A Java Implementation of Future Automotive Systems Technology Simulator (FASTSim) Fuel Economy Simulation Code Modules

Future Automotive Systems Technology Simulator (FASTSim) is a free and open-source tool developed by National Renewable Energy Lab (NREL). Among the attractive capabilities of the FASTSim is that it can perform computationally efficient fuel economy simulations of automotive vehicles with reasonable accuracy for standard or arbitrary drive cycles. The modeling capability includes vehicles with various types of powertrains such as: conventional vehicles (CVs), hybrid-electric vehicles (HEVs), plugin hybrid electric vehicles (PHEVs) and battery-only electric vehicles (BEVs). The public version of FASTSim available from NREL is implemented in Excel, which achieves the goal of good accessibility to a broad audience, but has some limitations, including: i) bottleneck in computations when importing arbitrary drive cycles, ii) slower computations in general than other scripting or programming languages, and iii) less portable to integration with other applications and/or other platforms. This paper documents the development of a free and open-source coding of the fuel economy simulation modules of FASTSim in Java programming language. It is demonstrated that the Java implementation produces the same results (within accuracy limits) as the Excel version for the various types of powertrains, with a test set including thousands of arbitrary drive cycles from California Household Travel Survey (CHTS). The computation speed of the Java implementation was bench-marked at approximately two orders of magnitude faster than the Excel version, which makes the Java implementation convenient for researchers seeking to analyze large sets of arbitrary drive cycles.