No wonder the Germans are so gung-ho on sending their diesels across the pond. Europe’s two-decade long diesel-keg party has been crashed by a new generation of super-efficient, clean and cheaper gasoline engines. A royal diesel-overproduction hang-over is inevitable. The Germans’ morning-after solution: send the stinky leftovers to enthusiastic Yanks waiting with open arms, who’ve conveniently forgotten their killer hangover from the last US diesel orgy.
In 1892, an experimental ammonia engine literally blew up in engineer Rudolph Diesel's face. Laid-up in a hospital bed, he pored over Nicolaus Otto’s pioneering work on the internal combustion engine. Diesel identified its weakness.
Diesel tumbled to the fact that the Otto engine’s efficiency was intrinsically compromised by the fact that it mixed fuel with air prior to compression. Too much compression resulted in uncontrolled pre-detonation. Diesel’s solution: inject fuel separately from the air to allow super-high compression and eliminating the need for a throttle (reducing pumping losses). Diesel's engine was roughly 30% more efficient than Otto's.
In 1989, VW/Audi ushered in the modern direct-injection (TDI) diesel. The group's oil burning powerplant set a high-water mark in the diesel’s long development. With Europe’s high fuel costs, the more expensive (yet efficient) diesel engine could now pay for itself quite easily. The calculation triggered Europe's diesel-boom, resulting in a 50 percent market share vs. gasoline-engined propulsion.
But Europeans have been paying a price (other than at the pumps): particulate emissions (Particulate Matter, or “PM”) and NOx pollution. Many European cities have serious particulate and diesel odor problems. Several European cities impose restrictions on diesels during PM alerts.
The new generation of “clean(er)” diesels that meet the US Tier2 bin5 standards cut PM emissions substantially, but not completely. Already, there are warnings that PM from “clean” diesels still poses a significant health risk.
The diesels coming our way carry several other penalties, especially versus the gas hybrid. The complicated and expensive NOx catalysts and urea injection schemes (“BlueTec”) cut efficiency by five percent. Meanwhile, the next Prius is projected to be 15 to 20 percent more efficient. And Toyota is bringing down hybrid production costs.
The diesel vs. hybrid mileage/cost gap widens… further. And the “clean” diesel’s just-barely compliant emissions still can’t touch the gas-hybrid’s practically breathable exhaust.
Then there's the elephant in the room: global warming. Clearly, the political winds are blowing against CO2. Diesel fuel has higher carbon content, resulting in 17 percent more CO2 per gallon of fuel burned than gasoline. With the diesel’s efficiency superiority down to 25 percent, a “clean” diesel emits only 13 percent less CO2 than yesterday’s gas engine. And that small gap is… wait… gone.
While the diesel’s efficiency peaked in 1989, and lost 5 percent to PM cleansing, gas engine development is on a roll. Engineers are systematically tackling all the inherent deficiencies that Diesel identified in his hospital bed. (No wonder Rudolf was considered paranoid; maybe he suspected that eventually the Otto engine would catch up.)
A farrago of new gas-engine technologies has converged, which Europeans have been quick to embrace. VW’s 1.4-liter 170hp TSI gas engine is a perfect example of the trend. The TSI starts off with the help of a supercharger (no turbo-lag), and then switches to turbocharging (no parasitic losses). With diesel-like torque and direct injection, it’s the best of both worlds.
A CO2 output comparison with two other similar-output VW engines is telling. Their 170 horse 1.4-liter TSI produces 174g/kms of CO2. Their 150hp 2.5-liter five cylinder engine (US Rabbit only) emits 240g/km. And their 170hp 2.0-liter TDI diesel (not US compliant) produces 160g/km.
American Rabbit drivers are paying a whopping 38 percent efficiency penalty compared to the Euro-Golf TSI, as well as giving up gobs of torque and twenty horsepower. If VW’s 170hp TDI were “cleansed” to T2b5 standards, its CO2 output would be no better then the gasoline TSI.
