Care to comment Jtabeb

[flintlock]

Re: Care to comment Jtabeb

You should write for a car mag GRG55. Excellent background on diesel engines.
Its my understanding the emission equipment on Diesel trucks has been what is causing most of their problems lately. The newer US requirements actually have reduced fuel mileage a good bit on the newer Cummins engines. Don't know about Powerstrokes.

[GRG55]

Re: Care to comment Jtabeb

You should write for a car mag GRG55. Excellent background on diesel engines.
Its my understanding the emission equipment on Diesel trucks has been what is causing most of their problems lately. The newer US requirements actually have reduced fuel mileage a good bit on the newer Cummins engines. Don't know about Powerstrokes.

I've heard the same about the "new" 6.4 litre Powerstroke introduced in the 2008 model year.

As for the emissions controls, you are correct they are getting extremely complex and prone to failures. The Mercedes Blutec engines are a nightmare of complex exhaust management technologies, including a diesel oxidation catalyst, a nitrogen-oxide absorber catalyst, an ammonia rich selective catalytic reduction unit, and a soot particulate filter. A reservoir containing an ammonia source fluid [AdBlue] has to be replenished periodically, and the engine monitors the particulate filter and changes the fuel injection process to raise the exhaust temperature to burn off the particulates when it senses the filter is starting to plug.

Talk about multiple failure modes. It's a fabulously clean diesel engine, but that mother is not going to be cheap to maintain on specifications, and it most definitely isn't the type of engine you'd want to use to run the kids to school and then off to the hairdresser after dropping the poodle off for obedience training.

[jtabeb]

Re: Care to comment Jtabeb

[quote=radon;149322]I would like to know that as well. 1K per acre a day is completely impossible. My back of the napkin gives an upper limit, assuming 100% solar energy conversion to diesel, of around 700 gallons/acre day based on isolation in the US, and the heat value of diesel. I used a the high isolation value of 7KWh/m2 per day. This is rarely found in the United States, and obviously 100% energy conversion is not possible. If they are making 1K gallons a day it would be nice to know where they are getting the extra energy.

I suspect it is closer to 1K per year due the the inefficiency of photosynthesis and other issues. Also most of the test sites I've read about have (generous) production estimates of 1 - 1.5K gallons per acre a year.

But where does this leave us for fuel replacement? Even if we use the generous value of 1500 gallons/acre a year we end up with around 4 gallons per acre a day. quote]

1500 gallons a year/acre is not very generous, you are using numbers from OPEN POND production, which is not the "cream of the crop" of current production techniques. (Again, you need to be thinking in 3D).

[jtabeb]

Re: Care to comment Jtabeb

I would like to know that as well. 1K per acre a day is completely impossible. My back of the napkin gives an upper limit, assuming 100% solar energy conversion to diesel, of around 700 gallons/acre day based on isolation in the US, and the heat value of diesel. I used a the high isolation value of 7KWh/m2 per day. This is rarely found in the United States, and obviously 100% energy conversion is not possible. If they are making 1K gallons a day it would be nice to know where they are getting the extra energy.

I suspect it is closer to 1K per year due the the inefficiency of photosynthesis and other issues. Also most of the test sites I've read about have (generous) production estimates of 1 - 1.5K gallons per acre a year.

But where does this leave us for fuel replacement? Even if we use the generous value of 1500 gallons/acre a year we end up with around 4 gallons per acre a day. In order to replace GNKs 400 million gallons a day would require 100 million acres. At 640 acres per square mile that comes to 150K square miles. That is about the size of Montana. Even if I am off by a factor of 10 development on that scale is completely unrealistic.

My knee jerk reaction is that this is primarily for public relations, and they are not saying how long it takes to produce 1000 gallons because it wouldn't make for a great press release. Until they get a handle on their real production costs, without subsidies, and volume on a commercial scale I'll hold off on getting excited.

I think you are right and I was wrong (YES I was wrong).

http://en.wikipedia.org/wiki/Photosynthetic_efficiency

Back to the drawing board. (You were dead on with the energy input requirements)

So it's back to we are screwed.

I come with about 13,000 gals per acre as a solar energy input limit. (that's too little)

(I'll entertain you all with another go as soon as I come up with a new one).

[jtabeb]

Re: Care to comment Jtabeb

Care of Yves at Naked Capitalism

http://www.guardian.co.uk/environmen...n-fuel-problem

"The brains trust of the Pentagon says it is just months away from producing a jet fuel from algae for the same cost as its fossil-fuel equivalent."

