Enhanced Thermochemical Energy Storage Stability of CaO-Based Composite Pellets Incorporated with a Zr-Based Stabilizer

Calcium looping is a potential thermochemical energy storage technology applied in a high-temperature working window. However, CaCO3/CaO materials are prone to encounter severe sintering, exhibiting poor thermal energy storage/release stability. To improve the thermochemical energy storage stability, different amounts (5, 15, and 30 wt %) of a Zr-based stabilizer were incorporated into CaCO3/CaO materials. Moreover, the graphite-casting method was adopted to prepare the Zr-stabilized, CaO-based composite pellets aiming to improve the practicability. The incorporation of the Zr-based stabilizer can effectively resist the sintering of CaO-based composite powders during a high-temperature precalcination process. It is mainly attributed to the large amounts of generated, nanosized CaZrO3 grains possessing desirable antisintering ability evenly distributed within the composites. Particularly, the Zr-stabilized, CaO-based composite pellets containing 30 wt % of CaZrO3 possess a relatively high compression strength of 2.28 ± 0.87 MPa and a desirable thermal storage density of 1.15 GJ/t after 20 cycles. Additionally, the graphite-casted, Zr-stabilized, CaO-based composite pellets have potential to be applied in a large-scale thermochemical energy storage system because the graphite-casting method is easy to be scaled-up.