Thermal Management: The Balance Between Comfort and Electric Vehicle Range

Passengers want to feel comfortable within their vehicle and for it to be cool enough when the ambient temperature is hot and vice versa. These elements have implications on how OEMs condition the battery, and this can affect range in a positive or a negative way, often more negative more than positive. Finding this sweet spot in terms of thermal management as the industry is constrained by range has never been more important. 

With this in mind, Automotive IQ interviewed Alessandro Riccio, Energy and Thermal Performance Engineer at Iveco Group to find out how OEMs can achieve the sweet spot between passenger comfort and range, as well as ways to manage, cool, and heat all the high-voltage and low-voltage components within the car depending on what the ambient temperature is. 

Interview topic discussions: 

• Balancing Passenger Comfort and Vehicle Range 

• Industry Trends 

• Battery Conditioning Impact 

• Challenges in Thermal Management 

• Positive and Negative Impacts 

• Different Approaches by OEMs 

• Comprehensive Temperature Management

Interview

Q: Can you share a bit about your role as an Energy and Thermal Performance Engineer at Iveco Group and how it relates to managing temperature within vehicles? 

A: At Iveco Group the role of the Energy and Thermal performance Engineer is responsible of the overall vehicle energy consumption both for the traction, and for the thermal contributes. It represents a key figure targeting the optimisation of the vehicle energy flows to increase vehicle range as much as possible. From an energy point of view, it considers all the aspects related to the vehicle resistance forces, while for the thermal side, the focus is mainly on cabin heating/cooling and HV components management. Both contributors are the main characters that can increase or reduce the vehicle range. For this reason, it is crucial to link energetic and thermal branches to optimise the overall vehicle efficiency. 

Q: In the context of managing temperature within vehicles, how do you define the optimum balance between passenger comfort and vehicle range? 

A: Properly managing the powertrain components’ temperature and controlling the climatic air inside the cabin is one of the most difficult challenges for the electric vehicle. The requirements used for the conventional ICE applications, in which heating and cooling are not so demanding from the energy standpoint, can’t be applied for electric vehicles and the introduction of the thermal perception is then crucial. 

The sensation of being in a comfortable state from the thermal point of view is strictly personal and subjective and can be different from each other. Nevertheless, a parameter able to quantify whether passengers are in a thermal comfort state or not does not exist. In general, a smart energy split is something that allows the mission to end safely, without range anxiety, and with a good thermal perception during all the driving experience. 

Q: To your knowledge, what are some notable trends or approaches that different OEMs are adopting to achieve the sweet spot between passenger comfort and range in their vehicles? 

A: Having a highly efficient energetic system is one of the most important and stimulating challenges of our generation, not only for the automotive environment but for every kind of application. The introduction in the automotive field of a direct/indirect heat pump is one of the most common interventions to improve energetic efficiency. If properly designed, the heat pump can ensure the same thermal comfort performance, compared to a PTC-based system, while increasing the distance covered. Another common-used approach is to modify the HVAC control logic with respect to the traditional ICE applications: a user-oriented control based on thermal perception, instead of posing the basis of the HVAC control on the average temperature inside the vehicle. 

Q: How does the conditioning of the battery play a role in achieving this balance, and what implications does it have on the overall vehicle range? 

A: The battery pre-conditioning plays a fundamental role in reaching an optimum balance. Heating/cooling the batteries is necessary to reach the optimal working window at which the energy storage system can work. The optimal operating points can be reached through the aid of external devices, such as compressors, PTCs, or other more sophisticated tools. A constant and prolonged use of these HV or LV components requires a lot of energy and consequently, the vehicle range decreases. 

A possible trade-off can be to cool/warm the battery enough to get close to the optimal condition, without having the heater or the cooler active for too long time. 

Q: Given the industry’s range constraints, what challenges do OEMs face in finding the sweet spot in terms of thermal management for both passenger comfort and vehicle range? 

A: The thermal system management is a crucial aspect for the BEV to avoid energy wasting. If correctly calibrated, the management allows us to reach an optimum balance between range and thermal comfort. Introducing adaptive thermal management shall be a key aspect to move from thermal comfort to thermal perception. Studying and learning the driver and passengers’ perception during the driving experience at different conditions can adapt the logic to the occupant’s needs. In this way, the driver won’t change the target temperature continually and the thermal system could work in optimal conditions owing to the prediction of the driver's perception. Also, the interaction between all the auxiliaries and the HV components is the key to properly exploiting all the heating sources (like e-motor, battery, etc.). 

Q: Could you elaborate on how conditioning the battery and managing temperature within the vehicle can have both positive and negative impacts on the vehicle’s range? 

A: The battery temperature has a critical throwback on the efficiency. Over certain limits, the battery is not able to guarantee the nominal characteristics in terms of charge and discharge currents, lifecycle, and warranties. A higher or lower temperature reduces the discharge and charge currents, thus limiting the vehicle maneuvers. Then, longitudinal performance and regeneration capability are strongly influenced by this limitation that modifies the vehicle drivability and the energy storage capability. The not fully achieved performance should push the driver to request more power through the pedal, thus stressing the battery and reducing the range. On the opposite side, the regeneration is not completely exploited by the battery, wasting useful energy to recharge the vehicle. 

Q: How do you manage, cool, and heat both high-voltage and low-voltage components within a vehicle, considering the ambient temperature? 

A: The ambient temperature plays an important role in correctly calibrating the logic to cool and heat both HV and LV components. It’s not necessary to request full power at the auxiliaries to heat/cool the HV components when their temperature is close to the upper/lower limit and the ambient temperature is not so extreme. During the moderate ambient temperature, it’s possible to try to completely avoid the heating or the cooling of such components to save energy. This approach can’t be used in extreme conditions when components warming and cooling represent a constraint.

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