Boeing 737: A historical reference for range improvements
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RegGuheert
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Carlos Ghosn has been quoted as saying that is the rate of capacity improvement they are seeing, but I cannot find the reference.donald said:
Here is another report which shows 7%/year: Comments on the History of Li-ion BatteriesSee Figure 3 about 18650 cell capacity. 1991: 1 Ah, 2001: 2 Ah
2009: Panasonic Develops New Higher-Capacity 18650 Li-Ion Cells; Application of Silicon-based Alloy in Anode: 4 Ah
I guess that last data point is a bit over 8%/year from 2001.
That says too little about much. The figures there relate to how much of the stuff they can pack into a cell of a give size, and so reducing the electrodes/etc., per my earlier post, will give that but not change the fundamentals of how much 'stuff' you need to carry those electrons from one side of the battery to the other.
Funnily enough, when it comes to energy per volume, NiMH is actually better than Li-ion for Wh/cc, but can be manufactured heavier (more dense).
Reduce separators, charge collectors, electrolyte, etc, means more of the active product can then be jammed in.
My point is that lead acid batteries, invented in 1850's, go at ~40Wh/kg while the best Li are around 200Wh/kg and cost 3 times as much for the same energy capacity. (That translates to Li being [only] 5~6 times better.)
That is not remotely like an improvement from the Wright bros. 5 kW piston engine to a modern 15,000 kW turbofan.
Funnily enough, when it comes to energy per volume, NiMH is actually better than Li-ion for Wh/cc, but can be manufactured heavier (more dense).
Reduce separators, charge collectors, electrolyte, etc, means more of the active product can then be jammed in.
My point is that lead acid batteries, invented in 1850's, go at ~40Wh/kg while the best Li are around 200Wh/kg and cost 3 times as much for the same energy capacity. (That translates to Li being [only] 5~6 times better.)
That is not remotely like an improvement from the Wright bros. 5 kW piston engine to a modern 15,000 kW turbofan.
RegGuheert
Well-known member
Actually, it exactly supports my statement:donald said:
RegGuheert said:
Go back and read the title of the thread. The Boeing 737 has ONLY ever been fitted with turbofan engines. Any discussion of propellers or piston engines is off-topic.donald said:
GRA
Well-known member
Much of the range change for the 737 over the years is due to turbofans with much higher [Edit: meant lower, but let's go with better] sfc owing to higher bypass ratios, closer tolerances, improved materials and more precise engine controls (DECUs). Much is due to improved wing design, and the rest due to lighter components. And we shouldn't forget FMS, GPS/INS and improved weather reporting as factors in real-world range.donald said:
While I'm in general sympathy with you that batteries have and do develop much more slowly than a/c and the main method for greater range at the moment is a bigger battery, the max. theoretical capacity of Li-ion is around 400Wh/kg. Although you never attain theoretical capacity there is still considerable room for improvement. Beyond that, and what we're starting to see now, is Li-Si, with Li-S possible within 5 years or so although certainly not guaranteed, and the Holy Grail of Li-Air at least a decade out, if ever. And then we have solid-state batteries which Toyota is working on, flow batteries, ultra-caps, fuel cells and assorted other techs that may find their way to the consumer.
TonyWilliams
Well-known member
donald said:
The thrust of a Boeing 737 engines has gone from 14,000 pounds to 26,300. Almost double.
The first engines used were NOT high bypass turbo-fans:
"The Pratt & Whitney JT8D is a low-bypass (0.96 to 1) turbofan engine, introduced by Pratt & Whitney in February 1963 with the inaugural flight of Boeing's 727. It was a modification of the Pratt & Whitney J52 turbojet engine, which powered the US Navy A-6 Intruder attack aircraft."
Boeing 737 engine types used:
JT8D
CFM56-3
CFM56-7
johnrhansen
Well-known member
I have worked on all 3 types of 737s. They are all completely different airplanes, and the new Max will be even more different. The 737-900er has more than twice the max takeoff weight the original 737-100 had. They have had 45 years and have built 8000 units. You'd expect some changes. What do you think electric cars will be like 45 years from now?
The thrust of the engine is like the power of the EV motor. The range is little to do with the mass of the engine versus its combustion efficiency, which is the like comparison with battery specific energy.
One way or another, a plane with the same all-up mass at take-off would have much the same range. You wanna squash energy into a smaller space? That'll be more energy storage, then.
I say, roll on these new battery technologies. Great! When? Range increase of 737 was incremental. Battery increases will be quantum as new technologies emerge. From what I know, other Li technologies are considerably unstable and their future adoption within the next decade very uncertain.
