PERFORMANCE ANALYSIS OF CONICAL SOLAR STILL BY INCORPORATING ENERGY METRICS AND EFFICIENCY ANALYSIS

Abstract

The design, installation and analysis of solar still is the need of the time as it can fulfil the freshwater need of the population without affecting adversely to the environment. The solar still is made in the form of a box having top surface made up of the glass or other similar materials and it uses the principle of greenhouse effect for its working. It can be easily fabricated using local available materials and works solely on solar energy and hence can be used even in the remote locations for getting freshwater from dirty water. The solar still can be of passive type or active type. In passive type of solar still, no heat is provided from the external heat source. If heat is provided from the external source to passive solar still, then the resulting solar still is active type and it addresses the low output of potable water from the passive type solar still. In the basin type solar still, the freshwater output is lower than the conical solar still (CSS) because of the shading effect in basin type solar still. In CSS, the transparent surface is provided in all the four directions which makes it susceptible to very low shading effect. Due to low shading effect, it has motivated researchers throughout the globe to work upon it. The present deals with the study on CSS analytically by incorporating several identical series connected evacuated tubular collectors (ETCs). The collectors have been connected in series because the series connection provides high temperature at low discharge which helps in increasing the output of potable water from the conical active solar still. The methodology involves the thermal modelling of NETC-CSS followed by energy, exergy, efficiency, exergy output per unit cost, enviroeconomic and productivity analyses. The thermal modelling means the development of characteristic equations using equations based on balancing heat for various components of NETC-CSS and solving these equations using the concept of mathematics for expressing unknown variables in terms of known variables so that the further analysis can be carried out using MATLAB. The output from MATLAB has been validated with data available in the literature and then further analysis has been carried out. v Concludingly, the optimized value for mass flow rate is determined to be 0.008 kg/s and optimized value for the number of evacuated collectors (N) is determined to be 15. Annual freshwater generation, energy, exergy, thermal efficiency and exergy efficiency for the proposed system are computed to be 2694.91 kg, 1796.61kWh and 170.19 kWh, 38.79% and 3.94% respectively. Annual freshwater yield, energy, exergy and exergy efficiency are higher respectively by 57.94%, 57.94%, 74.14% and 36.55% for the proposed system than the traditional conical solar still. A comparative analysis of results of present system with previously documented research represents that the increase in annual exergy, energy, thermal efficiency and exergy efficiency is 68.03% than modified solar still, 74.14% than conventional conical solar still, 61.12% than modified solar still and 72.59% than solar still with parabolic trough collector. While the exergoeconomic parameter is found to be 0.080 kWh/₹, the calculated annual productivity comes to 630.80% under optimal conditions with a 2% rate of interest. The production cost of fresh distilled water for NETC-CSS is ₹0.79 per kg, with a payback period of 4.03 years under a 2% rate of interest. The carbon credited for the NETC-CSS is valued at $5181 which corresponds to a carbon mitigation of 103.62 ton. This amount significantly surpasses that of a modified water-cooled solar still by 84.30%. The comparison highlights the superior environmental and economic benefits of the proposed system. Distilled water generated by use of NETC-CSS will be beneficial for use in batteries, various cosmetic products, as a coolant in automobiles, and in the pharmaceutical industry. In the battery sector, it will be used to maintain the proper chemical composition of battery cells, ensuring efficient performance and longevity. In the cosmetics industry, it will act as a key ingredient in the formulation of skincare products, where purity and pH balance are essential. It can be made suitable for human consumption by reintroducing essential minerals that are vi removed during distillation process. Small business of distilled water can be set up. It also finds utility in domestic settings, where it serves to purify harvested rainwater for household use.