Dynamic Estimation of a Reasonable Renewable Energy Utilization Rate Based on Minimum Total System Cost

Cost-effective renewable accommodation is essential for sustainable power-system planning. In power systems with high renewable penetration, using a high renewable energy utilization rate as a rigid target may require excessive investment in peak regulation, energy storage, and grid reinforcement to absorb a small amount of marginal renewable generation, which increases the total cost of power supply. This paper proposes a dynamic estimation method for determining a reasonable renewable energy utilization rate by linking planning and operation under the criterion of minimum total system cost. At the planning layer, the optimal renewable capacity expansion and its corresponding utilization rate are determined by minimizing the sum of annualized investment cost and comprehensive operating cost. At the operation layer, year-round chronological production simulation is combined with discrete search over curtailment penalty parameters to identify the utilization level that gives the minimum total cost under given system boundaries. A case study of the Gansu power grid shows that the reasonable planning-layer utilization rates in 2028, 2030, 2035, and 2040 range from 84% to 88%, while the operation-layer utilization rates in 2028 and 2030 are 90.81% and 91.84%, respectively. City-level decomposition further shows that resource-rich areas such as Jiayuguan-Jiuquan generally have lower utilization rates than most load centers. An equal-investment comparison shows that deep peak regulation of thermal power units improves the utilization rate the most but increases the power supply cost, whereas pumped storage gives better cost-reduction performance. The results indicate that reasonable renewable energy utilization rates should be evaluated on a rolling basis to support sustainability-oriented target setting and coordinated source-grid-load-storage planning.