Design, Fabrication and Performance Analysis of a Solar Powered Outdoor Air Purifier Integrating HEPA Filtration and Lime-Soda CO₂ Absorption

Saqib Khan; Sana Ullah; Mudasir Shah; Sheroz Tahir; Muhammad Zaid Bukhari; Taimoor Abbas Khan; Muhammad Salman Azhar

Authors

Saqib Khan Department of Mechanical Engineering, University of Engineering and Technology, Peshawar 25120, Pakistan
Sana Ullah Department of Mechanical Engineering, University of Engineering and Technology, Peshawar 25120, Pakistan
Mudasir Shah Department of Mechanical Engineering, University of Engineering and Technology, Peshawar 25120, Pakistan
Sheroz Tahir Department of Mechanical Engineering, University of Engineering and Technology, Peshawar 25120, Pakistan
Muhammad Zaid Bukhari Department of Mechanical Engineering, University of Engineering and Technology, Peshawar 25120, Pakistan
Taimoor Abbas Khan Department of Mechanical Engineering, University of Engineering and Technology, Peshawar 25120, Pakistan
Muhammad Salman Azhar Department of Mechanical Engineering, University of Engineering and Technology, Peshawar 25120, Pakistan

Keywords:

Outdoor Air Purifier, HEPA Filtration, Lime-Soda CO₂ Absorption, Solar Power, Air Quality Monitoring

Abstract

Rising air pollution in South Asian cities such as Peshawar, Pakistan, frequently pushes Air Quality Index levels far beyond WHO limits, yet commercial air purifiers, being grid-dependent and built for enclosed spaces, cannot protect people at high-exposure outdoor sites such as traffic intersections, bus stops, and school courtyards. No previously published system has been found to integrate HEPA particulate filtration with lime-soda chemical CO₂ absorption within a single solar-powered, grid-independent outdoor unit, forming the core novelty of this work. A prototype was modeled in SolidWorks and fabricated with a welded 304 stainless-steel frame housing an H-13 HEPA filter and a Ca (OH)₂ lime-soda bed, powered by two 200 W PV panels, an MPPT controller (93–97% conversion efficiency), and a 35 Ah battery, with monitoring via NDIR CO₂ and optical PM2.5 sensors, and evaluated through four replicate laboratory and field trials. The HEPA stage achieved a mean PM2.5 removal efficiency of 95.6% ± 0.86% (range 94.6–96.9%), reducing outlet concentrations to 1.5–8.5 µg/m³, within the WHO 24-hour guideline of 15 µg/m³. The lime-soda bed achieved a mean CO₂ reduction of 59.5% ± 0.37% (range 59.0–59.9%), lowering CO₂ from 995 ± 9.4 ppm to 405 ± 3.2 ppm, confirmed by mass-balance verification. The integrated system delivered a Clean Air Delivery Rate (CADR) of 286 m³/h, comparable to commercial units, and the solar-battery subsystem recharged fully within approximately 2 hours under typical local irradiance, sustaining continuous grid-independent operation with battery levels maintained above 70% throughout testing. These findings show the proposed purifier is a technically feasible, cost-effective, locally manufacturable solution for outdoor air quality improvement in developing countries, directly supporting the UN Sustainable Development Goals (SDGs).

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