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Volvo to Show Diesel Version of ReCharge Plug-in Hybrid Concept; 60-Mile Battery Range
11 January 2008
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| The layout of the ReCharge. Click to enlarge. |
Volvo will show a diesel-engined version of its ReCharge Concept plug-in series hybrid at the upcoming North American International Auto Show in Detroit. Volvo introduced a flex-fuel version of the ReCharge at the 2007 Frankfurt Motor Show. (Earlier post.)
The diesel ReCharge uses a four-cylinder, 1.6-liter turbodiesel engine (81 kW/109 hp) to drive a generator to power the four in-wheel motors when the 12 kWh lithium-polymer battery pack is depleted. The car has a battery-powered range of about 60 miles.
A full battery recharge takes 3 hours. A one-hour quick charge should provide enough charge to drive about 30 miles, according to Volvo.
The combustion engine starts up automatically when 70% of the battery power has been depleted. However, the driver also has the option of controlling the diesel engine manually via a button in the instrument panel. This allows the driver to start the engine earlier in order to maximize battery charge, for instance when out on the highway in order to save battery capacity for driving through the next town.
Volvo says that the ReCharge Concept is best suited to car drivers who cover moderate distances every day. A commuter who has less than 60 miles to drive between home and workplace can cover the entire round trip on electric power alone, making the car a Zero Emission Vehicle (ZEV) for most everyday driving.
For a 100 mile drive with full batteries, the first 60 miles will be with no fuel consumption and the remaining 40 miles will be at about 60 mpg. No more than 0.67 gallons of fuel is needed to go 100 miles—equivalent to 150 mpg.
A certain proportion of electrical vehicles will be necessary to meet the CO2 emission demands of the future. Since the Volvo ReCharge Concept combines an excellent battery range with a backup combustion engine, it is a very interesting concept.
The ReCharge Concept that we presented in Frankfurt a few months ago had a Bioethanol engine. The concept offers unprecedented flexibility to meet future challenges. By showing the car with a diesel engine, we demonstrate that the combustion engine for the generator can be matched to the preferences of each market. The diesel engine is one of the most energy efficient alternative available today.
This plug-in hybrid car, when used as intended, should have about 66 percent lower emissions of carbon dioxide compared with the best hybrid cars available on the market today. Emissions may be even lower if most of the electricity in intended markets comes from CO2-friendly sources such as biogas, hydropower and nuclear power.
—Magnus Jonsson, Senior Vice President Research and Development at Volvo Cars
The ReCharge Concept, based on the Volvo C30, has been developed at the Volvo Monitoring and Concept Center (VMCC), the Volvo Car Corporation’s think-tank in Camarillo, California. The central electrical components in the Volvo ReCharge Concept demonstrator—the engine-powered generator and the wheel motors—were developed together with British electromagnetic specialists PML Flightlink.
January 11, 2008 in Diesel, Plug-ins | Permalink | Comments (67) | TrackBack (0)
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Spectacular concept, can't find any info on when, or if, it will be produced, tho. Apparently they discharge a full 70% of the battery capacity, which accounts for some of the range advantage over the concept Volt, which is supposed to be ready by the end of 2010, but 60 miles range with of 0-100kph of around 9 seconds is not bad. Competition is a very good thing...
http://www.volvoclub.org.uk/press/releases/2007/recharge_concept.shtml
Posted by: Ziv | Jan 11, 2008 8:51:16 AM
Despite being a lifelong fan of Volvos, I think GM is ahead as of the moment in terms of production intent and realistic technology predictions (especially battery pack development), although maybe Volvo could get a hold of the Saft battery pack used in the Escape Hybrid.
In-wheel motors- that's a can of worms I won't touch for now.
Posted by: AES | Jan 11, 2008 10:03:42 AM
This may sound airheaded, but if these serial electric hybrids can earn 50 (Volt) or 60 (Volvo) mpg in charge-sustaining mode, isn't that pretty sweet? Forget the large batter nonsense. What is keeping companies from cutting costs and developing a small-battery format vehicle like that with very low electric range that will compete with the Prius? Bonus would be the flexibility to add more capacity later as the technology matures. Is a major impediment that the serial format really isn't as simple and effective as they have been pushing? ... Just a thought.
Posted by: Benny P | Jan 11, 2008 10:20:45 AM
@ AES, good call keeping hands off the in-wheel motors. I think it will be a long time, if ever, before they make sense. The saving grace may be that this is just a concept vehicle.
Posted by: Roy | Jan 11, 2008 10:25:23 AM
A 1.6L turbo diesel seems a little overkill for a genset application. Maybe they chose this engine because it was already a production engine, and they didn't want to invest in the development a dedicated powerplant for this concept? I would think that for a production model, a more practical ICE would be something quite small and simple which was designed to simply output the average power consumption in order to sustain the battery charge.
Posted by: Bob Bastard | Jan 11, 2008 10:30:47 AM
BennyP: I'm pretty sure that pretty soon you'll see offerings of all types and sizes. The all electric range chosen for the Volt was one that would cover at least 80% of all peoples' commutes. The idea is that those people will rarely require any gas at all, but can still take a long trip when desired. If you are going to charge sustaining mode then you're talking about regular HEVs (of which you will see more options very soon) If you're not going bother with a mid-sized range you might as well go parallel instead of serial.
Posted by: Neil | Jan 11, 2008 10:32:38 AM
Couldn't they get by on a 1 liter engine. I'd love to see a cyclone engine series hybrid www.cyclonepower.com
Posted by: s dogood | Jan 11, 2008 10:36:47 AM
This car, and the SubaruG4E for that matter, are all well and good, but for one thing: there is no apparent intent to bring either into production on any defined timetable. Call me when they commit to making the dang things and have both an estimated price point and a target release date. Until then it's just greenwash and I'm stuck following the progress of the Volt.
Posted by: Don | Jan 11, 2008 10:49:57 AM
Why are in-wheel motors the kiss of death? I thought they're making the motors lighter all the time, reducing the unsprung weight issue. Maybe I need to test drive one to evaluate the handling issue, or is there another problem with in-wheel motors?
Posted by: Mick | Jan 11, 2008 10:53:00 AM
I am sick of waiting for these cars. It's like we are reading sci-fi articles.
I would think the technology is there for plug in Hybrid diesel.
Posted by: Paul | Jan 11, 2008 10:59:40 AM
@Paul:
If we've learned anything from watching the auto industry, it that they will sell the current models until they are no longer profitable. Then they introduce new models with new features. So what would happen if we quit buying low mileage cars? I think that would motivate the car manufacturers to bring out the new stuff and perhaps new technology. Pass it along..."Don't buy now, wait for the electric drive models."
Posted by: Lad | Jan 11, 2008 11:55:49 AM
Agree!
Posted by: GdB | Jan 11, 2008 12:24:32 PM
Bob, I certainly agree.
This is getting close to what I have been trying to get car manufacturers to make for several years.
Sooner or later we will get a chance to buy one and it will be the Prius all over again.
Posted by: Lucas | Jan 11, 2008 12:51:36 PM
Lad:
Agree.
Our Ford Elite dealer's yard is full with oversized pick-ups, 4 x 4 Vans, SUVs, etc.
The $10K rebates did not sell very well.
They will have to be shipped to Alberta soon where those monsters are still popular. Gas is much cheaper there.
Posted by: Harvey D | Jan 11, 2008 1:17:59 PM
Great concept. Now gents and ladies, stop by your nearest Volvo showroom and just ask if they know when you can see a ReCharge. They'll stare and say, 'what's that?' Explain its the Volvo you want to BUY. They pass it on to the front office and... well, you know.
Posted by: gr | Jan 11, 2008 1:55:27 PM
@Bob Bastard -
it's a basic engineering concept that you need to walk before you can run. Getting the new batteries and electric drive control working is the first step.
Optimizing the genset will come later. Without any mechanical connection to the wheels, you could eliminate the crankshaft altogether if you wanted to. You could go with a fuel cell, as GM has already demonstrated. Or, you could go with a hermetically sealed stirling engine with internal linear alternators and electromagnetic synchronization of the pistons. How about a single-stage gas turbine with a secondary small steam turbine (based on alcohol as the working medium)?
My point is, there's no intrinsic need to stick with discontinuous combustion and all the fuel specificity, incomplete combustion, emissions and NVH that entails. Whether any of this makes *economic* sense is an entirely separate discussion.
In terms of energy security/global warming, even GM engineers (e.g. Dr. Grebe) will tell you that they could fit stop-start systems in 10-20 conventional cars for the incremental cost of manufacturing one plug-in hybrid, while delivering substantially higher aggregate benefits for the fleet.
Trouble is, what the American Joe Average wants is whatever pizazz and bragging rights the marketing gurus serve up. A little bit better than the norm is never anywhere near good enough. Everything has to be EXTREEEME TO THE MAX. First it was horsepower, then it was cupholders. So now its MPG's turn.
Posted by: Rafael Seidl | Jan 11, 2008 2:05:16 PM
I see a few of you questioning the use of in-wheel motors, as if it’s experimental and will never work. Fact is they’re already being used and one of the most promising solutions in my opinion.
See here:
http://www.e-traction.com/
Posted by: Mr. EE | Jan 11, 2008 3:16:43 PM
@Rafael-
I think your ideas for genset optimization are very interesting. I've seen you talk about that Stirling engine idea before - something you're working on yourself? ;)
With regards to eliminating the crankshaft - do you mean having each piston run in mechanical isolation of one another, with the electricity coming from a linear alternator, as per your Stirling engine concept?
Posted by: AES | Jan 11, 2008 4:01:26 PM
On the topic of unsprung weight, the Mini QED uses more powerful versions of the motors in Volvo ReCharge, the Mini QED’s unsprung weight increased by less than 2kg when compared to the original Mini. Plus you have the added advantage of a lower center of gravity. Thus unsprung weight should not be a problem with the Volvo ReCharge.
Source:
http://www.pmlflightlink.com/motors/hipa_faq.html
Posted by: Mr. EE | Jan 11, 2008 4:20:56 PM
Why hasn't anyone tried a rotary engine as a genset? I know you don't need the HP, but I would think that you would only need 250 cc displacement rotor for this purpose. The space and weight savings are undeneiable.
Posted by: Erevesto | Jan 11, 2008 4:31:00 PM
Four in wheel motors can have the advantage in ABS and traction control. It is hard to beat four independent drive/brake elements keeping the car straight when necessary.
Posted by: sjc | Jan 11, 2008 5:22:52 PM
http://www.cnn.com/video/#/video/tech/2008/01/11/hunter.extreme.hybrid.cnn
After watching this piece its obvious that 4rd parties
will make the car of the future. What I see is making a
car is not what it used to be. Components like a motor
body and batteries can be sourced and assembled and if
GM and Ford and other are not careful they will loose
complete control of the auto industry. The TaTa is an example. It may not be a fantastic ride but it gets you there for 2500.
Posted by: Bob T | Jan 11, 2008 6:07:09 PM
Re: wheel motors: take a close look at the data sheets referenced above and check out the mass, the diameter, the length, and the current required to get the torque. Then consider the cost of processing that current. Then multiply by the number of wheel motors you're talking about (minimum of two for a normal car).
The problem isn't whether they are technically feasible - they are. The problem is the cost and the weight. And what is the benefit of all that added weight and cost? You eliminate a simple, inexpensive, durable, light gearbox. It just doesn't make sense.
For a typical sedan (Taurus, Camry, Accord, Malibu, take your pick), you're going to need a minimum (repeat: minimum) of 60 kW motor and 2200 to 2300 Nm at the wheel (gradeability, acceleration, sustained highway speeds, passing performance). This is not a tire burner, its a family sedan with a sedate driver.
Now go check out the mass of the system you are putting together based on wheel motors. Don't forget to add the mass of the inverter and the long heavy cables needed to carry 1000A peak current for 10's of seconds without melting. Now don't forget what's going to happen to your bearings with all those radial loads imparted by the wheel loading on rough roads for 100,000 miles minimum.
Wheel motors are technically feasible - "ja, its doo-able" as one of my favorite German colleagues used to say - but its impractical, expensive, unsalable, etc., etc. It is very difficult to beat a nice planetary gearset, especially one that doesn't need to be shifted.
Cheers,
Posted by: Roy | Jan 11, 2008 6:16:52 PM
9x more energy in the pack in about the size of Prius HV pack. Dream on, way further than 2010! We won't have to wait that long for another "me too" to come up with the 80 miles range plug-in hybrid concept car.
Posted by: usbseawolf2000 | Jan 11, 2008 7:07:15 PM
LOL @ 1000A
No offense Roy but you are clueless, I’d explain why but I don’t have the time. Get your EE degree and then we’ll talk.
Posted by: Mr. EE | Jan 11, 2008 9:20:17 PM
I can't stand conspiracy theorists such as Ron Paul, Michael Moore or al Qaeda. But there is a science behind mega corporate collusion.
How much do you want to bet that for the next 7 years we will keep on hearing that the Volvo or Volt is not ready due to battery problems, and then all of a sudden the mega corps will open the gates and you will have 15 brand choices of serial plugins with 60 mile ranges?
Now call me a CT - but it aint stickin.
Posted by: JDT | Jan 12, 2008 12:15:47 AM
Roy, 1000A ? hehe
Besides, assuming equal efficiency in the motors (wheel or regular), why should the wheel motor need more Amps? Power = Current * Voltage (lets say 400 v.). So the current required should be same, no matter what transmission or gear ratio you have (assuming constant torque and efficiency).
Besides 4 in-wheels will each require 1/4 of the current, and about 1m longer for the cable length (4m * 1/4).
So current is
60,000 / (4 * 400) = 38 Amps per motor in steady state level driving. Probably 3 times that for the peak.
I think you are thinking of 12 volt golf cart batteries in parallel maybe?
Posted by: JDT | Jan 12, 2008 12:55:32 AM
Ooops, the 60KW output is peak, so the 38 A per wheel is peak.
So for steady state medium-speed level driving it would be about 15 A. That is a 14 guage wire (same stuff you have in your house behind the walls or 10 guage for peak, at about 20 cents a foot, and about 250 grams a meter).
The engine & power-train folks will no doubt lose their jobs badly. Much easier to manufacture an in-hub electric motor in Nigeria than a 350 cid in Michigan. Any wonder why the big autos are dragging their foot?
What is going to happen to all the high-paid transmission folks? How about kick-scooter repair trade?
Posted by: JDT | Jan 12, 2008 1:08:37 AM
On the topic of generators for series hybrids, the “Linear Combustion Engine” seems very promising it’s been demonstrated at 50% efficiency (it converts mechanical energy directly into electrical energy at the cylinder level)… Hopefully they’ll be able to workout some of the kinks in the control system. Apparently Volvo is working on a version, so this could get very interesting.
Sources:
http://www.lceproject.org/en/principle/
http://peswiki.com/index.php/Directory:Linear_Combustion_Electromagnetic_Engines
Posted by: Mr. EE | Jan 12, 2008 2:41:00 AM
@ AES -
You'd probably want to go with a Siemens-Rinia type engine, in which four separate Stirling cycles are linked in a ring topology because each of the double-acting pistons participates in two neighboring cycles. The desired phase difference between neighboring pistons is 90 degrees.
In the specific - and easiest - instance of a genset operated at constant speed and power, you would first use the linear alternators as motors to get the multiple free pistons moving with the desired phase differences, then precisely control the stator currents with PWM to maintain phasing. After all, in mechanical terms an electric machine is a damping element with either positive or negative coefficient. Each piston-alternator combo would also feature a spring that defines the natural frequency of the system. You end up with four coupled second-order differential equations, with non-linearities in the damping terms (gas dynamics + electromagnetic control).
It's not something I'm working on but based on what I've read about internal combustion free piston engines, I have a hunch this could be achieved with modern control systems. Not easy, mind you.
Of course, a crankshaft or wobble plate would be a substantially simpler way to synchronize the pistons. However, Stirling engines need a clean working medium (typically, hydrogen or helium) at high pressure to reliably deliver adequate power. External seals are a major headache, especially if they are on the hot side, so hermetically sealing the entire assembly is preferable. That leaves lubrication, though with true linear motion of the pistons solid lubricants on the piston rings may be good enough.
Another option - though perhaps more for stationary applications and modest temperature differentials (e.g. geothermal, industrial waste heat) - would be to replace the pistons with thin circular, concentrically corrugated plates (i.e. floppy in flexure). Even so, the diameter/stroke ratio would have to be high to reliably avoid metal fatigue. Also, the natural frequency of the mass-spring system tuned low enough to allow sufficient heat to be transferred in and out of the chambers in each cycle.
Posted by: Rafael Seidl | Jan 12, 2008 5:24:06 AM
Mr. EE and JDT,
Yikes. Take a look at the data sheets (summary) given as a PDF file on the website you (Mr. EE) cited above (www.e-traction.com) and you'll see that the 60kW motor requires 300A continuous and 1000A peak. I'm talking about the ac current to drive the motors, not the dc input current you pseudo-calculated above, JDT. You've calculated the DC input current to the inverter. I say pseudo-calculated because 60kW is presumably the output power of the motor at the shaft, and you have to account for motor losses (roughly 5 to 10%) and inverter losses (roughly 5%) and probably fairly high 3-phase line losses if the inverter is located remotely from the motors, as is probably necessary for packaging.
My last lesson for you newbie engineers is "why would wheel motors need more current?" The simple answer is because wheel motors need more torque. Keep in mind I'm talking AC current, which is what the switches in the inverter need to process, and which is what drives their cost through the roof. Torque in the motor is the product of current and magnetic flux. Flux for most of these motors is established by permanent magnets, and the current is sourced from the battery/generator/cap bank by the inverter. The battery (DC) current is NOT of the same amplitude as the motor (AC) current! If you have a 10:1 gearbox, you need to produce about 220 Nm to get the necessary wheel torque (in my simplified sedan example above). If you don't have a gearbox, you need to produce 2200 Nm to get the wheel torque. So you need a larger airgap diameter AND higher airgap torque, hence more current, relative to a motor with a gearbox. This is why the wheel motors use an "inside out" approach - ie., magnets on the outside - to allow the largest possible airgap diameter while still being able to fit the overall diameter within the ID of the wheel assembly.
So, Mr. EE, don't laugh too loudly, and go back to your ac circuits/motors book and take a look. And JDT, no, I'm not talking about a 12V system. You should also be aware that citing a 400V battery is a best case situation, and you have to design for a worst case situation, which is when the battery is at a lower state of charge and hence lower voltage.
Best of luck with your EE career Mr. EE -- maybe you should consider an MBA 'cause you won't be hacking it for long as an EE.
Cheers,
Posted by: Roy | Jan 12, 2008 6:16:36 AM
Roy I laughed because I thought you were referring to the motors in the Volvo. I linked e-traction as proof wheel motors work but those were designed for heavy buses and trucks, I wasn’t suggesting you strap four of them to a Volvo (that would be insane). Anyways, the peak amperage for each of the motors in the Volvo is around 100A.
About the battery, the generator will turn on long before voltage drops below a preselected threshold. Even without that I’m not sure what you think might happen, power electronics have come a long way.
Thanks for the luck though. ; )
Posted by: Mr. EE | Jan 12, 2008 7:51:39 AM
Ahem. The specs for the SM350-1 (leftmost column) takes only 300 amps peak. You'd only need 4 gauge cable to handle that.
Putting the PM armature on the outside is the mechanically optimal solution; you want the outside of the assembly to turn, not the inside. You don't want it to weigh 85 kg, but nobody said this thing was the pinnacle of technology.
And yes, I am an EE.
Posted by: Engineer-Poet | Jan 12, 2008 7:53:39 AM
@Engineer-Poet
Yeah, I think he was talking about the SM500/1 which is meant for large trucks and buses.
Posted by: Mr. EE | Jan 12, 2008 8:00:51 AM
Just to be clear the Volvo ReCharge uses Hi-Pa wheel motors (Not e-tractions), most likely the 18kg version.
see them here:
http://www.pmlflightlink.com/motors/hipa_drive.html
Posted by: Mr. EE | Jan 12, 2008 8:30:19 AM
Its amazing to see how fast an industry like the PC can introduce change and evolve the product compared to the auto industry. The car industry seems so slow its crazy.
One issue that I can see is the in the PC industry you have the potential for white box PC makers. Anyone can take a PC box of the shelf, pull the logic board and parts and make a working unit.
In cars, each car is a new package that needs to be tested, crashed, and then marketed.
Wouldn't it be great to have a common chassis - cabin, could be sold with minimal drive train. Then a cottage industry could be formed around competing over just energy storage and propulsion.
Like the Volvo c30 seems like a pretty nice starting point to me. Or maybe the Honda Fit. Let a lot of startups have a go at making the drive train. That might speed up progress here - and reduce market risk for the big car makers.
Posted by: roz | Jan 12, 2008 9:33:34 AM
The issue here is not the drive train (although every bit helps). Without a battery solution, the electric car is like a submarine with screen doors. PHEV adds at least $7000 to the cost of the car and increases gas mileage from 45 (Prius) to 70-100 (estimated). That adds up to 300 gallons per year. Very few consumers will switch to this risk technology that requires a power outlet near parking spots.
We need BATTERY-LESS electric vehicles similar to the San Francisco buses, light rail or Personal Rapid Transit.
Posted by: Realist | Jan 12, 2008 10:03:08 AM
Forget to include references on battery technology progress and PHEV costs.
US senate testimony from Advanced Automotive Batteries on PHEV
Posted by: Realist | Jan 12, 2008 10:22:01 AM
Realist:
$250/KWh ESSUs are coming and should be mass produced by 2010-12. If so, the 150 mpg Prius IV PHEV-60 (Km) battery pack may cost around $2.5K.
By that time, according to CIBC Bank, Oil will be $150/barrel or $1.5+/liter or as much as $6/US gal.
It seems that time will change the equation rather quickly. Future PHEVs may not cost much more than current inefficient ICE vehicles, and even much less if the 10-year operation cost are used.
Posted by: Harvey D | Jan 12, 2008 10:26:18 AM
I dont know about you guys, but I am excited about the Aptera. (www.aptera.com) I already put a deposit on one. Its not the prettiest looking vehicle, but at 300mpg for the PHEV version it can't be beat.
I think the coming years are going to find an interesting assortment of innovation in several different directions. I think the true innovations are going to come farther down the line when all these new technologies merge. Aptera is using a capacitor system that charges the batteries in just a few seconds and allows the car to continue driving. Why not do that with a diesel engine? Diesel is several times more efficient than gas. If it works with gas, why not with diesel?
Posted by: Ryan | Jan 12, 2008 10:42:16 AM
The series hybrid looks like a very smart approach the problem is that it results in very heavy and costly archictecture, the motors in wheels helps to improve the concept but still. I think the series hybrid architecture would work with a free piston engine type that simplifies and reduce the weight, but so far the autralian company who was working on this concept gave up, also the concept would make more sens with a diesel.
Anyway parallel or series the plug in is the futur no doubt about it, the barrier is still the cost and avaibility of the batteries. That's why the Aptera approach is ineresting, using a very light vehicle means smaller batteries then more affordable. Still a very long way before they sell a million vehicle like that.
I they developp Coal to Liquid solution massively they might keep the price of gaz around 3$ then this type of vehicle will not take off for antother 30years, sadly.
Posted by: Treehugger | Jan 12, 2008 12:04:00 PM
A lot depends on usage and perception. A town car would just get you to a close destination and back. For this, the EV would work. Commuting takes a lot of energy. Maybe we should live closer to where we work and/or telecommute more, but that is another topic.
Posted by: sjc | Jan 12, 2008 12:26:23 PM
U Wiscosin did this concept some 20 years ago
and 172 mpg on a converted general-morons GM Metro
and lead-acids. It was on display at one of the
earlier MREAs.
This is a much more refined version, no doubt,
but what took them so long ?
Posted by: Saline | Jan 12, 2008 1:29:57 PM
Plug in hybdrid is a nice concept but american people are fooling themselves if they think that it will keep them driving 5000 pounds SUVs and trucks for commuting at low price even with a gas price at 6$ a gallon (which will happen soon, no doubt about that), that is a dangerous illusion. First the electricity to recharge a PHEV is 80% from coal which is the dirtiest energy and generates a lot of green house gas. Second for a 5000pounds vehicle you need 20 or 25KWh batteries to drive 50 miles, I have no doubt that price of batteries will drop but it will be a long way before that such big batteries will be available at an affordable price.
Posted by: Treehugger | Jan 12, 2008 2:19:17 PM
In California, where many Hybrids are sold, the electrical generation mix includes nuclear, hydro, and gas, such that coal power is minimized.
We could build about 4 more Nukes in California and replace much of the fossil fuel generation, but the same wacko's that want to stop using coal, also do not want Yucca Mountain to open. And so we continue to burn coal like there was no tomorrow.
2009 is just around the corner and PHEV's should start showing up in the showrooms, with the Saturn Vue leading the charge.
Posted by: | Jan 12, 2008 3:34:33 PM
Nationwide 50% of the electricity comes from coal. In California 50% comes from natural gas. Charging off peak, even in the summers makes sense and the power companies say that they can handle quite a bit of that. Think of the 3x nominal load on California summer days and now you can see that we might be able to take quite a few cars charging at night.
Posted by: sjc | Jan 12, 2008 4:08:14 PM
The question is: do you need in weel motor?at list for now. I think that we can do simpler cheper propoltion just using 2 or 4 off the shell electric motors with small shaft to the weel. The motors will sit on the main fram of the car
Posted by: imagin | Jan 12, 2008 5:04:50 PM
"for the next 7 years we will keep on hearing that the Volvo or Volt is not ready due to battery problems..."
You might want to take a look at the progress the LG Chem/CPI Battery is making - not temperature tested yet but it doesn't look like a... conspiracy.
http://www.gm-volt.com/
Posted by: gr | Jan 12, 2008 5:57:47 PM
Let's have a cite:
http://www.eei.org/industry_issues/industry_overview_and_statistics/industry_statistics
I expect nuclear's contribution to double over the next 20 years at the expense of coal (add'l units will be built at current nuclear plants)
I bet Yucca never opens - high-level waste will simply be dry-casked on site.
Posted by: Bill | Jan 12, 2008 6:20:21 PM
@Ryan:
Diesel ICEs are 40% efficient at the crank at best; gasoline ICEs are about 25-30% at the crank. Both are minus about 15% less horsepower at the wheels.
ET AL:
The best use of in wheel motors I like to cite is in a Toyota Race Car: see: http://www.greencarcongress.com/2007/07/toyota-hybrid-r.html#more
All this stuff is doable; but, that nasty old profit motive and tied up investments keeps getting in the way of progress.
In any case, I believe recent breakthroughs in low-cost solar cells and battery technology point toward our future as quick-charged, long-range, light, efficient BEVs fueled by solar generated electricity.
see: http://www.motherearthnews.com/Alternative-Energy/2007-12-01/Solar-is-the-Solution.aspx
All the stuff and convolution going on right now in generating power and powering automobiles is all interim to the solar/battery solutions for personal transportation.
Posted by: Lad | Jan 12, 2008 6:23:42 PM
roz,
One such project is already underway: http://www.cmmn.eu/
"c,mm,n is mobility concept; a new way of developing, manufacturing and using cars. By making the blueprint of c,mm,n publicly available under an open-source licence we are able to develop truly sustainable mobility. Just like open-source software, c,mm,n focuses on services around the product. You can use c,mm,n to offer people a lease car, rental car or other mobility services. It is allowed to sell c,mm,n too. Just as long as you make any derived work publicly available again.
c,mm,n is currently in a concept stage. This means that there is a general view on the car, services and possible partners. Actual blueprints do not yet exist. Currently three non-working show models were built to communicate the concept. The aim is to develop a proof-of-concept car, to be demonstrated preferably at the Dutch biannual motorshow (AutoRAI) in 2009."
Posted by: Santos | Jan 12, 2008 7:45:49 PM
Roy, the engineering mistake you commit is that current is not just product of torque & flux, but product of torque, flux, and angular speed. So a 10:1 reduction gear will just increase your rotational speed by 10. Same current and same wire. You can't put a 1:100 gearbox and extend your range by 100! - I have assumed losses and torque are constant for a wide range of speeds, which I understand is realistic.
EE, the vehicle has a 60KW motor as per Roy's post.
Again, can Roy point out what is wrong with:
(60,000W / 350v.) / .8 (loss) / 4 (wheels) / 1.7 (3-phase) = 32 A peak, per wheel, 11 A steady-state.
This is a guage 10 wire (at peak). About 1/8" copper diameter. About 1.5 meters long. You would need 3 of these in 3-phase. Surely the manufacturer will use a higher guage than 10, because its so cheap, but it is still not a back breaker by any stretch of the imagination.
Numbers and equations pls. Roy. BTW, are 3 degrees in EE good enough, or shall I go into cultural studies?
Posted by: JDT | Jan 12, 2008 11:23:09 PM
Got ya JDT, I must of missed that. I just skimmed through what he wrote, saw “1000A” and stopped reading.
I'll see you in the MBA program. ; )
Posted by: Mr. EE | Jan 13, 2008 4:09:47 AM
imagin,
AFS Trinity and others have taken an off the shelf approach to their designs. I often thought that an AWD small SUV could be outfitted with an electric motor in back. That seems to be the design from AFS.
http://www.afstrinity.com/video.htm
Posted by: sjc | Jan 13, 2008 8:11:57 AM
EE, I don't think I can make it in MBA - too tough - but Cultural Studies where we discuss if the hair style of the Marsh Arabs are meant to signify their authentic and nuanced resistance to neo-colonialism by the big bad democratic west hell bent on robbing their $2 a barrell oil by paying $100 a barrell, seems easy enough. ;)
Posted by: JDT | Jan 13, 2008 2:07:33 PM
JDT, Mr. EE, and Eng-Poet,
Thanks for the responses. I propose we drop the personal jibes, and I’ll explain what I think the situation is. First, my apologies for the MBA and career remarks – it was mean to you and those readers with MBAs, and I shouldn’t have been nasty. Anyway, onward.
My initial post on the e-Traction motor was based on the single wheel, 60kW motor, and their own data sheet brought up the 1000A peak phase current. However, for the huge torque they are producing, that isn’t hard to buy. The point was that it is expensive to build an inverter to process that 1000A – to the degree that it would make it unaffordable for cars – and to cable it to the motor, even with solid busbar. I believe JDT points out e-Traction motors are for large buses, trucks, and/or off-road equipment, and so it isn’t germane to the discussion on a Volvo C30. True, and point taken.
Unfortunately, there isn’t enough technical data that I could find on the PML Flightlink site, so I can’t look as closely at that, but I will say they are impressive wheel motors with integrated inverters, so they only need to specify dc current, which I believe they only give for the 120kW HiPa drive machine as 400A, which makes sense (350Vdc nominal gives 140kW dc input, not unreasonable for 120kW shaft output).
I agree with Mr. EE that Volvo are probably using the 18 kg HiPa that is rated at 40kW (peak) and 350 Nm (peak), one in each wheel, for a total of 160kW (peak) and 1400Nm (peak) of wheel torque, which should be sufficient torque for a 1350 kg vehicle (C30). Neither the article above nor the PML Flightlink site indicate which machine is used. Peak is probably available for no more than 1 minute, depending on the cooling system.
But, to hit upon our disagreements and to address some of your comments about the calculations, I think some of the disconnect in our discussion maybe ac vs. dc currents, and an accurate understanding of how the typical HEV PM motor works. To keep consistent with the prior discussion, let’s leave shaft power at 60 kW. The ac current requirement, along with the available coolant temperature, determine the cost/size/weight of the inverter (and to a lesser extent, of the motor). On the ac side, three phase power into the machine is given by:
P(Watts)=sqrt(3)*V(line-to-line-rms)*I(line-rms)*power factor (PF).
Solving for phase current (peak in the sense of a sinewave peak), you get
I(line-peak) = sqrt(2)*I(line-rms)=(P(Watts)/efficiency)/(sqrt(3)*V(line-line-rms)*PF)
This is close to what JDT put into the blog above, but not quite the same. He’s divided by the number of motors, which won’t give the right phase current for a motor with the power rating of P. It will for a motor with P/4. Anyway, line-to-line voltage using space vector modulation (fairly standard PWM scheme in HEVs) is battery voltage/sqrt(2) or 0.707*Vbatt.
Efficiency, which is motor efficiency in this case, for constant power region is probably in the 95% range, and power factor is probably about 0.9. These numbers will vary somewhat from design to design, but are reasonable assumptions.
So, using these numbers, peak line current (motor phase current), is
I(line-peak)=1.414*(60000W/0.95)/(1.73*350V*0.707*0.9) = 232 Amps
Keep in mind, this is phase current, not battery current, and this is for the rated continuous operation, constant power region of motor operation. Usually, traction motor designers will call the rated torque that torque at which the constant power curve intersects the corner point speed, i.e, the speed at which the motor requires full available battery voltage to push the necessary current through the windings to overcome the back emf and the resistive losses in the stator. Electric or hybrid electric powertrain engineers will REQUIRE this point to be able to be met when the battery voltage is at its minimum acceptable level because they want the vehicle performance to be independent of battery voltage. For the batteries out there now, absent a boost converter a la’ Prius, this will be significantly below 350V used in the example above (probably in the 250 to 270V range).
Typically, the peak performance of the motor will consist of two parts: a peak torque spec (which is usually required only for 10 to 30 seconds) which nearly ALWAYS determines the maximum current requirement, and a peak power (which is usually required for 30 seconds to a minute or so, for acceleration and passing). The peak torque requirement is usually 2 to 3 times the continuous, rated number cited above. Because of magnetic saturation in the motor, the current required to produce this torque is GREATER than 2 to 3 times the current calculated above. Also, the losses are now increasing rapidly as you overdrive the motor, so the efficiency is dropping rapidly. So, if the short term torque needs to be 2 times the continuous torque, the phase current required to generate it will be more than 464 Amps, possibly significantly more, for this example.
