[ERTW]

I was reading the latest SAE Automotive Engineering magazine, and they mentioned Torotrak's Flybrid system.

"Fundamentally, you use the flywheel for acceleration and the engine for cruising."

"Under steady cruise condition, when the engine is lightly loaded, BSFC is rarely at its optimum value. While charging the flywheel, the engine is placed under slightly greater load and therefore operates more efficiently...Once the flywheel is energized, the engine is switched off and the stored kinetic energy released to power the vehicle, then the cycle is repeated."

"This 'boost and cruise' approach has contributed to Volvo's Flybrid demonstrator achieving a 25% fuel efficiency improvement in real-world driving...one case...the predicted BSFC improved from 470 g/kWh to 280 g/kWh when charging the flywheel."

Flywheels have high power density, instant charging, and extreme life.