Le Mans Hypercars (LMH), like those competing in the World Endurance Championship (WEC) and the 24 Hours of Le Mans, use sophisticated hybrid powertrains that allow them to seamlessly switch between full electric power and the internal combustion engine (ICE) while driving. This ability to alternate between power sources is a key aspect of the hybrid system, enabling efficiency, better energy management, and reduced emissions during specific phases of the race. The transition between these power sources is handled by advanced control systems that manage the electric motor, energy storage (batteries), and the combustion engine in real time. Polymers play a crucial role in ensuring the smooth and reliable operation of this process, especially in areas like thermal management, electrical insulation, and vibration damping.
How LMH Cars Switch from Electric to ICE Power
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Electric-Only Mode: In electric-only mode, the Motor Generator Unit (MGU) drives the wheels using power stored in the Energy Store (ES) (the battery). This mode is typically used in low-speed situations, such as when the car is exiting the pit lane or during slow sections of the track to conserve fuel and reduce emissions. In this mode, the internal combustion engine remains off, and the car runs silently on electric power.
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Hybrid Mode (Transition): As the driver demands more power—during acceleration or high-speed sections—the hybrid system seamlessly engages the internal combustion engine (ICE) to provide additional power. This transition is managed by the Energy Recovery System (ERS) and is automatic, with the car’s control unit deciding when to activate the engine based on speed, throttle input, and the state of the battery. The electric motor can still contribute torque alongside the ICE, providing a boost in power when necessary.
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ICE-Only Mode: At higher speeds or during long straights, the car may run primarily on ICE power. The hybrid system will still use the MGU to capture energy via regenerative braking, storing this energy in the battery for later use. The switch to ICE-only mode allows for maximum power output during fast sections of the race.
Throughout these transitions, the hybrid system ensures that the switch between electric and ICE power is seamless, preventing interruptions in performance and optimizing power delivery based on the track conditions.
Role of Polymers in the Hybrid System
Polymers are extensively used in hybrid systems, particularly in critical areas such as the batteries, motors, and electrical components, where they provide essential benefits like thermal management, electrical insulation, and vibration resistance. These properties help maintain the efficiency, reliability, and safety of the hybrid system during the constant switching between electric and ICE power.
1. Thermal Management
During the transition from electric power to ICE, both the electric motor and the battery generate significant heat. Managing this heat is crucial for maintaining system efficiency and preventing overheating, which could damage sensitive components or reduce performance. Polymers play a vital role in dissipating heat and protecting key parts from thermal stress.
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PEEK (Polyether Ether Ketone) is used in various components of the hybrid system due to its high thermal stability. It is often found in battery casings, motor housings, and insulating materials around the electrical systems, ensuring that these components do not overheat during the switch between power modes.
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Silicone-based polymers are employed in the gaskets and seals of both the motor and battery systems to ensure that heat is effectively managed. Silicone’s ability to withstand high temperatures makes it ideal for ensuring that these components remain secure and protected from thermal damage.
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Thermal management interfaces, such as thermal pads made from polymer-based materials, are used between key components to facilitate heat dissipation, helping maintain the optimal operating temperature for both the ICE and the electric motor during transitions.
2. Electrical Insulation
The transition between electric power and ICE involves the use of high-voltage electrical systems that must be carefully insulated to ensure safe operation. Polymers with excellent electrical insulation properties are critical in preventing short circuits and protecting the hybrid system's electrical components.
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PTFE (Polytetrafluoroethylene) and polyimide (PI) are used for insulating electrical components in the hybrid system, particularly in the wiring and connectors that manage the flow of electricity between the battery, motor, and control unit. PTFE is used for its excellent dielectric properties, while polyimide films (such as Kapton) provide reliable insulation in high-temperature environments.
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Insulation in wiring harnesses: The wiring that connects the electric motor to the battery and control systems must be insulated to prevent electrical shorts or energy loss. PTFE is commonly used as an insulator for these high-voltage wires, ensuring that the energy flow between components is efficient and safe during power transitions.
3. Lightweight Construction
Hybrid systems add complexity and components to a race car, so weight management is crucial for maintaining optimal performance. Polymers are widely used in the construction of motors, battery packs, and other hybrid components to reduce weight without sacrificing strength or durability.
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Carbon fiber-reinforced polymers (CFRP) are used in the housings of hybrid motors and battery enclosures, providing a strong, lightweight structure that minimizes the overall weight of the hybrid system. By using CFRP in non-load-bearing components, manufacturers can keep the hybrid powertrain as light as possible, improving acceleration, handling, and efficiency.
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Battery enclosures made from polymer composites ensure that the battery pack remains lightweight while offering the necessary protection from heat and vibrations. These enclosures also prevent damage during the energy transitions that occur during the race.
4. Vibration Resistance and Durability
Switching between electric power and ICE generates vibrations and mechanical stresses, especially as the motor ramps up or slows down. Elastomeric polymers are used to absorb these vibrations and ensure the hybrid system operates smoothly, protecting the components from wear and tear.
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Vibration-damping polymers, such as silicone and EPDM (Ethylene Propylene Diene Monomer rubber), are used in motor mounts, battery casings, and other hybrid components to absorb vibrations during transitions between power modes. This prevents mechanical damage and helps maintain the integrity of the hybrid system over time.
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Polymer bushings are also used in mounting the electric motor and its associated components, reducing the transmission of vibrations to the rest of the car, which is essential for maintaining the driver’s control and minimizing wear on other systems.
5. Corrosion Resistance
The hybrid system, especially its electrical components and battery packs, is exposed to a wide range of environmental factors, including moisture, dirt, and debris. Polymers provide essential corrosion resistance, ensuring that these components are protected from external elements.
- PEEK and PTFE are commonly used in seals and gaskets to prevent moisture and other contaminants from entering the sensitive areas of the hybrid system. These materials resist corrosion and chemical exposure, which is critical for maintaining the reliability and performance of the system during endurance races.
Conclusion
The hybrid powertrains in Le Mans Hypercars (LMH) are engineered to switch seamlessly between electric power and the internal combustion engine (ICE) while driving, optimizing power delivery for performance, efficiency, and energy recovery. Polymers play a vital role in enabling this process, providing essential benefits such as thermal management, electrical insulation, lightweight construction, and vibration resistance. By using advanced polymers in critical components like the motor, battery, and electrical systems, LMH manufacturers can ensure that their hybrid systems operate efficiently and reliably under the extreme conditions of endurance racing. This not only improves the performance of the cars but also enhances their ability to manage energy effectively throughout the race.