active solar stills are found more productive than passive ones and the thermal efficiency of active solar stills lie in the range of 50–70%, which is far better than passive still having 20–55% thermal efficiency. According to the literature studied in the paper, the maximum productivity of active solar still is 10 litres per day and in passive solar stills, it is 6 litres per day. The different approaches used to carry out the heat and mass transfer analysis of single and double slope active and passive solar stills are also discussed in the paper.
Highlights
Freshwater is an essential requirement of human life. 97.5% of saline water on earth is present in the form of seawater and only 2.5% of water is fresh [1, 2]
To increase the internal heat transfer rate of passive solar stills, heat-absorbing materials such as phase change materials (PCM), nanoparticles, and fine stones were used in the setup
Based on literature review it is found that the thermal efficiency of nanoparticles and PCM based solar still lies between 17–62% and 17.93–59.14%, respectively
Summary
Freshwater is an essential requirement of human life. 97.5% of saline water on earth is present in the form of seawater and only 2.5% of water is fresh [1, 2]. Researchers are making such devices that can convert impure water to potable water by using renewable resources. Solar still (SS) is a sustainable device that uses solar thermal energy to transform saline and dirty water into fresh water [3, 4]. The solar stills are mainly categorised into two parts, passive SS and active SS. Passive SS completely relies on natural resources (Solar Energy) while external devices are used in active SS like flat-plate collectors, PVT, electric water heaters, etc. These are economical and can provide adequate fresh water to remote villages. Passive and active solar stills are further classified as single and double slope SS [4]. In the last few years, researches in solar distillation systems are focused on minimising energy consumption, fabrication price, environmental impact and maximising productivity and thermal efficiency
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