Series hybrid no better than a gas car?
I am reading a book called Common Sense Not Required: Idiots Designing Cars and Hybrid Vehicles: My Career with Chrysler by Evan Boberg. Ever wonder why series hybrids, cars that have on-board generators to charge a battery that run an electric motor, are not available today? The technology to do it exists today. In the book Common Sense Not Required, Evan says it's because they are not better than gas cars. You tell me if his math is funny.
He starts off by saying a gas engine is normally 20 percent efficient BUT it has to warm up to that efficiency. No warming up for series hybrids so efficiency for that gas engine is 28 percent. That's conversion 1. Still with me?
Go below the fold for more.
The gas engine converts work into electricity at 95 percent efficiency. That's conversion 2.
Are we there yet? No. That energy will probably be stored in a battery. Conversion 3. That's 95 percent efficient as well.
Are we there yet? ...I will pull this car right over :D Conversion 4. Battery to the electric motor. Again, 95% percent efficient.
Finally, energy conversion 5, motor to road. Welcome to Wally World! As anyone that saw National Lampoon's Vacation knows, Wally World is closed. This is directly from the book; "(.28 X .95 X .95 X .95 X .80) results in overall efficiency of only 19 percent for the series hybrid. This is worse than the conventional car at 20 percent. And I'm being optimistic."
...but what about diesel? Evan covers that too. Next page. He says "a diesel powered series hybrid doesn't make sense either." Sniff. Evan then says Santa Claus is not real. Just kidding. He does not say that. He might as well because I am not feeling great about the Volt right now.
Someone please post in comments, "Dad just pretends to be Santa because the real Santa is busy making my gifts?"
[Source: Common Sense Not Required]
Reader Comments (Page 1 of 4)
Nathan 1:40PM (2/05/2008)
Imagine the volt has a trailer with a gas powered generator. You can attach it when your trip is more than 40 miles. Would you then be willing to call it an electric powered vehicle, or would you still claim its gas powered because that is an option?
Some electricity is generated using gas/diesel especially during peak power situations. Would you claim that the Volt failed at being electrically powered because it got electricity from a grid that had a minimal amount of gas powered generators?
Your argument is fundamentally flawed. The Volt can and will be electrically powered for 80% of its use. The fact that GM has decided to add functionality in the small highly efficient 75 hp engine does not make it less of an electric vehicle. The wheels are driven by electricity. The source of that electricity is irrelevant, and opens up numerous options for future capability.
On another note, here is an option for a future engine:
http://www.reuters.com/article/pressRelease/idUS170285+11-Dec-2007+BW20071211
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Brewja 9:04PM (7/08/2008)
Currently developing a series hybrid "kit" to be installed in existing vehicles. Only an 18HP ICE to recharge the capacitor/Battery pack. Average fuel consuption approx. 180-200MPG. WIll post video shortly. Current conversion is a '97 Isuzu Rodeo.
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Jonathan 1:47AM (10/19/2008)
Where would you get a DC generator to build your own series hybrid? I know of polar power but their dc generators are much more expensive than their ac generator versions. A 10kw dc generator/alternator is about $4000 a AC generator head is about $350. A huge difference. And both weigh about the same.
Any ideas where to get the 53kw generator that the volt uses?
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fred 5:53PM (11/03/2008)
i think the problem with comparing this article to the discussion seems to be that this author is talking about a series elctric vehichle not a series hybrid elctric vehicle. the difference being that a series electric whould be constantly powered by a genset like a locomotive. the problem being the difference in size results in a loss of effecientcy. most serial electric systems are on large systems because the effecientcy gains are higher the larger the system gets.
the difference in a series hybrid is that the engine only runs to return the battery to higher lvls of recharge and electrical energy is stored no wasted when no required, if a locomotive is sitting still with its deisels running at its lowest idle it still wastes energy even if it is not producing power, in a system like the volt the ICE motor only runs when there is room to store the power it produces.
the oother assumption that this article makes is that the initial conversion from chemical to rotative power has a max efficiency of 28% which is average for a ice engine. but the origanal ev-1 project had a 44kwh turbine in one of its series elctric cars that had a 35% efficiency lvl this vehicle made 60-150 mpg effecientcy. there are now some micro turbine gensets getting up to 43% efficiency
using a hydrogen fuel cell the genset could be even more efficiect.
the volt is definetly a series hybrid car not a pure electric, if pluged in it could greatly reduce the gasoline used but it will not replace gasoline. it is still a much better idea than curent hybrids that don't plug in and must use gasoline every time its used, the reason this is important is that most power stations can achieve much higher recovery of energy from fuel sources because they can recover the heat energy and tunr that into electricity. some coal plant can reach 85% recovery. and if we required alge co2 recovery from all coal power plants they would produce much less carbon.
the real advance for these vehicles will be if and when we can get supercapacitors up to speed as it would ellimiinate the waste and polution of batteries and provide higher recharge and discharge rates giving more capabilities to electric powered vehicles.
