Enhancing productivity and cost-effectiveness of single-slope solar stills using a multi-cavity built-in condenser: Experimental and performance analysis

A modified design of a completely passive single-slope solar still has been suggested in the current investigation. To increase the condensation rate and hence increase the unit productivity, a built-in condenser has been attached to the unit. The design of the built-in condenser has further been modified through the utilization of multi-cavity partitions. The systems proposed have been constructed and experimentally tested in Najaf city located at 31°59′29.1″N latitude and 44°20′17.6″E longitude over seven consecutive summer days. A conventional solar still (CS) with identical dimensions was also built and tested under the same operating conditions to assess the productivity and efficiency of the modified designs proposed. The findings reveal that splitting the built-in condenser into two partitions can raise the freshwater harvested there by up to 83.5 % resulting in a 16.7 % upgrade in the overall still productivity despite the 10 % reduction in the freshwater condensed over the glass cover. Compared to the conventional still, integrating a single- (SCCS) or double-cavity condenser still (DCCS) can improve net daytime productivity by up to 24 % and 44.8 %, respectively. A considerable portion of extra-distilled water is also available to collect overnight, where about 15 % and 17.3 % of daytime productivity can be further harvested in the SCCS or DCCS, respectively, thereby causing further improvement in their net daily productivity and thermal efficiency by up to 30.75 % and 55.96 % of what the CS offers. It is also worth reporting that the currently proposed stills have not been found only efficient but economically reasonable as well. The cost analysis conducted has proven their economic feasibility compared to some relevant designs available in the literature. The DCCS has been found the least expensive to produce freshwater with $CPL=0.0065\$/l/m^2$ compared to $0.0077\$/l/m^2$ when using the SCCS, which though being a bit more costly but still economically outstanding. Finally, the modified stills exhibited superior exergoeconomic and enviroeconomic performance, with the DCCS achieving 22.10 kWh/$ (energy), 5.8 kWh/$ (exergy), and enviroeconomic savings of $517.27, highlighting its cost-effectiveness and sustainability.