M. Morita et al., Evaluation of photobioreactor heat balance for predicting changes in culture medium temperature due to light irradiation, BIOTECH BIO, 74(6), 2001, pp. 466-475
Microalgal photosynthesis requires appropriate culture medium temperatures
to achieve high photosynthetic performance and to maintain production of a
high-quality biomass product. Enclosed systems, such as our conical, helica
l tubular photobioreactor (HTP), can accomplish high photosynthetic efficie
ncy and the small amount of culture medium used by these systems means that
the culture medium temperature may be effectively controlled. On the other
hand, because a high ratio of surface area to culture medium volume leads
to rapid heating under the illumination condition and substantial heat loss
at night, maintaining a suitable culture medium temperature is necessary t
o achieve efficient, commercially practical biomass production. In order to
predict changes in the culture medium temperature caused by changes in sol
ar irradiance and ambient temperature, it is necessary to understand the he
at balance within the photo bioreactor. We therefore investigated the heat
balance in three major parts (photostage, degasser, and helical heat exchan
ger) of our conical HTP, analyzed the time-dependent changes in medium temp
erature at various room temperatures and radiant energy inputs, and predict
ed changes in the culture medium temperature based on the characteristics o
f heat transfer among the three parts. Using this model, the predicted chan
ges in culture medium temperature were very similar to the changes observed
experimentally in the laboratory and under field conditions. This means th
at by calculating the time-dependent changes in the culture medium temperat
ure, based on measurements of solar energy input and ambient temperature, w
e should be able to estimate the energy required to maintain the culture me
dium temperature within a range where photosynthetic performance of microal
gae is high. (C) 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 74: 466-475
, 2001.