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Riding on The Wind

Plug-in hybrids usher a new era for wind power.

Fortnightly Magazine - December 2008

Energy’s utilities group.

Wind-PHEV Synergy

So how much windpower would it take to power our nation’s fleet of vehicles? The short answer is that meeting 100 percent of the energy needs of the light-duty vehicle fleet would require just over 150,000 MW of wind turbines (see Figure 1) . The 21,000 MW of wind turbines already deployed in the United States produce enough electricity to power almost 14 percent of the nation’s light-duty vehicle fleet.

Of course, PHEVs connected to the electric grid will not be charged exclusively by wind energy, although increased electricity use caused by PHEV charging can be offset directly by more use of wind power.

PHEVs and wind power work well together for a number of reasons. Most important, wind-energy output typically is highest at night in most parts of the United States, just as PHEVs are likely to be charged almost exclusively at night. As a result, PHEVs will serve as an important source of demand for wind energy, keeping nighttime wholesale electricity prices from falling too steeply as increasing quantities of wind power are added to the grid. Conversely, adding increasing amounts of wind power will help ensure large amounts of low-cost, emissions-free electricity is available to power the nation’s vehicle fleet.

PHEVs also have the potential to use their batteries as a form of energy storage, which helps accommodate variability on the electric grid by working to ensure that electricity supply and demand stay in balance. This service has tremendous potential value to utilities and grid operators, who today rely on expensive spinning and non-spinning generation reserves to alter the supply of electricity in response to changes in supply and demand on the grid. Increasing use of wind energy likely will result in modest increases in the need for these reserves, as the variability of wind energy output adds incrementally to the overall variability on the electric grid. PHEVs offer a potentially lower-cost way for grid operators to accommodate the overall variability on the grid, including that introduced by wind energy. “As smart-grid technologies evolve, the nation’s utilities could eventually tap into a wind power-charged, mobile fleet and draw energy out, thereby adding to the value of the wind power,” Bonavia says.

The simplest way PHEVs can serve as a form of energy storage is by altering their rate of charging in response to signals from the grid operator. Under this uni-directional response, the PHEV charges when there’s excess electricity on the grid and stops charging when electricity demand exceeds supply. As smart-grid technologies become more advanced, this response can become bi-directional, with the PHEV using its battery to add power to the grid when demand exceeds supply, as well as charging when supply exceeds demand. Of course, putting this concept to work will require innovative thinking about how the PHEV owner will be compensated for providing this service to the grid. Regardless, the tremendous potential for a symbiotic relationship between PHEVs and the electric grid will help ensure these obstacles are overcome.

An April 2006 study by the National Renewable Energy Laboratory assessed the