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

TL;DR

This paper proposes a solar-thermal direct air capture system using sand-based thermal storage, achieving low costs and high capacity factors, especially suitable for sunny regions with sandy terrain, advancing scalable CO2 removal.

Contribution

It introduces a novel solar-thermal DAC design with low-cost sand thermal storage, demonstrating competitive costs and high efficiency in both grid-connected and stand-alone modes.

Findings

Achieves CO2 removal costs of 160-200 USD/ton.

Exceeds 80% annual capacity factor in optimal conditions.

Potential for >26 Gt/year global DAC capacity in suitable regions.

Abstract

The dual challenge of decarbonizing the economy and meeting rising global energy demand underscores the need for scalable and cost-effective carbon dioxide removal technologies. Direct air capture (DAC) is among the most promising approaches, but its high energy intensity, particularly the thermal energy required for sorbent regeneration, remains a critical barrier to cost reduction and sustainable deployment. This study explores solar-thermal DAC systems that combine concentrated solar thermal technology with low-cost sand-based thermal energy storage to meet this demand. We analyze the techno-economic performance of such systems in both grid-connected and stand-alone configurations. Results show that solar-thermal DAC can achieve annual capacity factors exceeding 80% and CO2 removal costs as low as 160-200 USD per ton, making it competitive with leading DAC technologies. The proposed system operates most efficiently with short-cycle sorbents that align with solar availability. The stand-alone Solar-DAC systems, which rely solely on solar energy for both electricity and thermal energy, are particularly promising in regions with high solar capacity and sandy terrain, exhibiting minimal ambient sensitivity from temperature and humidity. An optimal 6000 ton/yr modular system design takes <1 km2 land-use requirement and potentially >26 Gt/year DAC capacity is identified for sandy terrain alone globally. In areas with sedimentary basins suitable for CO2 storage, solar-powered DAC offers a lower-cost alternative to geothermal heating, which often faces geological and economic constraints.