Experimental study and analysis of solar still desalination using phase change materials

•An experimental investigation to study the role of phase change material (PCM) present in a solar desalination unit is conducted.•Presence of PCM in the water of the solar unit produces two zones (charging and discharging) in which the temperature is strongly affected.•The temperature in the discharging zone remains constant. The length of this zone depends on the amount of PCM present.•Presence of PCM decreases the productivity of the unit during day time and increases the production during night time. A solar unit to investigate the effect of PCM on the temperature change of the water during the entire day (day time and night time) was designed. The unit is also used to test the effect of PCM on the amount of fresh water produced. Candle wax (tricosane) was used as PCM and its amount was varied to achieve the ratio of mass of PCM to mass of water of 0, 0.17, 0.35 and 0.51 respectively. The amount of water used was fixed throughout all the experiment at 3 kg tap water. The wax was placed in copper tubes immersed in water. The results showed that presence of PCM causes the appearance of two zones in which the temperature is strongly affected by the PCM. The first zone appears due to the melting of the PCM (during day time) and the second zone appears due to solidification (during night time) of the PCM. The effect of the PCM is prominent in the second zone where the temperature remains constant at the PCM melting point. The length of the solidification zone is proportional to the amount of PCM. Fresh water production is strongly affected by the presence of the PCM. During the day time fresh water production is inversely proportion to the value of R. However, during the night time fresh water production is directly proportional to the value of R.