Yves also posted this "game changer" recently:

http://www.physorg.com/news184310039.html

I was WRONG.

I will now proceed and go eat my Entire Humble Pie, (and then some large helpings of crow).

Disreguard my bad math here.

Options anyone else? (Cause, I just ran out of them).

Sorry guys. (Note to self, don't assume, it makes an ASS out of U and ME)

[bill]

Re: Care to comment Jtabeb

It's a fabulously clean diesel engine, but that mother is not going to be cheap to maintain on specifications, and it most definitely isn't the type of engine you'd want to use to run the kids to school and then off to the hairdresser after dropping the poodle off for obedience training.

How about the Amminex system?
page 23
http://www.amminex.net/images/storie...20handouts.pdf

http://www.amminex.net/

[Glenn Black]

Re: Care to comment Jtabeb

The algae systems are constrained by CO2 availability, sunlight, and cost. When you go for low cost, you have acres of shallow, flowing canals/ditches next to a power plant. Waste heat drys the algae, then you burn it. This chews up huge acrage. This system is constrained by sunlight per acre of pond surface. Going the other way, you have intense light in expensive flowing reactors which are very capital intensive.

Either way, it will be more than 20 years to commercialize, and fuel prices will be $3.50 per litre ($14 per gallon) to make it worthwhile. I have reviewed the technology & literature, and this is a pipe dream for the next little while. Eventually, it could work, after all this is where the oil originally came from that we are burning today.

[GRG55]

Re: Care to comment Jtabeb

How about the Amminex system?
page 23
http://www.amminex.net/images/storie...20handouts.pdf

http://www.amminex.net/

bill, this is a variation of the Mercedes AdBlue technology...and your post supports a couple of the points I made earlier.

At the risk of boring the rest of the iTulip community, here's what's going on:

The Mercedes BlueTEC diesel engine uses a series of catalytic conversions to deal with emissions, starting with an oxidation catalyst that reduces carbon monoxide [CO] and unburned hydrocarbons in the exhaust.

To deal with particulates [soot] Mercedes uses a filtration process that traps the material and then is "regenerated" or cleaned by periodically altering the fuel injection parameters to temporarily raise the exhaust temperature to burn off the trapped material.

That leaves the nitrogen oxides [NOx] to be dealt with. On their light passenger cars Mercedes has an interesting two step process. The first catalyst [NOx Absorber Catalyst] traps the NOx directly. Periodically the car's computers change the fuel injection parameters to run richer than normal, which drives the NOx off the first catalyst in a "batch" and feeds it to the selective catalytic reduction [SCR] unit, where the NOx is converted into nitrogen [N₂] and water vapour.

Although it's a creative solution for dealing with diesel NOx emissions there's a couple of problems. First, the SCR is unable to convert sufficient NOx to meet the emissions standards in California and four New England states. Second, the periodic "run rich" cycle reduces the overall fuel economy of the vehicle.

To address this, and create a diesel that they could sell in all 50 states, Mercedes introduced what they call their AdBlue system, adapted from a system in use on their heavy trucks and buses. AdBlue is simply liquid urea stored in a tank and injected into the exhaust system in atomized form just upstream of the SCR unit. Urea is an ammonia [NH3] source and serves as the hydrogen contributor to drive the conversion of NOx to water vapour [H₂O] and nitrogen [everyone remembers all that stuff about reaction kinetics from high school Chemistry class, right ;)]

Amminex appears to be an alternative ammonia source to storing and using liquid urea [AdBlue] on the vehicle, but is injected at the same point and does exactly the same thing - promote the conversion of NOx. I notice that Amminex requires heat to convert it from the stored form into an injectable form, and this heat comes from the engine coolant. Since most vehicles have the radiator at the very front, and the exhaust emissions converters and other equipment further back, that implies running auxiliary coolant supply and return lines behind the firewall, and down much of the length of the vehicle. The Amminex system also requires an auxiliary source of heat [presumably from the vehicle electrical system?] for engine cold start, until the engine coolant has reached sufficient temperature. So, at first blush, it would appear somewhat more complicated than the Mercedes solution...although there could well be safety or other advantages over carrying liquid urea in a tank on the vehicle, including [as you pointed out] better performance at lower, or varying, SCR operating temperatures.