And that’s just the jumping-off point. Start-stop technology, full valve control, and stratified direct-injection offer anywhere from 10 to 25 percent further improvement potential. Combine these goodies with mild-hybrid assist/regeneration, and the diesel party’s kaput. No wonder the Germans are all hard at work on mild-hybrid technology. It’s their best shot to keep up with Toyota’s CO2 meister, the Prius (102g/km).
A study by the consulting firm AT Kearny confirms the diesel's demise. It predicts that only 25 percent of Europeans will find diesels an attractive economic proposition by 2020.
Have Rudolf Diesel’s paranoid nightmares come true? Not totally. Diesels are a welcome mix to the party for larger vehicles that spend a lot of time on the open road. Count on GM’s new 4.5-liter “baby” Duramax diesel to be more popular with the light-truck crowd than the gas hybrid option. But when it comes to smaller vehicles, the numbers just don’t add up.
Although Rudolf Diesel’s engine WAS intrinsically more efficient, it turns out that Otto’s engine is a lot more clever at learning new tricks.
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Thanks for being so open minded about the Prius. But then again, facts are facts.
Consumer Reports imported a diesel SMART car from Quebec (i.e. it wasn’t US compliant – not even for non-California states) and gave it their test-over, and it obtained 42 mpg. They got 44 mpg with their tested 2005 Prius, and the Prius is obviously a lot more car than is a 2 seat SMART.
One thing that perplexes me no end is the fact that diesel fuel and gasoline both come from crude oil – so why was it that, when gasoline was $2.19.9 locally awhile back, diesel fuel cost $2.79.9 – but when gasoline went to $3.66.9 diesel was only $2.96.9?
Anyone out there in the oil industry want to address that one?
One other minor advantage to diesel is that at least when you put bio-diesel into the fuel tank, you don’t lose MPG as happens with virtually every car I’ve ever driven since 1979 and tested E10 in. I generally lose 7% to 20% MPG.
Glenn 126:
The most credible answer regarding diesel vs. gasoline cost is refinery capacity and demand. Diesel fuel demand has grown quite strongly over the past 5-7 years, creating tight supply, and high prices. The current run-up in gas prices is (supposedly) due to gasoline refinery problems.
In any case, the US petroleum industry is not ready for more diesel consumption, and a substantial increase in diesels on the road would just push up diesel prices higher.
Interesting article. Autobloggreen came to the same conclusion (through a series of articles here & there) that gasoline tech will improve a lot but diesel tech has pretty much matured. Let’s see if Honda can improve diesel tech further.
monteclat: “Let’s see if Honda can improve diesel tech further”.
Honda makes an excellent diesel for Europe, but it’s not more efficient than all the others. Sorry, but waiting for a “Honda miracle” is misplaced hope.
So how does biodiesel compare to regular diesel in terms of particulate matter, NOx, and CO2? Better, worse, about the same?
Jonathon: Interesting that you should ask. A recent (and scary) first study from Europe analysing biodiesel exhaust shows a very disturbing high number of carcinogenic substances. This was a blow to the biodiesel contingent.
Apparently, the super-high temperatures of combustion do some nasty things to bio-diesel. Kind of like baking/frying creates bad substances in cooking oil, but worse. It needs further study.
http://www.greencarcongress.com/2007/04/german_research.html
It’s possible that the TDI Rabbit could be cleaned up by a system that would collect the particulates, compress them into centimeter-sized spheres, and store them in a container for later disposal. However, who could guard against the “smart” asses who would leave the container off, thus resulting in Diesel Rabbits leaving a trail of these pellets…
Jonathon: My link was for an article about the effects of burning straight vegetable oil in diesel engines, not biodiesel.
There is not enough research to provide a clear picture of biodiesel exhaust vs. straight diesel. Some early work suggests advantages (for biodiesel), but there is not yet a deep understanding of the chemical changes that happen to some of the organic compounds. It may be problematic, like the straight vegetable oil. In anycase, we can’t grow enough to solve the problem.
Jonathon,
The NOx content of BioDiesel is directly tied to the feedstock that the BioDiesel was made from. Some vegetable sources make for very high NOx, and other bring it down to near zero.
Unlike gasoline, Diesel fuel of any sort emits NO CO2.
