Posted on 07/10/2007 10:01:37 AM PDT by Red Badger
Engine efficiency used to be all about fuel consumption if an engine used less fuel for a given output then it was deemed to be efficient.
But just as engine manufacturers were being commended for their ability to squeeze ever higher volumes of work from ever smaller volumes of fuel, along came the challenge of complying with exhaust emissions. And fuel efficiency and reduced emissions do not necessarily go hand in hand.
The solution was to find an alternative source of power that could be used alongside the existing fuel-guzzling, gas-emitting combustion engine. A power supply, moreover, that was inherently clean and could draw and store its "fuel" from the combustion engine when it had power to spare. This is the reasoning behind hybrid engines.
Hybrids are not a new concept. There have been vehicles in the past that used large flywheels to build up speed when the vehicle braked. When it was time to accelerate again the kinetic power stored in the rotating flywheel was fed back into the transmission.
Such designs were simple and reasonably successful in their day, but not suitable for all types of vehicle and probably not for those used in agriculture.
However, the recognition by engine makers that the energy used in braking was usually wasted as heat blown away on the wind has resulted in several interesting developments. It's worth bearing in mind that a 40t lorry stopping from 56mph on a level road produces (or, rather, loses) enough energy to run 840 bars on an electric fire. It amounts to the dissipation of the energy put into the vehicle when it is accelerated.
Tractor Hybrid Engine
One of the latest developments uses a hydraulic motor to pump oil into an accumulator to pressurise nitrogen gas to 300bar (4200psi) when the brakes are applied.
When the brakes are released and it's time to move off, the gas powers the oil back through the pump, which now acts as a motor, to help power the vehicle along.
Developed by Eaton Hydraulics, this form of so-called regenerative braking is said to be able to "re-use" up to 70% of the braking power and, as a result, save significant amounts of fuel.
It also reduces emissions because the engine no longer has to employ peak power to start the vehicle from a standstill. Eaton says it plans to have prototype vehicles up and running later this year.
Electrical power has also been used extensively in hybrid engines, both in the past and now. The key problem earlier designers encountered was the weight of the batteries, the time it took to charge them and the difficulties of disposing of them safely.
Things have moved on. Batteries now have shorter charging cycles and longer lives. A number of commercially available hybrid cars (including the Toyota Prius and Lexus 400 4x4) use a combination of electric motors and combustion engines.
Common to all regenerative braking systems, if they are to work as their designers intended, is a requirement for a suitable control system, something our flywheel designers were not fortunate to have.
For it is only with a computer-controlled system that more power can be made available to be stored in the batteries and, therefore, made available for the electric motor.
And on this front there is progress in the tractor sector. Deutz has introduced a prototype hybrid diesel engine for which it clearly has high hopes in the agricultural market. The prototype has a conventional, naturally aspirated, common rail, four-cylinder diesel engine rated at 72hp.
But conventionality ends at the flywheel. Here, instead of an identifiable ring of solid metal which the starter motor gearing would engage with, there is an electric generator/motor and all the coils and windings required. The manufacturer says this unit could also be retrofitted to existing engines.
Working on a 450V system, the electricity generated is stored in a bank of batteries. When there is a requirement for extra power, it can be released to produce an extra 40hp, a boost of 50%. Clearly, this power boost is not available all the time. In fact, at full output it is only there for a maximum of 50 seconds.
Why put such a system in place if it can only deliver any measurable input for such a short period of time? The answer is to do with the way the system is controlled.
The power demand on an engine is not constant. While a tractor at times may be working hard and requiring all available engine power, at other times it will not require anywhere near peak power.
So the average power requirement is significantly less than the full power available and it is this low average power and high peak power which makes hybrid drive possible.
When power demand falls below the average power demand the generator is employed to charge the batteries, with the power boost becoming available at peak power requirement.
These intervals between peak and low power may only be a few seconds, but the control system can switch from generator to motor mode just as quickly.
With this hybrid system, a smaller, less powerful (and presumably cheaper) engine can be used to achieve the same output. A smaller engine means less fuel is used - as much as 30%, says Deutz - and there is also a reduction in exhaust emissions.
Hybrid drive chart
Importantly, too, it could mean the engine being able to comply with the more stringent Tier 4 emission requirements that are coming, without having to resort to catalytic converters and other expensive emission-reduction techniques.
There are other advantages with this particular breed of hybrid engine. A separate starter motor is not needed and useful engine braking is available as the system switches over to electricity generation when the brakes are applied.
As to cost, Deutz says volume production should mean the system becoming a viable investment with a payback of about two years. The company also believes that there will be larger and more powerful hybrid engines of this type available in the future.
The intention is that prototype versions fitted to Same, Deutz Fahr and Lamborghini tractors as well as Atlas wheeled loaders will enter testing later this year.
fwmachinery@rbi.co.uk
It seems to me, the little time a tractor spends starting and stopping this is a waste. I would think the majority of the hours of a tractor are at constant speed without braking.
I wonder if this new hybrid technology with more computer reliance will result in more expensive maintenance and/or replacement when stuff starts failing?
![](http://images.google.com/images?q=tbn:R8sR7daexSBGmM:www.ted-kyte.com/3D/Pictures/Spark%2520Plug.jpg";)
Rest In Peace, old friend, your work is finished....... If you want on or off the DIESEL ”KnOcK” LIST just FReepmail me........This is a fairly HIGH VOLUME ping list on some days......
Who cares; what I want to know is what does this phrase mean? “run 840 bars on an electric fire...”
If I'm reading the article correctly, it isn't about starting and stopping, but rather variations in power demands on the engine (uphill vs downhill, etc.).
They tune the engine to run most efficiently at a given load, and then when the normal power demand drops off they add in the generators to charge the batteries, maintaing a constant load. When the power demands exceed the pre-set load point the batteries come online to make up the difference.
Shows a fundamental lack of understanding of how a tractor is operated.
Stick a solar panel on the roof for additional recharging and I’m sold.
“I wonder if this new hybrid technology with more computer reliance will result in more expensive maintenance and/or replacement when stuff starts failing?”
I’m betting you already know the answer to that question. ;-)
I dunno. British people should speak English.......
I don’t see the advantages in something running nearly 100% duty cycle. Yeah, commuter cars, etc., they are a great idea, but this is an odd application.
You couldn’t plow on rainy days..........
If this and other tractor companies are looking into it, it must have some projected use. But remember, this is EuROPe we’re talking about...........
Yeah, with those short fields, I’m sure there is heavy braking.
Damn, when i do my haying, only time I hit the brakes is to hitch on an empty trailer, or when I approach the barn. Never need to stop for a new beer or even to pee.
We British own truly immense electric-bar fires, capable of boiling entire rivers to steam at the flick of a switch. 840 bars is on the small side.
I have a hard time imagining a farm application where the power requirement for tractors drastically changes every few seconds. But my farm experience is limited to growing up in Ohio. I not aware of farming of fields of anything greater than gentle rolling hills. Anything else mostly likely gets terraced into flat sections.
You need one of those Lamborgini Tractors that was mentioned at the end of the article!.......
My farm experience is even less. I own a small tractor (Ford/NH 1520 4wd w/fe loader) that gets used mostly for brush hogging and landscape maintenance and that puts some varying load on it, but I don't think that's the normal usage pattern for a farm tractor.
European farmers generally live in a small village and not actually on their farms so I can see how this might work considering the commute from town and back.
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