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Here you'll find basic information about NREL's modeling and analysis capabilities for vehicle technology and fuels research. Also, see information about our Vehicle Systems Analysis Project.
Transportation Modeling
NREL's advanced vehicles and fuels modeling expertise focuses on integrating
computer-aided design, computer-aided engineering, finite element analysis,
design of experiments, and behavioral modeling to introduce quality and
durability early in the vehicle/component design process. We have
successfully designed lightweight vehicle components, improved battery
thermal management, optimized fuel cell stack components, and enhanced
power electronic cooling. Ongoing work involves applying our advanced
tools to further the goals of various DOE program areas, including fuel
cells, light- and heavy-duty hybrid vehicles, battery thermal management,
power electronics, and vehicle ancillary loads reduction.
ADVISOR (ADvanced VehIcle SimulatOR)
ADVISOR, a MATLAB-based modeling tool, enables a user
to simulate a conventional, hybrid, electric, or fuel cell vehicle over
a city or highway drive cycle and predict the vehicle performance (fuel
economy, emissions, battery power, heat generated, and other measurements).
ADVISOR includes vehicle models of engines, batteries, motors, exhaust
aftertreatment systems, transmissions, accessory loads, and other
characteristics. ADVISOR's quasi-static analysis of component performance
means that simulations are fast. Capabilities include component selection
and sizing for conventional, hybrid and fuel cell vehicles, energy
management strategies, optimization, and target development.
Thermal and Structural Finite Element Modeling
We employ state-of-the-art analytical tools to perform
thermal, fluid flow, structural, and packaging analyses. Our experimental
work focuses on obtaining data, validating predictions and estimates, and
investigating behaviors that are difficult to model.
Computational Fluid Dynamics (CFD)
NREL experts use Fluent and ANSYS Flotran software to simulate
flow and thermal conditions. Fluent is an unstructured, finite volume
based solver with good parallel performance. We use CFD to model the solar
soak temperatures and transient cool down (air flow, temperatures) of
vehicles to assess techniques for reducing the solar load in passenger
compartments and improving the distribution of conditioned air.
VSOLE predicts the transmitted, absorbed, and reflected
solar power at each window of a vehicle. It takes into account the sun's
angle of incidence and calculates the transmitted, reflected, and absorbed
power based on the radiation source, vehicle geometry, vehicle orientation,
and window glazing type.VSOLE1.0 is written in MATLAB and is easily accessed
with a graphical user interface. Included in VSOLE is a solar radiation
model that calculates the solar spectral irradiance incident on the vehicle
as a function of location, weather, and vehicle orientation. Weather data
are available for 239 locations in the United States and its
territories.
Human Thermal Physiological Model
The physiological model, which uses ANSYS software, is a
three-dimensional, finite-element model of the human body including the
thermal physiological and thermoregulatory systems. It consists of bone,
muscle, fat, and skin layers, as well as macro and micro blood circulation.
The model controls NREL's human thermal comfort manikin by predicting the
body's response to the environment, determining the segment skin
temperatures, sweat rates, and breathing rate, and transmitting the data to
the manikin.
Human Thermal Comfort Empirical Model
The psychological model uses temperature data from the
physiological model to predict local and global thermal comfort as a
function of local skin and core temperatures and their rates of change.
The psychological model is based on testing of human subjects exposed to
transient, nonuniform conditions.
Transient Air Conditioning Model
NREL has developed a transient A/C model within the
SINDA/FLUNT analysis software environment and has integrated it with the
ADVISOR vehicle systems analysis software. This one-dimensional,
thermal-hydraulic model contains generic component sub-models for the
fixed-displacement compressor, condenser, evaporator and expansion device,
and generic representations for the system piping network and simulation
of the system operational control strategy. It includes a dynamic
two-phase-flow analysis in the condenser and evaporator.
Technical Targets Tool (TTT)
TTT is a vehicle fleet and oil use model based on ADVISOR
vehicle analysis and VISION market penetration assumptions. It connects the
FreedomCAR light vehicle technical goals to their potential impact on
national transportation oil use. The tool allows the user to submit a set
of technical targets (for example, engine at X kW/kg, battery at Y $/kg)
to simulate 11 classes of new technology light vehicles. Such new technology
vehicles that meet market performance requirements are allowed to penetrate
the market. The tool's capabilities include estimates of annual oil use by
projecting new vehicle sales, average miles traveled, and conventional
vehicle fuel economy for each vehicle class or platform. To learn more, see our information about the Technical Targets Tool.
