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Areas
of Research Interest
Dr. Frey’s
research interests are broadly in the area of energy and the environment, and
specifically in: (1) measurement and
modeling of in-use vehicle activity, fuel use, and emissions for onroad and
nonroad vehicles; (2) modeling and evaluation of fossil-fuel-fired power
generation systems and associated air pollution control technologies; (3)
environmental exposure and risk analysis; and (4) quantification of variability
and uncertainty in environmental systems and models.
Measurement and Modeling of Activity,
Fuel Use, and Emissions of Onroad and Nonroad Vehicles
Dr. Frey
leads research at NC State to characterize and evaluate fuels, technologies,
and strategies for reducing vehicle fuel consumption and emissions in the
real-world. His research addresses on-road
light (e.g., cars, minivans, SUVs) and heavy vehicles (including trucks,
transit buses, and school buses), as well as construction vehicles and diesel
locomotives. He is a leader in the use
of Portable Emission Measurement Systems (PEMS) that can be temporarily
installed on a vehicle in order to collect data on vehicle activity, fuel use,
and emissions under real-world conditions.
He applies this methodology to policy-related research questions of
local, national, and international importance.
His work includes life cycle assessment of energy use and emissions for
the entire fuel cycle, not just for the vehicle. His results provide insight into priorities
for choices among fuels, technologies, traffic management strategies and
improvements to duty cycles in order to reduce fuel use and emissions. For example, we have found that improved
signal timing and coordination reduce emissions by 10 to 20 percent. Relieving congestion reduces emissions by as
much as 50 percent. Replacing older
vehicles with newer vehicles reduces emissions by as much as 60 to 70 percent,
while improving fuel economy. Dr. Frey’s
comparison of soy-based B20 to petroleum diesel for 35 in-use shows consistent
reductions in tailpipe NO emissions, as well as confirming 20 to 25 percent
reductions in emissions of CO, HC, and PM.
He is also evaluating other alternative fuels, additives, lubricants,
and technologies. Dr. Frey provides an
objective and quantitative method for real-world evaluation of new fuels and
vehicle technologies to accurately inform the policy debate regarding energy,
air pollution, and climate change.
Air
Pollution Characterization, Prevention, and Control for Power Generation and
Other Sources
Much of Dr. Frey’s work
involves characterizing emission rates from various types of emission sources,
including major stationary sources such as power plants, and mobile sources
such as highway vehicles. He is interested in identifying methods for
preventing the formation of air pollution, such as through better process
design in the case of power generation or through better management in the case
of highway systems. Air pollution control technologies are sometimes the most
effective approach for reducing emissions of air pollutants. For more than 20
years, he has done work in modeling and assessment of air pollution control
technologies. This work has been primarily with respect to coal-based power
generation technologies, but includes air pollution control from natural gas
and oil-fired power plants as well as from a wide variety of other emission
sources.
Electricity is often the
preferred form of energy delivery. Global growth in demand for power generation
provides an opportunity to introduce more efficient and environmentally cleaner
technologies. Dr. Frey’s research on advanced power generation technologies has
focused on coal-based systems, including: (a) advanced environmental control
technologies for conventional coal-fired power plants; (b) coal
gasification-based technologies, such as Integrated Gasification Combined Cycle
(IGCC); and (c) other power generation cycles, such as the externally-fired
combined cycle. This work has typically involved the development of detailed
performance, emissions, and cost models of each technology alternative and
applications of the models to answer key questions about technology feasibility
and research needs. A key feature of this work has been a quantitative approach
to characterizing uncertainty inherent in making predictions about the future
performance and cost of technologies that are currently in early stages of
research and development.
Exposure
and Risk Assessment
In exposure assessment, it is
important to take into account interindividual variability, which refers to the
real differences in activity patterns and other characteristics of one
individual versus another. These differences lead to variation in the frequency
and duration with which individuals come into contact with chemicals in various
types of environments (e.g., outdoors, home, work). Uncertainty refers to the
lack of knowledge that may exist due to limitations of existing data, including
small sample sizes, measurement errors, and lack of representativeness. All of
these sources of variation in exposure, and in our ability to accurately
predict exposures, pose significant challenges in performing exposure
assessments. Additional variability and uncertainty exists in making
predictions of the likelihood that an exposure will result in an adverse
effect. Dr. Frey is interested in the development and application of better
methods for quantifying and analyzing both variability and uncertainty in the
context of exposure and risk assessment.
Quantitative Analysis of Uncertainty
and Variability
Dr. Frey’s
research includes a common theme of quantitative analysis of variability and
uncertainty in energy and environmental systems. This type of analysis is
important in bridging the gap between technical analysis and public policy
making. Many times, scientists and engineers are asked to provide information
to policy makers that is not yet on a solid empirical and theoretical
foundation. Alvin Weinberg discusses this dilemma in detail in his article,
"Transscience" (published in the journal Minerva). Thus, partly as a matter of professional integrity, but
also because it helps focus research and enables decision makers to understand
the risks of being wrong, it is important to convey both what is known and what
is not known about the technical aspects of policy-related problems.
Dr. Frey has developed or
contributed to several software tools for evaluation or control of
environmental pollution, including the Integrated Enviromental Control Model,
AUVEE, and AuvTool. The latter are
probabilistic tools for quantifying variability and uncertainty in emission
inventories and for data sets, respectively.
He has also contributed to international guidance documents on
uncertainty, such as for NARSTO, IPCC, and WHO.
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