Impact of nano-enhanced phase change materials, thermoelectric generator, internal sidewall reflectors, and fins on the double slope solar still based on 4E and sustainability indicators

• The modified DSSS increased productivity by 118.7 % compared to the CSS. • The modified DSSS shows that water production costs about $0.045 per liter. • Using DSSS can cut down carbon dioxide emissions by 8.41 tons over a lifetime. • Improvement potential gets reduced by 5.52 % with a high sustainability index of 1.040. This experimental study elucidates the effects of simultaneous thermoelectric heating and cooling system (STHCS), hollow circular fins (HCFs), internal sidewall reflector (ISR), and nano-CuO (2.5 wt%) mixed phase change material (PCM) on the performance of double slope solar stills (SSs) for the application in the coastal regions of Bangladesh (88.6241°E / 24.3636°N). The STHCS operates with two pumps and a varying number of thermoelectric modules (TEMs). A comparative evaluation is presented based on the temperature variations, the productivity of fresh water, energy and exergy efficiencies, enviro-economic and exergo-economic aspects, waste exergy ratio, sustainability, and improvement potential of modified solar stills with conventional ones. Following the implementation of every modification in a specific double slope SS, the daily total distillation becomes 2.10 L/m 2 , resulting in an approximate 118.7% increase in water production ability than the conventional one. The energy efficiency is found to be 65.77%, with the cost of water production at about 0.045 $/L. A reduction of 8.41 tons of CO 2 emissions is possible to attain over a lifetime and payback period is reduced by 37.31%. This study evaluates the exergetic sustainability of various solar still configurations using key indicators, including the waste exergy ratio, improvement potential, and sustainability index. The highest sustainability index is determined for the SS oriented with all the modifications of about 1.040 with a reduction in improvement potential of about 5.52% compared to the conventional one. The modified configuration demonstrated superior performance and aligns with multiple Sustainable Development Goals (SDGs), notably SDGs 6, 11, and 13.