Particulate from BioDiesel is the same as petro-Diesel, and is mitigated completely by rainfall as it is heavy and will not stay suspended in the air with sufficient moisture.
Short of a 100% hydrogen- or solar-powered vehicle NO engine blows sunshine and kittens out the tailpipe. On the scale of relative evils, an engine running on BioDiesel is far better than any petroleum-powered machine.
At least with Diesel, you have alternatives, ALL of which can be home-brewed if you choose. You cannot say the same with gasoline.
–chuck
chuckgoolsbee: “unlike gasoline, Diesel fuel of any sort emits NO CO2″.
Chuck, sorry, but ALL diesel fuel emits CO2, as does burning any carbon based product. In fact, diesel emits 17% more CO2 per gallon than gasoline. That’s one of the key points of my article, and a negative for diesel in the push to reduce CO2 emissions.
Logically a hybrid diesel electric vehicle would be an optimum choice. The diesel ability to produce power at low RPMs for long periods of time would be ideal in a start/stop hybrid or a full hybrid. Combine all the other energy saving technology in the Prius (low resistance tires, slippery design, etc with a diesel engine and we’d probably see a 10% improvement in economy.
Chuck- I am with you here/ Bio fuels can make the diesel a good alternative since growing the fuel consumes CO2. Combined with the other emisisons systems a 100% bio, or a bio blend makes diesel an excellent green engine.
On the flip side, according to studies by UC Berkeley, there is not enough arable land in N. America to grow enough plant matter to replace fossil fuels, still, we can do what we can and use blends.
A drop-in gasoline substitute is available, and can be grown. It’s called Butanol. I understand BP in the UK are looking into mass production now. The conversion efficiency is something on the order of 70% (vs approximately 30% conversion efficiency for ethanol from corn) and the BTU’s are 5% less than gasoline (vs. 30% less for ethanol). Butanol (or bio-butanol if it is grown and made into Butanol) can also be pushed through our current petroleum pipelines, again, unlike ethanol.
Butanol is a 4-carbon chain alcohol (and deadly to imbibe). See http://www.butanol.com
Butanol is one reason why, in my humble opinion, the government should NOT emulate the soviets and try to force solutions (such as corn-grown ethanol) onto a “free” marketplace.
saabophile: “logically, a hybrid diesel electric vehicle would be an optimum choice”. If fuel cost $10/gallon, you would be right.
Between the much higher cost of a clean diesel ($2k to $3k), and the cost of hybridization ($2k to $3k), you would end up with a car costing so much more it would take maybe 20 years or more to amortize the costs (at today’s fuel costs).
Mild diesel hybrids are coming in Europe (Peugeot 308, MB S-class), but they won’t be economically viable in the US, and might not be in Europe.
Note how diesel and gasoline engines are converging. A staged turbo, direct-injection gasoline will prove to be more efficient in the end. Perhaps a higher carbon gasoline summer-blend will be produced to aid efficiency.
On a personal note: I *HATE* turbo-lag…Worse than torque-steer.
Oh…And…Great write-up Paul!
chuckgoolsbee did a better job nailing the ‘biodiesel’ alternative than 90+% of the rantings I’ve seen elsewhere.
I’m a big fan of biodiesel… but it needs to be refined to the point where the quality is consistent.
Most biodiesel applications offer lower fuel economy than straight diesel. However, if you use top grade bio-diesel in combination of bio-diesel, there can be a substantial decline in the overall pollution that takes place.
Yes, this is only a partial solution. But it also happens to be a heavily underutilized one that can improve the environment and our oil dependency.
I think the diesel/hybrid combination may turn out to be the new standard. A VW Lupo of the late 90’s can attain a real world mileage of 70 to 75 mpg and the inclusion of a battery for city traffic would cut overall emissions immensely. For a small city commuter, that may be the most efficent opportunity in the marketplace.
Jonathon,
In 2001 the EPA did a study of Biodiesel made from soybeans. At 100B, biodiesel produces 67-68% less unburned hydrocarbons, 45-50% less Carbon Monoxide and Particulate matter (I’m giving these numbers in ranges, because I’m just looking at a graph rather than searching through the 126 page document), and 10% more nox.
