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Electric & Hybrid Cars: New Load, or New Resource?

The industry must join a growing chorus in calling for new technology.

Fortnightly Magazine - December 2006

measurement called area control error (ACE)—a measure that characterizes the instantaneous mismatch between supply and demand. Control area operators are required by the national and regional reliability organizations to carry sufficient regulation reserves equal to approximately 1.5 percent of the control area’s peak demand for power in a given day. These reserves must provide both regulation up and regulation down, depending on the ACE, in response to a signal sent by the control area’s energy management system, which go out literally every two to six seconds. If demand is greater then supply at any given moment, then regulation up is required, and a signal would go out requiring generators to increase the power delivered to the grid. In contrast, in a situation when demand is less than supply, the AGC signal would call upon the regulation reserves to reduce the power delivered to the grid. In the case of a distributed storage system like a PHEV, regulation up entails discharging of the battery and regulation down entails charging of the battery pack.

The second most valuable category of fast-response, short-duration ancillary services is referred to as spinning reserves. These typically are provided by generators that are spinning and ready to deliver power to the grid in a matter of minutes when called upon in the case of a contingency. These reserves are used only when a scheduled generator trips offline or a transmission or distribution facility fails, and must be up to full power within 10 minutes. Experience shows that spinning reserves rarely are called upon and when they are called, are required for only a short amount of time. In fact, the PJM Interconnect, the regional transmission organization (RTO) serving the Atlantic coastal states and much of the Midwest, experienced 105 events that required deployment of spinning reserves in 2005 with an average duration of 12 minutes.

The central issue dictating the potential V2G revenue from providing these ancillary services is the quantity of power in kilowatts (or capacity credit) per vehicle or fleet. Ultimately, the regulatory authority responsible for qualifying resources to participate in ancillary services markets, like an independent system operator (ISO), RTO, or regional reliability councils, establish methods to determine the amount of power a resource is able to sell in a given market.

Although emerging competitive markets for grid services purport to be technology neutral, the rules are written to accommodate the incumbent technologies and are not necessarily appropriate for new technologies such as a fleet of V2G capable vehicles. For example, the Northeast Power Coordinating Council, the reliability council covering the Northeastern section of North America, requires minimum run times of one hour for resources providing 10-minute spinning reserves. In practice, however, spinning reserves rarely are called, and when they are, the typical dispatch duration is much less than one hour. Thus, as discussed below, a one-hour dispatch requirement severely would limit the per-vehicle power a PHEV would be able to sell in a market for spinning reserves, and fails to appreciate the value of a rapid and accurate response that a V2G system is capable