Examining the Benefits of Optimal Spatial Diversification of Wind Capacity

Abstract

This study examines the benefits of optimal spatial diversification of wind capacity as an option to reduce wind curtailment and, therefore, to increase the utilization of wind capacity. Wind generation concentrated at sites with the highest energy capture, once aggregated, does not utilize the installed wind capacity at the highest possible rate due to wind curtailment. Contrary to the expectations, wind generation at sites with lower energy capture but with wind generation patterns that minimize wind curtailment results in a higher utilization of installed wind capacity. Such a configuration requires an optimization scheme to model power system flexibility and wind generation and to allocate capacity with the objective of maximizing the utilization of wind capacity, defined by the term “effective capacity factor”, CFE, (i.e. average system wide wind generation less curtailment, divided by installed capacity.) In order to measure the benefits of optimal spatial configuration of wind capacity, a base-case configuration is defined which approximates the dominant trend in the wind industry. In the base-case configuration, capacity is allocated to sites in the order of their energy capture (capacity factor) until the capacity limit for the selected sites are reached. The improvement of CFE in the optimal configuration over the base-case configuration is then used as a measure to quantify and illustrate the benefits of optimal spatial diversification. The results of this study show that the CFE of the installed wind capacity in the system improves by 2% to 4% in the optimally diversified configuration at low levels of wind penetration (10% to 20%) and subject to moderate to strict power system generation constraints. For medium levels of wind penetration (20% to 30%), there is no observed benefits since ramping complications fade away at higher levels of penetration. At high levels of penetration (25% to 40%), the minimum generation level constraint results in 5% to 10% CFE improvement in the optimally diversified configuration. Storage is modeled in the system, as an alternative method of comparing the optimal and basecase configurations. The storage capacity that would be saved by optimally diversifying the wind capacity is determined for different levels of wind capacity installations and subject to varying levels of power system flexibility. Power system generation flexibility is modeled by two key parameters of minimum generation level and ramping capability.

The benefits of optimal configuration over the business-as-usual base-case configuration are significant at low and high levels of wind penetration whereas the benefits are almost absent at medium levels of wind penetration. This is explained by the role that the key parameters of the generation fleet play at different levels of penetration.