I'll park the argument that range isn't as important as some folks might want to think (I don't want a bigger battery - I have never needed an EV with a longer range in a year, and I don't want to be lugging around dead mass that has cost me a fortune to buy), but I will suggest that as cars need to get bigger to carry more batteries to go farther, then the next limitation is cost. I don't think capacity is the big issue, Model S proves that even if you make the car over 2 tonnes no one is particularly bothered and people still rave if it has got a big range.
If you could make a 3 tonne EV out of cheaper batteries and offer it at a substantial discount to a comparable 2 tonne Li-battery car, then what would you do? What difference that it weighs 3 tonnes if it is not substantially less efficient and goes 500 miles?
One way or another, a plane with the same all-up mass at take-off would have much the same range. You wanna squash energy into a smaller space? That'll be more energy storage, then.
I say, roll on these new battery technologies. Great! When? Range increase of 737 was incremental. Battery increases will be quantum as new technologies emerge. From what I know, other Li technologies are considerably unstable and their future adoption within the next decade very uncertain.
I'll park the argument that range isn't as important as some folks might want to think (I don't want a bigger battery - I have never needed an EV with a longer range in a year, and I don't want to be lugging around dead mass that has cost me a fortune to buy), but I will suggest that as cars need to get bigger to carry more batteries to go farther, then the next limitation is cost. I don't think capacity is the big issue, Model S proves that even if you make the car over 2 tonnes no one is particularly bothered and people still rave if it has got a big range.
If you could make a 3 tonne EV out of cheaper batteries and offer it at a substantial discount to a comparable 2 tonne Li-battery car, then what would you do? What difference that it weighs 3 tonnes if it is not substantially less efficient and goes 500 miles?
JeremyW
Well-known member
Better aerodynamics is an area where we could seriously see improvements in range of smaller cars. Problem for the traditional automakers is that these aero requirements don't look like the traditional look. Tesla has shown it is possible to create something aerodynamically slippery but still look good. I recently acquired a first gen Honda Insight and that thing is pretty slippery. Unfortunately it was made during a time of very inexpensive gas prices. But something that looks like that with 20kWh under the floor could sell really well, if marketed towards long distance commuters.
I think the stickler for batteries is more cost than energy density/weight related. Although going from 40 to 200 Wh/kG is an order of magnitude. There's no "translating" with lithium's cost. That's a separate consideration because lead acid has established large scale and recycling that factor in it's price.
I think the stickler for batteries is more cost than energy density/weight related. Although going from 40 to 200 Wh/kG is an order of magnitude. There's no "translating" with lithium's cost. That's a separate consideration because lead acid has established large scale and recycling that factor in it's price.
RegGuheert
Well-known member
Not so. There are huge losses in an airplane traveling hundreds of mile per hour. You can increase the range by increasing the efficiency. For instance, Boeing increased the range of the 787-9 by about 1% by improving the laminar flow over the vertical tailfin using a system of tiny holes and a system to blow air out of them to reduce the wind resistance. They have made many aero adjustments to the design of the 737Max to gain a half-percent here and another half-percent there. Over the course of 50 years, thousands of such improvements have been made and the range is improved as a result. Yes, the fuel capacity has increased, but both the take-off weight and the range have increased by a much greater margin.donald said:
None. And this truth is eloquently communicated by my reference story about historical improvements in usable range while making no mention of batteries or jet engines. Simply put, none of us know by what means the range improvements will come about, but I can confidently say that they will happen because that is what the history of technology teaches me.donald said:
I'd agree with that, but I do hope that we are not all forced to pay the cost (both cash, and inefficiencies) of large battery capacities if we don't want them. Clearly, 22kWh is plenty for us folks here to have thought 'that makes sense'!RegGuheert said:
I guess I'd therefore rephrase 'range improvements' to 'range extension'. It implies the current range is somehow deficient. I'm happy with my range. Perhaps an extra 30% to cope with the reduced winter range, but the summer range is fine.
The automotive industry has a habit of giving customers what they think they want, not what they actually want, leading to a self-justifying circle because if that's the only thing available then of course people buy it. (Example like the US market kept pushing big cars whilst the Japanese came and stole the show with small efficient cars.)
In reality, you could add 50 miles for every 100kg of extra battery right now. The Leaf chassis wouldn't take much more, but a mid-sized car design/redesign could be easily constructed right now to take an extra, say, 400kg bringing the total to a, say, 250 mile, 60kWh capacity, but at a cost of some extra $20k, probably $30k after additional engineering of a heavier-duty chassis. That's why I think current battery capacity/range is an issue of cost, not technology, and why I'd say a lower cost technology rather than higher specific capacity is likely to win the day for EVs.
