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Guest essay by Eric Worrall
The pressure to conform to tightening vehicle emissions standards and fuel efficiency specifications is intense. Everyone knows about the recent Volkswagen Emissions Scandal, in which Volkswagen rigged the test to produce better results.
As part of the push for better fuel efficiency, which feeds through into a better emission profile, car manufacturers are replacing Steel components with Aluminium. Aluminium is lightweight, cheap, has good corrosion resistance, and has a low melting point, compared to steel – it is easy to cast, machine and weld.
The following graph shows the dramatic rise over the last few years, in the use of Aluminium for manufacturing cars.
There’s just one issue with this green triumph – refining Aluminium is incredibly energy intensive. Aluminium is smelted using Electrolysis. A pot of Aluminium salt is heated up to melting point, then a huge electric current is run through the molten salt for many hours, even days, to separate out the metallic Aluminium.
The following is a breakdown of the source of the electricity used to electrolyse the Aluminium. Note the surge in coal – the last column, for 2014, represents 400,572 gigawatt hours of electricity generated from coal, to smelt the world’s Aluminium.
World Aluminium also reports that in 2014, around 53.127 million metric tons of Aluminium were produced, up from 48.774 million tons in 2012.
Much of the rise from 48.774 million tons to 53.127 million tons can be accounted for by the rise in Aluminium used to manufacture cars, up from 5395 million pounds to 6886 million pounds. Converting to tons, Aluminium usage in cars surged from 2.6 million tons in 2012, to 3.4 million tons in 2015, a rise of 0.8 million tons. Aluminium production surged by 53.127 – 48.774 = 4.353 million tons. Therefore, if my calculation is correct, car manufacturing has consumed around a fifth of the rise in Aluminium smelting over the last few years. The electricity used by this increased smelting activity has mostly been produced from coal (note this calculation is using 2014 Aluminium production figures and 2015 automobile Aluminium manufacturing figures – so it is an approximation).
Obviously quite a lot of Aluminium is being used for goods other than cars – Aluminium is incredibly versatile and useful. But if you have already done the R&D, and tooled up to produce Aluminium components for cars, it is obviously also a lot easier to produce other useful Aluminium products.
While the rise in coal generated electricity to smelt Aluminium is dramatic, Aluminium smelting is only one of a range of factors driving the rise in global coal usage. The 400 GwH TwH used in Aluminium production is only a small portion of the rapidly growing multi-terawatt hours of electricity produced every year (40% of which is generated from coal, according to World Coal). But the rise in Aluminium car components, largely driven by stringent emission regulations, and pressure to improve fuel efficiency, is making a significant and increasing impact on global CO2 emissions.
Correction – in the last paragraph the electricity used for Aluminium production in 2014 should read 400 TwH, not 400 GwH (h/t Björn)
If only Polititians could match the improvements in effiency made by motor manufacturers in the last few years,we could all be paying much less tax. Sadly, many of them are incapable of running
a free evening in a brewery, the reason my friends is they have never run anything which involved using their own money!!!
It takes a lot of energy to produce primary aluminum from raw materials, but aluminum is one of the most recycled, and recyclable, materials around.
And, recycling aluminum uses only about 5% of the energy required to create aluminum from raw materials
In Europe, 95 % of the aluminium scrap from cars is currently being recycled.
http://www.hydro.com/en/About-aluminium/Aluminium-life-cycle/Recycling/
So, I am not sure that steel is better for the environment than aluminum when all factors are counted in.
/Jan
Recyclingness is a nice smoke and mirrors greeny word that make one all irrational and happy.
1) The production of aluminum right now does not include the use in transportation vehicles like trucks, trains, cars. If it did, there would be 20X more aluminum mines.
2) ~85% of the steel produced is also recycled. That would be the case for high strength steels as well, which as I noted above, would make cars lighter cheaper and stronger than Aluminum.
3) The red herring of the greens, ie “fuel consumption” is driving regulators to reduce the weight in a vehicle NOT because of the fabrication energy required, but for the long term fuel use considerations. In which case FRPs plastics and High strength steels out perform aluminum but several factors.
Recycle-ability of the automobile frame is nearly an irrelevant factor when all factors are counted.
Aluminum Yield stress = 18 ksi
HSS yield stress = +200 ksi
SG Al = 2.7
SG Steel =8.0
Strength to weight Al 18/2.7= 6.7
Strength to weight of HS Steels 200/8= 25
High Strength Steel is 3.7 X better than Al
Then there is the issue of collision safety. The Fed dictate collision performance.
