Comprehensive analysis and experimental study on the novel intermittent solar-electric onion drying technology

The thermal performances and quality attributes of dried onion using stationary solar-electric drying (SED), intermittent solar-electric drying (ISED), and intermittent solar-electric drying with sensible storage medium (ISEDS) were compared. The tempering in processing time by 60 min elevated the drying time and reduced the diffusivity from 3.67 × 10−6 m2/s using SED to 2.06 × 10−6 and 2.11 × 10−6 m2/s using the ISED and ISEDS, respectively. The obtained drying efficiency was 21.05 %, 35.69 %, and 35.39 %, respectively, for the SED, ISED, and ISEDS. The average SEC values were found at 0.76 and 0.66 kWh/kg using ISED and ISEDS, respectively. The sustainability index (Si) and waste exergy ratio (WER) values were Si = 1.99, 1.45, and 1.51 and WER = 0.49, 0.63, and 0.61, respectively for SED, ISED, and ISEDS. The improvement potential (IP) of 1.69, 1.84, and 1.74 W were obtained using SED, ISED, and ISEDS, respectively. For SED, ISED, and ISEDS, the payback period (Pb) values were estimated at 1.08, 0.75, and 0.70 years, with the highest annual savings (Sj) obtained using the ISEDS at 16203.3 CNY. Better visual quality was observed for ISEDS. Compared to stationary drying processes using high-extensive energy dryers, intermittent solar drying is a promising technique for preserving agri-food products.