報告書番号

U99054

タイトル（和文）

微生物によるCO2固定 １０． -螺旋状チューブラーリアクターでの受光に伴う熱収支評価-

タイトル（英文）

Microbial CO2 fixation 10. Evaluation of heat balance in cone-shaped helical tubular photobioreactor

概要 （図表や脚注は「報告書全文」に掲載しております）

螺旋状チューブラーリアクターでの年間を通じた効率的培養法を提案するため、リアクター内での熱収支の把握・評価法について検討した。室内で光照射条件及び室温を変化させ、様々な条件下においてリアクター各部の温度の経時変化を調べ解析した結果、各部での熱収支に関する相関関係を得た。この関係を用いて、培養液温の変化を予測した結果、夏季の屋外条件下において、実験結果と計算結果は良好に一致した。さらに、中温性クロレラを屋外培養した際に、加熱、冷却に必要となるエネルギー量を予測した。春季、秋季では加熱及び冷却はほとんど必要ないが、夏季では冷却を必要とし対策を講じる必要性が見られた。そこで、高温耐性クロレラを用いて夏季に屋外培養を行った結果、冷却を必要とせず高い生産性が得られた。季節によって温度特性の異なる藻類株を組み合わせることにより、年間を通じた効率的な光合成生産が達成できると考えられた。

概要 （英文）

When the photobioreactor incorporating microalgae is used for CO2 fixation/conversion under field condition through the year, it is necessary to keep the culture medium temperature to an appropriate range for an effective production of microalgal biomass. In this report, we evaluated the heat balance in photobioreactor for predicting the change of culture medium temperature and proposing an efficient photosynthetic production through the year. Based on the investigation of heat balance at three major parts (photostage part, degasser part and helical heat exchanger part) of the cone-shaped helical tubular photobioreactor (HTP), the experimental results of time-dependent changes of temperatures were analyzed at various illuminated and temperature conditions. The predictions of time-dependent changes of culture medium temperatures were examined using the heat transfer characteristics among three parts. The calculated results showed the similar time-dependent changes of temperatures to the experimental results in the laboratory experiments. Also, we could predict the time-dependent change of culture medium temperature under field condition. The prediction of time-dependent change of culture medium temperature caused by the changes of input radiance and temperature was considered to be possible using the analytical method based on the evaluation of heat balance in the cone-shaped HTP. Furthermore, the energy required for heating or cooling was predicted using above analytical method when the cone-shaped HTP would be used under field condition in Abiko City, Chiba Prefecture in Japan. Because we predicted that the culture medium temperature was maintained within an appropriate range of Chlorella sp. strain HA-1 (CRIEPI isolates, mesophilic strain), we considered that little energy for heating or cooling was necessary in spring and autumn. On the other hand, the culture medium temperature was predicted to be more than 40 ｻ}C in fine weather in summer. We decided that the application of high temperature tolerant Chlorella, which we isolated from a hot spring, was appropriate to the summer season. The efficient photosynthetic production was considered to be achievable through the year by the combination of various strains that had different characteristics to temperature, for example by the combination of mesophilic strain in spring and autumn and high temperature tolerant strain in summer.

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