The whole discussion above reinforces my point that these vehicles are complex and not really suitable for lots of short trips or chronic stop-and-go service. The various catalysts often don't work well until they have been warmed up into the operating temperature range by the exhaust gases, the complex physical and chemical processes work better when they are not interrupted and restarted repeatedly, and the risk of contaminating, de-activating or physically breaking down [substrate thermal cracking] these catalysts [which are extremely expensive to replace] is much greater the more on-off, and thermal cycles the engines and systems are subjected to. As much as I have slagged electric cars in some of my posts, they would seem a better choice for urban short trip service [once someone actually introduces a real electric car, which would still seem some way off yet]...but I wouldn't be driving one across the Mojave.

The Europeans seem to have plenty of diesel engines that do the stop and go thing just fine, how are they doing it? More aggressive electronic controlled heaters for idle time? Big heavy flywheels to act as both a constant idle load and to store excess kinetic energy for use on demand like batteries in a hybrid?

I failed to point out one other thing in my previous answer to the above. NOx is the most difficult emission component to deal with in diesel exhaust. The current European NOx emission limits are far less stringent than USA standards - by a factor of 8 to 10 times lower depending on the state. Because of this the emissions control systems on European diesel cars are currently much less complex than what we have in North America. That means the European version of the car is less expensive to build, buy and service than the equivalent model sold in the USA or Canada [for example, I have no idea what Mercedes will charge for an AdBlue tank replacement, but I doubt it's anywhere near as cheap per gallon as the diesel that goes into the fuel tank... ]

All these sequential converters and filters in the exhaust system also contribute to the reputation in North America of diesels being anaemic performers. For example the current generation VW Jetta TDI sold in Canada and the USA is 30 hp less than the same car in Europe [140 hp vs 170 hp - a significant difference]. The one thing that is required to get a diesel to perform is "let it breathe"...that means to the highest degree possible unblock the intake air system [hence the popularity of turbochargers on diesel engines] and unblock the exhaust system.

I think all of this contributes to the remarkable difference in diesel market share in Europe versus the USA.

[thriftyandboringinohio]

Re: Care to comment Jtabeb

I think you are right and I was wrong (YES I was wrong).

http://en.wikipedia.org/wiki/Photosynthetic_efficiency

Back to the drawing board. (You were dead on with the energy input requirements)

So it's back to we are screwed.

I come with about 13,000 gals per acre as a solar energy input limit. (that's too little)

(I'll entertain you all with another go as soon as I come up with a new one).

Don't be so hard on yourself, it's easy to get a basic calculation wrong in engineering work. (but you did make me chuckle, a million gallons per acre per year...)

And don't be so gloomy -many of the alternative fuels have been studied seriously and proven to be good solutions that cost too much today. When we're a little further past peak cheap oil the cost equations will change and they'll become cost effective. We have great hope that a basket of these solutions (especially conservation) can pick up the load and save our bacon when darker days arrive.

[thriftyandboringinohio]

Re: Care to comment Jtabeb

bill, this is a variation of the Mercedes AdBlue technology...and your post supports a couple of the points I made earlier.

At the risk of boring the rest of the iTulip community, here's what's going on:

The Mercedes BlueTEC diesel engine uses a series of catalytic conversions to deal with emissions, starting with an oxidation catalyst that reduces carbon monoxide [CO] and unburned hydrocarbons in the exhaust.

To deal with particulates [soot] Mercedes uses a filtration process that traps the material and then is "regenerated" or cleaned by periodically altering the fuel injection parameters to temporarily raise the exhaust temperature to burn off the trapped material.

That leaves the nitrogen oxides [NOx] to be dealt with. On their light passenger cars Mercedes has an interesting two step process. The first catalyst [NOx Absorber Catalyst] traps the NOx directly. Periodically the car's computers change the fuel injection parameters to run richer than normal, which drives the NOx off the first catalyst in a "batch" and feeds it to the selective catalytic reduction [SCR] unit, where the NOx is converted into nitrogen [N₂] and water vapour.

Although it's a creative solution for dealing with diesel NOx emissions there's a couple of problems. First, the SCR is unable to convert sufficient NOx to meet the emissions standards in California and four New England states. Second, the periodic "run rich" cycle reduces the overall fuel economy of the vehicle.

