June 30, 2009

Overnight Charging Of Plug-In Hybrids Lessens Strain On Power Grid

As long as owners of hybrid plug-in vehicles charge their cars overnight, utilities will be able to manage the increased power demand without the need to build new power plants, according to the a new report by New York's Independent System Operator (NYISO).

"If New York motorists start plugging in significant numbers of plug-in hybrid vehicles (PHEVs), we will see new demands on the grid," said Stephen Whitley, NYISO President and CEO, in a report issued Monday.

Indeed, report predicts that PHEVs and fully electric vehicles will increase power demand in New York state about 2 percent by 2030.

"However, if deployed with technology and incentives to encourage favorable charging patterns, PHEVs can offer valuable new ways to store electricity produced in off-peak periods. That energy storage potential could enhance the grid's use of windpower," he said.

Windpower projects tend to produce more electricity in the early morning hours, a period when current demand for electricity is fairly low. 

"The NYISO has found that, in general, the production profile of wind resources in New York correlates very well with off-peak charging of PHEVs, creating the potential for a synergy between wind generation and transportation energy needs," the report said.

PHEVs are expected to hit the market in significant numbers in the coming years.  President Obama has called for a million plug-in hybrids on U.S. roads by 2015.

The NYISO report assumes there will be U.S. sales of 1.5 million plug-in hybrids by 2016, and 50 million by 2030, 2.5 million of which would be sold in New York.

Other studies by the Electric Power Research Institute, the National Resources Defense Council and the U.S. Energy Department's Oak Ridge National Laboratory predict that 25 percent of all U.S. auto sales will consist of plug-in hybrids by 2020.

The NYISO report supports the position of wind power advocates, who say the no-emissions, renewable power source will complement the use of plug-in hybrids, since winds are typically higher at night.

Indeed, charging vehicle batteries during high-demand daytime hours could strain the grid, particularly during the summer months, creating a need for expensive new power plants, the report showed.  

"Rate design to encourage off-peak charging, coupled with time-of-use rates, and smart grid/advanced metering initiatives, would facilitate favorable charging behavior," the report said.

Utilities and hybrid vehicle makers say the second generation of plug-in cars will harness "smart" use of power, which will utilize a two-way communication scheme to curb power use during the costliest and most stressful times for the power grid.

Although a plug-in hybrid will not emit carbon dioxide when running on its electric motor, some worry they will indirectly increase CO2 emissions from power plants that burn fossil fuels.

However, if PHEVs are recharged overnight, they can run on wind power, which would lessen the need for increased generation from fossil fueled power plants, NYISO said.

Plug-in hybrid vehicles use traditional electric outlets to charge their batteries, which in turn power an electric motor.  The hybrids also rely upon a gasoline internal combustion engine.

A copy of the NYISO briefing paper, Alternate Route: Electrifying the Transportation Sector, can be found at


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