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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

and reduced cycling of generation facilities. The economic value of these benefits, which are a function of the cost structure for each individual utility operating within a particular geographic location, was not calculated.

What’s the Real Potential For PHEVs?

Conventional thinking suggests that PHEVs would plug in at night and recharge during the late evening and early morning hours—end of story. This perspective is limited, and misses a significant value proposition that is made possible by the fact that vehicles are parked over 90 percent of the time. These idle resources, if connected to the grid when parked, could be tapped to provide any number of grid services.

It should be noted here that we consider only the stored energy in the onboard battery pack of a PHEV as available for vehicle-to-grid (V2G) power, unlike earlier studies of PHEVs providing V2G power. 6 We do not consider remote starting of vehicles to access the liquid fuel onboard as reserve energy for V2G power. While this is technically feasible, the control and safety issues associated with starting engines remotely are a cause for concern and thus we do not consider this as a near-term option. PHEVs have larger battery packs than HEVs, and unlike a pure battery-only electric vehicle, the entire available energy in a PHEV can be used for V2G services given that when the owner begins the next trip the vehicle can use the liquid fuel to drive the vehicle.

While the authors know of just one demonstration project, 7 V2G has been analyzed primarily from a theoretical perspective. 8 While no major technical barriers to V2G emerged from the demonstration project or the research, several issues bearing on the economic potential of cars providing grid support services were identified.

While V2G-capable cars could provide peak power or serve as a demand-response resource, their economic values do not generally justify the expense. 9 These services are needed for just a few hours each year, and thus the potential revenue from providing these services is limited. Research on the subject found that the most promising markets for V2G power are for those services that the electric industry refers to as ancillary services. These are services that grid operators must obtain 24 hours per day 7 days per week, and thus take advantage of the extended availability of the vehicle fleet to provide these services.

Earlier studies identified two specific ancillary services, for which hourly wholesale markets exist, as particularly promising for V2G power—regulation and spinning reserves. Vehicles with an electric-drive system and battery storage, like those found in PHEVs, particularly are well suited to provide these services, which fall under the general category of operating reserves. These services require fast and accurate responses to electric-grid operator signals, and typically are used for short durations. Grid operators across the country require each of these services for every one of the 8,760 operating hours in a year, and they represent a multi-billion-dollar combined market.

Regulation (frequency response) services today are supplied by generators on automatic generation control (AGC), which are deployed based on a