RegGuheert
Well-known member
Agreed. I don't think we'll be forced to do it. The market should provide differentiated solutions given time.donald said:
Like you, we find the range of the LEAF (when new) to be suitable for most of our needs. But that is not true for most of the people I have spoken with who live near here. The reason is that very many commute 60+ miles, which is not manageable in cold, windy weather or with a degraded battery.
It will be interesting to see what Nissan (and others) do as they have access to a wider array of battery technologies/capabilities.donald said:
Actually, the Insight is only a couple percent better in total drag than both the current Prius and Model S, despite being significantly smaller.JeremyW said:
http://www.caranddriver.com/features/drag-queens-aerodynamics-compared-comparison-test-drag-queens-performance-data-and-complete-specs-page-7" onclick="window.open(this.href);return false;
Stick the LEAF drivetrain into an Insight and you'll probably get about 15% better (+-5%) range on the freeway where aero drag is around half the energy used to move the vehicle. A nice improvement for sure, but nothing earth shattering.
JeremyW
Well-known member
http://www.curbsideclassic.com/automotive-histories/automotive-aerodynamics-drag-area-size-matters/
25% difference between the Insight and S. It's significant. But it's due to the Model S' size. It's a big car but still produces very very impressive numbers! The Honda Insight also weighs 1,847 pounds while the Model S is 4,785 pounds. Doesn't matter during highway cruising unless you're going up a hill...
The Insight does exactly what I need at the moment. Take me and some luggage far distances as efficiently and as cheaply as possible.
http://www.caranddriver.com/feature...ns-performance-data-and-complete-specs-page-7
25% difference between the Insight and S. It's significant. But it's due to the Model S' size. It's a big car but still produces very very impressive numbers! The Honda Insight also weighs 1,847 pounds while the Model S is 4,785 pounds. Doesn't matter during highway cruising unless you're going up a hill...
The Insight does exactly what I need at the moment. Take me and some luggage far distances as efficiently and as cheaply as possible.
You can't use the manufacturer's quoted drag number for reasons quoted in the C&D article. C&D tested the Insight themselves, and in their wind-tunnel it was no-where near 0.25 Cd. Look at the LEAF. Nissan says that it has a Cd of 0.28, but C&D measured 0.32.JeremyW said:
But Cd is quite critically dependent on how you go to measure frontal area. You could take the lower edge from the bottom of the front spoiler, which could be set much higher than the actual under-tray of the car (which it appears to be on the Leaf) and whether you take the aerodynamic cross-section of the tyres into account.
The bigger the car gets, the easier it is to get a good Cd figure. However, with a bigger car come bigger tyres and other elevated rolling resistances, together with a heavier mass to accelerate and decelerate.
Mass is interesting for EVs because it makes much less difference than it does to ICE. The reasons are because you need to carry around a much heavier engine in the heavy ICE so you can off the line promptly, but for most of the time when you are cruising around gently, or idling, that large ICE is now a liability. EVs always have oodles of torque and can have a small motor to achieve some surprisingly high instantaneous power outputs (as you rarely need full power for very long in a road car). Further, because of recuperation of KE you get back most of what you put in, whereas at least 70% of that original input energy is thrown away in a [non hybrid] ICE when you stop.
Clearly, aerodrag is very low for the Model S, which is great, but is not the end of its efficiency story. Induction motors have poor efficiency under acceleration because it is an asynchronous design, the magnetic version of a torque converter with no lock-up if you like. I'm aware of Tesla's claims about its motor, but, personally, I think this is the factor largely responsible for lower energy efficiency figures than the Model S' aero-power alone would have you believe.
The bigger the car gets, the easier it is to get a good Cd figure. However, with a bigger car come bigger tyres and other elevated rolling resistances, together with a heavier mass to accelerate and decelerate.
Mass is interesting for EVs because it makes much less difference than it does to ICE. The reasons are because you need to carry around a much heavier engine in the heavy ICE so you can off the line promptly, but for most of the time when you are cruising around gently, or idling, that large ICE is now a liability. EVs always have oodles of torque and can have a small motor to achieve some surprisingly high instantaneous power outputs (as you rarely need full power for very long in a road car). Further, because of recuperation of KE you get back most of what you put in, whereas at least 70% of that original input energy is thrown away in a [non hybrid] ICE when you stop.
