Integration of direct air capture with solar tower and chimney power plants: energy, economic and carbon assessments

The integration of concentrating solar power and direct air capture (DAC) systems remains limited by the high energy penalty, intermittency, and the lack of efficient system-level designs for waste heat utilization and cost reduction. This study evaluates the energy, economic, and carbon performance of an integrated system in which a DAC unit is installed between the towers of a solar tower power plant (STPP) and a solar chimney power plant (SCPP). This system aims to leverage the STPP waste heat to reduce DAC energy penalty, enhance SCPP electricity generation, and capture substantial amounts of CO₂. The feasibility of the system is analyzed under nine scenarios involving different waste heat recovery and supply configurations for CO₂ desorption and power generation. Furthermore, sensitivity analyses are performed, exploring the impact of key technical and economic parameters on overall performance. The integrated system reduces the electricity production costs by up to 35% compared to a conventional STPP, while further reductions in electricity costs can be achieved through lower interest rates, reduced capital and operating expenditures, and higher carbon taxes. Environmentally, the integrated system achieves a net CO₂ avoidance of up to 316 ktCO₂e/year for a STPP of 123 MW_e. Across all scenarios, harnessing the STPP condensation-based waste heat recovery combined with heat pumps or using STPP’s low-pressure steam for CO₂ desorption provides the most promising pathways for low-energy and cost-effective CO₂ capture. These configurations open new opportunities for simultaneous electricity generation and carbon removal with reduced energy and cost burdens.