Advanced Light-Duty Powertrain and Hybrid Analysis (ALPHA) Tool
- Overview of ALPHA Model
- ALPHA v3.0
- ALPHA v3.0 Peer Review
- ALPHA v3.0 Simulations to Generate Response Surface Equations
- Response Surface Methodology
- ALPHA v2.2 Technology Walk Samples
- ALPHA v2.1 Calibration Samples
- ALPHA v2.0 Simulation Samples
- ALPHA v2.0 Peer Review
- Publications Concerning ALPHA v2.0
- Overview of Testing and Integration with Modeling
- Engine Mapping Process Documents
- ALPHA v1.0
Overview of ALPHA Model
EPA’s ALPHA model is a full vehicle simulation model which estimates the greenhouse gas (GHG) emissions from light-duty vehicle sources. It is a physics-based, forward-looking, full vehicle simulator, capable of simulating various vehicle types and powertrain technologies.
ALPHA is an in-house vehicle simulation model used by EPA for research and rulemaking purposes and is not intended to be a commercial product. ALPHA v3.0 was used by EPA to inform the analysis for the 2027+ LMDV rulemaking. ALPHA v2.2 was used by EPA to inform the 2016 Draft Technical Assessment Report of light-duty vehicle greenhouse gas standards for model years 2022-2025, as well as the 2016 Proposed Determination under the Midterm Evaluation.
The ALPHA model shares an underlying structure with EPA's Greenhouse Gas Emissions Model (GEM) used for medium- and heavy-duty vehicle compliance calculations. ALPHA is under active development and the versions of the model presented below represent the state of the package at particular points in time.
ALPHA v3.0
The two primary changes in ALPHA v3.0 are the addition of electrified vehicle architectures (including hybrid, plug-in hybrid, and battery electric vehicles) and a robust structure to allow large numbers of simulations to characterize current and future fleets.
A basic description of ALPHA v3.0 can be found in ALPHA’s documentation (pdf) (451 KB, September 2022).
ALPHA v3.0 - Peer Review
EPA contracted with ICF International to perform a peer review of the ALPHA v3.0 Full Vehicle Simulation Model. The concepts and methodologies upon which the new electrified vehicle models rely were examined by peer reviewers to determine if these algorithms can deliver sufficiently accurate results. This peer review process was carried out under EPA’s peer review guidelines. The model and subsystems were unlocked for complete transparency. Independent subject matter experts provided their review and comments on the methodologies used in the model.
Peer Review of Electrified Vehicle Simulations within EPA’s ALPHA Model (pdf) (February 2023, EPA-420-R-23-004)
ALPHA v3.0 Peer Review Simulations (zip)
(September 2022)
This file contains files provided for EPA’s peer reviewer of ALPHA v3.0 (version as of 2022.9.28).
Running the peer reviewed version of ALPHA requires Matlab/Simulink with StateFlow 2020. Further details are in the readme.txt file provided in the zip file.
ALPHA v3.0 - Simulations to Generate RSEs
EPA used ALPHA v3.0 simulation results to create response surface equations (RSEs) needed for estimating fleet compliance during the 2027+ LMDV rulemaking for onroad vehicles. ALPHA is used to simulate combinations of technologies (each known as a technology package) across different values of vehicle and loading parameters. Each set of these ALPHA simulation outputs are processed to create the RSEs needed for the specific technology package addressed. These RSEs are subsequently used within OMEGA, EPA’s Compliance Modeling Tool, to quickly reproduce the ALPHA model estimates for CO2 in real time for the various vehicle technologies. ALPHA's role in the creation of the RSEs for use within OMEGA is shown in the figure below.
Below are two examples of ALPHA 3.0 Output data.
- ALPHA Outputs Used to Create RSEs for the Multipollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles (LMDV 2027+ Rulemaking)
This file contains the .csv files with the ALPHA Outputs used to generate all the Response Surface Equations (RSEs) used in the analysis to support the final LMDV 2027+ rulemaking. Further details are in the readme.txt file provided in the zip file.
ALPHA3-Outputs-and-RSEs1 (zip) (March 2024) - ALPHA Outputs Used to Create a Sample RSE for OMEGA
This file contains the sample set of ALPHA Outputs used to demonstrate how to generate the sample Response Surface Equation (RSE) explained in the Regulatory Impact Analysis (RIA) portion of the final LMDV 2027+ rulemaking documentation. Further details are in the readme.txt file provided in the zip file.
