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熱を活用する: 流動層反応器が再生可能エネルギーを蓄える方法
伏見研究室は、再生可能エネルギーからのエネルギーを蓄えるための流動層反応器の効率を改善する新しいモデルを開発しました。このモデルは、システム内の熱と物質の輸送をよりよく管理するために、異なるタイプの反応器を組み合わせています。
この研究は、太陽光や風力などの再生可能エネルギー源で一般的な、変動する熱供給に対処するために、これらの反応器がどのように機能するかに焦点を当てました。伏見研究室は、窒素または蒸気を流動化ガスとして使用し、反応器が安定した温度を維持できるかどうかをテストしました。
彼らは、窒素が熱供給の変化に対してより敏感であり、蒸気と比較して大きな温度変動を引き起こすことを発見しました。これは、窒素での脱水プロセスが温度により依存しているためです。
システムの効率は、熱化学的熱蓄積効率とエネルギー蓄積効率の2つの方法で測定されました。蒸気の場合、これらの効率はそれぞれ14.1％と34.1％でした。窒素の場合、それらはそれぞれ29.9％と62.7％と高くなりました。
効率の違いは、蒸気中の水の潜熱によるものです。研究はまた、熱供給を増やすことで効率が向上することを示しました。これは、反応温度に達するために必要な時間が短縮されるためです。
要するに、流動層反応器は再生可能エネルギー供給の変動を効果的に吸収できるため、エネルギー蓄積のための有望な技術です。
Harnessing Heat: How Fluidized Bed Reactors Can Store Renewable Energy.
Fushimi Lab (research group) has developed a new model to improve the efficiency of fluidized bed reactors, which are used to store energy from renewable sources. This model combines different types of reactors to better manage the heat and mass transport within the system.
The study focused on how these reactors can handle fluctuating heat supplies, which is common with renewable energy sources like solar and wind power. By using either nitrogen or steam as the fluidizing gas, the researchers tested how well the reactors could maintain a stable temperature.
They found that nitrogen was more sensitive to changes in heat supply, causing larger temperature fluctuations compared to steam. This is because the dehydration process in nitrogen is more dependent on temperature.
The efficiency of the system was measured in two ways: thermochemical heat storage efficiency and energy storage efficiency. For steam, these efficiencies were 14.1% and 34.1%, respectively. For nitrogen, they were higher at 29.9% and 62.7%.
The differences in efficiency are due to the latent heat of water in steam. The study also showed that increasing the heat supply improved efficiency because it reduced the time needed to reach the reaction temperature.
In summary, fluidized bed reactors can effectively absorb fluctuations in renewable energy supply, making them a promising technology for energy storage.
Takayuki Uchino, Chihiro Fushimi: Fluidized bed reactor for thermochemical heat storage using Ca(OH)2/CaO to absorb the fluctuations of electric power supplied by variable renewable energy sources: A dynamic model,
https://doi.org/10.1016/j.cej.2021.129571
Abstract: A simplified dynamic model of a Ca(OH)2/CaO–containing fluidized bed reactor was developed by combining a continuously stirred tank reactor model in the solid phase with a series of continuously stirred tank reactors in the gas phase for mass transport. The heat supplied to the thermochemical heat storage system was allowed to fluctuate to evaluate the absorption of variable renewable energy fluctuation. In addition, the performance of the fluidized bed was assessed using nitrogen or steam as the fluidizing gas. For nitrogen, the fluctuation of bed temperature increased with the increasing time step of heat change. The bed temperature was affected by the magnitude of the fluctuation of the supplied heat more strongly for nitrogen than for steam, mainly because the rate of dehydration under these conditions was more strongly dependent on temperature than in the case of steam. The thermochemical heat storage efficiency (calculated by considering reaction heat) and energy storage efficiency (calculated by considering reaction heat and sensible heat) equaled 14.1% and 34.1% for steam and 29.9% and 62.7% for nitrogen, respectively. The differences between the efficiencies for steam and nitrogen were ascribed to the latent heat of H2O. Sensitivity analysis showed that both efficiencies increased with increasing heat supply because of the concomitant decrease in the time required to heat the system to the reaction temperature. During this time, thermochemical heat storage did not occur, which resulted in lower efficiency. Therefore, the fluctuation from variable renewable energy can be absorbed by using thermochemical heat storage.
Keywords: Variable renewable energy (VRE); Thermochemical heat storage; Ca(OH)2/CaO; Fluidized bed; Dynamic simulation