||Compared to terrestrial plants algae with high productivity characteristics, they are optimistically considered as a potential candidate to be biomass fuels. Based on the solar energy point of view, this study is to investigate the path of energy absorption by the microalgae vertical photobioreactor at outdoor culture, and establishes a numerical model to estimate the average received seasonal light intensity and the optimal arrangement for a set of vertical photobioreactors at open field. Taking Kaohsiung as an example, the projected daily Solar altitude, Solar azimuth and Solar radiation, coupled with the loss of Snell's law and Fresnel equation is used to obtain the actual light intensity penetrating into the wall of container. The light attenuation in the culture medium is estimated according to Bill Lambert law. This study also established a model to explore the shadow effect created by other nearby photobioreactors when a large scale production of microalgae implemented. |
The results are as followings: The vertical photobioreactor reflection losses throughout the year averaged about 10.9%; during spring and autumn it captures the largest amount of solar radiation, then winter, and summer is minimum, since during summer time the sun is moving upright overhead causing the light reflects more and less penetrates into the container. Taking diameter 50 cm vertical photobioreactor for example, the average light intensity in the medium of algae in about 500 (μmol∙m-2∙s-1), while the winter solstice day average light intensity algae solution changes at least, the greatest change in the summer solstice. The shadow effect study shows that the arrangement of the east-west direction spacing has more impact than north-south, and their EW gap of spacing between each barrel should be at least 80% height, while NS direction could be moderately reduced.