Decarbonizing power systems is crucial for climate change mitigation. Achieving a reliable and resilient near-zero emissions power system, however, remains a challenge. Current approaches often focus on high shares of renewable energy (solar PV and wind), but their intermittency poses significant risks to stability and reliability. To address this, energy storage and extensive transmission infrastructure are needed, potentially increasing costs. This study explores an alternative: integrating a high share of renewable energy with fossil fuels utilizing CCUS. This approach offers several advantages. First, abated fossil fuel power generation can provide firm, low-carbon electricity, reducing reliance on extensive energy storage and transmission. Second, CCUS-equipped fossil fuel plants are less vulnerable to weather extremes than other low-carbon sources. Third, while currently expensive, CCUS technology is rapidly developing. The study aims to quantitatively compare the cost-effectiveness, reliability, and resilience of a 100% renewable system versus a high-renewable system incorporating CCUS-equipped fossil fuels, specifically focusing on China due to its unique energy context and heavy reliance on coal.

Existing research has investigated 100% renewable systems and fossil fuel systems with CCUS separately. Some studies suggest the feasibility of 100% renewable systems globally and nationally, emphasizing the importance of long-duration storage and expanded transmission. Conversely, other research, particularly integrated assessment modeling (IAM), highlights the economic benefits of including CCUS-equipped fossil fuels to complement renewables for deep decarbonization. However, direct comparisons of these approaches under the same modeling framework, especially considering high-resolution temporal and geographical details, have been lacking. Existing power system optimization models generally lacked the detailed facility and geological constraints of CCUS-enabled power plants, leading to potential biases. This study addresses these gaps by providing a high-resolution integrated assessment of both approaches under a unified framework.

The researchers constructed a high-resolution integrated power system assessment model for China's 31 provinces (excluding Hong Kong, Macau, and Taiwan). The model integrates six interlinked modules: (1) hourly electricity demand prediction for 2050; (2) hourly solar PV and wind power generation potential estimation; (3) a CCUS source-sink optimal matching model for retrofitting existing fossil fuel plants; (4) an integrated simulation model for hourly power system supply-demand balance, considering energy storage duration, interprovincial transmission capacity, and CCUS-constrained fossil fuel generation; (5) a cost-competitive analysis model; and (6) a simulation model for the impact of extreme weather events on power generation and shortages. The model simulates 10,450 scenarios by combining different storage durations, transmission capacities, and shares of abated fossil fuel power generation with CCUS. Specifically, the model downscales annual renewable energy potential to hourly data using historical climate information. Electricity demand is predicted using econometric models and downscaled to the hourly level, incorporating workday and non-workday load variations. The CCUS source-sink matching model identifies optimal links between fossil fuel plants and CO2 storage sites, considering geological constraints and transport distances. The integrated simulation model analyzes power system reliability and calculates the power shortage rate under each scenario. Cost-competitive analysis then identifies the lowest-cost power mix. Finally, simulations of extreme weather events (snowstorms, sandstorms, droughts, and heat waves) assess system resilience.

The study reveals three major findings: (1) Incorporating CCUS-equipped fossil fuels (up to 20%) significantly reduces the need for transmission capacity and short-term energy storage to achieve a specific power shortage rate, leading to lower costs compared to a 100% renewable system. For example, to achieve a low national power shortage rate, a system with 20% abated fossil fuels requires less transmission capacity and shorter energy storage duration compared to a zero-fossil fuel system, resulting in a 3.0% decrease in the levelized cost of energy (LCOE). (2) The optimal cost-effective power system configuration involves approximately 16% abated fossil fuel power generation, resulting in a 2.5% reduction in overall system cost ($16.8 billion) compared to a zero-fossil fuel system, while maintaining high reliability (99.9%). (3) The lowest-cost system (with 16% abated fossil fuels) shows higher resilience to extreme weather events than the zero-fossil fuel system. Power shortages during snowstorms, sandstorms, and droughts were significantly lower (54%, 56%, and 57%, respectively) in the system with abated fossil fuels. The study also finds that long-term energy storage, such as hydrogen storage, can play a vital role in achieving even higher reliability standards, particularly when stringent power shortage targets are set. The optimal power system configuration suggests a significant contribution of CCUS-equipped fossil fuels, particularly in regions with high electricity demand and limited renewable resources. The regional distribution of CCUS plants shows a concentration in central and coastal regions, reflecting the distribution of existing fossil fuel plants and suitable CO2 storage sites.

The findings challenge the sole reliance on 100% renewable energy systems for deep decarbonization, particularly in contexts with significant existing fossil fuel infrastructure. The study demonstrates that a carefully designed system incorporating CCUS-equipped fossil fuels can achieve both lower costs and greater resilience. The integration of CCUS technology offers a practical pathway to reduce emissions from the power sector while maintaining reliability. This approach also addresses potential concerns regarding stranded assets and job losses associated with a rapid phase-out of fossil fuel power plants. The results emphasize the importance of considering both reliability and resilience when designing future power systems. The inclusion of detailed geological constraints and high-resolution temporal analysis provides a more accurate and nuanced understanding of the system's performance under various scenarios. The findings are relevant not just to China but also to other countries facing similar challenges in decarbonizing their power sectors.

This study presents a high-resolution analysis of decarbonization pathways for China's power sector, demonstrating the economic and resilience benefits of integrating CCUS-equipped fossil fuels into a predominantly renewable energy system. The findings highlight the need for a balanced approach that considers both cost-effectiveness and the vulnerability of renewable energy to extreme weather events. Future research could explore the optimization of biomass co-firing with CCUS to achieve complete net-zero emissions and the development of more sophisticated models that incorporate additional factors, such as policy and technological uncertainties.

The study relies on several assumptions, including projections of future electricity demand, renewable energy potential, and the cost of various technologies. Variations in these assumptions could affect the optimal power system configuration. The model also simplifies certain aspects of the power system, such as intra-provincial transmission and the detailed modeling of grid dynamics. The resilience analysis is based on historical extreme weather events; future events might differ in intensity and duration, potentially affecting the results.