# Utilizing Energy Storage for Operational Adequacy of Wind-Integrated Bulk Power Systems
## 4 Application of the Proposed Operational Adequacy Framework
### Impact of ESS Operating Strategies on Operational Adequacy
Moreover, the possibility of variation in wind regime for different days or evaluation period is presented through consideration of Regime 2 beside Regime 1. Regime 2 has a higher average wind speed and a different wind power distribution. Figure 10b shows the expected operating costs of the operational planning with both wind regimes calculated based upon the operating costs data in Table 2.  
It is evident that Regime 2 has higher average wind speed and thereby, the wind generation offsets more conventional generation. This results in larger environmental benefits and more economic operation, as observed from the results. Operating costs with Regime 2 are almost 7.97% and 6.89% lower than that with Regime 1 for wind-coordinated and grid-supported strategies, respectively. Also, with this regime, the system risk was higher with the wind-coordinated strategy compared to the grid-supported strategy. However, it is noticeable that the grid-supported strategy fails to achieve an acceptable operational adequacy with this wind regime. The system should, however, comply with the operational adequacy reference. Figure 11 shows the operational adequacy evaluated by considering different percentages of expected wind generation for the unit commitment decisions. It is seen that acceptable operational adequacy is achieved with 70% of expected wind generation and 60% of wind generation in the grid-supported and wind-coordinated ESS operational strategies, respectively. This kind of approach helps system operators to preplan the optimal wind generation to be included in operational planning to limit system risk within an acceptable level. This also allows the system operator to assign an operating capacity value to the wind power which can be helpful for system operators to quantify the contribution of wind farms participating in the electricity market. Despite the lower operating capacity value achievable from the wind-coordinated operational strategy, it might be able to offset more conventional generation than the grid-supported operational strategy, resulting in higher environmental and economic benefits. Figure 11: Operating capacity value of wind power with different ESS operational strategies. Figure 10: Impact of operational strategy and wind regimes on (**a**) operational adequacy and (**b**) operating cost. The presented mitigation measure to maintain operational adequacy restricts the operating capacity value, which is not desirable for wind farms and ESS from their sustainability perspective. A possible solution that enables wind farms and ESS to maintain a higher operating capacity value has been presented. Figure 12 presents the operational adequacy evaluated for such an alternative operational planning. This option envisions the possibility of support from mobile energy storage like battery banks, which can be a separate resource on its own. A 10 MW, 75 MWh battery energy storage (BES) is assumed to be added by the wind farm and energy storage combination. With BES, the operational adequacy improves noticeably, but still violates the adequacy reference. Thus, another option is further explored. The grid-supported operational strategy is considered to ensure enough charge to be available during peak hours. With this option, the operational adequacy improves significantly, bringing it closer to the reference value. Thus, this alternative also resolves the challenge of the limitation in the investment and thereby the size of wind farm-owned ESS. The possibility of assistance from mobile ESS during a favorable wind regime presents the possibility of maintaining a higher operating capacity value and accruing higher revenue from electricity markets. This can be instrumental in the sustainability of wind farms. Besides, conventional generators required are also reduced, which brings greater environmental benefits at lower operating costs.