TirithRR wrote:
gbaji wrote:
As far as a generator, I'm not sure how effective that would be, but I assume you could do that.
Nothing like carrying a generator to convert gas into heat, into mechanical energy, into electricity, then using that electricity to charge your electric car so it can convert that into mechanical motion...
Lol! Yeah. Although, interestingly enough, it can be more efficient than converting gas into heat, into mechanical energy, then running a driveshaft directly (even with a transmission in the middle). It's the principle behind the Volt (not implemented as well as it could have been unfortunately). The idea is that any internal combustion motor has an "ideal" RPM rate at which it will generate the most mechanical energy for the amount of fuel consumed. Deviating from that ideal results in significantly decreased conversion of the fuel into mechanical energy (ie: power to the wheels). But driving a car requires a constant amount of changing mechanical energy needs. Accelerating, coasting, idling, etc. Connecting an internal combustion motor directly to a drive shaft is incredibly inefficient because you have to meet those changing mechanical needs by changing the rpms of the motor itself. So the motor is being used inefficiently pretty much all the time.
If you run a generator at a constant (efficient) rpm rate, and then store that energy somehow (like say a flywheel or a battery), and then draw on that stored energy as needed to drive the car, then you'll actually expend less total fuel operating the vehicle than you would otherwise. The Volt is the first example of a large scale production attempt at this (it's not a perfect example, but it's close). Part of the problem is that we're caught almost in a definitions war between "electric" and "hybrid", which actually result in the Volt being used in a less than efficient manner. Ideally, the generator should always be kicking in based on load on the battery system over time, but instead it's designed to drive purely electrically for the first X miles (so as to simulate being a plug in electric car), then shift to using the generator to charge things. The problem is that you actually decrease the total range potential doing this because you're waiting until your battery is already about half discharged before activating the generator. If you think of it as being a super efficient gas powered car rather than an electric car, you could have the generator active all the time, significantly increasing the time you can run the car before the battery runs out.
It's really about what you want the vehicle to do. Do you want it to be an electric car, with a generator that extends range (but not super efficiently at that point), or a gas powered car that leverages a battery system to store energy and make the fuel use as efficient as possible (a true
Series Hybrid)? I'd prefer the latter since it would allow you to leverage existing fueling systems while massively increasing efficiency. Done properly, it should be possible to operate such vehicles as direct replacements for existing internal combustion powered cars, with even long trips being possible. It's a pet peeve of mine that even though this is technically possible right now, various bits of infighting amongst the different EV/hybrid schools of thought have prevented this from being realized. The "all or nothing" approach to electric vehicles largely means we have to choose between a car that has a very limited cruising range *or* not bother with one at all. I happen to think that's counter productive and harmful to the implementation and adoption of new technologies and actually has resulted in an increased fuel dependency than we should have right now.
Edited, May 27th 2014 8:05pm by gbaji