Are electric vehicles green?
Published: November 3,2011
Everyone thinks they know that electric vehicles are green. EVs reduce our reliance on petroleum gas and wean the United States from dependence on foreign oil. But a nagging question lurks not far below the surface. If the electricity used to charge EVs comes from coal plants spewing greenhouse gases into the air, does plugging in EVs make the environment greener or browner?
A new study suggests the answer is unequivocally “greener,” but for an unexpected reason. EVs can increase the use of renewable energy, like wind and solar, in ways that few people anticipated. To understand why, we need to become familiar with one of the main challenges for renewable energy: its variability.
The power grid must constantly balance the amount of energy generated against the amount of energy consumed. In other words, the amount of energy produced and consumed must be equal at all times. Traditional power plants are a great grid resource because at the drop of a switch they can ramp up and down to match load changes throughout the day and as seasons change. But renewable energy sources can’t compete.
Based on all data collected since the dawn of time, Mother Nature is completely insensitive to our energy use patterns. The wind is just as likely to blow in the middle of the night, when electricity use is low, as it is in the early evening, when electricity use is high.
This variability places significant strains on the power grid. To ensure that enough energy is available when we need it, storage or reserve energy generation is often required. But that is expensive and only addresses undersupply of energy. This past summer, the Pacific Northwest experienced the other side of the problem – too much electricity was generated without the consumption to match it.
This is where electric vehicles ride to the rescue. Most people think of EVs as electricity consumers, but a recent study by the Pacific Northwest National Laboratory shows that a partially charged EV represents a potential asset for grid operators. Charging an EV while at work or at home is flexible use. The owner cares only that the car is fully charged when he or she wants to use it.
Advanced battery technologies can recognize grid conditions and constantly vary the rate at which the battery is charged, based on how much electricity is being generated and used. With electric vehicles’ charging cycles able to start and stop, new reserve power plants would not need to be constructed and renewable generation would not need to be cut off. The most advanced battery technologies would not only vary the charging rate but would release energy stored in the battery onto the grid as needed.
The PNNL study reviewed the likely increase in renewable energy over the next decade and electric vehicles’ ability to provide the shock absorption (or balancing services, to use the technical term) needed to support new renewables. The rise of renewable portfolio standards and other factors are expected to add another 10 gigawatts of wind power – enough energy to serve about 3 million households – to our regional grid over the next decade.
The PNNL study found that the balancing services needed could be met if 13 percent, or about 2.1 million, of the vehicles in the seven Northwest states were EVs and equipped with advanced battery technologies that could vary the charging rates based on supply and demand on the grid. With grid-friendly technology permitting the release of energy from the battery to the grid, the EVs’ penetration could be reduced to 8 percent, or 1.4 million vehicles. The study identified importance for charging stations to be available at work and in public places in order to take advantage of EVs balancing capacity.
Presently, there are only a small number of EVs on the roads, but significantly more are expected. Grid operators will not be betting on EVs entirely. Other potential balancing approaches include: 1, better forecasting for wind generation; 2, switching from coal to natural gas plants; 3, improving storage technologies for renewables; and 4, demanding response resources – think electricity rates that vary to reflect the supply.
Even if we don’t have 2.1 million electric vehicles on the road by the end of the decade, the PNNL study shows that they can play a critical role in the support of renewable energy. Until we reach the 2.1 million mark, drive like the wind!
David White, a partner at Tonkon Torp LLP, is co-chairman of the firm’s energy practice group. Contact him at 503-802-2168 or firstname.lastname@example.org.