Clett,
I understand your interest in long-range electric vehicles and up-to-date battery technology :idea: , but I think your suggestions can be very misleading for most readers, and I would like to make some comments around 2 important ideas :
- :!: a hybrid car is NOT an electric (or even part-electric) car
:!: a plug-in hybrid is NOT a "non-plug-in" hybrid
What is a hybrid, first ? Although the Prius, the Insight and the HCH use electric motors, hybrid does
not mean part-electric. Just like all computers today run on electricity, but the very concept of a computing machine has nothing to do with electricity. The main idea in the hybrid concept is that energy can be much more efficiently used than it is in conventional vehicles because of
important fluctuations in the power necessary to propel the vehicle. In everyday driving, the power demand fluctuates from high positive values (quick overtaking, steep roads, high speed driving...) to low values (cruising at moderate speeds) or even
negative ones when braking or driving downhill. The engine of a conventional car is designed to meet the maximum power requirements, and therefore is less efficient at medium or low power demands; and the negative power is simply wasted (transformed into heat) by the brakes : that makes 2 potential efficiency improvements on which engineers have been working.
I think a little sketch would be helpful to illustrate my explanations, but since I can't include any attachment, let's tell a story...
Let's think of the power fluctuations as a hilly curve, sometimes positive, sometimes negative, but with a positive mean value. The abscissae represent the time, and the ordinates the power: that makes any area under a portion of the curve measure an energy. The purpose of a hybrid system is to make this curve smoother for the engine,
but not for the driver, by planing down the highest peaks and filling in the valleys. This is possible as long as there is no net energy creation, i.e., the same amount of energy stored in the battery when the power demand is less than the max. engine power output is used when the power demand exceeds the engine max. power output. It is just like making a new rather flat road in a hilly area, using soil excavated somewhere to fill in depletions somewhere else. Doing this, you improve significantly the two points I mentioned above. You can by the way use a different engine cycle (Atkinson for the Prius) which is not as good at producing high power output but better at thermodynamic efficiency. All this is possible in present hybrid cars using a big battery as an energy reservoir and an electric motor to "help" the engine and produce electricity.
But as long as the hybrid system is a non-plug-in one, it means that
all the energy comes from gasoline (or petrol :wink: ), even the energy recovered during regenerative braking because kinetic energy was produced at the first place by the engine... As a consequence, the
only aim an engineer must strive towards (in order to save fuel) is to make the engine run in its most efficient zone,
not to use the electric motor as often as possible. Increasing battery capacity will not necessarily improve fuel economy: the energy capacity must be comparable to the size of the "hills" and "valleys" in a tipycal power demand curve, that's it. Although around 2kWh might seem "tiny",
it is in fact enough for everyday driving conditions in a Prius: entirely depleting the battery or, conversely, being at maximum charge (and hence not being able to recover more energy), are
EXTREMELY RARE events in a Prius driver's life. It happened to me
once in more than 30 000 km, and because I intentionnally "tested" the car on the Mont Ventoux.
That means a 50 kWh battery in a non-plug-in hybrid car would be technical and economical nonsense; maybe 5 kWh in a couple of years when production costs will be much lower, but certainly never 10 times more.
The situation would be different for a plug-in hybrid, because electricity can be produced in various (and some of them non-polluting) ways. But this is a completely different car, with a completely different energy management strategy. In order to maximize efficiency and minimize emissions,
a thermal engine must be warm. Therefore, even if you have plenty of electricity at your disposal in a huge battery, turning the engine off for a long time is not a good strategy. The only possibility to take advantage of a large capacity battery in a plug-in hybrid would then be to run only on electricity at the beginning (for short trips) and when the charge level is low enough to start the engine as in a "non-plug-in" hybrid, but
without making it recharge the battery up to the start level (otherwise you will never have any benefit to plug it in!). This is technically feasible, but has one shortcoming: it makes the battery operate over a wide range of states of charge, and this is not very good for its life expectancy.
Now let's comment your suggestions :
1) Ditch the teeny 1.8kWhr NiMH battery pack for a 50kWhr LiS pack.
2) Increase motor power output to 90kW (sufficient to take the car to over 100mph on battery power alone).
3) Lose the complicated/expensive transmission business and move to a series arrangement (currently parallel) where the engine is only there to power a generator, not to move the wheels through a gearbox.
4) Include a recharging socket so the car can be powered either by electricty from home or petrol as and when the consumer feels like it.
5) Modify the engine to run on either bioethanol or biodiesel.
Point 1) has already been addressed above.
Point 2) : 90kW is not necessary for 100 mph. The current Prius 53kW thermal engine can take alone the car at 100 mph (without any drain on the battery). And motor power is one thing, but battery output power is another one (current one is 25 kW for the Prius, if I'm right).
Point 3) : The Prius is not a parallel hybrid, nor a series one... it combines both thanks to the remarkably clever "power split device". Furthermore, this PSD is mechanically
much simpler than a conventional (manual or automatic) gearbox. The complexity is in the electronic control of the whole stuff, but this is a general tendency of today technology to replace mechanics by electronics, and is in general economically sound.
Point 4) has already been answered.
Point 5) seems to be a good idea, but the problem is to find alternative fuels : Toyota will not build a car if you can fill up the tank only in very special places. Today, Diesel engines have a better efficiency than Otto ones, and technology is available to make them "clean" by eliminating almost all particulates and nitrogen oxydes. They can be made much less noisy too. But there is still a technical problem with the high compression ratio, which makes them difficult to start and stop in a seamless, unobtrusive way.
If engineers can solve this problem, let's bet Prius III will be a Diesel-hybrid with a 3 or 4 kWh battery... :wink:
PS : Plea
ze f
ill free (everybody) to correct my english... i'ts always fun
n to l
urn something !