“The NOx content of BioDiesel is directly tied to the feedstock that the BioDiesel was made from. Some vegetable sources make for very high NOx, and other bring it down to near zero.”
Do you have a source for this? I don’t think it’s true. You guys here are probably sick of me getting into the details, but I’m a chemist, and as a result, I’m always thinking of the chemistry going on in a process.
In any IC engine, you have the stuff you want to burn, which are hydrocarbons (Gasoline, Diesel Oil, Biodiesel, Veggie Oil, etc) extra stuff that’s with the stuff you want to burn (Sulfur, and other impurities), stuff the government mandates to “clean” up the emissions (Ethanol, MTBE, etc), and the atmosphere (Nitrogen, Oxygen, and small amounts of whatever else came in through the intake).
The simple combustion reaction is
Hydrocarbon + Oxygen –> Water + CO2
So In the best case scenario, burning gasoline, diesel, biodiesel, or whatever you only make Water and CO2. Nothing bad about either of those (except MAYBE CO2 – but I’m going to reignite that debate). You also get a little CO if there’s not enough oxygen to go around. But CO –> CO2 is easy for the catylitic converter to take care of.
Now where does the bad stuff come from.
1) There’s lots of sulfur dissolved in crude oil when it comes out of the ground. This is normally a good thing as it makes the oil more lubricative but it’s a bad thing when you burn it because it ends up making SO2 out of the tail pipe which mixes with atmospheric water to turn into sulfuric acid (better known as acid rain). So by removing sulfur from our fuel (ever heard of light sweet crude? sweet means low sulfur) we get less acid rain, which is generally agreed upon as a good thing.
2) The second bad thing is particulates. Particulates are generally called “soot”. While they are carcinogenic, they’re not THAT bad. They’re big (i.e. you can see them as opposed to the nasty stuff you can’t see). Your body does a good job filtering big things before they can cause a problem. So in general particulates aren’t that bad because your body can filter them. And if we wanted to they’re big enough that we can filter them on their way of of the tailpipe too. Particulates are an easily solvable problem if someone would put their mind to solving it.
3) The last bad thing I can think of right now is NOx. So where does the NOx come from? There is no nitrogen (or very very little) in the fuel we burn. But the atmosphere is 80% nitrogen, so that’s where it comes from.
Nitrogen + Oxygen –> NOx
But it takes lots of energy (heat) to make NOx out of nitrogen and oxygen. So if you lower combustion temperatures you get less NOx and if you raise combustion temperatures you get more NOx.
So really NOx production doesn’t depend on the fuel (directly), but on how the fuel is burnt.
Lean mixture: More Oxygen than Fuel –> Burns hotter –> More NOx less CO
Rich mixture: Less Oxygen than Fuel –> Burns colder –> More CO less NOx
(Side note – in a gasoline engine, the oxygen sensor keeps oscillating the mixture between Rich and Lean so that the engine alternates between NOx and CO production. The cataylic converter takes the O off of the NOx and puts in on the CO which results in Nitrogen and CO2 as products which are much less harmful than the incoming NOx and CO)
Anyway. here’s the conundrum: Unlike a gasoline engine, a diesel engine always runs lean. As a result of the lean mixture and the high compression (which is why the diesel is more efficient than the gasoline engine) the cylinder temperatures are very high. That means that it makes NOx, and lots of it.
So if you want to reduce NOx you need to reduce the combustion temperatures. The only (easy) way to do that is to reduce compression and now were back to gasoline type efficiencies. I bet it could be done with water injection, but I don’t think people want to fill up a gas tank and a water tank.
Likewise, with all the direct injection gasoline engines coming out, they’re going to be raising compression ratios to get more efficiency, and those engines are going to be making more NOx.
NOx is something we really can’t get rid of easily because there’s so much Nitrogen in the atmosphere, we’ll never keep it out of the cylinder. We can convert it to CO2 and N2, but that requires CO to steal the O off of the NOx, and unless the engine runs rich, you don’t get that (That’s what the Regen in the new Powerstroke diesel does. Every so often, the computer just dumps lots of fuel in and cuts off the intake, that makes a bunch of CO which then cleans the NOx out of the catalytic converter – and of course reduces your MPG)
Ok, that was a long post and I started to ramble. But I hope that you can now see that it’s not a simple problem. There are many competing variable that we have to work with and some of them are in direct opposition to others.