Taylor 11:16PM (11/24/2008)
These guys are small and need investors, but I think they are onto something:
http://www.GenovationCars.com
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Mike 2:01AM (7/08/2009)
"This is worse than the conventional car at 20 percent. And I'm being optimistic."
No, you're not; you're actually just wrong. Much of the time, electrical energy isn't stored in the battery, it's stored in a capacitor. Motor-to-road losses are lower in electrical cars. Generator engines don't need to run continuously and are more efficient than regular engines. Etc.
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Sam Abuelsamid 5:58AM (8/06/2007)
The problem with this overly simplistic analysis is that it seems to assume that the engine will be running continuously and in the same manner as a conventional vehicle. With the plug-in series hybrids that are being worked on now, the engine will not in fact be running during most of the operation of the vehicle. The batteries will provide sufficient capacity to cover most of the period with grid power.
Secondly a series hybrid engine will be running at constant speed and load and can be optimized for that duty cycle. That means that it can actually be made to run at higher efficiency than an engine that has to be able to smoothly handle operation for 600-6000rpm. The overal efficiency of the whole system can be dramatically increased.
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Tim 9:39AM (8/06/2007)
The Volt is NOT primarily a “series electric” car and it is NOT a hybrid! The Volt is a BATTERY ELECTRIC CAR with a RANGE EXTENDER because the PRIMARY power comes from the electric grid. The 40 mile battery electric range will completely cover over 80% of ALL daily commutes. The primary purpose of the “range extender” is to help the average driver feel comfortable with the fact that they won't be left in the middle of nowhere with a dead battery. This fact will make it GENERALLY accepted thus far superior to the EV-1 or any pure electric car! GM has stated that the future is electric. However the AVERAGE driver must be made to feel comfortable with electric drive. It’s a paradigm shift. The Volt BEV and all PHEV’s for that matter are but the NEXT logical step the FULL electrification of personal transportation.
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Jason 11:39AM (11/17/2008)
I would love to believe in the Volt, but alas, I cannot. A reported 40 mile electric range means that plenty of people will still see a daily duty cycle of the gas generator. Mainly, my fear is that 40 miles, while sufficient for most commuting, even mine, is an idealized figure. More likely, it will get 20 or so miles before the engine kicks in to start recharging the batteries, so they don't go dead before the end of the 40. If a PHEV comes along with more like a reported 60-80 mile range, then real-world trials seem more likely.
Tony Belding 9:41AM (8/06/2007)
Evan Boberg is right. This is exactly why parallel hybrids have been used thus far, because they have fewer energy conversions -- and associated losses -- than a series hybrid. Other factors being equal, the parallel system will win on efficiency.
Sam Abuelsamid is also at least partly right. A series hybrid does, in theory, allow you to use different kinds of engines which are more efficient than the conventional gasoline engines but cannot be used in conventional non-hybrid cars because they don't respond well to being throttled. In a series hybrid they can run at a constant full-throttle condition, or be shut off completely when they aren't needed.
So, why haven't car companies done this? Why didn't Evan Boberg take this possibility into account? It opens a whole can of worms: what kind of engine *are* you going to use, then? Gas turbine? Wankel/Rotapower? Stirling engine? There are several possibilities, but none of them are proven in automotive applications. Car companies have huge capital resources and knowledge invested in conventional piston engines, so they obviously want to use what they can pull off the shelf.
Next point. . . Sam says PHEV serial hybrids, with plug-in charging, change the balance. Yes. . . If you can run part of the time, or most of the time, off grid electricity, then that's a huge boost to your efficiency. But Evan Boberg doesn't address that. His experience in the auto industry was some years back, and Li-ion cells were not in the picture yet, so he probably had no reason to think about PHEVs or factor them into his argument.
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Daniel.Car 9:43AM (8/06/2007)
You gain efficiency over regular gas engine because you lose the transmission. Warm up isn't an issue, because the series engine has to warm up also.
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Tony Belding 9:49AM (8/06/2007)
Tim, if you don't think the Volt is a PHEV then I don't know what is. If you go down the Volt's projected specifications, they read exactly like the wish list of PHEV advocate groups like CalCars, Plug-In Partners, etc. It's as if GM took the PHEV recipe these groups had been calling for and copied it word-for-word.
You wrote, "The Volt is a BATTERY ELECTRIC CAR with a RANGE EXTENDER because the PRIMARY power comes from the electric grid." Yes. That is exactly what a PHEV is. That's the definition of a PHEV.
GM: "It's not a tree! It's a large, woody, perennial plant! Unlike trees, it has a single stem or trunk growing to a considerable height and bearing lateral branches at some distance from the ground!"
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Ablert 11:27AM (8/06/2007)
What impact does regenerative braking have on his numbers?
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Lascelles 10:30AM (8/06/2007)
Ablert asked "What impact does regenerative braking have on his numbers?"
