Developing a Model to Quantify Emissions from Heavy-Duty Construction Equipment as Related to Job Site Activity Data

Published: January 2015

Client: Caltrans

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Executive Summary

The primary goal of this program was to develop a model to estimate emissions from off-road construction equipment as a function of fuel use. All of the emissions are produced by the combustion of the fuel and the amount of fuel burned is dependent upon the activity of the equipment, i. e. the physical work that the equipment is doing. As the equipment is asked to work harder the engine has to put out more power which requires using more fuel. Electronically controlled engines have an Electronic Control Module (ECM) which controls the speed, fueling rate, horsepower output etc. For diagnostic purposes there is an output jack where an instrument can be attached to read all of the signals from the ECM. While many of the signals are proprietary and can only be interpreted by the Manufacturers instruments, several of the signals which relate to the work that the engine is doing are publicly available. Therefore a secondary goal was to measure these publicly available signals to determine engine response and fuel use for a large subset of off-road equipment for comparison to the responses observed during actual in-use emission testing and estimate the emissions based upon the fuel usage. Between a 2010 joint program with the California Air Resources Board (CARB) (Durbin, et al., 2013) and Caltrans (Barth, et al., 2012) and a 2012 program with CARB (Johnson, et al., 2013), emissions were measured from 27 pieces of off-road construction equipment. The equipment included 4 backhoes, 6 wheel loaders, 4 excavators, 2 scrapers (one with 2 engines), 6 bulldozers, and 4 graders. The engines ranged in model year from 2003 to 2012, in rated horsepower from 92 to 540 hp, and from 24 to 17,149 hours of operation. The 27 pieces of equipment include 7 pieces of Tier 2 equipment, 15 pieces of Tier 3 equipment, and 5 pieces of Tier 4i equipment… The emissions measurements were made on a second-by-second basis using a portable emissions measurement system (PEMS) to develop relationships between NOx and PM and other emissions and fuel use. Analysis of the data indicated that a model could be developed based upon two modes of operation defined as idle and work and not on specialized physical activity such as trenching, scraping, backfilling, etc… The data for each piece of equipment was partitioned into idle and non-idle based primarily on the engine speed. The standard idle speed was determined for each vehicle from the dataset and the data was partitioned into mini events where mini events are defined as sections of continuous and uniform activity modes that end when the activity mode changes. The objective of this analysis was to create a tool that can be used to estimate emissions from off-road construction equipment based upon data readily available to the equipment owners. The developed model, Off-Road Equipment Emission Estimator (ORE) model is a stand-alone Excel spreadsheet with a graphical user interface and the ability to load parameter files to facilitate running the model.

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