In North America diesels are for trucks, where they do a good job, now with a catalytic converter and EGR.
In Europe diesels became popular in cars since the price of diesel fuel was substantially less than gasoline.
The diesels in European cars that come to North America are very quiet, smooth, more economical than the equivalent gasoline engine in the same model car. Plus the diesels have incredible low end torque which is an interesting feature.
There has always been a love / hate relationship with diesel powered cars in North America. It will continue for a few more years.
A few additions to an excellent article –
- The Diesel torque-shove that people love is, to some degree, achieved through overboost. Unfortunately, a Diesel on overboost belches smoke (less politely, one could say it farts). The overboost belch is not an element of most emission ratings but is a real, and probably unhealthy, annoyance. (Especially when you are on a bike or motorcycle, behind one of those acceleration junkies).
- Diesel is nasty — smelly and sticky on a gas station forecourt. It sticks to your shoe soles and is slippery and doesn’t wash off in the rain. Your hands stink upon filling up.
- For the enthusiast, Diesels are quite often downright unpleasant to drive. The acceleration of a shopping cart up to 1500rpm, then a great surge of torque up to 3000rpm, but nothing after 4000: I don’t like ‘em.
- People like to con themselves into thinking that Diesels are economical, but higher purchase prices and higher repair costs mean that you have to drive most Diesels more than 15k miles a year for them to make any sense at all.
“Lean mixture: More Oxygen than Fuel –> Burns hotter –> More NOx less CO”
This is why Audi/VW FSI engines do not go lean burn in the States…Can’t pass 2007 emissions law.
I dunno. Last summer I drove the Citroen C6 diesel and the Audi A8 diesel, impressive rides, both. The carbon content issues aside, it does seem that a litre of diesel in either of those 2 cars goes farther than a litre of petrol would in the Otto cycle equivalents. Physics is physics. I’m just guessing, but one easily imagines various boffins in Japan, Germany and yes, even the US, hard at work on the next generation of diesel-hybrid systems…
Paul, you are right about CO2… I was thinking/reading “carbon monoxide” while typing/not recognizing “carbon dioxide.”
–chuck
A few other things to consider:
-The well to tank efficiency of diesel is higher than gasoline i.e. it takes less energy to get it to you
-Better metering of fuel can do a lot to reduce particulate emissions. Boost has nothing to do with it; it’s the injectors putting too much fuel into the cylinder when you mash the gas pedal.
-The theoretical thermodynamic efficiency of a Diesel cycle is higher than an Otto cycle. Stratified charge gasoline engines operate on a Diesel cycle instead of the Otto cycle.
-I believe all diesel in the US is now low sulfur
Martin said:
“People like to con themselves into thinking that Diesels are economical, but higher purchase prices and higher repair costs mean that you have to drive most Diesels more than 15k miles a year for them to make any sense at all.”
I paid $17k for a VW Jetta TDI in 2002. I have driven it 110,000 miles with less than $1000 spent for servicing it so far (Service, not maintenance. I’m obsessive about oil & filter changing and basic maintenance, which i do myself.) One third to one half of the fuel I have used in the car I have made myself, at almost zero cost. If I were to average out the monies I’ve paid for fuel since 2002 I’d say it was well under $2 per gallon. The car averages 48-52 MPG, and most of my driving is on highways.
So, some top of my head math: Roughly 2200 gallons to travel that 110,000. So around $3960 paid into fuel.
Had I been driving an 18 MPG SUV all these years for all those miles at $2.45 a gallon I would have paid almost $15,000 in gasoline.
I’ve almost saved the entire purchase price of the car in fuel savings alone. Some con eh! =)
–chuck
chuck: your examples is taking an apples to oranges comparison to an irrelevant extreme. Europeans do their math carefully, and the extra cost of the diesel doesn’t pan out for less than the annual mileage Martin gave. Even less so with our lower fuel costs.
chuckgoolsbee:
I’ve almost saved the entire purchase price of the car in fuel savings alone. Some con eh! =)
Until the gov’t comes after you for all the fuel taxes you’ve cheated them ;)
Thank You, Gracias, Danke, Merci for this wonderful bit of clearly stated knowledge. Its like a breath of non-polluted mountain air.
