Achieving near-zero emissions and cost-effective hydrogen production through the Allam cycle and solid oxide electrolysis cells integration

Various studies have been conducted to reduce the levelized cost of hydrogen (LCOH), but green hydrogen still has a relatively high LCOH. This study proposes the thermal integration of the Allam cycle with a solid oxide electrolysis cell (SOEC), resulting in improved energy efficiency, a reduction in LCOH through electricity sales, near-zero CO₂ emissions, and water resource recycling. The Allam cycle is a power plant that utilizes supercritical CO₂ as a working fluid, while SOEC is an electrolysis process that produces hydrogen from steam. Both processes require high-temperature heat. Additionally, the Allam cycle generates deionized water as a byproduct, which can be used in SOEC. The integrated process demonstrates an energy efficiency of 58.69 %, superior to the general Allam cycle, which exhibits approximately 55 % energy efficiency. Furthermore, the LCOH is reduced to $1.983 due to the sale of generated electricity, which is lower than the $5.00 for green H₂ produced via SOEC and comparable to the $2.00 for blue H₂. Continuous advancements in SOEC technology may enable the LCOH to fall below $1.5, which would be similar to that of grey H₂. The carbon emissions are reduced to 0.07 kg-CO₂/kg-H₂, demonstrating a 97.08 % reduction compared to the 2.4 kg-CO₂/kg-H₂ emissions of blue H₂. A sensitivity analysis was conducted for variables affecting LCOH, indicating that the LCOH remains lower than that of green H₂ in all scenarios. This study contributes to achieving net-zero emissions and a feasible LCOH in the future.