Le Mans Daytona Hybrid (LMDh) and Le Mans Hypercar (LMH) cars competing in endurance racing series like the IMSA WeatherTech SportsCar Championship (IMSA), World Endurance Championship (WEC), and the 24 Hours of Le Mans utilise advanced hybrid powertrains to balance performance, efficiency, and sustainability. These hybrid systems combine traditional internal combustion engines (ICE) with electric motors and battery packs to optimise power delivery and energy recovery, which is crucial for the long and grueling endurance races that define these championships.
The hybrid systems in LMDh and LMH cars are designed to offer a combination of high performance, energy recovery (regenerative braking), and improved fuel efficiency, allowing the cars to deliver exceptional power output while adhering to modern motorsport's sustainability goals. Polymers play a significant role in the construction of both motors and battery systems, providing key advantages such as thermal management, lightweight properties, electrical insulation, and corrosion resistance. Here's how these hybrid powertrains work and where polymers are used in their components.
How Hybrid Powertrains Work in LMDh and LMH Cars
1. Internal Combustion Engine (ICE)
The ICE in hybrid LMDh and LMH cars is typically a high-performance, fuel-efficient engine that operates alongside the electric motor. Depending on the manufacturer, these engines can be either turbocharged or naturally aspirated and are often V6, V8, or V10 configurations. The ICE provides the bulk of the power for high-speed sections and long straights while also supplying power during intense acceleration.
2. Electric Motor and Motor Generator Unit (MGU)
The electric motor, also known as the Motor Generator Unit (MGU), operates alongside the internal combustion engine to provide additional power and improve efficiency. The MGU performs dual functions:
- It harvests energy during braking (regenerative braking) and converts it into electrical energy, which is stored in the battery.
- It deploys stored energy from the battery to drive the car’s wheels, providing extra power during acceleration or at key moments in a race (such as overtaking).
The MGU assists the ICE by delivering a boost in torque, improving acceleration and enabling the car to reach higher speeds more quickly. This dual power delivery system helps to balance performance with fuel efficiency, as the electric motor can take over or assist in low-speed or high-torque situations, reducing the reliance on fuel.
3. Energy Store (Battery)
The battery in hybrid race cars is an essential component of the powertrain, as it stores the energy harvested during regenerative braking. The energy stored in the battery is then used by the electric motor to provide additional power when needed. These high-performance battery systems must be lightweight, efficient, and capable of withstanding the extreme demands of endurance racing.
The batteries used in LMDh and LMH cars are typically lithium-ion or solid-state batteries, capable of storing large amounts of energy and delivering high power outputs quickly and efficiently.
4. Regenerative Braking
One of the key advantages of hybrid powertrains is the regenerative braking system. When the car brakes, the MGU captures the kinetic energy generated by braking and converts it into electrical energy. This energy is then stored in the battery and can be redeployed to drive the electric motor. This process reduces energy wastage and improves overall efficiency.
Role of Polymers in Hybrid Powertrains
Polymers are used extensively in the construction of hybrid powertrains, particularly in the motors and battery systems, because they provide essential benefits like lightweight construction, thermal management, electrical insulation, and corrosion resistance. These properties are critical to ensuring that the motors and batteries can perform reliably under the extreme conditions of endurance racing.
1. Polymers in Motors
Hybrid motors, or MGUs, operate at high speeds and temperatures, requiring materials that can withstand these stresses while maintaining efficiency. Polymers play a crucial role in various parts of the motor.
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Electrical Insulation: The electric motor generates significant amounts of electricity, which needs to be safely contained to prevent short circuits or electrical faults. Polymers like PTFE (Polytetrafluoroethylene) and polyimide (PI) are used as insulation for wires and electrical windings within the motor to prevent electrical leakage and ensure efficient energy transfer.
- PTFE is commonly used for wire insulation due to its excellent dielectric properties and high-temperature resistance.
- Polyimide films, like Kapton, are used for their ability to maintain structural integrity at extreme temperatures and provide electrical insulation in tight spaces within the motor.
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Thermal Management: Motors generate a lot of heat during operation, and overheating can severely affect performance. PEEK (Polyether Ether Ketone) and silicone-based polymers are used in cooling systems, motor housings, and gaskets to manage heat and protect the motor from thermal damage.
- PEEK is highly resistant to heat and mechanical stress, making it ideal for motor components exposed to high temperatures.
- Silicone polymers are used for gaskets and seals that help maintain the motor’s cooling systems by containing fluids and managing airflow around critical areas.
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Lightweight Components: Motors in hybrid systems need to be as lightweight as possible to optimise the overall weight of the car. Carbon fibre-reinforced polymers (CFRP) are often used in the construction of motor housings and structural components to provide strength while minimising weight. This is crucial for ensuring that the hybrid powertrain does not add excessive weight to the vehicle, which could negatively impact performance.
2. Polymers in Batteries
Batteries in hybrid race cars must store large amounts of energy, deliver it efficiently, and be able to withstand the extreme conditions of endurance racing. Polymers are essential for ensuring the safety, efficiency, and durability of these high-performance battery systems.
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Electrical Insulation: Lithium-ion and solid-state batteries generate high voltages, making electrical insulation a critical factor in battery design. Polyimide and PTFE are used to insulate battery cells and wiring, ensuring that the electrical currents remain contained and preventing short circuits or overheating.
- Polyimide films are often used to separate battery cells, providing insulation and maintaining safety within the high-voltage environment of the battery pack.
- PTFE coatings and linings are used for wiring and connectors to protect against electrical discharge.
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Thermal Management: Hybrid batteries generate significant heat during energy storage and deployment. Polymers like PEEK and silicone-based materials are used in battery housings and cooling systems to manage heat effectively.
- PEEK is used for battery enclosures and cooling channels due to its ability to withstand high temperatures without deforming or degrading.
- Silicone-based polymers are employed in thermal interfaces to help dissipate heat away from the battery cells, ensuring that the battery operates within a safe temperature range and preventing thermal runaway.
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Corrosion Resistance: Batteries are exposed to harsh environments, including moisture, fuel, and chemicals. Polymers such as PEEK and PTFE offer corrosion resistance, protecting battery components from degradation caused by exposure to these elements.
- PEEK is often used for battery housings and protective covers because it is lightweight, strong, and resistant to both corrosion and high temperatures.
- PTFE coatings are used to protect electrical connectors and terminals from chemical exposure, ensuring the long-term reliability of the battery system.
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Lightweight Construction: Weight is a critical factor in endurance racing, where every kilogram saved contributes to improved performance. Polymers such as CFRP are used in battery casings and protective structures to provide a lightweight yet strong solution, reducing the overall weight of the battery system without compromising safety or performance.
Conclusion
The hybrid powertrains used in LMDh and LMH cars represent the cutting edge of endurance racing technology, combining internal combustion engines, electric motors, and battery systems to deliver high performance, fuel efficiency, and energy recovery. Polymers play a crucial role in these systems by providing lightweight materials, thermal management, electrical insulation, and corrosion resistance in the motors and batteries. These advantages ensure that the hybrid powertrains can perform reliably in the demanding environments of IMSA, WEC, and Le Mans, helping teams achieve the balance between performance, efficiency, and sustainability that defines modern endurance racing.