| Energy shortages and environmental pollution due to the large-scale use of fossil fuels is the key factor restricting development of human society at present and in the future. Therefore, the study of renewable and clean energy is gradually taken seriously. Wherein energy microalgae is widely concerned, due to its advantages of fast-growing, high oil production rate and do not take up farmland compared with traditional biomass. Photobioreactor is the key equipment carrying out large-scale,low-cost cultivate of energy microalgae. Its design and optimization depends on a detailed understanding of the radiation character compactly. Due to the difficulties of real-time measurement, the study of microalgae radiation characteristics aimed at the stationary growth phase. However, due to the growth and metabolism of micro algae cells, radiation characteristics of microalgae will vary with the growth process.At present, the radiation characteristics of microalgae during the growth is still lacking.In this paper, by design a photobioreactor can realize real-time measurement conveniently, measured the spectral radiation characteristics of Chlorella during growth experimentally, obtained the microalgae radiation characteristics data during the full growth, and on this basis, comparative analysis the impact on the optical field distribution forecast within the flat photobioreactor of use of only stable radiation characteristics and use of full growth radiation characteristics by numerical simulation.Experimental results show that during the different growth stages, Chlorella vulgaris spectral absorption cross section in the blue and red bands present three peaks(435 nm, 485 nm, 676 nm), which agree with the intracellular chlorophyll a and carotenoids absorption regional, and the wavelength dependence of the scattering cross section spectrum is more gentle. Spectral absorption cross sections throughout the growing period vary widely, up to 186% maximum variation. The microalgae has a strong forward scattering characteristics, the measured scattering asymmetry factor of about 0.97. Numerical simulations indicate that, for the analysis of the photobioreactor local optical field intensity distribution, using only the stable radiation characteristic data compared with the radiation characteristics data of growth, the relative deviation of average incident radiation up to 50%,indicating that it’s necessary to measure the growth radiation characteristics for the design and optimization of photobioreactor. The research methods and measurement results of this paper have a reference for the study of the microalgae growthradiation characteristics and the corresponding optical field distribution analysis within the photo bio-reactor. |
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