Modeling, design optimization and field testing of a solar still with corrugated absorber plate and phase change material for Karachi weather conditions

Abstract

Solar still has been regarded as one of the cheapest and environment-friendly methods to convert brackish water into drinkable water. Despite being promising, solar still has not been employed on a large scale due to its inferior productivity. This paper presents the modeling, experiments, and analysis to augment the productivity of solar still modified with a corrugated absorber plate and Phase Change Material (PCM), under the climatic conditions of Karachi, Pakistan. A detailed literature review was conducted to ascertain the initial design parameters and the absorber plate configuration. A mathematical model based on the mass and energy balance equations of the solar still elements was developed using MATLAB. A parametric study was performed using the MATLAB model to optimize parameters such as the glass cover thickness for maximum productivity. The model results showed that a solar still with a glass thickness of 4 mm was more productive than that with a glass of thickness of 5 mm and 6 mm. Suitable materials for the absorber plate, still cover, body, insulation, and thermal energy storage were determined using the weighted rating method. Thereafter, the solar still Computer Aided Design (CAD) model was developed using Solid works and after a comprehensive market survey and assessment, the still was fabricated. Testing was performed during a hot spring month from 19th April to 26th April, 2020 (1450 readings, over 120 h). The results showed that the solar still with the PCM produced 4.5 L/day of fresh water at a cost of 42.34 USD/m3. In comparison, the solar still without PCM produced 4.1 L of fresh water per day at 43.6 USD/m3 which indicated that solar still with PCM was more productive and economical. The experimental data was also compared to the MATLAB mathematical model predictions. The temperature trend of still elements (basin, glass exterior, glass interior, water, and PCM) predicted by the MATLAB mathematical model and the experimental data matched fairly well.