Marine microalga Chlorella vulgaris (henceforth referred to as C. vulgaris) was used in this study. The unialgal and axenic cultures of C. vulgaris was inoculated in 100 mL Erlenmeyer flask containing ASN-III medium and maintained in thermostatically controlled culture room at 25 °C with 1500 lx white fluorescent light illumination under 12:12 h L/. Briefly, C. vulgarisculture at stationary phase was centrifuged at 6000 rpm for 10 min, and the pellet was taken and supernatant was discarded. The pellet was added with distilled water, and again centrifuged at 6000 rpm for 10 min to remove any salt residues in the biomass pellet. The salt-free fresh biomass pellet was taken in a preweighed Petri. In the present study, box-type passive/direct type solar thermal dryer was designed and fabricated. A structural frame with the dimension of 20 cm × 15 cm × 11 cm (length × width × height) was designed for fabrication. The schematic diagram of BTPSD is shown in Fig. 8. The entire setup was fabricated with transparent glass materials, and the black. The known quantity of salt-free fresh biomass pellet (0.1 g) from “Harvesting of biomass for drying experiments” section was taken in a preweighed Petri dish and placed above the copper receiver plate of BTPSD. The solar dryer along with biomass was kept as due south facing with a 21 °tilt angle. Similarly, preweighed petri dish containing biomass. The performance of BTPSD with 4 cm TIM thickness was compared with the hot air oven system. The performance was evaluated based on the moisture removed, moisture content, the total energy required, and drying rate. The moisture content of the biomass depends on the relative humidity and temperature of the surrounding air. 1. i. Moisture content (MC.