Thank you also Miked for your review of chemistry for us non-chemists. I knew there was reason I should have studied harder when taking chemistry, I have been at a loss more than a few time when trying to understand the world around me.
I’ve got an MB GL320 diesel on-order. It costs $2500 less than the gas GL450. (To be fair, it’s got a V6 vs. the gasser V8, which accounts for the up front savings.) So I’m saving $2500 up front and saving a pile of money on fuel via better fuel mileage and, for now, cheaper prices at the pump. I can’t envision a scenario whereby I’ll spend more money over the life of the GL320 compared to the GL450 which takes Premium gas. No matter how many or how few miles I drive.
I’ve read and re-read the analysis of NOx, CO, CO2 etc in the comments and came away very confused. I think every side of this arguement has facts and statistics to back up their assertions. In my simple mind, it’s very simple. I’m spending less up front, I’m getting more miles per gallon of “petrolium product”, I’m using a fuel that takes less energy to refine and I’m emitting less CO2 per mile. The NOx and PM are open questions but they’ve been knocked down considerably, even without the ad-blue in my 2007 GL320. So, on the whole, it seems like a good thing. And if gasser engines are so much better by 2020, then that’s fine, I’ll be ready to replace the GL320 by then anyway.
“In my simple mind, it’s very simple. I’m spending less up front, I’m getting more miles per gallon of “petrolium product”, I’m using a fuel that takes less energy to refine and I’m emitting less CO2 per mile.”
Yes, and I think that’s the correct view to have. Over all diesel is the better choice when you’re talking about miles driven per amount of energy required to get it to you from the well. It generally also wins on miles driven per dollar, and miles driven per amount of CO2. It may lose on miles driven per amount of NOx. But in the end you need to optimize on what you care about.
SUV’s – SUT’s – Pick Ups should all have a diesel option at a reasonable price to raise the fuel economy of these vehicles.
Just like commercial trucks have all gone from gas to diesel, the same conversion should be going on with all these “trucks” that are used as cars.
Beyond cross overs every manufacturer should be offering a diesel option or only diesel in the bigger SUV’s and pick ups.
Paul,
Another thing many diesel-haters out there forget when they compared the technology of Benz-engines (Otto cycle) vs Diesel is that the Otto-cycled ones have had 40 year longer technological development curve.
May I remind you that the diesel engines in the MB in the 70 were not fundamentally different that they were in the first MB engines in the 30. If you do the same comparison for gasoline an engine from the 1930 and one from the 1970 are 2 different beast entirely.
Diesels have come a long, long way since the GM fiasco in the 80 and when they catch-on the many subtleties that gas engine have enjoyed so far, gas engine are not going to look that great.
The example of the super charged and turboed gas engine above is pure BS!!!! You can do the same with a diesel engine for that matter and have no turbo lag as well, you can even do that with a Variable Vane turbo or a twin turbo setup. You argument does not hold.
Another argument that does not hold is the one that mentionned that Diesel produces more cO2 per gallon than Gasoline… well duh!!!! is also 25% more nergy dense, the comparison only holds if you compare kg of CO2/kW or Btu in the liquid and at the wheel.
Thermodinamically Diesel engines are only up to 10% more efficient than gasoline engines.
Diesel fuel holds 25-30% more usable energy per gallon…
Even is gasoline engines become complex enough to reduce the efficiency gap they will never, ever manage to fill the gap of content of energy per gallon!!! and that is the bottom line.
Now the nature of the diesel engine will forbid it to ever ever be cleaner than the gasoline engine.
So the question is not if Diesel or Gasoline are better or worse than the other. The question is what as a society will be the choice given the advantages and disadvantages of either.
Diesel more efficient, but heavier and dirtier.
Gasoline lighter built, cleaner but less efficient.
