Composite Flywheel Systems: Another Piece of the Electric Car?

We recently received this question from one of our readers in response to our post regarding battery backup solar systems:

Is there such a thing as a small, composite flywheel system? My reading lately makes me curious about this. Although there would be a bigger initial cost, the savings in maintenance and the rapidity of start-up should make up for this. They have braking flywheel systems in hybrids, right? Can backup power banking source from the same places as the braking flywheel manufacturers? -Jade Queen

Well, Jade, there is indeed such a thing as a small, composite flywheel system and all Toyota Prius hybrids do have flywheel systems that recover braking energy. Unfortunately that is as far as these systems go with present technology. Chrysler, Toyota, and other auto manufacturers are working on designs that could spread the usefulness of flywheel systems.

But before I go any further, let’s briefly examine composite flywheel systems. A flywheel system basically works by accelerating a rotor (flywheel) at a very high speed and maintaining the ensuing energy as rotational energy. Energy is fed back by decelerating the rotor. Conventionally, electricity was used to spin the flywheel, but newer systems use mechanical or kinetic energy (i.e., the Prius’ braking flywheel system). Composite flywheels are made from strong carbon fibers and can spin at incredibly high speeds exceeding 50,000 rpm.

There are a number of reasons why flywheel systems are still rare or limited in today’s automobiles. A big one has been safety; a rotor spinning at that speed, should it break, has a powerful destructive force. Therefore, flywheels must be enclosed in a very strong shell or casing, which is a vacuum to reduce friction; that complicates car design.

However the advantages of flywheel systems keep researchers and investors eager. Flywheel systems are much more efficient than conventional battery systems by kinetically recovering energy and saving on fuel use. They also reduce carbon emissions and could play a big part in staying or reversing the effects of global warming.

But any mass production of automobiles using flywheel energy systems to a greater degree than today’s hybrids is far off and may fall prey to improvements in lithium-ion battery advancements, but that’s not keeping down designers, the potential is too great.

Flywheel systems are most popular in car racing (see this excellent article on flywheels from Green Car Advisor) at the moment because they provide, as Jade points out, a sudden burst of energy and rapid acceleration. They are also relatively low maintenance, needing little more than the occasional change of the bearings over a long period of time. In addition to car racing, flywheel systems are also used for rail buses in England.

As for solar backup battery banks and flywheel systems integrating, I can find no information on that, although the possibility is certainly there, tackling the hurdles of size (to store enough energy to backup power a home), volatility, and cost.

These new composite systems are certainly tough and much lighter than steel, but the best they offer at this time seems to be some power for acceleration or running the AC in the car. Yet the way technology advances these days…Ideas seem to become realities as fast as we can come up with new ideas. So thank you Jade for an excellent question and we shall see.

Photo Credit: Flybrid Systems

Posted on January 28th in Solar Products by Dan.