ALPHA3 Outputs2 (zip) (September 2022)
Response Surface Methodology
Response surface methodology (RSM) provides a way to incorporate ALPHA results of various vehicle technologies simulated over thousands of vehicle and roadload combinations into simple response surface equations (RSE) using an industry standard statistical methodology. The RSM computationally accesses a complete set of ALPHA model results using a collection of response surface equations (RSEs). The RSEs can then be used to quickly reproduce the ALPHA model results within other models, such as EPA’s OMEGA model, to characterize any future vehicle's GHG emissions based on its size, weight, power, and road loads.
EPA commissioned RTI International to conduct an independent peer review of the Response Surface Equations methodology.
Peer Review of EPA’s Response Surface Equation Report (pdf) (2.09 MB, May 2018, EPA-420-R-18-006)
ALPHA v2.2 Technology Walk Samples
In response to stakeholder comments on the MTE Proposed Determination, EPA utilized a version of ALPHA capable of executing this sample technology walk analysis to further corroborate EPA’s assessment that vehicles equipped with conventional technologies can support compliance with the MY2025 targets without the need for extensive electrification. These ALPHA runs are referenced in the Response to Comments for the 2017 Final Determination on the Appropriateness of the Model Year 2022-2025 Light-duty Vehicle Greenhouse Gas Emissions Standards under the Midterm Evaluation.
ALPHA v2.2 Technology Walk Samples (zip)
This file contains a series of ALPHA V2.2 simulations (as of 2017.01.12) used to support a sample technology walk analysis. Running this version of ALPHA requires Matlab/Simulink with StateFlow 2016b. For convenience, a plaintext form of the workspace for each ALPHA run is provided in an m-file format. Further details are in the readme.txt file.
ALPHA v2.1 Calibration Samples
EPA used ALPHA simulation results to inform its calibration of the Lumped Parameter Model (LPM), an EPA desktop computer application that estimates the effectiveness (CO2 reduction) of various technology combinations. A subset of the numerous ALPHA simulation results studied during the MTE process were identified as key simulations used to inform the calibration of the LPM.
ALPHA v2.1 Calibration Samples (zip)
This file contains a series of ALPHA V2.1 simulations (as of 2016.11.18) used to inform the calibration of the Lumped Parameter Model. Running this version of ALPHA requires Matlab/Simulink with StateFlow 2016b. For convenience, a plaintext form of the workspace for each ALPHA run is provided in an m-file format. Further details are in the readme.txt file.
ALPHA v2.0 Simulation Samples
EPA used ALPHA simulation results to inform its calibration of the Lumped Parameter Model (LPM), an EPA desktop computer application that estimates the effectiveness (CO2 Reduction) of various technology combinations. A subset of the numerous ALPHA simulation results studied during the MTE process were identified as key simulations used to inform the calibration of the LPM.
-
ALPHA v2.0 Simulation Samples (zip)
This file contains a series of ALPHA V2.0 simulations (as of 2016.07.07) of the same type used to inform the calibration of the Lumped Parameter Model.
Running this version of ALPHA requires Matlab/Simulink with StateFlow 2014a. For convenience, a plaintext form of the workspace for each ALPHA run is provided in an m-file format. Further details are in the readme.txt file.
ALPHA v2.0 Peer Review
EPA engaged ICF International to perform a peer review of the ALPHA Full Vehicle Simulation Model. This peer review process was carried out under EPA’s peer review guidelines. The entire model and all subsystems were unlocked for complete transparency. A number of independent subject matter experts provided reviews and comments on the methodologies used in the model.
-
Peer Review of ALPHA Full Vehicle Simulation Model (pdf) (567 KB, EPA-420-R-16-013, October 2016)
-
ALPHA v2.0 Peer Review (zip)
This file contains the files provided to peer reviewers for ALPHA v2.0 (as of 2016.05.05).
Running the peer reviewed version of ALPHA requires Matlab/Simulink with StateFlow 2014a. Further details are in the readme.txt file.
Publications Concerning ALPHA v2.0
Throughout the MTE process, EPA’s goal was to publish as much of our research as possible in peer-reviewed technical papers and journals. These publications describe in more detail the development and use of the ALPHA model.