I have heard that part of the reason for diesel’s popularity in Europe is because it is taxed less than gasoline – the government does not want to piss off the truckers. Anyone know how true this is? I have seen it come up every now and again when diesels are discussed.
rashakor: You mised the point about the supercharger/turbocharger combination. It allows one to use a much smaller gas engine (VW’s 1.4 TSI, for example) to replace a larger gas engine. The smaller one will run substantially more efficiently, and thus it approaches diesel efficiency.
The primary reason for diesel’s popularity in Europe is the European truckers’ lobby. Because of this lobby, diesel cannot be taxed through the roof, like gasoline is in Europe, making diesel relatively cheap. European carmakers have responded by producing diesel cars; but in the absence of government intervention like in the US, diesel cars do not make much sense.
Biodiesel doesn’t make any economic or environmental sense at all – biodiesel is a farmer subsidy program.
For those who are more concerned about US dependence on foreign oil than they are about CO2 emissions . . . coal can be converted into a liquid fuel that can be used in a diesel engine, though not in a petrol engine. Granted, I believe the tech to do so still requires much development as it’s not a very efficient conversion. And of course it does NOT address the CO2 problem. But it does help make the US self-sufficient for motor fuel . . . I heard a quote that called the US the ‘Saudi Arabia of coal’.
Paul,
Thanks for a great article. Up to your usual high quality standards.
Although I agree with you about diesel versus ultra-efficient gasoline engines (like VW’s TSI), I start to diverge on the hybrid issue. They make more sense than even diesel in some cases for someone leasing the car for 3 years, but they most definitely have not proven anything in the long term. Diesel engines have a reputation for longevity in the U.S. In part, this is because they are more durable than petrol engines. And in part it’s because eccentric fools buy diesel cars and those people are more likely to be fastidious maintainers.
In spite of all of this, I think many of us are very concerned about (1) the long term durability of hybrid cars and (2) the ecological impact of the battery creation and eventual disposal. These questions are not answered, nor can they easily be answered right now.
What we do know is that with proper maintenance and investment – two things to which “buy-use- trash” Americans are becoming increasingly hostile – diesel engines can have a healthy 250,000 mile lifespan.
Gas engines, of course, can also last a long time – my daily driver right now is a petrol V8 with 202,000 miles on it. But the more technology we add (like super-turbo chargers), the more there is to break. The more expensive it is to fix, the more cars just get trashed instead, the more spare parts that get trucked across the country and flown by jet over the oceans.
I don’t mean to sound like an insufferable hippie at all. Rather, I’m trying to highlight that it’s a very, very small look at the puzzle to compare engines on the basis of “mpg” or particulate emissions per mile driven.
Even coal gasification – which was used by the Germans during the second world war – is just another of a range of economically infeasible options, given the low price of oil at this time. US dependence on foreign oil is largely a figment of paranoia and xenophobia; oil comes from a wide geographic range of sources and no conflict, unless of unimaginable scale, will alter the global market for oil dramatically.
A reasonable cautious strategy is to not drill in the Alaskan refuge and leave the oil there for the improbable case of a global catastrophe.
That is not to say there is not a case for increasing taxes on gas. The US may be caught off guard and be stuck with inappropriate technology if the inevitable – rising and gas oil prices – will start to become more prominent. But this Ph.D. economist cannot see anything but emotional motivations for the use of subsidies, biodiesel, ethanol, or coal gasification.
Glenn: Easy. Different demand levels and fractional distillation.
Demand is pretty self-explanatory. (The demand levels also explain why diesel goes up in the winter when gasoline goes down – not because more oil is “turned into diesel instead of gasoline”, but because more of the base oil is being burned in the northeast as home heating oil.)
As for the distillation… in a barrel of crude, there are what carbon-chains there are.
Some of them are gasoline-length, some are diesel-length (others are shorter (petroleum gas), in between (kerosene), or longer (lubricating oil, bunker fuel)).
The only way to change the proportions is relatively expensive chain-cracking or joining, which raises prices if you have to resort to it.
The cheapest state, all else being equal, is where demand is proportional to the proportions of each in the output from the oil.
dkulmacz,
The South Africans have been producing oil from coal for 50+ years. Note that doing so costs ~$35-40/bbl, so for much of that time it was a political “you can’t sanction us” statement. Now, of course, SASOL is making money hand over fist.
