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<p>Thermochemical energy storage (TCES) under direct irradiation mode is a promising technology that promotes the widespread utilization of high-temperature concentrated solar energy. However, poor cyclic stability and solar absorption for calcium carbonates, high cost for cobalt oxides, and safety issues for powder-form materials hinder the practical applications of the TCES systems. This work innovatively proposed a compressed reactive TCES unit composed of 10%-volume of modified Co<sub>3</sub>O<sub>4</sub> in the center and 90%-volume of modified CaCO<sub>3</sub> around the center. The modified calcium-based compacted material (CaCO<sub>3</sub>M-p) exhibits 20.5°C lower onset temperature, 13.9 kJ mol<sup>−1</sup> lower activation energy, and faster kinetics than the commercial CaCO<sub>3</sub> powder (CaCO<sub>3</sub>-u) in the energy storage process. Both the cyclic stability in 15 cycles and solar absorption of the CaCO<sub>3</sub>M-p are boosted, which are 1.25 times and 18.3 times those of the CaCO<sub>3</sub>-u, respectively. While compaction reduces the reactive performances by narrowing the porous, the Mn/Mg co-modification has a more significant effect in increasing the above properties by creating lattice defects and introducing impurities. The modified cobalt-based compacted material (Co<sub>3</sub>O<sub>4</sub>M2-p) presents similar reactive and optical properties as raw Co<sub>3</sub>O<sub>4</sub> powder, yet it elevates the average conversion rate in 30 cycles to 1.75 times that of compressed raw Co<sub>3</sub>O<sub>4</sub>. Modification by microcrystalline cellulose is the key to this improvement, as it reduces activation energy and promotes decomposition kinetics for compacted Co-based materials. The compressed reactive TCES unit demonstrates outstanding energy storage density and power. The 10%-volume Co<sub>3</sub>O<sub>4</sub> improves external radiation absorption and reinforces internal heat transfer, enhancing the unit’s energy storage rate. Moreover, Co<sub>3</sub>O<sub>4</sub> also contributes to energy density, raising the total density to 0.4217 MWh m<sup>−3</sup>, exceeding the 0.2468 MWh m<sup>−3</sup> limit of CaCO<sub>3</sub> powder. The compacted materials and composite unit advance the practical use of TCES in solar energy storage.</p>

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Compressed reactive unit of CaCO3 and Co3O4 with improved solar absorption and energy density for thermochemical energy storage

  • 期刊论文

  • 发表日期：

    2025年4月17日

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  • Sijia Guo,
  • Xikun Tian,
  • Jun Yan,
  • Chaolin Shang,
  • Changying Zhao

摘要

Thermochemical energy storage (TCES) under direct irradiation mode is a promising technology that promotes the widespread utilization of high-temperature concentrated solar energy. However, poor cyclic stability and solar absorption for calcium carbonates, high cost for cobalt oxides, and safety issues for powder-form materials hinder the practical applications of the TCES systems. This work innovatively proposed a compressed reactive TCES unit composed of 10%-volume of modified Co3O4 in the center and 90%-volume of modified CaCO3 around the center. The modified calcium-based compacted material (CaCO3M-p) exhibits 20.5°C lower onset temperature, 13.9 kJ mol−1 lower activation energy, and faster kinetics than the commercial CaCO3 powder (CaCO3-u) in the energy storage process. Both the cyclic stability in 15 cycles and solar absorption of the CaCO3M-p are boosted, which are 1.25 times and 18.3 times those of the CaCO3-u, respectively. While compaction reduces the reactive performances by narrowing the porous, the Mn/Mg co-modification has a more significant effect in increasing the above properties by creating lattice defects and introducing impurities. The modified cobalt-based compacted material (Co3O4M2-p) presents similar reactive and optical properties as raw Co3O4 powder, yet it elevates the average conversion rate in 30 cycles to 1.75 times that of compressed raw Co3O4. Modification by microcrystalline cellulose is the key to this improvement, as it reduces activation energy and promotes decomposition kinetics for compacted Co-based materials. The compressed reactive TCES unit demonstrates outstanding energy storage density and power. The 10%-volume Co3O4 improves external radiation absorption and reinforces internal heat transfer, enhancing the unit’s energy storage rate. Moreover, Co3O4 also contributes to energy density, raising the total density to 0.4217 MWh m−3, exceeding the 0.2468 MWh m−3 limit of CaCO3 powder. The compacted materials and composite unit advance the practical use of TCES in solar energy storage.