Multi-stage power-to-water battery synergizes flexible energy storage and efficient atmospheric water harvesting

We propose and demonstrate a multi-stage power-to-water (MSP2W) battery that synergizes flexible energy storage and atmospheric water harvesting (AWH) to address renewable energy intermittency and freshwater scarcity simultaneously. This system integrates high-temperature magnesium oxide-based thermal energy storage (TES) with a modular multi-stage AWH device, using a Reline-based ternary solution to enhance sorption kinetics and enable efficient scalability. The multi-stage AWH configuration, with up to three stages, enhances water production by 51%, reducing energy consumption by 26%, consistent with theoretical analysis. The MSP2W prototype achieves daily water production of 3060 g, fully meeting an adult's demand. The specific energy consumption is as low as 1.13 kWh kg^-‍1, outperforming existing active AWH systems. The niche area of MSP2W is identified, even competing with desalination costs (<20 USD ton^-1 of optimal levelized cost of water). The system demonstrates scalability and cost-effectiveness, with the potential to fully mitigate water scarcity in regions with high renewable energy surpluses.