I did not mention it but he says his example does not include regenerative braking.
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Luke 10:31AM (8/06/2007)
I would have thought that a series hybrid would be more efficient than a parallel hybrid for the following reasons:
1. The engine used in series hybrid does not need to be built for huge sudden loads, such as pulling away from the lights, so can be much smaller, lighter and therefore operate more efficiently.
2. The smaller engine would itself be lighter than an equivalent ICE, making the vehicle more efficient.
3. The series ICE would be able to run at a constant load, so could be perfectly geared and tuned for maximum efficiency, as opposed to a parallel hybrid's ICE, which must rev through a range within each gearing.
4. There is a weight saving over a regular hybrid, because the gas engine does not need to be couple to the wheels.
Additional, series hybrid would be more efficient than an standard ICE car for the following reasons (shared with parallel hybrid):
5. Can reclaim kinetic energy using regenerative breaking.
6. Part of the journey can use energy derived from the grid, which is way more efficient than a self-contained ICE.
And to top it all off, the multiple sequence of efficiency ratios he mentions simply gives more opportunity for improvement, whereas existing ICE cars have only one area for efficiency to improve (actual engine efficiency), which has already been flogged to death for the past 100 years.
eg.
.28 X .95 X .95 X .95 X .80 = .19, but:
.29 X .96 X .96 X .96 X .81 = .21
, and that only assumes a 1%(!) increase in efficiency of a small, perfectly geared, constant speed generator, over a large lumbering, 800 - 6000 RPM 200kg standard ICE engine.
Welcome back, Santa...
Luke Coverdale
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Tim 10:31AM (8/06/2007)
Tony- A Plug-In "Hybrid" will not run at ALL speeds (up to 120 MPH) WITHOUT an operating ICE. Name ONE that will...
The Volt doesn't NEED the ICE for the average 40-mile HIGHWAY commute.
Yes, there are a lot of bushes that look like trees. NO, spiders are NOT insects or "bugs and the Volt is not a “Hybrid.” It’s a BEV with a range extender.
Just because a dog has 4 legs, doesn’t make it a horse and a house cat is NOT a lion.
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Peter 10:43AM (8/06/2007)
Things missing:
Mechanical Transmission losses for the regular automobile.
That any serial hybrid is likely plug in hybrid which improves the numbers.
When running with the ICE on, you don't need to include battery conversions in all the efficiency calculations. It can be generator-> electric motor.
Increased efficiency from running the hybrids engine in most efficient range.
Using alternate generation engines that are more efficient than automotive ICE.
Regen braking and stop and go savings. Which is big, this is where current hybrids get most of their advantage.
In short: of course if you treat the series hybrid as nothing more than an transmission/drive shaft replacement, you are not going to see an increase in efficiency.
The whole point is to open the door to a range of possibilities unavailable without being hybrid, like plug in, regen braking, or things not available even in parallel hybrids like replacing the ICE with something more efficient at electricity generation.
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werepants 10:55AM (8/06/2007)
Sounds suspect to me, but even if this fellow was right,(which he isn't since he neglects several of the major benefits of hybrids, and seemingly ignores real life examples like heavy duty train engines,) it would still be in our interest to pursue cars like these.
Electric drive allows the transmission to be done away with, removing a great deal of inefficiency and complexity, increasing reliability. Electric motors require next to no maintenance, and even the supplemental ICE will run at very controlled, optimized loads and speeds, which I imagine will stress the engine much less.
Safety applications are plentiful when you consider electric, independent AWD. No differentials to worry about, and you can computerize the power distribution for optimal stability, speed, traction, whatever. There is an electrified MINI that has the equivalent of VSC or EBD, except rather than just removing power selectively, it can apply power too. You have the benefits under acceleration, and I imagine being able to turn a certain wheel at any time could have benefits for braking, also.
When you throw in all the efficiency benefits like regenerative braking and charging from the grid, it's a no-brainer. I'm excited for a Volt 2, with ultracapacitors, and shortly thereafter a Volt 3 running on ultracaps alone, and chargeable in 5 minutes.
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Scatter 10:55AM (8/06/2007)
Can someone confirm these back of the envelope calculations?
A series hybrid that needs say 250wh/mile travelling at 70mph will need 17.5kW of power. Taking the 86% combined efficiency of the electric drive system that means you need a bit over 20kW (say 25kW just to be on the safe side).
That’s a 34bhp engine to get you from A to B compared to maybe 100+bhp in a conventional car. How can that not be more efficient? Or are my calculations screwy?
Also does he give any reasons why diesels are not possible?
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beelzabush 9:35AM (8/09/2007)
Once the batteries are depleted( after the hoped for 40 miles) you are running the car on the small one liter?) engine. will a 4-5 passenger car work with a small engine like that? I dont think so. You're electric vehicle (except for a tiny low speed NEV) is still waiting for a battery that hasn't been invented yet. How about the hydrino hydride battery still on the blackboard at blacklight power?
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