Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Mechanical and Aerospace Engineering


Byard Wood


The work presented here investigated two methods of improving productivity in microalgal photobioreactors: applying temperature cycles intended to maximize photosynthesis and minimize respiration, and development of a mathematical model that predicts improvements in photon utilization using temporal light dilution (flashing).

The experiments conducted on diurnal temperature cycles with Dunaliella tertiolecta in 30-L outdoor photobioreactors showed that a properly chosen temperature cycle can improve mass and energy productivity by 18% over an identical photobioreactor with a constant temperature. However, excessively large temperature cycle amplitudes reduced productivity. A 4-7% increase in energy content was observed in microalgae exposed to temperature cycles. The physiological reason for this could not be established.

A relationship similar to the Bush Equation was obtained that related photon utilization efficiency to flashing frequency, load factor, Photosystem II (PSII) concentration and reaction frequency, and chlorophyll content. The model was validated by the experimental data of a number of researchers.