Ching-Shin Norman Shiau Postdoctoral Research Fellow e-mail: cshiau@alumni.cmu.edu Nikhil Kaushal Research Assistant e-mail: nkaushal@alumni.cmu.edu Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 Chris T. Hendrickson Professor Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 e-mail: cth@cmu.edu Scott B. Peterson Research Assistant Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA 15213 e-mail: speterson@cmu.edu Jay F. Whitacre Assistant Professor Engineering and Public Policy, and Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 e-mail: whitacre@andrew.cmu.edu Jeremy J. Michalek 1 Associate Professor Mechanical Engineering, and Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA 15213 e-mail: jmichalek@cmu.edu Optimal Plug-In Hybrid Electric Vehicle Design and Allocation for Minimum Life Cycle Cost, Petroleum Consumption, and Greenhouse Gas Emissions Plug-in hybrid electric vehicle (PHEV) technology has the potential to reduce operating cost, greenhouse gas (GHG) emissions, and petroleum consumption in the transportation sector. However, the net effects of PHEVs depend critically on vehicle design, battery technology, and charging frequency. To examine these implications, we develop an opti- mization model integrating vehicle physics simulation, battery degradation data, and U.S. driving data. The model identifies optimal vehicle designs and allocation of vehicles to drivers for minimum net life cycle cost, GHG emissions, and petroleum consumption under a range of scenarios. We compare conventional and hybrid electric vehicles (HEVs) to PHEVs with equivalent size and performance (similar to a Toyota Prius) under urban driving conditions. We find that while PHEVs with large battery packs minimize petroleum consumption, a mix of PHEVs with packs sized for 25–50 miles of electric travel under the average U.S. grid mix (or 35– 60 miles under decarbonized grid scenarios) produces the greatest reduction in life cycle GHG emissions. Life cycle cost and GHG emissions are minimized using high battery swing and replacing batteries as needed, rather than designing underutilized capacity into the vehicle with corresponding production, weight, and cost implications. At 2008 average U.S. energy prices, Li-ion battery pack costs must fall below $590/kW h at a 5% discount rate or below $410/kW h at a 10% rate for PHEVs to be cost competitive with HEVs. Carbon allowance prices offer little leverage for improving cost competitiveness of PHEVs. PHEV life cycle costs must fall to within a few percent of HEVs in order to offer a cost-effective approach to GHG reduction. DOI: 10.1115/1.4002194 Keywords: plug-in hybrid electric vehicle, greenhouse gas emissions, environmental policy, design optimization, mixed-integer nonlinear programming, battery degradation, vehicle design 1 Introduction Plug-in hybrid electric vehicle PHEV technology is consid- ered a potential near-term approach to addressing global warming and U.S. dependency on foreign oil in the transportation sector as the cost, size, and weight of batteries are reduced 1. PHEVs use large battery packs to store energy from the electricity grid and propel the vehicle partly on electricity instead of gasoline. Under the average mix of electricity sources in the U.S., vehicles can be driven with lower operation cost and fewer greenhouse gas GHG emissions per mile when powered by electricity rather than by gasoline 2. PHEVs have the potential to displace a large portion of the gasoline consumed by the transportation sector with electricity since approximately 60% of U.S. passenger vehicles travel less than 30 miles each day 3. Several automobile manu- facturers have announced plans to produce PHEVs commercially in the future, including General Motors’ Chevrolet Volt, which will carry enough battery modules to store 40 miles worth of electricity 4 and Toyota’s plug-in version of the Prius, which will carry enough batteries for approximately 13 miles of electric travel 5. The structure of a PHEV is similar to that of an ordinary hybrid electrical vehicle HEV, except that the PHEV carries a larger battery pack and offers plug-charging capability 6. PHEVs store energy from the electricity grid to partially offset gasoline use for propulsion. The hybrid drivetrain has several advantages in terms of improving vehicle efficiency. First, the electric motor enables the engine to operate at its most efficient load most of the time, utilizing the batteries to smooth out spikes in power demand. Sec- ond, having an additional source of power in the form of an elec- tric motor enables designers to select smaller engine designs with higher fuel efficiency and lower torque capabilities. Third, HEV and PHEV powertrains enable energy that is otherwise lost in braking to be captured to charge the battery and enable the engine to be shut off rather than idling when the vehicle is at rest. We focus on the split configuration in our PHEV study because of its flexibility to operate similarly to a parallel or series driv- 1 Corresponding author. Contributed by the Design Engineering Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received December 20, 2009; final manuscript received July 15, 2010; published online September 20, 2010. Guest Editor: Steven J. Skerlos. Journal of Mechanical Design SEPTEMBER 2010, Vol. 132 / 091013-1 Copyright © 2010 by ASME Downloaded From: http://mechanicaldesign.asmedigitalcollection.asme.org/ on 10/11/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use