Necessary Emission Space for Provincial Power-Sector Carbon Budgeting Under Security Power Supply Constraints: Evidence from Jiangsu Province, China

The power sector is a priority area for carbon mitigation at the provincial level. Existing studies on provincial power-sector carbon budgets mainly focus on abatement potential and the allocation of aggregate emission budgets, while giving insufficient consideration to the thermal capacity that must be retained to satisfy peak-load and supply-security requirements and the associated emission boundary. Taking Jiangsu Province as a case study for 2026–2030, this paper converts the installed capacity of different generation resources into firm capacity at peak load, combines it with the planning reserve margin to estimate the security-supply thermal capacity requirement, and quantifies the corresponding necessary emission space under specified planning assumptions. The results show that, under a 15% planning reserve margin, the security-supply thermal capacity requirement increases from 120.32 GW in 2026 to 128.43 GW in 2030, despite continued growth in the firm-capacity contribution of non-thermal resources. The cumulative necessary emission space over 2026–2030 is 1275.62 Mt CO2, accounting for 56.85–59.27% of the allowable emission space across the emission-intensity scenarios. Across the combined supply-security and emission-intensity scenarios, the maximum reducible proportion declines from 47.27% to 36.44%. Monte Carlo analysis further shows that the absolute magnitude of necessary emission space is particularly sensitive to the equivalent annual utilization hours associated with security-supply thermal capacity. These findings suggest that provincial power-sector carbon budgeting should first identify the necessary emission boundary under specified supply-security conditions and then allocate abatement tasks within the remaining adjustable abatement space.