Research Publications

Plug-in hybrid electric vehicle (PHEV) technology provides a means of coupling transportation and power infrastructures by charging an onboard vehicle battery from the electrical grid. This coupling mechanism can have both environmental impacts, and impacts on the electric utility system. In order to quantify these impacts a PHEV environmental impact assessment model was developed and applied to the state of Michigan. Two approaches were taken in modeling the PHEV consumption properties. First, average consumption rates were assumed for both fuel and electricity. Average values for fuel economy and battery charge depletion rate were derived from academic papers, manufacturer publications, and EPA fuel economy statistics of both conventional vehicles and hybrid electric vehicles. Second, previous work related to naturalistic drive cycles was used to determine electricity and fuel consumption rates in different situations. This previous work developed a stochastic methodology to synthesize naturalistic drive cycles based on actual driving behavior in Southwest Michigan. The synthesized naturalistic drive cycles represent a more detailed characterization of real-world driving behavior than the driving schedules used by the EPA for vehicle fuel efficiency calculations. This study used both the average consumption rates, and the drive cycle informed consumption rates to conduct an environmental assessment for a Michigan PHEV fleet. National Highway Transportation Survey (2009) data was used to determine when vehicles would travel, be parked, and available to charge. Using this, the total electricity and fuel consumption could be calculated, as well as the hourly PHEV electricity demand. We compare the two modeling approaches by examining both the electrical load profile and the pollutant emissions associated with each of the consumption scenarios. The PHEVs compared are both modeled as compact class vehicles with series operation, similar to the 2011 Chevrolet Volt.