Investigation Of Structured Light Distributions for Algae Photobioreactor

Open Access
Gill, Manan
Area of Honors:
Engineering Science
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Noel Christopher Giebink, Thesis Supervisor
  • Barbara Shaw, Honors Advisor
  • Judith A Todd, Faculty Reader
  • algae
  • photobioreactor
  • flashing light effect
Fossil fuel dependance is one of the foremost issues of the modern age. Solar energy can meet demand but is hampered by storage and cost concerns. Biofuels are an attractive option for harvesting solar energy because they offer a storage medium that would not require significant changes in infrastructure. One issue plaguing biofuels is that an unsustainably large area of land would be required to produce enough fuel to meet demand. Algae are therefore considered one of the most promising candidates for biofuel research due to very high oil yields for a fixed production area. If algae are going to be used on a large scale, the amount of oil produced in a given area must increase. Artificial photobioreactors (PBRs), such as thin glass plates or tubes with algae suspended inside, are a topic of great research interest for increasing the density grown in a given volume. These have offered significant gains over ponds, most simple but inefficient method of growing algae, by eliminating shading losses from cells on the surface of the pond. Another increase in culture density is obtainable by flashing light at the cells. This lowers their susceptibility to damage from very intense light and can save power by energy only when the cells can optimally make use of it for photosynthesis. In order to more effectively make use of this flashing light effect in a passive system, novel PBRs will have to be constructed. It would be useful to be able to compare possible designs prior to physical construction by using a mathematical model for algae growth given the geometry of the reactor and illumination pattern. The contribution of this work is a three dimensional model for predicting algae growth, written in MATLAB. Two dimensional models have previously been developed and were extended into the third dimension. Additionally, arbitrary illumination patterns are easily added to model the effects of concentrating optics, gratings, etc. Square waves were implemented to test for a passive way to achieve the flashing light effect. Although an increase in production efficiency was found when cell motion was constant, brownian motion eliminated all benefits except that of concentrating the light. In the future, this model may be used with optical modeling programs to compare possible PBR designs.