Robbie,
As a Ph. D. economist I’d like to hear your take on the last sentence…
Paul, I must have missed something because your 12th paragraph, about CO2 comparison, confuses me. You say that the TSI engine produces 174 g/km, and that the TDI engine produces 160 g/km. With those numbers, the diesel is already producing less CO2 than the TSI, but you say that cleaning the diesel up would result in no better emissions than the TSI. If the TDI starts out cleaner, cleaning it further can only widen the gap in favor of the diesel.
Did you jumble the CO2 outputs? It seems likely the 240 g/km was supposed to be attached to the diesel, and the two smaller numbers belong to the gasoline engines.
Good article, Paul. I’m intrigued by the VW 1.4 liter TSI engine you mentioned. Maybe one of the European reviewers can let us all know if it’s as cool as it sounds.
If you stop fuel production at the diesel stage at the refinery, you save 12% of your imported raw material – which is a huge number.
I’ve seen diesel engines run on pulverised coal and on COW (coal/oil/water) as fuel in mining operations.
The point being that diesels will run on almost any combustible fuel and in the long run that may prove to be a huge advantage.
At least the diesels don’t need tune ups very often and won’t need $5000 batteries or $? electric motor replacements.
Hybrids are as much a dead end as steam engines have proved to be.
And who would have thought that in 1930?
Engineer:
As you note, coal gasification in South Africa was extremely heavily state subsidized, in order for South Africa to be able to achieve energy independence during Apartheid. If coal gasification or liquefaction could be done profitably, then there would be plants sprouting up all over West Virginia as we speak, and the US would be the Saudi Arabia of the world. It simply isn’t going to happen, according to any analysis I have read.
crazybob: CO2 output occurs regardless of how the exhaust is cleansed of particulates. It’s the intrinsic primary result of all combustion. What I was saying about the TDI engine is that when diesels have their particulates “cleaned”, that process (blue-tec, etc) decreases the efficiency of the engine, thereby increasing its CO2 output.
philbailey: “hybrids are as much of a dead end as steam engines proved to be”.
I’m going to speculate that if you were around in 1930, you would have said the same thing about diesel locomotives (”dead ends”), especially since they’re all practically hybrids (diesel/electric).
Paul
Wait and see and I told you so, are not very satisfying sentiments. But if you want to put $100 on it and get back to me in five years, I might have to crow, but I’ll try not to.
Rashakor: Another argument that does not hold is the one that mentionned that Diesel produces more cO2 per gallon than Gasoline… well duh!!!! is also 25% more nergy dense, the comparison only holds if you compare kg of CO2/kW or Btu in the liquid and at the wheel.
Thermodinamically Diesel engines are only up to 10% more efficient than gasoline engines. Diesel fuel holds 25-30% more usable energy per gallon…Even is gasoline engines become complex enough to reduce the efficiency gap they will never, ever manage to fill the gap of content of energy per gallon!!! and that is the bottom line.
The relative energy density is only important in determining how much space must be sacrificed to gas tank, and maybe price. by far the most important thing is relative CO2 emissions. If diesels lose that edge, they lose their biggest raison d’etre.
Speaking of Apples-to-oranges, I think it’s a little unfair to compare diesels which are available today (or within the next couple of months), with some hypothetical gas engine of tomorrow. The TSI is an interesting engine, but if you’re going to critique diesels for drivability, why not mention the fact that the TSI’s main fault has been it’s non-linear power delivery?
One thing is certain, diesels and gas engines are becoming more and more similar: turbocharging, direct injection, etc. But they aren’t at efficiency parity yet.
I think it’s more than a little disingenuous to phrase the argument in a way that makes it sound like the european mfg. are dumping their useless, unwanted diesels on an ignorant public, when today, and for at least the next couple years, diesels will have an efficiency advantage.
Some things may change this: HCI, Li-ion batteries, plug-in hybrids. But all of those things are the proverbial “3-5 years away”, which is just engineer speak for “god only knows”. Diesels are (more or less) here today.