Fuel Cell Models
NREL has several models that predict the electrical,
thermal, and fluid performance of a fuel cell system. These models are
coupled with ADVISOR to predict fuel cell performance through a drive cycle.
They range from simple efficiency versus power models to detailed system
models that include the effects of flow rates, radiator characteristics,
compressor performance, etc.
Air Conditioning Fuel Use Model
This model predicts the amount of fuel consumed by
air-conditioning (AC) in light-duty vehicles in the United States, the
European Union, and Japan. The model incorporates the effects of climate
(temperature, humidity, radiation), personal thermal comfort (clothing
level, time a vehicle has soaked in the sun), use characteristics (time
of day and month driven), distance traveled, fuel economy impact, and
vehicle registrations on total AC fuel consumption.
SABER Electric Modeling
SABER is a mixed-signal design and analysis tool. We
can use it independently or in co-simulation with ADVISOR where MATLAB
electrical models are substituted with more detailed SABER electrical
models. This co-simulation leverages the large database of SABER models.
We have used the model to predict fuel economy of vehicles with a detailed
set of electrical loads (wipers, lights, AC, etc.) and control
settings.
Digital Functional Vehicle (DFV)
Our main focus with DFV was to build virtual prototypes
such as ProEngineer that integrate CAD, CAE, topology optimization, design
for six-sigma quality, and reliability based optimization techniques such
as ANSYS. These tools can thermally analyze batteries, model fuel processor
fluids, and perform structural investigation and topology optimization of
fuel cell components.
Fuel Ignition QSAR (Quantitative Structure Activity Relationship)
Modeling
We use this modeling tool to correlate the molecular
structure of a fuel component with its ignition properties in a compression
ignition engine. We can draw a molecule and estimate its cetane number (or
auto-ignition temperature) from the model. NREL currently has an empirical
Quantitative Structure Activity Relationship model that was developed from
pure component cetane number data in the literature. We are developing a
more fundamentally based model that uses molecular modeling tools and
combustion chemistry insight. These models can be used to screen potential
oxygenates for blending with diesel fuel or to identify optimal fuel
components for advanced combustion engines.
Engine Modeling
NREL uses several commercially available one-dimensional
engine modeling codes to help support and guide numerous R&D
activities. Specifically, these codes are used to evaluate an array of
advanced engine technologies, emission control systems, and fuel performance
parameters that would otherwise be too costly or time consuming to test in a
laboratory. For example, we are currently evaluating the performance and
emission impacts of advance combustion strategies, multiple injection events
in diesel engines, exhaust gas recirculation strategies, and cylinder
deactivation.
Air Quality Modeling
NREL co-funds air quality simulation modeling efforts and
collaborates in this effort with the Coordinating Research Council (Atlanta,
Georgia). Two recent projects are: 1) development of ambient air quality
models for air toxics exposure assessment and 2) a study of the effects of
weekend emission changes and those changes on elevated weekend ambient
ozone levels in the Los Angeles Basin.
Transportation Analysis
Analysis of energy, market, and industry trends helps shape future technical programs and identifies promising opportunities to advance vehicles and fuels in the U.S. NREL's transportation analysis projects measure transportation program benefits and evaluate markets for advanced vehicle technologies and fuels.
Energy Trends Analysis
Advanced vehicles and fuels researchers use the VISION model to simulate energy use, oil savings, and carbon emissions of alternative vehicle technologies. We conduct ongoing analyses on vehicle and fuel attributes, develop models, periodically conduct surveys, and communicate analytic results through reports and presentations. Check out some of our studies: Future U.S. Highway Energy Use: A Fifty Year Perspective, and Consumer Views on Transportation and Energy (PDF 811 KB), Download Acrobat Reader.
Vehicle and Fuel Deployment Analysis
NREL analyzes a variety of trends and patterns in the use of alternative fuels and advanced vehicle technologies. Analysis of data reported by regulated fleets helps guide the strategies and tactics of the mandatory programs. In addition, analysis of industry and use trends across the vehicle sector helps identify opportunities for near-term displacement of imported petroleum.
Research Expertise
Laboratory Capabilities
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