Clearly, aerodrag is very low for the Model S, which is great, but is not the end of its efficiency story. Induction motors have poor efficiency under acceleration because it is an asynchronous design, the magnetic version of a torque converter with no lock-up if you like. I'm aware of Tesla's claims about its motor, but, personally, I think this is the factor largely responsible for lower energy efficiency figures than the Model S' aero-power alone would have you believe.
FWIW: In round-brush strokes, switched reluctance motors are the most efficient, with the disadvantage that they have more complex and costly rotors and control electronics (i3 has one, and is the most energy efficient EV at the moment). Then come externally excited rotors such as Renault ZE use (per Fluence/Zoe/Kangoo) and have a little extra manufacturing complexity than the slightly less efficient permanent magnet rotors (of, eg., Leaf), though the cost argument to avoid neodymium magnets is currently a strong one. In last efficiency place are induction motors as Tesla use, but are cheap and easy to make and should be very robust.
It seems to me that the disadvantages of mass and other rolling resistances is largely offset in larger EVs by being able to create a more aerodynamic body. In fact, these two factors seem well-balanced for all the EVs out there at the moment, which I say because if you list all EVs in order of their motor efficiency, as I describe above, you also get a list of EVs in order of their overall mi/kWh.
However, I'd further point out that all electric motors are very efficient and when I talk about one being more efficient than the other, there is, of course, varying overlaps between the type because we're only ever talking about an efficiency range in the 93~98% range. The corollary is that there's already very little improvement to be gained by aerodynamics or motor improvements because to get better aero you need bigger cars, so the pros and cons are generally in balance, and there is only ever another max. 5% efficiency to be gained out of motor improvements. So, all EVs will, and are going to be, in the range 125 to 155 Wh/km. You're simply not going to see the OOM sort of differences in EVs than between, say, a 7mpg Cadillac Eldorado and a 70mpg euro-diesel. It's only ever going to be a max. 30% energy-efficiency difference between the best and worst. So bigger range = more battery capacity. That's all it comes down to.
It seems to me that the disadvantages of mass and other rolling resistances is largely offset in larger EVs by being able to create a more aerodynamic body. In fact, these two factors seem well-balanced for all the EVs out there at the moment, which I say because if you list all EVs in order of their motor efficiency, as I describe above, you also get a list of EVs in order of their overall mi/kWh.
However, I'd further point out that all electric motors are very efficient and when I talk about one being more efficient than the other, there is, of course, varying overlaps between the type because we're only ever talking about an efficiency range in the 93~98% range. The corollary is that there's already very little improvement to be gained by aerodynamics or motor improvements because to get better aero you need bigger cars, so the pros and cons are generally in balance, and there is only ever another max. 5% efficiency to be gained out of motor improvements. So, all EVs will, and are going to be, in the range 125 to 155 Wh/km. You're simply not going to see the OOM sort of differences in EVs than between, say, a 7mpg Cadillac Eldorado and a 70mpg euro-diesel. It's only ever going to be a max. 30% energy-efficiency difference between the best and worst. So bigger range = more battery capacity. That's all it comes down to.
RegGuheert
Well-known member
Current production vehicles shipping today already go outside of your range on both ends:donald said:
TonyWilliams with Reg's annotations in RED said:
It already is greater than 30% (The least efficient of the four cars above uses 48% more electricity than the most efficient.) and the range of efficiencies will grow over time.donald said:
But I agree with your bottom line that the bulk of the range improvements in EVs will come from the battery.
Spark: 95 miles/19000Wh = 200 Wh/mi = 125 Wh/km.
(Chevrolet appear to claim the 82 mile range, though = 19000Wh/132km = 144 Wh/km)
(ref http://www.chevrolet.com/spark-ev-electric-vehicle.html" onclick="window.open(this.href);return false; )
There are 1.61 km in a mile - even an Amurcan' mile!
Merc appear to claim 185km from a 28kWh battery. (Is that all useable battery, though, or is that the useable capacity?) = 151Wh/km
(ref: http://www.emercedesbenz.com/autos/mercedes-benz/b-class/2014-mercedes-b-class-electric-drive-coming-to-america/" onclick="window.open(this.href);return false
(Side note: There was a mediaeval Arabic mile of ~1.8km length, which is what someone appears to have chosen to use in the last post. Just to mention... they didn't have EV's in mediaeval Caliphates. :lol: )
I don't regard the Rav 4 as a passenger car of the same class. Of course larger vehicles will take more energy. I'm talking about a regular 2-5 seater 2WD passenger car, around whom a body design of some moderately optimised aerodynamics can be designed. That is, Euro passenger class Segments A to F (also as defined by NCAP as 'passenger cars').
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