There are a small number of electric cars
running around these days, but they still haven't caught on much yet.
That's a real shame, as I think that they're a good thing and are
perfect for inner-city driving. There's a number of reasons why they're
aren't a lot more on the road though -
- The cost & weight of the batteries is very high.
- The batteries need charging for a substantial amount of time.
- The range of the cars of only about 100km or so.
- The electronic controllers require expensive components, and generate a lot of heat.
- They don't sound cool.
Ok, I can't do much about the last point :), but I have some ideas on the other ones. Again, I have no doubts that many, many engineers all around the world have thought of all of this, but just in case they haven't .... here's my ideas on the car.
I think that a better idea, instead of
using of using large, heavy duty electrical component is to go the
other way - Use multiples of smaller batteries and four (or
more) smaller electric motors. The reasoning behind this is simple - If
you have a handful of large, powerful batteries, then you also require
large, powerful electrical controllers. I think that a series of
smaller batteries, say, a hundred or so, with plain ol' electric relays
switching them on and off as the power demands went up & down would
be much better. That way, there'd be a hundred step in the power, from
zero to full power. To make the power delivery totally smooth, the
power from the 'last battery in line' would be routed through a
(relatively) small power controller. It could be made quite small,
because it would only be regulating the power from one small battery
instead of a handful of large batteries all at once. The relays would
have to be quite tough, but this isn't a problem with modern electrical
equipment. Relays also 'lose' very little power, and the single power
controller could also be made quite efficient so the whole lot would, I
think, have a lot less losses than current systems.
The other area I think that could use improvement is in the mechanical power generation. Current cars (pun intended!) use one large electric motor. I believe that the smaller the electrical motor, the more efficient they are, so I think that a better way would be to use four motors in parallel, with each of them only coming on line as needed. If used with a small sprag clutch, they have no drag when not running. Since one motor would have to be running all the time, that one would be directly connected so the car would have a reverse gear. It would also provide the regenerative braking, ie, when you have your foot off the throttle or are braking, the electric motor acts like a generator to charge the batteries a little. For cruising, just the one motor - maybe two - would be used. For accelerating or higher speeds, three or four motors (or however many there are) would cut in, in turn.
The central 'brain' in the car that controls all the batteries and motors would swap the switching of those in a sequence that shares the load, so no one unit would work harder (apart from the directly connected motor) than any other, thus making them last longer.
While I think that this increased
complication may increase the range & maybe the performance of the
car, it's still not enough. An electric car needs an on-board charging
system to be really useful. This has been done before, or course, and I
have nothing much new to add to it ... I think! The best way I can
think of doing this is by using a small - about 100cc - petrol powered
engine that spins at very high revs, say, up at about 20,000rpm. The
reason for this is simple - the generator that would charge up the
batteries would have to be spun at high speed, but not at 20,000rpm;
about 3,000rpm for the typical car alternator is plenty to make up to
100amps. By having the engine spinning at high revs and geared down to
much lower revs, it could drive a generator much bigger than it
otherwise would be able to. And because the engine would be spinning at
a constant revs, it could be highly optimised and therefore quite
The trick to charging the batteries would be to have a relatively simple computer that makes the batteries 'take turns' as to which ones are being used to drive the car and which are being charged. It could even out the electrical loads in & out of the batteries, so that no one battery would be too low in charge.
A bank of solar cells on the roof, bonnet, and boot all help the cause of making power to charge the batteries when the car isn't running.
Since the car would be mainly intended for city use and hence low speeds, aerodynamics wouldn't be super-important. I think that the more important area to look at would be drivetrain and tyre drag. There wouldn't be much in the way of a gearbox, as electric motors make good torque at all revs, so the only real area of work to be done is in the differential. But I think that if the electric motors were arranged so that there were one set per rear wheel, then no differential would be needed. (So, there'd be two complete sets of drive motors in the lower rear of the car) The other are that would have to be looked at is tyre drag; a set of high pressure (50psi+) tyres that have very low rolling friction would reduce drag a lot.
For the creature comforts, hot air could
be made by using a water/air heat exchanger from the electric motor bay
in the car. Water? What water? I think that for longevity and
performance, the electric motors would have to be cooled, and the best
way to do that is to have a water jacket running around the sides of
the motors. The small petrol engine would also need some cooling, so
perhaps the water/air heat exchanger could double up in that job as
well. I think that the best water path would be from the coldest water
- enter the electric motor used the least, then gradually to the most
(keeps the water colder for longer, until it gets to the electric motor
that works the most), then to the petrol engine, then to the water/air
heat exchanger (radiator), then back to the electric motors again. The
water pump on the petrol engine could do all the pumping.
For cool air, I really can't think of any other way apart from using a conventional car air-conditioner system. Perhaps best driven by the petrol engine ...
(actually, I do have a plan for a cooling system - see here for details)
One last thing - A good radio would be needed, to cover up the noise of all those blasted relays clicking away! :)
As usual, this is just my ramblings, as
so it'll never happen .... But if it does, let me know!
On to the -
- Geothermal power plant
- Laptop computer electronic circuit simulator
- Anti-aircraft missile system
- Horizontally opposed diesel aircraft engine
- Listening spy device
- Super cooler device
- Radar Jammer
- Land speed record car contender
- Water speed record contender