Seite - 4 - in Hybrid Electric Vehicles

considerable research efforts toward reducing emissions and fossil fuel dependency without sacrificing vehicle performance. Recently, manufacturers developed technologies to reduce the NOx and particulate emissions of diesel engines, such as selective catalytic reduction and diesel oxidation catalyst [4, 5]. Moreover, common rail fuel injection has led to higher-effi- ciency diesel engines [6, 7]. Partial substitution of fossil diesel fuel with biodiesel is an appeal- ing option to reduce CO2 emissions [8, 9]. In the Brazilian transportation sector, the addition of biodiesel to fossil diesel fuel has been increasing since 2012 [10]. Heavy-duty construction and agricultural vehicles also have an environmental impact. In Agricultural Industry Advanced Vehicle Technology: Benchmark Study for Reduction in Petroleum Use [11], the current trends in increasing diesel efficiency in the farm sector are explored. Figure 1 shows the diesel demand in the United States, highlighting that in the agricultural and construction machinery field, the demand has remained relatively constant since 1985, representing a significant portion of the total fuel consumption. Similarly to the automotive sector, considerable efforts have been dedicated in recent years toward reducing the energy consumption of construction and agricultural machines without compromising their func- tionality and performance, taking into account the restrictions imposed by the recent emission regulations [12, 13]. Engine calibrations have been optimized to reduce exhaust pollutants in accordance with the U.S. Environmental Protection Agency emissions tiers. This was Figure 1. Historical diesel consumption in the United States. “Farm” includes agricultural diesel use; “off-highway” includes forestry, construction, and industrial use [11]. Hybrid Electric Vehicles4