Aluminum is cr@p when it come to collisions.
Well, but then the stringent vehicle emission standards should be driving the car industry to replace aluminum by steel, not the other way around.
Moreover, why are not airplanes made of steel if it has so much better strength to weight ratio?
There are obviously more to this than the strength to weight ratio you have found.
/Jan
Yes there is more to this.
Back in the day when lotsa aircraft needed to be built in a hurry, ergo the hoover dam and the west coast aluminum industry…for wars…steel was ordinary. Some of the aircraft components are still steel notwithstanding weight due to strength needs, ie landing gear. Anything that suffers fatigue and high stress cannot be aluminum. Steel is used in those components still.
Nowadays, 75 years later we have FRP carbon fiber pressure hulls for Airbus A320s etc and the A380. No aluminum, no steel. Also nowadays we have new high strength low alloy steels which are extremely tough and strong. Like I said much stronger than aluminum per kg.
Again safety is also a fed regulated aspect of automobiles. Collision protection requires extremely high strength passenger compartment.
Aluminum is used in aircraft because it is available and is a known and well studied material. Habit.
Now that specialty steels are available, they will be used, as I had done in a semiconductor processing application in 1995. Hydro forming car frames can be done with 1020 to 1080 steels but not Al 6061. It cracks. It is just a mater of time when the automakers see a cost benefit for retooling their production lines for thinner stronger materials.
Structural considerations like area moment of inertia which is Modulus of elasticity dependent also becomes a consideration.
All that being said, you said, “stringent vehicle emission standards should be driving the car industry…” Well that’s the rub isn’t it. YOU believe that government can legislate a cooler planet and a sunny day. It can’t. Look at the collision standards vs the weight standards. They are in polar conflict.
Emissions like NOx and SOx and soot are under control. Now CO2 is under the “emissions” umbrella. Since CO2 is plant food, the EPA etc have no right to regulate CO2. Therefore vehicle weight is a matter of economy only.
Aluminum is a buzz word. Fake technology. A shiny thing to grab ones attention. Sexy.
Ford reduced the weight of its 7300 lb F250 by using aluminum but had to increase its thickness to make it “sound better” (lower modulus of aluminum problem) Ford make the fenders out of aluminum. They should have made them out of plastic or FRP but truck enthusiasts would not be happy… marketing.
Serious engineers use concrete and steel and carbon/glass fiber composites.
What are suspension bridge cables made from? The Burj Dubai?
Also… Why are ships (cargo and oil and container) NOT made of Aluminum?
1) Salt water Corrosion
2) Cost
3) Fire risk.
Cars on coastal locations would rot and fall apart due to aggressive interaction of NaCl and Al at weld sites.
I have already replaced my COATED aluminum wheels 2 times since 2006.
Airplanes don’t suffer as much salt exposure since they are glycol washed in winter and operate at 20-35,00 feet.
“Paul Westhaver
November 22, 2015 at 11:24 pm
Also… Why are ships (cargo and oil and container) NOT made of Aluminum?”
HMS Sheffield.
Greenies and Warmistas cannot see beyond the end of their nose. They cannot connect the dots and see, amongst many other unexpected consequences, that making aluminum takes electricity, that iron is made with coal, and closing coal facilities would increase all prices greatly.
Handy reference guide to environmental organizations
Start Guide: Environmental organizations sub-grouped into 8 categories.
8.2, Environmental Groups Focused On Climate Change
US Climate Action Network
Climate Crisis Coalition
350.org
The Climate Reality Project
http://www.startguide.org/orgs/orgs08.html
The Big Lie consists in finding the most outrageous opposite of the truth, and proclaiming it with a straight face.
“I am a liberal, so do what I say!”
LOL
When I read through the article I thought that the quoted 400 GWh of annual electric energy usage for total world production aluminium had to be somewhat in error so I went to the World Aluminium page that is the source of bottom figure in the article , and dug a little deeper into energy use statistics for aluminium found there, sure enough the 400 GWh number shoud have been written as 400 TWh (400000 GWh ) , and furthermore 400TW hours is only the part of the total use of electricity that is generated by coal plants worldwide to produce primary aluminium ( i.e. new and therefore does not include recyled ber cans etc ). With that out of the way here are some facts that I garnered from the data om the World Aluminium web site:
Total world production of primary aluminium estimate :
in 2014 was 53.12 million tons and 47.78 million tons in 2012, i.e. +5.34 million ton in 2 years.
the energy used for production was:
in 2014 690 TWh, 400 TWh from coal, 68 TWh from gas&oil and 222 TWh from Hydro$Nukes.
in 2012 601 TWh, 319 TWh from coal, 46 TWh from gas&oil and 236 TWh from Hydro$Nukes.
