Two automotive engineers, E.D. Tate and Peter J. Savagian, recently presented a paper at the annual meeting of the Society of Automotive Engineers entitled “The CO2 Benefits of Electrification E-REVs, PHEVs, and Charging Scenarios.”  The paper examined the opportunity to reduce carbon emissions through the use of extended-range electric vehicles (E-REVs), such as the Chevrolet Volt, and Plug-In Hybrid Electric Vehicles (PHEVs).  The engineers examined several scenarios with respect to charging patterns, battery size and other factors.

The results of the study were both interesting and informative. 

The study concluded that virtually reduction in fuel consumption occurred as a result of installing a very large battery (larger than 16 kWh) in a car, and that there were rapidly decreasing benefits in installing a battery that was larger than 8 kWh.  Given that batteries currently cost about $1,000 per kWh of capacity, using a smaller 8 kWh battery instead of a 16 kWh battery could cut the cost of a vehicle by about $8,000 while consuming only slightly more liquid fuel.  Moreover, the study also concluded that: 1) unrestricted charging opportunities, such as the chance to recharge a battery at home and work, instead of requiring the car to be charge overnight at home, would place significantly less burden on the electrical grid; and 2) for small batteries, a PHEV and E-REV achieve similar reductions in carbon emissions.  In fact, the authors concluded that “charging scenarios influence the fraction of a full EV days almost as strongly as the battery size.”

The study suggests that it is more cost-effective to use an 8 kWh battery than a 16 kWh battery and recharge it at home and at work, than to have a larger, more expensive battery.  That observation is particularly interesting when one sees what is happening in the market.  The Prius uses a smaller battery (less than 2 kWh), and it is expected that the plug-in Prius will use double the battery capacity (less than 4 kWh of capacity) of the non-plug-in version, and have a range of about 15 miles in the charge-depleting mode before converting to operating the charge-sustaining mode.  The plug-in Prius has not been priced yet, but doubling its battery will cost less than an additional $2,000; even with other equipment necessary, its price premium should not be more than $4,000 above the standard Prius, which currently sells for about $22,000.  In contrast, the Chevy Volt is expected to use a 16 kWh battery and cost about $40,000.  Given that the study suggests that the Prius approach would yield nearly the same fuel savings as the Volt approach wile costing perhaps $10,000 less than the Volt, one can easily envision the challenge that the Volt might have competing against the plug-in Prius in the marketplace.

But what makes this report most interesting, perhaps, is that fact that Messrs. Tate and Savagian are both employed by General Motors.  

Previous Post  

Next Post

WaPo mostly right on energy security
May 14, 2012

Natural Gas and America’s Power Mix
May 11, 2012

King of the Hill
May 4, 2012