E-Mobility Engineering 015 l EMotive Scarab off-road truck dossier l In Conversation: Giulio Ornella l Hall effect and magnetic sensors focus l Challenge of batteries for heavy-duty EVs l Alpha Motor Corporation digest l Automated charging insight l HVAC systems focus

Focus | HVAC systems Acknowledgements The author would like to thank Dan Jacques at Allegro Microsystems Michael Bires at AVL, Wolfgang Wenzel and Anita Bongards at BorgWarner Corporate Advanced Engineering, Steve Clarke at Hanon Systems, Max Vizzini at STMicroelectronics, and Leopold Gurtner at Webasto Group for their help with researching this article. says, in avoiding the loss of large amounts of heated/cooled air every time passengers embark or disembark, for example, suggesting the need for some kind of airlock and an efficient recirculation system. However, there are limits to the use of recirculation as window fogging has to be avoided, as does exposing occupants to airborne pathogens such as Covid. Buses might benefit even more than cars from heating and cooling targeted on occupied seats rather than conditioning the entire volume of air in the vehicle, he adds, along with predictive controls informed by the route plan. If decentralised HVAC systems are more efficient for a single vehicle, we can imagine that this is even truer for buses, the control software and hardware expert comments. Besides their higher energy consumption for heating and cooling compared with cars, bus HVAC systems tend to have greater distances between their air outlets, despite the need to provide a homogenous climate for the passenger cabin, according to our HVAC, battery and charging systems expert. Buses also need separate climate control zones for the driver and passengers. Furthermore, airflow needs to be controlled very carefully in buses because, for example, passengers have different ranges of tolerance to it, while bus systems must be easier to service and repair than in cars. Simulate early, and often Because HVAC has such an impact on an EV’s energy efficiency, and an intimate relationship with the powertrain thermal management system, and because climate control zones with targeted heating and cooling has to be integrated, the system has to considered early in the vehicle’s design life. This makes engineering simulations essential. The simulation expert recalls that 6 or 7 years ago, a vehicle development project might run for 4.5 years, with prototypes available for at least 2.5 years. These days, however, everything has to be done in not much more than 2 years, he notes. For this reason, his company has developed a virtual validation of entire simulated vehicles, supported by a ‘model connect’ platform that enables all its own simulation software tools to be linked together, along with other tools used by vehicle OEMs, for example. Using component data gathered from tests or simulations, a complete HVAC system can be modelled with all the subsystem interdependencies at very early stages of the development process. That speeds up the optimisation process. What’s more, simulations enable thorough exploration of the influences of design, boundary conditions and drive profiles on overall efficiency, performance, durability, safety and comfort. As well as enabling developers to evaluate performance early on, virtual testing also allows them to address other critical areas such as NVH and long-term durability before investing in physical prototypes to test. It also reduces overall development time and cost by minimising the number of physical prototypes required, the HVAC systems builder notes. With HVAC specifically, he adds, CFD is valuable for understanding airflow, enabling the development and validation of more compact systems for a given level of performance. Applying FEA is particularly useful for ensuring long-term durability and minimising NVH in HVAC systems. For example, FEA simulations help engineers determine the optimal number and location of module attachment points to reduce noise and vibration. Drilling down further, the design of HVAC module doors (which open and close to manage airflow) can be analysed to ensure smooth movement and proper sealing, robustness and elimination of objectionable noises, he says. Future HVAC and climate control development will be characterised by a relentless drive for efficiency while reducing complexity and cost – goals that can conflict with each other, so engineers will have to consider the inevitable trade-offs very carefully. AVL’s Model Connect platform enables multiple component and subsystem models to be linked for simulating complete systems early in development (Courtesy of AVL) 72 Autumn 2022 | E-Mobility Engineering