Assessment of energy storage for transmission-constrained wind

• We assess the potential for energy storage to economically decrease wind curtailment or decrease system costs.
• We assume that the wind is under contract via a power purchase agreement.
• Maximum viable energy storage costs were $780/kW with ten hours of storage capacity.
• Sizing the energy storage to reduce a small portion of curtailment supports higher unit cost batteries.
• Significant curtailment persists even with high capacity energy storage.

Grid-scale energy storage is one option to reduce curtailment and increase deliverability of transmission-constrained wind. This study examines four hypothetical wind and transmission projects in the United States to quantify the reduction in curtailment under various energy storage configurations and determine the cost targets that energy storage must achieve to become a viable solution for use with remote wind. The delivered cost of wind is determined using a power purchase agreement approach and six AC transmission voltage classes are considered. The findings show that curtailment reduction can be achieved with energy storage costs as high as $780/kW with ten hours of storage capacity, a value that is 50–85% lower than current cost estimates for redox and sodium sulfur batteries. Batteries with higher power ratings result in greater curtailment reduction, but also lower maximum viable costs. Sizing the battery to reduce a small portion of curtailment allows for higher utilization of the storage and supports higher cost batteries. Using energy storage to increase wind installed capacity can also be economically viable, but at costs lower than those for curtailment reduction. The results were most sensitive to the elimination of wind subsidies, the installed cost of transmission, battery efficiency degradation, and battery cycle life. The study did not show economic viability for the use of energy storage to reduce transmission voltage class.