Design Optimization and Global Impact Assessment of Solar-Thermal Direct Air Carbon Capture.

The dual challenge of decarbonization and rising global energy demand underscores the need for scalable, cost-effective carbon dioxide removal technologies. Direct air capture (DAC) is promising, but its high energy intensity, especially the heat required for sorbent regeneration, remains a barrier to cost reduction and sustainable deployment. This study evaluates solar-thermal DAC systems that combine concentrated solar thermal technology with low-cost sand thermal energy storage. We analyze techno-economic performance in grid-connected and stand-alone configurations. Results show that solar-thermal DAC can achieve annual capacity factors above 80%, with baseline core-technology CO2 removal costs of $160-$200 per ton and deployment-adjusted costs of roughly $300-$350 per ton after accounting for financing, labor, and land-related assumptions. The system performs best with short-cycle sorbents aligned with solar availability. Stand-alone solar-DAC, powered entirely by solar heat and electricity, is particularly promising in high-solar, sandy regions with low ambient sensitivity to temperature and humidity. An optimized 6000 ton/yr modular design requires <1 km2 of land, and sandy terrains alone could support >26 Gt/year of DAC capacity globally. In sedimentary basins suitable for CO2 storage, solar-DAC offers a lower-cost alternative to geothermal heating.