So total increace in energy use in two years time was 89 TWh , and there were some notable
changes in composition of the energy mix, the coal share rose from 53% of the total to 58% , gas&oil share increase rose from 7.7% to 9.9% and Nuclear%Hydro fell from 39.3% down to
32.2%, ( and note the birdblenders and friers share stod still at 0% for both years/sarc).
All in all there is a well discernible trend of a movement of aluminium smelting activity away from the energy sectors that have the least CO2 emission intensity, i.e Hydro & Nuclear to the more CO2 eimission-intense fossil fuel sector and even there the coal growth outdoes the natural gas by a ratio 2.5:1. Definitively not the what you would want if you reduced CO2 emissions are the goal.
But , I lingered a little longer over the production and energy use number of the sector, and could not help noticing few other things that are pertinent to this subject.
One was that f.x that China that in 2014 is estimated to have produced little over 50% of the total world production of primary alumininum (27.5 vs. 53 million tons) also had an increase of 5.36 million tons production from 2012 to 2014 nearly an exact equal of the world production total increase. This one fact also very likely explains th increased share fossil fuel powered production over the same period as its production of the 27.5 million tons were produced with 374.1 TWh of electricity and of that only 37.4 TWh or 10% came from hydroelectic power stations, and the other 90% solely from coal plants.
Another little trivia from this excursion of mine was that Europe ( Russia included as far as I can tell ) who is still a player in this game, albeit a minor one with 13.8% of the world share of the production, has radicllay different power mix in 2014 84% of the electricity used by the aluminium smelters there came from Hydroelectricity , another 7% from Nuclear and only 6% from fossil-fuelled powerplants, comparable numbers for the total world energy use in alumium production were in 2014 : 31% from Hydro , 1% from Nuclear, and 58% from Coal, and 10% from gas&oil.
And hile the total energy increace of 89 TWh used for primary aluminium production , in Europe that number went down by 10.5 TWh (123.8TWh 2012 to 113.3 TWh in 2014,and tonnage produced fell 567 thousand tons, from 7.93 to 7.36 million tons ), while China’s increased production stood in for 84.2 TWh increase in energy use in their production.
Finally one more thing I took away , if you divide energy used by the tonnage produced you get the energy intensity for the production in f.x KWh/kg or MWh/ton etc , I did so with the World numbers and also the Europa data and got an 12.99 KWh/Kg produced for the world average, and 15.39 KWh/Kg produced in Europa , the smelters in europe are 15% less efficient than the world on the average it seems , a bit strange in a region that hold’s the championship title in exorbitant electricity price.
Interesting analysis. “Europe… has radicllay different power mix in 2014 84% of the electricity used by the aluminium smelters there came from Hydroelectricity” probably explains “12.99 KWh/Kg produced for the world average, and 15.39 KWh/Kg produced in Europa , the smelters in europe are 15% less efficient than the world on the average it seems , a bit strange in a region that hold’s the championship title in exorbitant electricity price.”
I suggest that the electricity price for the smelters is not so high as it is mostly HE.
News flash: The best-selling vehicle in the USA, Ford F-150 pickup truck, has gone to an aluminum body for the last two years. 700 lbs lighter, better fuel economy, everyone loves them. This probably accounts for virtually 100% of the increase in automotive aluminum.
6061 is Aluminum El-Cheapo, the 7000 alloys have strength over 30,000 psi…
The only issue with alloy bodies on trucks like the F-150, which is fitted to a steel ladder frame chassis, is corrosion of dissimilar metals. Probably not an issue in the US where salt is not (I think) used on roads in winter, like the UK. Landrovers were notorious for this.
Patrick Yes.
I have a spool of magnesium alloy 1mm thick and 3″ wide. I bolt it to my under carriage and it corrodes instead of my steel car. The hydrogen half cells of iron and aluminum and in my case magnesium are relevant.
Steel is noble, relative to aluminum.
Aluminum is sacrificial. The first things to go are connection sites. All marine engineers know that sacrificial zinc anodes are placed on steel hull vessels to protect the hulls for rust.
