Electric vehicles have never been more popular, yet fears around being left stranded by an exhausted battery remain a key reason why some car buyers resist making a purchase. Bigger batteries are not always the solution because of the direct link with higher costs and high impact on weight. A re-engineering of the most energy-consuming auxiliaries is mandatory and the thermal management function is on top of the redesign request list. Heat Pump solution is considered one of the best way to save energy and reduce the impact on vehicle range of heating and cooling function, but the automotive application requires a careful definition of the system features to avoid unjustified growing up of complexity as well as an unneeded system over-sizing. The paper aims to give an overview on the heat pump design best practices through a virtual performance comparison of different lay-out configurations, which have been selected starting from a benchmark analysis crossed with a detailed vehicle segment-oriented functions selection. Control strategies role, costs, and target requirements have been used as drivers for…

Hybrid Electric Vehicle (HEV) powertrains are characterized by a complex design environment as a result of both the large number of possible layouts and the need for dedicated energy management strategies. When selecting the most suitable hybrid powertrain architecture at early design stage of HEVs, engineers usually focus on fuel economy (directly linked to tailpipe emissions) and vehicle drivability performance solely. However, high voltage batteries are a crucial component of HEVs as well in terms of performance and cost. This paper introduces a multitarget assessment framework for HEV powertrain architectures which considers both fuel economy and battery lifetime. A multi-objective formulation of dynamic programming is initially presented as off-line optimal HEV energy management strategy capable of predicting both fuel economy performance and battery lifetime of HEV powertrain layout options. Subsequently, three different HEV powertrain architectures are considered as test cases for the developed HEV assessment methodology including parallel P2, series-parallel P1P2 and power-split layouts. A comparison of numerical results for the three HEV powertrain test cases is then performed in terms of optimal fuel economy…

The rapid development of CO2 reduction policies pushes an equivalent effort by the OEM to design and produce Battery Electric Vehicles (BEV) in order to lower the global CO2 emission of its fleet. The main effort has been done primarily to the electric traction architecture (electric traction motor and battery energy storage). Anyway, the BEV autonomy range is still a weak point and this is even more critical when the customer operates the air conditioning system to reach and maintain the cabin comfort. The aim of this work is to present how the cabin design have to evolve in order to allow the reduction of the energy demand by the Air conditioning system allowing the vehicle to increase the autonomy range.

With the passage of Kigali Amendment to the Montreal Protocol in 2016, HFC-134a will need to be phased down in all markets worldwide due to its high global warming potential (GWP=1300). Meanwhile, global adoption of electric vehicles is accelerating. Improved MAC and heat pump efficiency is critically important to extend vehicle range. Engineers must design MAC and heat pump systems using low-GWP refrigerants that are simultaneously cost-effective, energy efficient, safe, reliable, affordable for consumers, and able to provide both cooling and heating of the cabin and thermal management of vehicle components like power electronics and batteries. This is a challenging and complex task. Fortunately, solutions are available, but they may diverge from traditional direct expansion systems of the past. This paper: 1) documents the global history and market status of the development of alternatives to HFC-134a, including secondary-loop (SL-MAC) systems; 2) outlines the existing and expected regulations demanding low-GWP MAC refrigerant and high fuel efficiency; 3) explains the importance of comprehensive LCCP analysis when evaluating MAC climate impacts instead of focusing on only one component…

This paper presents a methodology for the thermal analysis of a cylindrical Li-Ion battery cell. In particular, the 18650 format is considered. First, an electrical current drain cycle is applied to measure the electrical internal resistance of the cell and to estimate the consequent thermal energy release. A battery cell is then dissected and the inner structure is reproduced in detail with the adoption of microscopic images. By this way, the heat generation areas and the different thermal paths are correctly identified. Thermal Finite Element analyses are performed faithfully reproducing the inner geometry of the cell, and different cooling strategies are compared. The numerical results are then validated versus experimental evidence obtained considering the thermal behaviour of a small section, made by three cells, of a water cooled battery pack. The proposed approach can drive the design process towards more efficient battery pack cooling strategies. The numerical model may be then applied to perform thermo-structural analyses and, consequently, structural failures of the battery cells might be predicted.

