Seasonal behavior and techno economical analysis of a multi-stage solar still coupled with a point-focus Fresnel lens

A multi-stage solar still (MSS) was coupled with a point-focus Fresnel lens for the desalination of saline water. The system was tested in field conditions at The Petroleum Institute, Abu Dhabi. A transient mathematical model was developed for the system. Modeling results show a deviation of about 5% in daily yield of MSS when compared with the experimental results. Based on the average hourly direct beam radiation data for a complete year, the model was used for the determination of seasonal behavior of a MSS. The systems’ seasonal behavior shows that maximum productivity of 10 kg/m² d (based on evaporation area) was achieved in the months of May and June, while the productivity was the lowest at 4.8 kg/m² d in the month of December. Different design parameters were tested to enhance the daily output of the current system. The parametric optimization study suggests that a maximum daily productivity of about 5 kg/m² d or 11.4 kg/m² d (based on solar collector area) can be achieved through the system. Cost optimization was performed for the determination of parameters that will result in maximum MSS daily output at lowest expense. The cost optimized parameters were determined for five stages, with 1.0 m² evaporation area for each stage, 10 cm stage spacing and a Fresnel lens of area 2.2 m². The unit production cost competes well with earlier developed solar desalination systems and the payback period is about one year.