# New energy saving car?? **URL:** \ **Category:** Factual Questions\ **Created:** [July 26, 2001, 7:37pm UTC](https://boards.straightdope.com/t/new-energy-saving-car/73889 "2001-07-26T19:37:37Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![horhay\_achoa](https://avatars.discourse-cdn.com/v4/letter/h/ccd318/32.png) [@horhay\_achoa](https://boards.straightdope.com/u/horhay_achoa)\ **Post date:** [July 26, 2001, 7:37pm UTC](https://boards.straightdope.com/t/new-energy-saving-car/73889/1 "2001-07-26T19:37:37Z")
I don’t know a lot about this stuff, but I want to see what you all think. Is it possible to make a car that uses the rotation of the tires to generate energy to power the car. I know that it can’t be 100 percent self powered, but if you started it going with a small gas or electric engine, would it be possible to have the rotating tires power turbines to supply energy? I imagine the gas/ electric engine would have to kick in when going up hills, but when ever the car is coasting it could be storing up energy. Is this possible? ---
**Author:** ![Dr.Lao](https://avatars.discourse-cdn.com/v4/letter/d/2bfe46/32.png) [@Dr.Lao](https://boards.straightdope.com/u/Dr.Lao)\ **Post date:** [July 26, 2001, 7:56pm UTC](https://boards.straightdope.com/t/new-energy-saving-car/73889/2 "2001-07-26T19:56:14Z")
In a word: No. Rotating tires don’t produce any energy, they are energy. If you use them to power a turbine they will slow down and eventually stop. You will not get any more energy out of the tires than you put into them initially. In fact, because of frictional losses, you will get less out of them than you put into them. ---
**Author:** ![sewalk](https://avatars.discourse-cdn.com/v4/letter/s/b3f665/32.png) [@sewalk](https://boards.straightdope.com/u/sewalk)\ **Post date:** [July 26, 2001, 8:35pm UTC](https://boards.straightdope.com/t/new-energy-saving-car/73889/3 "2001-07-26T20:35:50Z")
In a word:No. Just like the good doctor said, but in a very subtle way, yes. Most, if not all, current electric designs use regenerative braking meaning that electrical energy is generated by braking and routed back into the battery. This lets you recapture _some_ of the enrgy used to propel the car. Obviously, you still need some large power source for getting the car in motion, climbing hills, and overcoming friction. ---
**Author:** ![zut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zut/32/2875_2.png) [@zut](https://boards.straightdope.com/u/zut)\ **Post date:** [July 26, 2001, 8:36pm UTC](https://boards.straightdope.com/t/new-energy-saving-car/73889/4 "2001-07-26T20:36:08Z")
In a word, maybe. Depends on what your question is; your OP could be interpreted in two different ways. If your question is, “Can you hook a generator up to a car’s wheels to produce energy from the spinning wheels while the car is driving?” then the answer is no, as **Dr. Lao** says. If your question is, “Can you hook a generator up to a car’s wheels to _recover energy when the car is braking_?” then the answer is yes. This is called “regenerative braking”; do a Google search on that term if you want to learn more about the concept. Of course, you understand that the amount of energy you recover with regenerative braking is much less than what the engine originally outputs; however, on an electric or electric hybrid car runnung in stop-and-start traffic, the energy savings can be pretty substantial. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [July 26, 2001, 10:44pm UTC](https://boards.straightdope.com/t/new-energy-saving-car/73889/5 "2001-07-26T22:44:41Z")
Also some trucks use a pneumatic regen braking system ---
**Author:** ![muffinman](https://avatars.discourse-cdn.com/v4/letter/m/e8c25b/32.png) [@muffinman](https://boards.straightdope.com/u/muffinman)\ **Post date:** [July 28, 2001, 8:19am UTC](https://boards.straightdope.com/t/new-energy-saving-car/73889/6 "2001-07-28T08:19:31Z")
> [@](#): > > \*Originally posted by zut \* > > If your question is, “Can you hook a generator up to a car’s wheels to produce energy from the spinning wheels while the car is driving?” then the answer is no, as **Dr. Lao** says. Not meaning to be a nitpicker, but the answer is yes, although not from the wheels. The spinning engine produces energy which is captured by the alternator while the car is driving (or more correctly, running). Were it not for this, you would still have to charge a hybrid with a power cord. A hybrid (gas-electric) car works in this manner, though not with turbines. Energy from the running gasoline engine is converted into electrical energy. That energy is used to power an electric motor when such use is more advantageous. Thus, it is able to drastically reduce energy consumption, though of course, not to complete self-sufficiency. BLAH! In fact, most Diesel locomotives use the engines only as generators, and actually move the train using electric motors.