Also “crevice corrostion” is a problem. Small batteries using salt water as electrolyte manifest at junctions between stainless, or iron or copper and aluminum. zinc and magnesium.
here:
http://www.tifab.com/pdf/Galvanic%20Series.pdf
6061 can’t be formed. It cracks. this is 75 year old knowledge. 6061 is 6X more expensive than steel and 1/2 as strong.
Ford is using them as a marketing scheme. Otherwise they would have done it 50 years ago. And no not everybody loves them.
http://www.ford-trucks.com/forums/forum276/
“Paul Westhaver
November 22, 2015 at 11:03 pm
It is just a mater of time when the automakers see a cost benefit for retooling their production lines for thinner stronger materials.”
I worked for Honda in the UK. Apart from structural steel used in the frame, the body panels were made thinner by 0.1mm, same steel, just thinner. They were stronger too…because they were *formed* differently.
I drive a Volkswagen but it isn’t a diesel its gasoline driven, or petrol as we British call it.
Personally I don’t care one little bit whether Volkswagen cheated the emissions tests or not, who cares anyway? It makes no difference in the great scheme of things, except to silly greenies.
And …all car makers game the test.
Now for some calculations as to whether replacing steel with aluminum causes an increase or decrease in energy consumption: The above chart indicates about 590,000 GWH of electricity was consumed in 2014 to produce 53.127 million metric tons of aluminum. This works out to 11.1 KWH per pound of aluminum. Assuming a combined generation, transmission and distribution efficiency of 35% for coal-generated electricity used by aluminum smelters and 100% of the increase of electricity demand for aluminum is satisfied by coal, each extra pound of aluminum requires 31.7 KWH of chemical energy from coal.
Let’s assume a car has its weight reduced by 400 pounds to reduce its curb weight by 10%, by using 400 pounds of aluminum in place of 800 pounds of steel. (I don’t actually know if a 1:2 ratio is typical or common.) Let’s assume that a car of this weight has its fuel economy increased from 28 to 29 MPG by this weight reduction. (Perhaps city MPG increased from 23 to 25, highway MPG unchanged at 33.) This is hypothetical, but I estimate these are reasonable numbers.
The 400 pounds of aluminum in the above hypothetical car requires 12,680 KWH to produce. Increasing overall MPG from 28 to 29 in a car that lasts 200,000 miles results in 185 gallons of gasoline saved. A gallon of gasoline has 36.6 KWH, so 246 gallons saved means 9,015 KWH of chemical energy saved. Uh-oh, it looks like adding aluminum to cars might not pay off unless the car lasts about 280,000 miles or aluminum saves gasoline more than I estimate or electricity for aluminum production is produced and delivered more efficiently than I estimate.
I just realized that the aluminum gets more miles for energy savings if it gets recycled for use in a car again, or if the car is made with recycled aluminum.
Why is it that smelting steel uses electricity generated by coal, and electric cars get electricity to charge their enormous batteries from windmills and unicorn farts?
Electric cars are coal powered.
Nice calcs.
Suggest you redo calculation , using and correct units in figures from the given source . Electricity usage was 690,000 GWh for the production of 53.127 metric tons of aluminium. It comes out as 12.99 KWh/Kg aluminium or ~ 5.9 KWh per pound aluminium, not 11.1
Rio Tinto stopped smelting aluminium in the UK some years ago because of the high cost of power required for the Alcan cell. Steel plants are also closing down because of high power costs largely as a result of the Climate Change Act introduced by the Labour government in 2008; this bill is also responsible for closing coal fired power stations forcing up power costs making UK manufacturing uncompetitive. Lefty environmentalists and warmists favour the use of electric cars little knowing that petrol driven internal combustion engines are more efficient producing lower overall emissions than power generators using fossil fuels.
Unfortunately, because of our traitor-in-chief’s war on coal, prb’ly none of the increased aluminum production is occurring in the US — maybe just across the borders into Canada and Mexico, or more likely, overseas. And people wonder why there is such a large & increasing trade imbalance for the US….
Alcoa in the US is a much larger producer of aluminium than Alcan in Canada.
This liberal knows that using aluminum in cars/trucks has an EROEI (energy returned on energy invested) that will pay off in a dozen years, and that when the truck is scrapped, the aluminum can be recycled to make more efficient vehicles and save far more energy than was required to reduce the alumina into aluminum. It is ‘foolish’ to waste fuel.