Diffusion Strategy of Water Electrolytic Hydrogen in Desert Energy Systems and Ecosystems

Deploying photovoltaic (PV) systems in desert regions can support both decarbonization and ecological restoration, but conventional photovoltaic-to-grid (PVtG) strategies face increasing integration costs, curtailment, and value deflation as deployment scales up. This study proposes a novel water–energy–ecology coupling mode for desert PV development by integrating PVtG with onsite photovoltaic-to-hydrogen (PVtH) systems through segmented temporal partitioning. To evaluate this nexus, we develop a nonlinear multiscale framework that enables consistent evaluation of how local PV deployment decisions translate into system-wide decarbonization, financial cost, and biomass outcomes. Using the Kubuqi Desert—the seventh largest desert in China—as a testbed, we identify the scaling law of PV utilization by evaluating eight temporal partition strategies across PV capacities up to 25 gigawatts (GW). The results show that pure PVtG strategies exhibit diseconomies of scale, increasing unit cost by 1.6 × 10⁻³ USD·(kW·h)⁻¹. In contrast, hybrid strategies that allocate peak generation to PVtH reduce system costs by up to 1.0 × 10⁻³ USD·(kW·h)⁻¹. The cost-efficient 25 GW strategy annually withdraws 25.25 million tonnes (Mt) of water, delivers 25.30 TW·h of electricity, and produces 0.36 Mt of green hydrogen. This strategy achieves a 24 Mt reduction in CO₂ emissions and a 4 × 10⁴ t increase in biomass. This hybrid approach outperforms alternatives such as carbon capture and grass pads, with total cost savings of 0.90 billion USD. Sensitivity analysis further reveals that water availability and grid-side storage strongly affect the optimal partition trajectory, while carbon prices of 12.86–15.43 USD·tCO₂⁻¹ can close the financial gap without subsidies. To support implementation, water and land regulations and segmented power purchase agreements (PPAs) are recommended.