Using the carbon dioxide basis, the photobioreactor system had to be designed with a large transparent surface area to allow sunlight to reach the algae. Different designs for accomplishing this were considered. The photobioreactor system requires a large volume of water and a large surface area that receives exposure to sunlight. The large volume of water is required because ethanol is produced at a very low concentration and is based off of the amount of carbon dioxide coming out of the gas sweetening process. A large area exposed to sunlight maximizes the conversion of carbon dioxide. Using the concentration of ethanol produced and the amount of carbon dioxide entering the process, a volume was calculated for the photobioreactor system.
Initial designs were for matrices of transparent tubes of various configurations. It was then hypothesized that the same results could be obtained using a network of large shallow ponds. The ponds would be covered to trap the carbon dioxide that leaves the solution and would also contain any liquid that may evaporate. The ponds would easily allow for a space time adjustment during times of maintenance as well as the ability to bypass portions in need of repair.
Photos of ponds: