Nissan Previews Upcoming Hybrid and New All-Electric Vehicles, New Fuel Cell Stack
06 August 2008
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| Nissan’s new parallel hybrid system. Click to enlarge. |
At its Advanced Technology briefing in Tokyo, Nissan Motor unveiled prototypes of its original hybrid electric and new all-electric vehicles, both powered by lithium-ion batteries from the Nissan-NEC joint-venture, AESC (Automotive Energy Supply Corporation) (earlier post). Nissan plans to introduce production versions of the hybrid and the EV in 2010.
Hybrid Electric Vehicle (HEV). The hybrid system employs two new Nissan technologies: a parallel-powertrain hybrid system and a high-performance rear-wheel drive hybrid system. The parallel-powertrain system uses two clutches in which one motor is directly connected to the V-6 engine and transmission via two separate clutches.
The parallel-powertrain hybrid system eliminates the need for conventional torque converters, contributing to higher responsiveness and linear acceleration for improved driving feel, Nissan said.
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| The four modes of hybrid system operation. Click to enlarge. |
AESC produces laminated lithium-ion cells using a manganese spinel cathode material (LiMn2O4). For its next generation cathode material, it is working with nickel-mixed Mn spinel. The battery pack for the new hybrid delivers twice the power density of the lithium-ion pack Nissan introduced in Japan in the Tino hybrid in 1999.
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| The new Li-ion battery enables higher power density. Click to enlarge. |
To realize higher power, the electrodes are thinner to reduce internal resistance, and the lithium in the electrode material is closer to the electrode plate. A new passage inside the electrode material facilitates electron transfer, reducing electrical resistance within the material, and increasing power output.
The laminated structure enables a larger surface area to improve cooling efficiency.
Nissan is currently testing prototypes of the hybrid system on the road in Japan and the US.
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| Mule with new Nissan EV system. The production version will have a unique bodystyle. Click to enlarge. |
Electric Vehicle (EV). The latest generation electric vehicle prototype features a front-wheel drive layout and uses a newly developed 80 kW motor and inverter. The advanced laminated compact lithium-ion batteries are installed under the floor, preserving cabin and cargo space.
The production vehicle to be introduced in 2010 will have a unique bodystyle and is not based on any existing Nissan model.
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| The new pack for the EV features a new anode material and offers higher energy density. Click to enlarge. |
The Li-ion pack for the new EV has twice the energy density and 1.5 times the power of the battery pack introduced in the Hypermini in Japan in 2000. This enables a longer cruising range, and better acceleration. The pack also supports quicker regeneration to conserve energy consumption.
To increase the energy capacity, AESC is using a new graphite carbon anode material that is coated more thickly on the electrode to increase capacity.
Fuel Cell Stack. Nissan’s new fuel cell stack doubles the power density of the previous generation stack. The new fuel cell stack also achieves a 35% cost reduction mainly due to half the use of platinum.
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| The new fuel cell stack. Click to enlarge. |
Test fleets incorporating the improved fuel cell stacks will be operational by the end of this year, and Nissan is targeting commercial production in the 2010s.
The doubling of the power density is achieved through improved conductivity of the electrolyte layer within the MEA, where the main chemical reaction occurs, coupled with a more densely-packed cell structure.
To create a more densely-packed cell structure, Nissan replaced the older carbon separator with a new thin metal separator. A specific coating applied to the separator helps improve conductivity and prevents chemical corrosion, leading to increased efficiency and durability throughout the fuel cell stack’s life-cycle.
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| The new thin metal separator (bottom). Click to enlarge. |
Higher durability electrode material results in a 50% reduction of the platinum required compared to the previous generation. This in turn, provides a significant breakthrough in the cost of these components.
The combined improvements in the cell result in double the power density, which enables a downsizing of the fuel cell stack size by one-third along with a significant reduction in cost, without sacrificing performance. Compared to the previous generation, the new generation stack’s power output is increased 1.4 times from 90 kW to 130 kW. Stack size is reduced by 75% to 68 liters from 90 liters, which allows for improved packaging flexibility.
Viva Nissan! Free-market capitalism (with limited, but strong government) is the best path to prosperity!
Posted by: ejj | 06 August 2008 at 05:26 AM
For EVs:
The advanced laminated compact lithium-ion batteries are installed under the floor, preserving cabin and cargo space.
The same location for batteries as in Mitsu MiEV - also very logical in terms of vehicle dynamics, extra weight placed low and between wheel axles.
But impractical for frequent battery swapping, unless somehow from underneath the car.
Posted by: | 06 August 2008 at 06:06 AM
A clutch? Two clutches? Feh.
Posted by: richard schumacher | 06 August 2008 at 06:07 AM
It was my comment for battery location.
Posted by: MG | 06 August 2008 at 06:10 AM
After a quick google I read that the 2001 Hypermini Li-ion battery had an energy density of 90 Wh/Kg.
180 Wh/kg would be quite an achievement for a Mn spinel.
Posted by: Andrew | 06 August 2008 at 06:29 AM
Seconded, well spotted Andrew.
Posted by: clett | 06 August 2008 at 06:41 AM
Good for nissan. It's great what a company can do when the UAW isn't bleeding it dry.
Posted by: Bryan | 06 August 2008 at 06:45 AM
My bad .. It is Mitsibishi with the spinel.
I haven't seen what chemistry Nissan is using.
Posted by: Andrew | 06 August 2008 at 06:47 AM
Irritating article with lack of numbers, oh well..
The twin clutch idea would be better with the electric traction wheels in the front, better for regenerative braking. 130kw fuel cell is pretty big, how much would it cost at 50kw?.. probably an arm and a leg still.
It is good nissan is working on EV
Posted by: Herm | 06 August 2008 at 08:10 AM
The science of making fuelcell is moving fast with real and regular breakthroughs. They should study how to make hydrogen fuel at the service station if they want to sell these fuelcell cars. It's what is missing the most actually, how to make hydrogen at the point of sale.
Actually there is 2 shell stations, one in washinton and one in los-angeles that use water electrolysis at the station to make hydrogen. It looks a good method but there is numerous other methods that can be experimented to do the same. One is with ammonia as a catalyser, i heard that it is cheap and the other is with aluminium powder and gallium as catalists. There is other methods too..
Posted by: a.b | 06 August 2008 at 10:00 AM
OK Nissan, we'll take 1 EV in 2010 in the USofA. Just give us a call when it's ready.....
Posted by: Rich | 06 August 2008 at 10:05 AM
Great! No torque destroyer, I mean converter.
Posted by: GdB | 06 August 2008 at 01:13 PM
This is good news for light vehicles evolution (electrifiction).
If all majors (except the Big 3) have Hybrids, PHEVs and BEVs on the market by 2010, what will that do to the Big 3 sales? Wouldn't they quickly become minor producers?
Posted by: HarveyD | 06 August 2008 at 01:23 PM
Question the need fr a V6 engine in combination with 80KW electric motor for a hybrid.
The 35% reduction in cost for a fuel cell stack still means that material shortage and cost will allow only a limited production, even if H2 ever becomes more widely available. That the increase in power density has been used to increase the increase the power from a very healthy 80 KW to an unnecessary 130KW
This would be twice the requirement for most users.
Batteries with improved regen (maybe they could benefit from capacitors here) show good priorities.
As it unlikely to ever be a commercial success in other than small application , high end vehicle, I guess that the developers will be pleased with their effort.
Posted by: arnold | 06 August 2008 at 03:02 PM
1. It appears the second clutch is always on (so, why is it there?);
2. There is no mention of a transmission, but for the engine to function at both low speeds and high speeds there must be one;
3. Presumably the transmission is aft of the motor so that the motor can also take advantage of the transmission and thereby offer both low speed and high speed torque.
4. This would appear to be the Honda design but with a larger motor so that the engine need not always operate to drive the vehicle.
Posted by: jzj | 06 August 2008 at 04:34 PM
"...connected to the V-6 engine and transmission..."
If Honda and Toyota are any indication of market acceptance, the V6 Highlander SUV seems to sell, where the V6 Accord did not. There are other factors, but just an observation.
Posted by: sjc | 06 August 2008 at 06:16 PM
jzj:
The second clutch may be off when the engine is idling (car stopped) but it is driving the motor/gen to recharge batteries.
Actually this setup could allow this motor/generator to be also used as alternator, possibly as starter as well (not sure).
The place of transmission:
One possibility is aft of the motor (as you suggested), which would be like Honda IMA design.
Another possibility is that transmission is before the motor (ie post-transmission motor), which would make it more like Enova design (possibly with a reducer aft the motor).
On the picture it appears that there is more room for transmission between engine and motor, than on the other side ot the motor.
Posted by: MG | 06 August 2008 at 08:41 PM
Its inevitable that fuel cells will push into cars after they start to invade comercial vehicles in the next few years.
Already from what I have seen the fuel cell is nearly ready to beat diesel busses. Its already poised to replace a ton of generators and they plan rather large demo fleets.
If what I have been seeing works out as expected we should start to see lux cars with fuel cells h2 tanks AND normal fuell tanks and reformers popping up in just 4-6 years.. as well as a ton of fuel cell busses and comercial vehicles.
Posted by: wintermane | 07 August 2008 at 11:17 AM
Back to speculation where the transmission is located.
This gives the clue:
The parallel-powertrain hybrid system ..... contributing to higher responsiveness and linear acceleration for improved driving feel,...
If motor and engine used the same transmission then there wouldn't be linear acceleration.
But if there is no transmission between motor and wheels, (almost) linear acceleration is possible, like in Tesla roadster or some other electric cars, without gear shifting during acceleration.
Also deceleration using regen braking can be very smooth as it avoids downshifting.
So during gear changes (very short intervals) motor provides all traction to the wheels.
Motor and clutch (de)activation, must be well synchronized for "improved driving feel".
Given that el. motors can provide high torque in much wider range than ICEs, it is much more beneficial to use motor after transmission, and it must be that Nissan does it here, ie transmission is placed between motor and engine, not between motor and wheels.
Posted by: MG | 07 August 2008 at 11:01 PM
MG -- Nice close reading of the text, well-reasoned speculation on your part (although I'm not sure why there is such a lack of clarity in the press release).
But I'm just not sure I understand your contention that 'it is much more beneficial to use motor after transmission': There is no apparent disadvantage in allowing the motor to use the transmission; Transmissions these days are nearly seamless in power delivery; Doing so would provide this less-than-Tesla-powerful motor the opportunity to pull at highway speed instead of possibly running out of high-end torque (I'm sure they work to flatten the torque curve and have it run well at higher rpm, but still...).
Posted by: jzj | 08 August 2008 at 10:42 AM
If the motor is capable of high torque, like the Prius' drive motor,then the transmission can be much reduced in size (and in internal friction loss) if it is put in front of the motor. On the other hand, if only a puny motor with little torque is used, like Honda IMA scheme, then the motor should be put in front of the transmission so that its torque can be magnified by the larger transmission, which will be heavier and having more internal friction. A good electric motor has very little internal friction, so a large electric motor can advantageously replace a traditional automatic transmission unit with torque converter.
If cost permitting, the simplest and most efficient transmission would be the serial-parallel gas-electric arrangement, in which there is a generator driven by the engine and an electric motor driving the wheels. At low speed or acceleration, the car is in serial hybrid mode to avoid mechanical gear loss, wherein the engine is decoupled from the wheel. At cruise, the car is at parallel hybrid mode with the engine directly mechanically coupled to the wheels to avoid electrical loss.
Posted by: Roger Pham | 08 August 2008 at 05:24 PM
jzj -- Thanks for the compliment.
I may have overstated the benefits of post-transmission motor layout, possibly carried by Nissan cited advantages. But they had probably done extensive research and testing before adopting it.
I agree that there is no disadvantage in allowing the motor to use the transmission.
But if the torque curve is mostly flat in wide (enough) rpm range, as in case of Tesla induction motor (you can see on their site - flat up to 6,000 rpm), then there is no advantage either.
In the supposed Nissan layout, to magnify motor torque you can place reducer aft motor (instead before it, or use them at both ends to optimize combined engine and motor torque output).
From the supplied picture, it seems that Nissan used induction motor, rather than a PM one.
During very short intervals, when gears are shifted, motor can be safely overloaded to the peak power (often can be double or more nominal power).
When accelerating, motor is there to provide extra torque, and probably much more during shifts.
It is also possible that the supposed layout (post-transmission motor) provides additional fuel saving when changing gears (ie accelerating) if the required intermitent power surge is provided mostly by motor, less by engine, allowing for smoother and more efficient engine operation.
Posted by: MG | 08 August 2008 at 06:30 PM
MG (and Roger): In sum, I take it you would agree that synergy drive has the advantages of lower transmission friction losses, lower transmission weight, smoother operation, and fundamentally simpler and less expensive transmission construction, but the disadvantage of requiring a second motor; whereas this design has the advantage of requiring only a single motor, but the disadvantages of a potentially higher degree of transmission friction losses, "shifty" operation, and potentially greater transmission weight, complexity, and cost. Assuming well-sized drive motors (i.e., motors capable of highway speeds without engine assist) and adequate battery pack power, then either design should be capable of straight electric drive, blended motor-engine drive, or straight engine drive (with battery recharging): at that point, the only issue becomes the battery pack's energy storage limit.
Posted by: jzj | 09 August 2008 at 12:05 AM
jzj,
Absolutely.
Posted by: Roger Pham | 09 August 2008 at 03:25 PM
jzj,
I do agree with almost all of your claims (disagree with none).
But I must say that I'm not competent to discuss internal design of transmissions and some related issues.
Posted by: MG | 09 August 2008 at 07:14 PM