Power-to-heat amine-based post-combustion CO₂ capture system with solvent storage utilizing fluctuating electricity prices

A thermal power plant employing amine-based post-combustion CO₂ capture (PCC) stands as a key technology for low-carbon, stable power sources aiming to economically achieve net zero CO₂ emissions in the electric power sector. However, the high cost associated with amine-based PCC has prevented its swift implementation. This study proposes a novel power-to-heat amine-based PCC system featuring solvent storage tanks. This system provides CO₂ absorption during the operation of the thermal power plant and facilitates CO₂ desorption through a heat pump driven by exceptionally inexpensive electricity procured during peak power generation periods from the grid. To demonstrate this concept, we evaluated the profitability of the proposed system using mathematical modelling and the calculation of the capital expenditure (CAPEX) and fixed operating expenses. The mathematical model optimizes the operational modes of the system facilities based on actual annual electricity prices. The results demonstrated that the novel PCC system decreased the average cost for energy consumption during the CO₂ stripping and compression process per tonne of CO₂ by approximately 30% compared with the conventional, flexible PCC system with venting. Consequently, it increased the net present value by approximately 15%. This showcases the feasibility of the power-to-heat amine-based PCC system in electricity markets prone to extreme fluctuations in electricity prices, where prices plummet during periods of surplus and escalate during peak demand. Notably, results also revealed that despite the low-capacity factor of the power plant (<30%) in such markets, retrofitting an amine-based PCC system into fully depreciated existing natural gas combined cycles yielded positive net present values even without economic incentives like credits for captured and stored CO₂ or grant funding for CAPEX. This suggests potential economic sustainability of the system, even in the imminent rise of inexpensive variable renewable energy. However, the results also indicated that such a low-capacity factor and high PCC CAPEX require high CO₂ price (350–400 USD/t-CO₂) to incentivize carbon capture and storage (CCS) adoption in a power plant in the market. Therefore, reduction in PCC CAPEX should be emphasized as a future challenge in the scenario of swiftly employing thermal power plants equipped with CCS as a dispatchable firm power source. Finally, implementing the power-to-heat amine-based PCC system will bolster power supply reliability and alleviate the curtailment of power generation caused by variable renewable energy sources.