@cristina.
...Most of the noise is heavy traffic, buses and HGVs, and they use too much energy to be electrified right now. Some hybridisation is going on but the engines still make noise, in fact more so because they use smaller engines running at higher loads which tends to create more, not less, noise if the engine is having to operate.
Cristina, Donald makes a valid point here, but I think there's a solution to this problem associated with Hybrid EV heavy-goods vehicles.
Background:
A few weeks ago I took my wife & a friend on a cross-country trip in my Ampera. Total distance meant I had to use petrol for 50% of this mileage. If I make my petrol engine work hard by going up steep hills (and some of these were
very steep), it gets noisy inside the car, and outside, making it less pleasant for my passengers and aggravating my tinnitus.
So I simply switched to electric mode to do the "heavy-lifting" up hills, and used the petrol on the flat & descending when it runs at a medium rotational speed (rpm) and is extremely quiet.
HGV Design
Applying this same process to the HGV noise problem, the correct design for HGV EVs is to make sure that:
a) The electric drive system is the
main motor powering the wheels (Ampera has 112 kW electric motor)
b) Have the petrol/diesel engine the
smaller one (Ampera has 56 kW petrol-generator)
c) Provide a battery of
sufficient capacity to to do the
hardest task (might be UKs longest motorway hill-climb fully-loaded for HGV for example. For a bus in Winchester this be climbing Romsey Road hill).
Hybrid EV cars
Not all hybrid EVs are designed the same, and these three points above are
critically important if I'm
determined to minimise my noise-levels when the vehicle is working at full power. Ampera satisfies all 3 conditions for cars, no others do!
Current Hybrid EV limitations
If you look closely at the current rash of PHEVs on sale now in UK, Golf GTe (= e_Tron), Outlander, BMW 330e, Prius, Mercedes C350e,...) ALL these MUST use the petrol/diesel at full power when running at full power. This is because
all these have a
large ICE engine, with a
small electric motor/generator added-on, to provide efficiency improvements by regenerating when braking. They all have
small batteries, because that's all that is required to store regen energy, and by making it
just large enough to do about 20 to 30 miles on electric-only low-speed driving, they can achieve very high apparent mpg using current tests. The one big advantage they have over Ampera design is thay keep their full passenger capacity, typically being 5 seaters. Ampera loses the middle rear-seat due to the battery being much larger, so is reduced to a 4-seater.
Ampera
So far, the ONLY hybrid EV (that I'm aware of, and is well-known) is the Ampera (Volt in USA) which is designed the
correct way round, so full-power work can be done using electricity alone, quietly. This lets me run the (ICE) engine at a steady rate for a long period of time to provide the required total amount of mechanical energy to do the required task.
BMW i3 - comes close
There is one other PHEV which comes close, the BMW i3, as this has a large electric motor and large battery and small ICE, meeting the 3 criteria above. Sadly the ICE is so pathetically feeble that it only acts as a continuously-running very-low-power dynamo generating a modest topup for the battery system. The ICE in this car hasn't been integrated into the drivesystem to any great degree, and in effect simply provides the equivalent of having a slightly larger battery in the first place. It cannot cover several hundred miles non-stop at half-power (high-speed motorway cruising) rates.
BMW don't even capture any of the waste heat to provide cabin warming! ICE on this car looks very much like an afterthought, and it's possible that this design decision was influenced by Californian legislation requiring the ICE range to be considerably less than the Electric range, which rather negates the main purpose of the hybridisation in the first place! The i3 is really not a true hybrid for these reasons, it's a genuine electric car.
Voltec drivesystem versatility
Ampera can be both - pure EV, or pure ICE (petrol) with no range-limit and
still capable of 112 kW full-power working even when the battery is
fully drained, and when the engine can only provide
half the required power! This apparent "impossibility" does
not break the laws of physics, because even when "fully drained", the battery still has 20% of the capacity remaining, enough to cover brief full-power surges needed for overtaking/hill-climbs, which takes the battery into "negative-territory" if you like, i.e. below normal "zero" level of 20% full. The car can only do this because it has a large battery to begin with, so has a larger "emergency-reserve".
ICE in Hybrid HGV EVs
Once you have an HGV with the 3 criteria above satisfied, you will have a vehicle which has the electrical power & range to do the hardest task electrically and quietly. These tasks typically come in bursts - after a hill-climb, there's the descent when power-requirement is far lower, and by running the ICE at a modest speed, it can output the required power without running noisily, as the battery is acting as a buffer to provide the peaks.
As petrol engines are economical when NOT being run on tickover, they would be more suited to HGV use in a hybrid EV design, than they are for petrol-only use (where their very-low-power and tickover inefficiency is poor compared to diesel). The petrol ICE would run at a steady "middling" speed set at optimum efficiency for long stretches of time, and when the battery has plenty of charge and loads are light (flat town-driving, low-speeds, tickover while loading/unloading) the petrol ICE will shut off completely and the battery does all this work.
Diesel Hybrid HGVs
Even diesel designs can benefit from being integrated into hybeir EVs, as the range of engine speeds and power is less demanding, so the actual mechanics and cost can be less. There's no fundamental need in a diesel hybrid HGV to have a dual-mass flywheel with complex friction-damper in as cars do, as the weight considerations aren't so severe, and it should be easier to control diesel emissions if run at steady, constant speed designed to maintain the traction battery at near-to-full levels, allowign very gentle slowing and speeding-up of the diesel rpms.
This is actually exactly how the Ampera is designed to run, and it is the ONLY Hybrid EV car to work like this, aiming to run the petrol at steady speeds with no running at tickover.
This drive system (Voltec) is worth studying in some detail - it appears complex at first, but as you get to understand it you will realise just how elegant it is, and what a brilliant job was done by the engineers designing it.
Conclusion
The more I drive my Ampera & follow these forums, the more I learn, and the more I realise
still needs to be learnt about this remarkable transition we're in. The amount of wisdom & skills others in here have is quite astonishing. I think your area of research is important, and please let us all help you as much as we can. The word needs to get out, and there's a huge education job still to be done.
At the very least, please get someone to give you a ride in an Ampera - it's quite an experience! Rather like being in a Tesla, but without any range-anxiety, ever!
(Apologies to any Tesla owners who have read this far - couldn't resist a slight dig! And, yes, I
am jealous...
)
