Ternary Deep-Eutectic-Solvent Tuned by Carbon-Quantum-Dot for Large-Concentration-Glide and Highly-Stable Membrane-Mediated Microchannel Absorption Thermal Battery with Swirling Enhancement

Buildings are responsible for 20–40% of the world’s energy use and 90% of Hong Kong’s electricity consumption. Advances in energy efficiency and low-GWP refrigerant are both essential for building decarbonization. Utilizing renewable/waste energy is promising, but intermittent energy availability causes inefficiency and under-utilization. Thermal batteries play a significant role in low-carbon energy transition by balancing the supply-demand mismatch. Compared to existing thermal batteries, absorption thermal batteries (ATBs) show great advantages in energy storage density, energy storage efficiency, charging temperature, response rate, and flexibility (discharged for cooling/heating/dehumidification). Besides energy decarbonization, ATB also merits refrigerant decarbonization by using zero-GWP natural fluids like H2O. All these advantages facilitate more sustainable utilization of renewable/waste energy forbuildings.However, existing ATB technologies face four major challenges preventing wider application: (1) high crystallization risk (low reliability), (2) high material cost (low costeffectiveness), (3) poor transport property (low efficiency, slow response), and (4) large reactor size (low density). This proposal seeks to address these deficiencies by developing novel ternary deep-eutectic-solvent (DES) tuned by carbon-quantum-dot (CQD) for membrane-mediated microchannel absorption thermal battery (MMATB) with swirling enhancement. Ternary DESs fabricated by inexpensive methods can eliminate crystallization even under high concentration glides while maintaining excellent transport properties. CQDs can stably enhance heat/mass transfer of ternary DESs without deposition risks. The MMATB offers ultra-high compactness via large specific surface area and bidirectional heat/mass transport switching within single reactor.Additionally, groove-induced swirling flow and machine-learning-based geometry optimization further enhance heat/mass transfer with reduced pressure drop, particularly benefiting DES adoption in MMATB.Preliminary studies demonstrate high viability and cost-effectiveness of the MMATB. Numerical and experimental methods will be employed to complete the following objectives: (1) Model and prototype development of MMATB using CQD-tuned ternary DES for large-concentration-glide and highly-stable energy storage; (2) Characterization of thermophysical properties, sorption kinetics, heat/mass transfer and cycling stability of CQD-tuned ternary DES with various compositions; (3) Investigation of transient charging/discharging behaviors and energy storage performance of MMATB under various working conditions; and (4) Machine-learning-based multi-scale absorbent-battery-building co-optimization to maximize overall performance for different application scenarios. This research is significant for developing highreliability, cost-effective, high-efficiency, fast-response and high-density energy storage, offering promising building decarbonization solutions. The energy savings are estimated to be 50–80% with payback periods of 2–4 years. It will contribute towards healthy indoor environment, carbon neutrality, and sustainable development goals inHong Kong and around the world.