To address this, and create a diesel that they could sell in all 50 states, Mercedes introduced what they call their AdBlue system, adapted from a system in use on their heavy trucks and buses. AdBlue is simply liquid urea stored in a tank and injected into the exhaust system in atomized form just upstream of the SCR unit. Urea is an ammonia [NH3] source and serves as the hydrogen contributor to drive the conversion of NOx to water vapour [H₂O] and nitrogen [everyone remembers all that stuff about reaction kinetics from high school Chemistry class, right ;)]

Amminex appears to be an alternative ammonia source to storing and using liquid urea [AdBlue] on the vehicle, but is injected at the same point and does exactly the same thing - promote the conversion of NOx. I notice that Amminex requires heat to convert it from the stored form into an injectable form, and this heat comes from the engine coolant. Since most vehicles have the radiator at the very front, and the exhaust emissions converters and other equipment further back, that implies running auxiliary coolant supply and return lines behind the firewall, and down much of the length of the vehicle. The Amminex system also requires an auxiliary source of heat [presumably from the vehicle electrical system?] for engine cold start, until the engine coolant has reached sufficient temperature. So, at first blush, it would appear somewhat more complicated than the Mercedes solution...although there could well be safety or other advantages over carrying liquid urea in a tank on the vehicle, including [as you pointed out] better performance at lower, or varying, SCR operating temperatures.

The whole discussion above reinforces my point that these vehicles are complex and not really suitable for lots of short trips or chronic stop-and-go service. The various catalysts often don't work well until they have been warmed up into the operating temperature range by the exhaust gases, the complex physical and chemical processes work better when they are not interrupted and restarted repeatedly, and the risk of contaminating, de-activating or physically breaking down [substrate thermal cracking] these catalysts [which are extremely expensive to replace] is much greater the more on-off, and thermal cycles the engines and systems are subjected to. As much as I have slagged electric cars in some of my posts, they would seem a better choice for urban short trip service [once someone actually introduces a real electric car, which would still seem some way off yet]...but I wouldn't be driving one across the Mojave.



I failed to point out one other thing in my previous answer to the above. NOx is the most difficult emission component to deal with in diesel exhaust. The current European NOx emission limits are far less stringent than USA standards - by a factor of 8 to 10 times lower depending on the state. Because of this the emissions control systems on European diesel cars are currently much less complex than what we have in North America. That means the European version of the car is less expensive to build, buy and service than the equivalent model sold in the USA or Canada [for example, I have no idea what Mercedes will charge for an AdBlue tank replacement, but I doubt it's anywhere near as cheap per gallon as the diesel that goes into the fuel tank... ]

All these sequential converters and filters in the exhaust system also contribute to the reputation in North America of diesels being anaemic performers. For example the current generation VW Jetta TDI sold in Canada and the USA is 30 hp less than the same car in Europe [140 hp vs 170 hp - a significant difference]. The one thing that is required to get a diesel to perform is "let it breathe"...that means to the highest degree possible unblock the intake air system [hence the popularity of turbochargers on diesel engines] and unblock the exhaust system.

I think all of this contributes to the remarkable difference in diesel market share in Europe versus the USA.

You make good points. I did some research with 3M and Donaldson in the 1980's on diesel particulate traps on heavy duty transit bus engines. Our early prototype systems regenerated by alternating between two ceramic traps; one catching particles, the other burning off its load, then switch. Advances in engine controls and the move to four-stroke diesels made them unnecessary for particulate emissions under those regulations.

Diesel particulate emissions have two components –the soluble fraction and the carbonaceous core. Each particle is a little lump of dry charred fuel much like a microscopic charcoal briquette (the carbonaceous core), covered with a thick oily coating of condensed higher hydrocarbons in the C-12 to C-22 range (the soluble fraction, it can be dissolved in a test tube).

The soluble fraction can be removed in a conventional catalytic converter, leaving only the carbonaceous core. It was enough for those engines to pass particulate standards.

A regenerating particulate trap makes sense in combination after the catalytic converter.

And my understanding of NOx generation is that combustion temperatures are a huge factor, one must burn cool enough to reduce the conversion of atmospheric nitrogen into oxides of nitrogen, but of course cooler combustion works against both hydrocarbon emissions and efficiency.

The modern advanced engines are marvels of technology, subtle and complex.

[GRG55]

Re: Care to comment Jtabeb

You make good points. I did some research with 3M and Donaldson in the 1980's on diesel particulate traps on heavy duty transit bus engines. Our early prototype systems regenerated by alternating between two ceramic traps; one catching particles, the other burning off its load, then switch. Advances in engine controls and the move to four-stroke diesels made them unnecessary for particulate emissions under those regulations.

