Flywheel Hybrids

[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.

[serialk11r]

There's some magazine out there where some guy got to drive a Porsche 911 GT3 Hybrid, and I'm pretty sure this is a big reason why you don't want one in a street car: He said when the flywheel spun up, it was extremely loud.

[Cobb]

Sounds like a KERs system. The Insight does back ground charging to do something similar, however it actually lowers mpg and disabled lean burn.

[user removed]

The issue with flywheel and hydraulic hybrids is how do you provide the identical amount of power to the drive wheels (for constant speeds) regardless of the capacity or level of "charge" of your storage system. The issue that has remained unresolved is how to provide that power without sacrificing efficiency, wheel to wheel (complete regeneration cycle), that is above 80%. You can not have more than the absolute minimum of power conversions to accomplish that 80% wheel to wheel efficiency.

Gas electric hybrids will never reach that level and the application of power needs to be directly to the driven wheel and from that same driven wheel directly to storage. Flywheels are great for capacitive storage but not so great for storage based on energy density, which is the argument of the electric advocates.

10 years ago hydraulic hybrids were at 76-78% wheel to wheel, about twice the percentage of electric vehicle regeneration. The weakest point was the hydraulic to mechanical connection, which in the 2006 EPA version was a bent axis pump-motor (an ancient design) driving the differential at the same speed as the propeller shaft. The RPM was too high to realize the true potenital of a hydraulic drive, which reguires much lower revolutions to avoid losses to the volume of fluid moving through the system.

Flywheels and hydraulic accumulators both have very high efficiencies for storage, but the issue is power transfer. The greatest room for improvement is in the powertrain.

Check out US patent number 7677208 for my solution.

regards
mech

[a8ksh4]

How about a flywheel system like this:

Flywheel <-> AC Motor <-> F-Controller <-> D-Controller <-> AC Motor <-> Drivetrain

Power transfer to the vehicle is achieved by putting F-Controller in regen mode and D-Controller in power mode.

Power transfer to the flywheel is the reverse: D-Controller goes in regen and F-Controller goes in power mode.