Design optimization of large-scale attached cultivation of Ettlia sp. to maximize biomass production based on simulation of solar irradiation

Abstract

In support of successful biomass production of green microalga Ettlia sp. through attached cultivation, estimation of footprint biomass productivity and optimization of the system was evaluated through comprehensive simulation of solar irradiation. Both temporal and spatial variation of solar irradiation and biomass productivity on the surface of the microalgae-attached panel (MAP) with every combination of design factors (tilt angle, facing direction, height, and distance of the MAP) were closely studied. While an increase in the height to the distance ratio (HDR) increased footprint biomass productivity, fixing the distances at their minimum made steeper tilt angle more favorable for footprint biomass productivity by having a smaller minimum distance. Footprint biomass productivity over the height revealed another important design index, a critical height, where footprint biomass productivity becomes maximum and saturated. Ultimately, three optimum conditions were identified based on economic circumstances: (1) double-side vertically standing MAP facing east/west, (2) 1 m high single-side MAP facing south with seasonal optimum angles, and (3) over 2.5 m high single-side MAP facing west with seasonal optimum angles. Corresponding estimated yearly average footprint biomass productivities were 22, 11, and 11.5 g/m2/day at the height of 3 m, 1 m, and 3 m, respectively.