Hybrid Power Trac

[woodlandfarms]

Well boys, here it comes

Green Car Congress: DEUTZ Introduces Mild Hybrid Drive for Off-Road Construction Equipment

 

[SnowRidge]

I like how some environmental writers can eviscerate facts with just a few words.

"Currently, all functions on the Weyhausen loader’s equipment side are still hydraulically driven. The next step will be to power the loader totally by a full hybrid drive system, delivering eventual emission-free operation."

Sure, magically that diesel is going to have no emissions because it is part of a hybrid drive. This hype is similar to the people that claim a plug in hybrid car can get 80 miles to the gallon, conveniently ignoring the energy used to recharge the batteries when the vehicle is plugged in.

 

[BobRip]

This hype is similar to the people that claim a plug in hybrid car can get 80 miles to the gallon, conveniently ignoring the energy used to recharge the batteries when the vehicle is plugged in.

I agree that marketing guys can really hype, but the plug in hybrid does have an advantage since electrical generation from a stationary power plant is much more efficient than from a portable engine. I think 2.5 times is about right. The big trouble with hybrids is battery life and initial system cost. Better batteries have been the potential solution to electric cars for a century, but potential is still the right word. Also a battery holds about 1% as much energy as gasoline of the same weight.

They are not forgetting the energy form the power grid, it's just a lot cheaper.

 

[Bob999]

the plug in hybrid does have an advantage since electrical generation from a stationary power plant is much more efficient than from a portable engine. I think 2.5 times is about right.

I don't think those figures are correct. Electric utility generation only converts about 35% of the energy from the fuel into electricity--a figure that I think is comparable to modern diesel engines conversion of btus in the fuel to usable power to the road.

I think the advantage of the stationary power plant is in the environmental controls that can be applied to large plants to reduce emissions as compared to doing it in small engines.

 

[BobRip]

I don't think those figures are correct. Electric utility generation only converts about 35% of the energy from the fuel into electricity--a figure that I think is comparable to modern diesel engines conversion of btus in the fuel to usable power to the road.

I think the advantage of the stationary power plant is in the environmental controls that can be applied to large plants to reduce emissions as compared to doing it in small engines.

Modern power plants with combined cycle (turbine run by natural gas, with steam generated by waste heat to run steam turbine) run above 60%. On a portable system you have to include the transmission loss, cold start running (which is much reduced by plug in hybrid) and not running the engine at optimal speed and power. With the plug in hybrid you can keep the engine at the most efficient engine speed and load during the charging and then shut it down. Since an engine on a normal vehicle is sized for acceleration horsepower it is not run at it's most efficient speed most of the time. That 35% is the best efficiency, not the average. There are many factors and variables, but this is where they get the claimed improvements.

I agree with your comment on pollution.

 

[SnowRidge]

Railroads are already using hybrid yard switchers.

Diesel electric locomotives have electric traction motors on the axles. They are conventionally driven by a diesel prime mover powering an alternator or generator to supply juice to the traction motors.

In the hybrid, a much smaller diesel is used to recharge a massive battery bank. The battery bank actually provides power to the traction motors. The diesel starts and stops automatically and runs at a constant speed when it is charging. It is much easier to control emissions on an engine that runs at a constant speed/load than it is to control them in variable speed/load operations. Hence, lower emissions to get the job done, but not zero emissions as some people would have you believe.

 

[Bob999]

Modern power plants with combined cycle (turbine run by natural gas, with steam generated by waste heat to run steam turbine) run above 60%. On a portable system you have to include the transmission loss, cold start running (which is much reduced by plug in hybrid) and not running the engine at optimal speed and power. With the plug in hybrid you can keep the engine at the most efficient engine speed and load during the charging and then shut it down. Since an engine on a normal vehicle is sized for acceleration horsepower it is not run at it's most efficient speed most of the time. That 35% is the best efficiency, not the average. There are many factors and variables, but this is where they get the claimed improvements.

I agree with your comment on pollution.

In my post I was thinking of, and referring to, a coal or nuclear fired steam plants which are the dominant source of electricity in this country. I agree with your comment about turbines fired with natural gas and fitted with a secondary system to improve overall efficiency. My understanding is that such secondary systems can, in theory, be fitted to mobil applications but are not because of size, weight, and economic considerations.

 

[ponytug]

Dear Bob999,

Your numbers are accurate for the older generation of plants, but the current (80's onward) plants have efficiencies well over 35%, approaching 50+% in the best coal fired plants. You are right that nuclear powered plants are for the most part less efficient, as they run at lower pressures (and therefore temperatures, and therefore are less efficient).

Partly the improvements are improvements in design with better attention to heat flow, and partly they are due to scale. The largest plants now are in the gigawatt range. Additional heat recovery stages can improve the onsite efficiency well above these values. Technologies such as fluidized bed burners add another 10%, and integrated gas combustion cycle plants exceed 60%

Unfortunately, mobile internal combustion engines just aren't that efficient for a host of reasons that include not running at the optimal speed, varying load, startup losses, poor heat recovery/displacement, and, importantly, scale. They are just small.

One does have to weigh transmission losses of electrical power against the generation efficiency, but even so, it puts electric vehicles ahead, and way ahead, if one is considering environmental emissions per mile. Even adding in battery costs/disposal/recycling fees, you are still ahead.

Now we can have a serious discussion about just how much energy you could store in a battery pack on a tractor relative to the work needed. (Short answer, foggettaboutit). For forklifts, maybe, for Power-tracs....not the way I use one, which is high throttle, ripping along, but, as in most things, YMMV.

Further reading at
Carbon flow


US National Energy Flow
(Highly recommended diagram of how energy is used in the US.)

All the best,

Peter

In my post I was thinking of, and referring to, a coal or nuclear fired steam plants which are the dominant source of electricity in this country. I agree with your comment about turbines fired with natural gas and fitted with a secondary system to improve overall efficiency. My understanding is that such secondary systems can, in theory, be fitted to mobil applications but are not because of size, weight, and economic considerations.

 

[RegL]

Pony,
I have done a little reading on some of the EV conversion sites and I think, for some, an electric Power Trac could work. I use mine commercially and , except for field mowing, I don't think I actually put more than 2 or 3 hours of run time on it during the day most of the time. It seems that the electric motors are very compact so after removing the engine and fuel tank, there would be lots of room for batteries. And unlike a road vehicle, where weight is a negative, it would be good in the tractor. I sure like the idea of a quiet PT. Might be a fun experiment if someone came across an old PT with a blown engine.

 

[SnowRidge]

An electric/hydraulic PT would be quite a challenge. I think finding an affordable DC motor of the size required to drive the pumps might be difficult. It would have to be fairly large. I don't think there would be enough room left for a decent battery bank. At least a 48 volt system would be required, but even that would probably be too low. 96 volt and 120 volt DC motors are available, but working with DC systems that high can be shockingly painful (pun intended).

An AC motor would be preferable, but then a high capacity inverter would be required. They aren't cheap, and they aren't small. Adding one to the mix would seriously increase the complexity of the conversion. And you still have the shock hazard.

Still, I would like to see someone attempt the conversion. It would be, umm, quietly entertaining.