Diesel particulate emissions have two components –the soluble fraction and the carbonaceous core. Each particle is a little lump of dry charred fuel much like a microscopic charcoal lump (the carbonaceous core), covered with a thick oily coating of condensed higher hydrocarbons in the C-12 to C-22 range (the soluble fraction, it can be dissolved in a test tube).

The soluble fraction can be removed in a conventional catalytic converter, leaving only the carbonaceous core. It was enough for those engines to pass particulate standards.

A regenerating particulate trap makes sense in combination after the catalytic converter.

And my understanding of NOx generation is that combustion temperatures are a huge factor, one must burn cool enough to reduce the conversion of atmospheric nitrogen into oxides of nitrogen, but of course cooler combustion works against both hydrocarbon emissions and efficiency.

The modern advanced engines are marvels of technology, subtle and complex.

Interesting [to me at least ] Thanks for that information. Are you an SAE member?

The other major contributor to NOx generation is the air-fuel ratio.

So called "lean burn" engines, that have air-fuel ratios well above the stoichiometric combustion ratio [e.g excess air], reduce emissions of unburnt hydrocarbons and improve fuel efficiency, but generate a lot of NOx.

[thriftyandboringinohio]

Re: Care to comment Jtabeb

Interesting [to me at least ] Thanks for that information. Are you an SAE member?

The other major contributor to NOx generation is the air-fuel ratio.

So called "lean burn" engines, that have air-fuel ratios well above the stoichiometric combustion ratio [e.g excess air], reduce emissions of unburnt hydrocarbons and improve fuel efficiency, but generate a lot of NOx.

I was an SAE member some years ago; have my name on a couple SAE papers; and was even a speaker at few SAE technical conferences for alternative fuel and low emissions engines. I've been out of the game for many years now, though, and never had your hands-on racing engine exerience.

[gnk]

Re: Care to comment Jtabeb

This whole thread can be summed up with one word.

HOPE!!

For all of the skeptics, I say what is your idea? If you have no quasi technology to hope for than we are all domed – at least most of the non elite (lol) which I am a part of are done.
I HOPE it works the alternatives are not something I want to confront.

Not JMHO - do the math - it all works out.

We have too much hope.

Hope is a two edge sword.

Hope delays our reality. Hope continues the business as usual paradigm. Hope makes us profligate users of resources.

In the end, hope will be more destructive to society than the natural depletion of the resource we call petroleum will be. Why? Because hope delays preparedness.

:eek:

[DToM67]

Re: Care to comment Jtabeb

Starving Steve,

I have seen others here call you crazy, and now it's my turn to do the same.

Dirt in the fuel..?? In a diesel engine...???
What are you talking about..??

Anyone who understands diesel engines knows that first and foremost that you have to filter all the dirt and water out of diesel fuel before it gets to the fuel pump, or you aren't going anywhere.

I'm a former marine engineer, who maintained a number of different diesel engines on a number of different boats over a number of years. Of course you have to give the engine clean fuel...that's a no-brainer. That's in diesel engine owner 101. That's why 10 and 20 micron filters are used. That's why fuel takes a trip through a centrifuge on the bigger boats, to remove the dirt and water, and then off the the day tank.

Well Steve, I suggest that you not buy and use a computer because eventually you will get a virus, or a hacker will steal your credit card info, or the hard drive will crash...etc...it won't work for you....don't go that route...

bobola, I too have wondered... and what you have to understand about Steve is that when he wants to know something he checks his gut.;)

[media][/media]

[Rajiv]

Re: Care to comment Jtabeb

JT,
I think you have made an error in your calculations

There are 4047 sq m in an acre. The surface of the earth on the average recieves 4800 wh of energy per sq m ~ 0.13 gallons of gasoline.

So the maximum amount of enrgy at 100% efficiency of conversion would be 4047*365*0.13 = 192,000 gallons of gasoline per acre. However photosynthetic efficiency on the average is only 4.5% -- which leads to a theoretical production of 8641 gallons of gasoline per acre per year. This would be for pond algae. Bio reactor algae I believe could possibly ~ double this. However, there appear to be problems of scaling with the bioreactors -- for example fouling of the tubes by algal growth itself -- which would require frequent cleaning of the bioreactor tubes -- which would cut into the net energy out.