Low-cost, net-negative carbon coproduction of electricity and methanol via solar-driven steam electrolysis with enhanced syngas-to-methanol conversion

Integrating methanol synthesis into concentrated solar power systems enables efficient electricity and fuel coproduction, but existing coproduction systems struggle to balance cost and carbon emissions. This study proposed a novel system using calcium looping (CaL)-stored heat and surplus power to couple solar energy with renewable electricity. Solar-driven bi-reforming with non-traditional raw material molar ratios enhances methane conversion during syngas production. CaL-driven solid oxide steam electrolysis facilitated syngas-to-methanol conversion. These measures jointly addressed the challenge of low-cost fuel production, carbon neutrality, and high energy efficiency. The system achieved a methanol production capacity of 191.84 t/h, coupled with a net-negative CO2 emission of −0.036 t per ton of methanol and an overall energy efficiency of 57.34%. Compared with the syngas-based methanol synthesis process, it achieved an 8.52% increase in yield and a 21.07% relative enhancement in energy efficiency. Exergy analysis identified heliostat fields (49.88% efficiency) and solid oxide electrolysis cells (68.77% efficiency) as major exergy-loss components. Economic analysis demonstrated a levelized cost of electricity as low as 160.50 $/MWh and a levelized cost of methanol at 346.96 $/t, considering changes in renewable electricity prices. The proposed system offers promise for sustainable clean energy production.