Breaking the Solar Load-Demand Mismatch: Adsorption Cascade Cycle with Mil-101 Achieving Yearlong Thermal Management

Abstract

Climate extremes amplify thermal stress, whereas building thermal management infrastructure exacerbates this crisis through positive feedback mechanisms. Solar-powered systems present a promising pathway, yet their intermittency and suboptimal thermal conversion efficiencies create implementation barriers for carbon-neutral buildings. This research presents a chemical-physical adsorption cascade cycle with MIL-101 and CaCl2 that achieves a breakthrough by lowering the desorption temperature to 70 °C. This thermal management capability enables reconciliation of thermal loads and demand through temporally decoupled energy storage and dispatch mechanisms. The reduction in desorption temperature enables the system to perform energy storage during the spring, summer, and autumn seasons and then release heat through adsorption in winter. The maximum energy storage density reaches 1673 kJ/kg, with a maximum heat storage efficiency of 0.64. In the summer cooling mode, the coefficient of performance can reach 0.37. Additionally, it can still supply cooling capacity even in extremely high temperatures (40°C) in summer. The cycle integrates the flexible desorption temperature of physisorbents with the robust adsorption kinetics intrinsic to chemisorbents. This study resolves long-standing contradictions in the interdependence between desorption and adsorption temperatures, while unlocking transformative potential in low-grade thermal energy utilization and thermal management for carbon-neutral buildings.

Keywords: Ammonia adsorption, energy storage, Seasonal thermal management, Solar thermal batteries