The energy storage devices of electrified vehicles (Hybrid Electric Vehicles and Battery Electric Vehicles) are required to operate with highly dynamic current and power outputs, both for charging and discharging operation. When calculating the vehicle CO2 emissions and electrical energy consumption from a trip, the change in electrical energy content at vehicle-level has to be accounted for. This quantity, referred to as the electricity balance in the WLTP regulation, is normally obtained through a time-integration of the current or power supplied by the vehicle batteries during operation and the efficiency factor is often assumed to be unitary (as in the official type-approval procedure). The Joint Research Centre has collected experimental data from different electrified vehicles with regards to electrical energy use and battery State Of Charge (SOC) profile; the latter was used as a reference to quantify the actual vehicle electricity balance from a trip or driving cycle. In this work, the approach of using a simple Coulomb counting method with unitary efficiency for charging and discharging for the quantification of the vehicle electricity balance…

Axial cooling fans are commonly used in electric vehicles to cool batteries with high heating load. One drawback of the cooling fans is the high aeroacoustic noise level resulting from the fan blades and the obstacles facing the airflow. To create a comfortable cabin environment in the vehicle, and to reduce exterior noise emission, a low-noise installation design of the axial fan is required. The purpose of the project is to develop an efficient computational aeroacoustics (CAA) simulation process to assist the cooling-fan installation design. This paper reports the current progress of the development, where the narrow-band components of the fan noise is focused on. Two methods are used to compute the noise source. In the first method the source is computed from the flow field obtained using the unsteady Reynolds-averaged Navier-Stokes equations (unsteady RANS, or URANS) model. In the second method, the azimuthal modes of the flow field obtained using the steady RANS with the moving reference frame model are treated as the sound source. While the first method is able to resolve any…

The advancing electrification of the powertrain is leading towards new challenges in the field of acoustics. Film capacitors used in power electronics are a potential source of high-frequency interfering noise since they are exposed to voltage harmonics. These voltage harmonics are caused by semiconductor switching operations that are necessary to convert the DC voltage of the battery into three-phase alternating current for the electrical machine. In order to predict the acoustic characteristics of the DC-link capacitor at an early stage of development, a multiphysical chain of effects has to be addressed to consider electrical and mechanical influences. In this paper, a new method to evaluate the excitation amplitude of film capacitor windings is presented. The corresponding amplitudes are calculated via an analytical force based on electromechanical couplings of the dielectric within film capacitors. As a next step, these calculated excitation amplitudes can be used in a FE simulation by applying volumetric strains on capacitor windings. This allows to consider the structural dynamic properties of different capacitor geometries. In order to lower the computational costs, a…

The public transport in India is gradually shifting towards electric mobility. Long range in electric mobility can be served with High voltage battery (HVB), but HVB can sustain for its designed life if it’s maintained within a specific operating temperature range. Appropriate battery thermal management through battery cooling system (BCS) is critical for vehicle range and battery durability This work focus on two aspects BCS sizing and coolant flow optimization in Electric bus. BCS modelling was done in 1D CAE by using KULI software from M/s Magna Steyr. The objective is to develop a model of battery cooling system in virtual environment to replicate the physical testing. Electric bus contain numerous battery packs and a complex piping in its cooling system. BCS sizing simulation was performed to keep the battery packs in operating temperature range. Iterations were carried out to maintain uniform flow at the battery packs as well as to sustain target coolant flow requirement in order to maintain thermal uniformity across the battery packs 1D simulation is vital when it comes to analyzing…

As the global warming due to carbon footprint is very alarming, vehicle emissions are getting stringent day by day. In such situation vehicle hybridization or fully electric vehicles are of obvious choices. However in any of the cases the battery cooling is a big concern area. As the heat produced by the battery need to be dissipated within no time to prevent failure, it is of utmost need to develop and understand the battery cooling system. Present paper describes the experimental investigation of a battery cooling circuit. A complete bench comprising of both primary and secondary circuit is used for the testing. The primary circuit has a cooling unit with TXV, condenser and electric compressor run by high voltage. The secondary circuit consists of a chiller (integrated with TXV) unit responsible for battery cooling. The whole circuit typically resembles with one of dual air conditioning unit and uses one of known refrigerant used in vehicle AC system. However each circuit is connected with a valve for controlling the loop. The battery heat was represented by…