- "Estimating GHG Reduction from Combinations of Current Best-Available and Future Powertrain and Vehicle Technologies for a Midsized Car Using EPA’s ALPHA Model," SAE Technical Paper 2016-01-0910, 2016, doi:10.4271/2016-01-0910, Kargul, J., et al. (pdf)
- "Modeling of a Conventional Mid-Size Car with CVT Using ALPHA and Comparable Powertrain Technologies," SAE Technical Paper 2016-01-1141, 2016, doi:10.4271/2016-01-1141, Newman, K., Doorlag, M., and Barba, D. (pdf)
- "Modeling the Effects of Transmission Gear Count, Ratio Progression, and Final Drive Ratio on Fuel Economy and Performance Using ALPHA," SAE Technical Paper 2016-01-1143, 2016, doi:10.4271/2016-01-1143, Newman, K. and Dekraker, P. (pdf)
- "Investigating the Effect of Advanced Automatic Transmissions on Fuel Consumption Using Vehicle Testing and Modeling," SAE Int. J. Engines 9(3):2016, doi:10.4271/2016-01-1142, Moskalik, A., Hula, A., Barba, D., and Kargul, J. (pdf)
- “Development and Testing of an Automatic Transmission Shift Schedule Algorithm for Vehicle Simulation,” SAE Int. J. Engines 8(3):2015, doi:10.4271/2015-01-1142, Newman, K., Kargul, J., and Barba, D. (pdf)
- “Benchmarking and Modeling of a Conventional Mid-Size Car Using ALPHA," SAE Technical Paper 2015-01-1140, 2015, doi:10.4271/2015-01-1140, Newman, K., Kargul, J., and Barba, D. (pdf)
Overview of Testing and Integration with Modeling
ATAB has integrated benchmarking and modeling activities to ensure robust data. The following presentation highlights the benchmarking and modeling activities relating to light-duty GHG emissions.
Engine Mapping Process Documents
Integrating Test Data for Light-duty GHG Technology and modeling results for engines into the ALPHA model requires a process for translating test results into a full map representing all phases of engine operation. The following documents explain the process for creating ALPHA engine maps for key engine packages.
- Process for Generating Engine Fuel Consumption Map: Ricardo Baseline Standard Car Engine Tier 2 Fuel (pdf)
- Process for Generating Engine Fuel Consumption Map:Chevy Malibu 2.5L I4 engine using Tier 3 fuel (pdf)
- Process for Generating Engine Fuel Consumption Map: Mazda SKYACTIV 2.0L engine using Tier 2 fuel (pdf)
- Process for Generating Engine Fuel Consumption Map: Ford F150 EcoBoost 2.7L Tier 2 Fuel (pdf)
- Process for Generating Engine Fuel Consumption Map: Future Atkinson engine with cooled EGR and cylinder deactivation (pdf)
- Process for Generating Engine Fuel Consumption Map: Ricardo Cooled EGR Boost 24-bar Standard Car Engine Tier 2 Fuel (pdf)
- Process for Generating Engine Fuel Consumption Map: Honda Civic L15B7 1.5L Turbo 130kW Engine 91 RON Fuel (pdf)
- Process for Generating Engine Fuel Consumption Map: Toyota TNGA 2.5L 150kW Atkinson Engine Tier 2 Fuel (pdf)
ALPHA v1.0
The initial version of ALPHA, used for off-cycle technology evaluations, is provided for historical purposes. The software is a freely-distributed, desktop computer based application, built on MATLAB/Simulink. EPA is no longer using this version of ALPHA.
The downloadable installation file below (in a zip format) contains the ALPHA v1.0 tool. The model documentation provides details on how to launch and run the simulation tool.
- ALPHA User's Guide for Off-Cycle Credit Evaluation v1.0 (pdf) (1.27 MB, EPA-420-B-12-051, August 2012)
This document contains descriptions of how to launch and use the ALPHA tool for off-cycle technology evaluation. -
ALPHA v1.0 Installation File (zip)
This file contains the ALPHA v1.0 application files written in MATLAB/Simulink. This version was used in EPA’s Model Year 2017-2025 Final Rulemaking for Light-Duty Vehicle Greenhouse Gas Emission Standards.