Energy, Exergy, and Emissions Analyses of Internal Combustion Engines and Battery Electric Vehicles for the Brazilian Energy Mix

Abstract

Exergy is a thermodynamic concept that ponders the quality of energy. It evaluates the irreversibilities of a machine, demonstrating its capacity to perform work associated with energy conversion. This article focuses on directing public policies and vehicle development toward their most proper usage worldwide. In the urban mobility scenario, there is an obvious demand to decrease greenhouse gas (GHG) emissions. In addition, the internal combustion engine (ICE) experiences considerable energy losses through heat exchange through the radiator and exhaust flow gases, which are not considerable in battery electric vehicles (BEVs) since there are no exhaust gases subsequent to combustion, nor combustion itself. This work presents longitudinal dynamics simulations of passenger vehicles to understand the magnitude of exergy destruction in ICEVs and BEVs, considering the Brazilian and European Union electric energy mix. Overall, the method can be applied to any other country. The simulation and model parameters were configured to match production road vehicles commercialized in the Brazilian market based on different versions of the same model. Two vehicle dynamic duty cycles were used, one relating to urban usage and another to highway usage, resulting in an overall exergy efficiency of around 50–51% for BEVs considering the exergy destruction in power plants. In contrast, ICE has an average efficiency of 20% in the urban cycle and around 30% in the highway cycle. By comparing the overall equivalent CO2 emissions, it is possible to conclude that EVs in the European energy matrix produce more GHG than ICE vehicles running on ethanol in Brazil. Nevertheless, there are increasing uses of coal, natural gas, and oil thermal electric power plants, raising the question of how the transition may occur with a general increase in electrification since there is an increasing electric expenditure in all sectors of society, and the renewable energy plants may not meet all of the demand.

Toward a Direct CO2 Tax for the Brazilian LDV Fleet

“…This figure excludes EVs and HEVs for the following reasons. First, their sales are still not representative; these vehicles have other incentives, and Well-to-Wheel (WTW) emissions can vary substantially depending on which emission factors are used for electricity and battery production [4,8]. It is beyond the scope of this article to discuss whether ethanol or electricity makes more sense for Brazil; nevertheless, it is necessary to bear in mind that both have the same carbon footprint [4,8].…”

“…First, their sales are still not representative; these vehicles have other incentives, and Well-to-Wheel (WTW) emissions can vary substantially depending on which emission factors are used for electricity and battery production [4,8]. It is beyond the scope of this article to discuss whether ethanol or electricity makes more sense for Brazil; nevertheless, it is necessary to bear in mind that both have the same carbon footprint [4,8]. They may not be adversaries and can complement each other to substitute fossil fuels gradually, but these next steps are outside the focus of this manuscript.…”

“…As shown by Fusco and Mady [4], LDVs are lighter and more energy-efficient [9], given that electrification achieves a reduction in CO 2 eq after about 40,000 km. Moreover, the advantages of decarbonization have still not been proven in the Brazilian scenario since the carbon footprint of ethanol is similar to that of electrical energy [8]. For instance, there are statements in the literature regarding the efficiency of sport utility vehicles (SUVs) [32] concerning sedan cars and smaller models.…”

“…Moreover, sugarcane is already fixed in some regions and is part of the national industry with the biorefineries [7]. These manuscripts concluded that ethanol is the transition fuel needed to decarbonize the individual sector since the carbon footprint of ethanol is similar to the country's electrical energy mix [8].…”