Analysis of the Total Unit Energy Consumption of a Car with a Hybrid Drive System in Real Operating Conditions

Abstract

The market demand for vehicles with reduced energy consumption, as well as increasingly stringent standards limiting CO2 emissions, are the focus of a large number of research works undertaken in the analysis of the energy consumption of cars in real operating conditions. Taking into account the growing share of hybrid drive units on the automotive market, the aim of the article is to analyse the total unit energy consumption of a car operating in real road conditions, equipped with an advanced hybrid drive system of the PHEV (plug-in hybrid electric vehicles) type. In this paper, special attention has been paid to the total unit energy consumption of a car resulting from the cooperation of the two independent power units, internal combustion and electric. The results obtained for the individual drive units were presented in the form of a new unit index of the car, which allows us to compare the consumption of energy obtained from fuel with the use of electricity supported from the car’s batteries, during journeys in real road conditions. The presented research results indicate a several-fold increase in the total unit energy consumption of a car powered by an internal combustion engine compared to an electric car. The values of the total unit energy consumption of the car in real road conditions for the internal combustion drive are within the range 1.25–2.95 (J/(kg · m)) in relation to the electric drive 0.27–1.1 (J/(kg · m)) in terms of instantaneous values. In terms of average values, the appropriate values for only the combustion engine are 1.54 (J/(kg · m)) and for the electric drive only are 0.45 (J/(kg · m)) which results in the internal combustion engine values being 3.4 times higher than the electric values. It is the combustion of fuel that causes the greatest increase in energy supplied from the drive unit to the car’s propulsion system in the TTW (tank to wheels) system. At the same time this component is responsible for energy losses and CO2 emissions to the environment. The results were analysed to identify the differences between the actual life cycle energy consumption of the hybrid powertrain and the WLTP (Worldwide Harmonized Light-Duty Test Procedure) homologation cycle.

Study of energy consumption of a hybrid vehicle in real-world conditions

“…Average engine system operating parameters during travels carried out in the hybrid engine system's standard operating mode average energy expenditure per kilometre travelled of which amounts to 234.9 Wh/km, which is equal to 0.72 MJ/km. This difference results mainly from the efficiency of the power units used [29].…”

“…Complex speed profiles occur in reality, where the profile's kinematic parameters (speed, acceleration) are averages of many simple profile components (simple modules). The average values can be calculated from equations (3) and ( 4), where the average speed of a complex profile can be calculated from dependency [29]:…”

Energy consumption of a passenger car with a hybrid powertrain in real traffic conditions

“…An important issue is the possibility of reducing fuel consumption by recovering car kinetic energy in its retarded motion phase, where in most cases energy is dissipated by the braking system to the environment. Hence, the introduction of Hybrid Electric Vehicle (HEV), was aimed at reducing the loss of energy in the drive system through its energy recovery [16,21,26]. In such cars, there is an integrated hybrid drive system with two energy storages (fuel and electricity), as well as two independent drive units (combustion and electric), which drive the vehicle together.…”

“…Architecture of the parallel hybrid electric vehicle [7] It results from the greater versatility of such a drive system solution in everyday use, both in urban and extra-urban traffic [2,5,18,19]. Many authors conduct research on this type of hybrid drive systems in relation to the emission limits of harmful components [15,16] as well as in terms of total energy consumption in normal operating conditions [12,13,20] or in relation only to the electric drive system [6,19]. The real test that verifies such hybrid drive systems in terms of energy consumption is road measurements under real operating conditions.…”

Energy Management Strategy for an Electromechanical-Hydraulic Coupled Power Electric Vehicle Considering the Optimal Speed Threshold

“…PHEVs usually use a small internal combustion engine powered by fossil fuels with an electric motor, which can increase the range of the vehicle but not eliminate the use of fossil fuels [9]. In terms of average values, the appropriate value for the combustion engine is 1.54 (J/(kg•m)) [10]. FCEVs are considered to be one of the cleanest vehicles that do not use fossil fuels, but they are limited by the hydrogen infrastructure and the procurement cost of fuel cells, which will have a low penetration rate in the coming years [11].…”