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My interests are broadly
in energy and environmental systems, including: modeling and evaluation of advanced
energy conversion (e.g.,combustion, gasification)
and environmental control systems; measurement and modeling of real-world
fuel use and emissions of onroad and nonroad vehicles; development and application of
methods for quantification of variability and uncertainty and for
sensitivity analysis in systems models; and exposure and risk
analysis. Air pollutant emissions of
interest include criteria pollutants, hazardous air pollutants (“air
toxics”), particulate matter, and greenhouse gases. More details on my teaching, current and past research activities, publications,
professional advisory
activities, research group, and computer laboratory are available in the links above.
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Latest News:
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Brandon Graver, an MS student working with Dr. Frey, was
featured in the Southeastern Transportation Center’s Summer 2010
Research Spotlight for his work on measuring the activity, energy use, and
emissions of passenger railroad locomotives.
·
Dr. Frey is starting a new collaborative research
project, with Co-PI Dr. Nagui M. Rouphail, that will focus on the linkage between travel
simulation and vehicle emissions models and their application to evaluation
of traffic management strategies and emissions impacts. The new project is sponsored by the U.S.
Environmental Protection Agency and was selected via a scientific peer
review process under the STAR grants program. The project will be administered as a
cooperative agreement with the U.S. EPA.
·
Dr. Frey’s group has recently published two new papers in
Environmental Science and Technology. One paper, by postdoctoral research
associate Dr. Hyung-Wook Choi
and Dr. Frey, is regarding a method for quantifying the
real-world energy use and emissions of a plug-in
hybrid electric school bus.
The other, by Dr. Frey, Dr. Kaishan Zhang
(now with the California Air Resources Board, and Dr. Rouphail
(director of the Institute for Transportation Research and Education
located at NCSU) is regarding a method for modeling the
emissions of individual vehicles based on second-by-second data obtained
from Portable Emissions Measurement
Systems.
   
·
Brandon Graver, an MS student working with Dr. H.
Christopher Frey, received the first‐place Masters‐level platform paper award at the 2010 Annual Meeting of
the Air & Waste Management Association.
·
Dr. Frey and colleagues have recently published in Transportation Research Record a
methodology for inventorying construction fleet emissions. The method is based on the use of
representative real-world measurements of construction vehicles obtained by
means of a portable emissions measurement system (PEMS). Recommendations are made about
development and practical applications of emissions inventories for
construction fleet management.
·
Dr. Frey and collaborators have recently published in Environmental Science and Technology
a methodology for estimating high-resolution, regional on-road vehicle emissions and
the associated reductions in air pollutant emissions from vehicles that
utilize alternative fuels or propulsion technologies. The fuels
considered are gasoline, diesel, ethanol, biodiesel, compressed natural
gas, hydrogen, and electricity. The technologies considered are internal
combustion or compression engines, hybrids, fuel cell, and electric. Road
link-based emission models are developed using modal fuel use and emission
rates applied to facility- and speed-specific driving cycles. The methodology makes use of
second-by-second data from field measurements using Portable Emission
Measurement Systems (PEMS) in order to develop correction factors for
real-world driving cycles.
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In addition to previous studies in Dr. Frey’s group that
compared energy use and emissions of dump trucks and construction vehicles fueled with B20 biodiesel versus petroleum
diesel, we have recently published a similar study in Transportation Research – Part D that focuses on eight cement mixers. These three studies include a combined
total of 35 vehicles that were tested for approximately one day on each of
the two fuels. In general, these
studies support the finding from dynamometer tests that substitution of B20
for petroleum diesel leads to reductions in tailpipe emissions of carbon
monoxide, hydrocarbons, and particulate matter. While there are differences in the effect
of B20 on the emissions of nitrogen oxides from one vehicle to another, on
average there was little change. These
studies also establish duty cycles for multiple types of vehicles, including
dump trucks, cement mixers, front-end loaders, backhoes, and motor
graders. The newly measured duty
cycles, coupled with modal emission rates obtained from in-use measurements
using Portable Emission Measurement Systems, enable estimation of the
effect of variations in vehicle operations on emissions.
News Archive
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