Pathways to cost-effective electrochemical CO₂ reduction: Role of energy mix, intermittency, and weather conditions in formic acid production

The electrochemical reduction of CO₂ to formic acid represents a promising avenue for renewable energy storage and carbon utilization. Its feasibility depends on electricity supply configuration, intermittency, and regional energy characteristics. This study introduces an intermittency-aware, system-level framework that explicitly addresses hourly renewable variability and modular electrolyzer load-following under dynamic power conditions, in contrast to conventional techno-economic assessments that assume a steady-state electricity input. A dynamic model incorporating a three-compartment electrolyzer, downstream separations, and renewable intermittency is developed across four locations with varying weather and grid profiles. Economic and environmental performance is evaluated, including levelized cost of formic acid, net present value, return on investment, CO₂ abatement cost, and global warming intensity under conservative, moderate, and optimistic scenarios across the period 2030-2050. Wind-rich locations enable renewable-only CO₂ electrolysis, achieving levelized formic acid costs of 0.46-0.50 $/kg by 2050, below current market prices, while reaching negative CO₂ abatement costs. Hybrid PV-wind systems approach competitiveness (0.53-0.57 $/kg) without storage, whereas battery integration becomes unfavorable beyond short durations (>4 h). Grid electricity significantly degrades economic and environmental performance, especially under carbon pricing. Overall, CO₂ electrolysis viability is strongly location-dependent and governed by renewable quality, limited storage, and constrained grid use.