Optimal tilt angles of enclosed reactors for growing photoautotrophic microorganisms outdoors

The relationship between the tilt angle of a flat-plate photobioreactor and productivity of Spirulina platensis was evaluated along with the annual seasons under the climatic conditions of south Israel (latitude approx. 31°). The reactor tilt angle exerted a significant effect on the optimal population density and thus on the productivity of cell mass, owing to its control over the amount of solar radiation entering the reactor. A direct relationship between solar energy and productivity was observed: the higher the amount of solar energy that was admitted by varying the reactor tilt angle according to season, the higher was the productivity that could be sustained in the culture. Small tilt angles of 10° to 30° in summer and larger angles in the vicinity of 60° in winter resulted in maximal productivities for these seasons. Photosynthetic efficiency was calculated for the different tilt angles for all seasons. Efficiency was low in the winter due to temperature limitations. In summer it was highest in the 90° reactors, indicating that for optimal tilt angles in this season (in regards to productivity) a significant amount of radiation could not be effectively used by the culture. The results suggest a potential benefit in orientating and tilting reactors at various appropriate angles to the sun on a seasonal basis: up to 35% enhancement in annual output rate is estimated to be achievable.

[1]  A. Zemel,et al.  Validation of models for global irradiance on inclined planes , 1992 .

[2]  Ari Rabl,et al.  Active solar collectors and their applications , 1985 .

[3]  J. Myers,et al.  On the Mass Culture of Algae. II. Yield as a Function of Cell Concentration Under Continuous Sunlight Irradiance. , 1959, Plant physiology.

[4]  B. D. Hunn,et al.  Determination of average ground reflectivity for solar collectors , 1976 .

[5]  Yuan-Kun Lee Enclosed bioreactors for the mass cultivation of photosynthetic microorganisms: the future trend , 1986 .

[6]  P. Hartig,et al.  On the mass culture of microalgae: Areal density as an important factor for achieving maximal productivity , 1988 .

[7]  L. O. Lamm A new analytic expression for the equation of time , 1981 .

[8]  H Guterman,et al.  A flat inclined modular photobioreactor for outdoor mass cultivation of photoautotrophs , 2000, Biotechnology and bioengineering.

[9]  G. Torzillo,et al.  A two‐plane tubular photobioreactor for outdoor culture of Spirulina , 1993, Biotechnology and bioengineering.

[10]  J. Ryther,et al.  Photosynthesis in the Ocean as a Function of Light Intensity1 , 1956 .

[11]  J. C. Goldman,et al.  Outdoor algal mass cultures—II. Photosynthetic yield limitations☆ , 1979 .

[12]  P. Falkowski,et al.  Potential enhancement of photosynthetic energy conversion in algal mass culture , 1987, Biotechnology and bioengineering.

[13]  A. Richmond,et al.  Production of spirulina biomass: Effects of environmental factors and population density , 1982 .

[14]  Yuan-Kun Lee,et al.  Effect of photobioreactor inclination on the biomass productivity of an outdoor algal culture , 1991, Biotechnology and bioengineering.

[15]  G. C. Zittelli,et al.  A vertical alveolar panel (VAP) for outdoor mass cultivation of microalgae and cyanobacteria , 1991 .

[16]  F. E. Round,et al.  Progress in Phycological Research , 1994 .

[17]  Ephraim Cohen,et al.  A closed system for outdoor cultivation of Porphyridium , 1989 .

[18]  Giuseppe Torzillo,et al.  Production of Spirulina biomass in closed photobioreactors , 1986 .

[19]  Daniel Feuermann,et al.  Accurate field calibration of pyranometers , 1992 .