Using wind-availability forecasts in day-ahead unit commitment can require expensive real-time operational adjustments. We examine the benefit of conducting interim recommitment between day-ahead unit commitment and real-time dispatch. Using a simple stylized example and a case study that is based on ISO New England, we compare system-operation costs with and without interim recommitment. We find an important tradeoff-later recommitment provides better wind-availability forecasts, but the system has less flexibility due to operating constraints. Of the time windows that we examine, hour-20 recommitment provides the greatest operational-cost reduction.

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Recent technical, market, and policy developments in the electricity industry are increasing interest in and need for energy storage. We examine the potential for using the flexibility of an aggregation of tank electric water heaters as a source of virtual energy storage. Specifically, we examine the operational performance of and operating profit that is earned by a fleet of water heaters that provide energy shifting and frequency regulation. We contrast this performance and operating profit to that of a lithium-ion battery. We find that water heaters do not achieve the same level of performance or operating profit that a battery does. However, when accounting for the capital costs of the two technologies, water heaters are superior, insomuch as they have a better cost-to-profit ratio. We find that both water heaters and batteries earn significant operating profits from frequency regulation as opposed to energy shifting. Water heaters have a stronger bias towards frequency regulation, due to temporal constraints on load shifting. Relaxing these constraints improve water-heater performance slightly.