Optimal Deployment of Emissions Reduction Technologies for Construction Equipment

Abstract

ABSTRACT The objective of this research was to develop a multiobjective optimization model to deploy emissions reduction technologies for nonroad construction equipment to reduce emissions in a cost-effective and optimal manner. Given a fleet of construction equipment emitting different pollutants in the nonattainment (NA) and near -nonattainment (NNA) counties of a state and a set of emissions reduction technologies available for installation on equipment to control pollution/emissions, the model assists in determining the mix of technologies to be deployed so that maximum emissions reduction and fuel savings are achieved within a given budget. Three technologies considered for emissions reduction were designated as X, Y, and Z to keep the model formulation general so that it can be applied for any other set of technologies. Two alternative methods of deploying these technologies on a fleet of equipment were investigated with the methods differing in the technology deployment preference in the NA and NNA counties. The model having a weighted objective function containing emissions reduction benefits and fuel-saving benefits was programmed with C++ and ILOG-CPLEX. For demonstration purposes, the model was applied for a selected construction equipment fleet owned by the Texas Department of Transportation, located in NA and NNA counties of Texas, assuming the three emissions reduction technologies X, Y, and Z to represent, respectively, hydrogen enrichment, selective catalytic reduction, and fuel additive technologies. Model solutions were obtained for varying budget amounts to test the sensitivity of emissions reductions and fuel-savings benefits with increasing the budget. Different mixes of technologies producing maximum oxides of nitrogen (NOx) reductions and total combined benefits (emissions reductions plus fuel savings) were indicated at different budget ranges. The initial steep portion of the plots for NOx reductions and total combined benefits against budgets for different combinations of emissions reduction technologies indicated a high benefit-cost ratio at lower budget amounts. The rate of NOx reductions and the increase of combined benefits decreased with increasing the budget, and with the budget exceeding certain limits neither further NOx reductions nor increased combined benefits were observed. Finally, the Pareto front obtained would enable the decision-maker to achieve a noninferior optimal combination of total NOx reductions and fuel-savings benefits for a given budget. IMPLICATIONS This paper describes a model that was developed to help decision-makers/feet managers deploy emissions reduction technologies to maximize the benefit of emissions reductions and fuel savings from their construction equipment feet. The model is based on a cost-effectiveness analysis. The model was demonstrated with three different emissions reduction technologies having different operational and performance characteristics. The model structure is quite flexible and thus can be adapted and applied to any type of emissions reduction technologies and can be implemented on on-road and nonroad sources.