To get to the dc side current, its easiest to work in power from the shaft to the battery terminals, then divide by the appropriate voltage. Shaft power (60kW here) divided by a nominal efficiency of the motor (95% here) divided by the inverter efficiency (assume about 95% also) divided by the battery voltage (optimistically assume 350V here) and you get
60000W/0.95/0.95/350V = 190A
At my postulated lower voltage point of 270V, it would be about 250A DC, peak, per 60 kW motor. For operation other than at constant power, it is much more involved to compute the DC current, because efficiency is varying all over the map and modulation index gets into the picture, it becomes complex. It doesn't matter though, because the high power conditions are what define the worst case DC current.
JDT indicated that “current is not just product of torque and flux but product of torque, flux and angular speed” and also asked “why should the wheel motors need more amps?” The answer is that torque, not power, drives the ac amps. Angular speed factors in, but not in the way just mentioned. For these PM motors, airgap torque is given by
T = (3P/2)*(lambda-PM * iqs + ids*iqs(Ld-Lq)
where P is the number of poles, lambda-PM is the magnet strength (flux), Ld is the direct axis inductance, Lq is the quadrature axis inductance, and ids and iqs are the direct and quadrature axis currents, respectively. The peak stator current mentioned above (232 amps, for example) is equal to sqrt(ids**2 + iqs**2).
Where angular speed factors in is in the VOLTAGE that is needed on each phase to force id and iq through the windings, because as JDT accurately points out, it is in part a function of the speed. Staying with the direct (d) and quadrature (q) axis notation, the two voltages are:
vd = rs*ids + p_lambda-ds – omega*lambda-qs
vq = rs*iqs + p-lambda-qs + omega*lambda-ds
Here, rs is stator winding resistance (per phase), p-lambda-ds is the time derivative of the d-axis flux, omega is the electrical angular speed (P/2 times the mechanical speed). The “qs” variables are the q-axis equivalents. Note also that lambda-PM = sqrt(lambda-ds**2 + lambda-qs**2).
The voltages here (vd and vq) relate to the phase voltage as v-phase = sqrt(vd**2 + vq**2), and v-phase relates to the line-to-line voltage mentioned above as
v-line-line = sqrt(3) * v-phase.
So, from this, if you have patience and a sharp pencil, you can see the dependency of required voltage on rotational speed, but the current magnitude to produce a given torque is unaffected by speed, but its split into d-axis (related to field weakening current) and q-axis (mainly torque current) is definitely affected by speed.
Sorry to bore you half to death with such a long post, but my opinions on e-drives are informed by 20-plus years working directly on it nearly every workday. There are compelling reasons to use a gearbox, and the transmission designers don’t need to worry about their jobs. Putting four motors and four inverters into the environment of the wheel is generally a roundabout way to solve the problem of electric propulsion, when one motor and one inverter will do the trick, and you can put it in a more friendly location (with respect to vibration, corrosion, shock, etc.). Traction control, ABS, and electronic stability control are handled well by existing technology and, while the wheel motor approach can provide this functionality, that does not outweigh the obstacles (cost, weight, compexity, risk of inadvertent steering input, etc.) penalties, in my opinion.
Posted by: Roy | Jan 14, 2008 4:48:32 PM
Torque equation above (T) requires an additional closing left parenthesis at the very end of the equation. With regrets,
Posted by: Roy | Jan 14, 2008 4:59:50 PM
Shoot me please... a closing right!! parenthesis in the torque equation, and P is the number of pole pairs, not poles.
Posted by: Roy | Jan 14, 2008 5:12:42 PM
All this talk of current and torque is all good but you have to remember that unless your looking for a smoke show a verhicle only needs as much torque at the wheels as traction can provide. A 1350kg vehicle (assume 50/50 weight distribution) puts
1350/4 = 337.5 kg * 9.81 N/kg = 3311 N of normal force at each wheel
Now a sticky race tire can give give a coefficient of friction better than 1 but the kind of long lasting low rolling resistance tires that will be used on a efficient vehicle will be more like 0.7. So...
3311 * 0.7 = 2318 N tractive force max per wheel.
Say a 60cm tall wheel, 0.3m radius,
2318N * 0.3m = 695.3 Nm of torque. max.
so as a quick approx take the weight in Kg at each wheel and double it to get the max torque at that wheel.
338*2 = 676
of course this only works for a 60cm tall wheel.
Now you can bring in weight distribution and transfer all you want but how much excess do you really need? 1400Nm!!!? Whats the point, you wont go any faster?
Posted by: Jesse 67 | Jan 15, 2008 11:03:02 AM
I like the idea of in-wheel motors.. the motors/controllers need to only be sized 1/4 of the single motor solution (for 4wd).. and each motor can be a reasonably small motor for a lightweight car and not a 6000lb SUV behemoth..
Mass production of these electronic components will bring the cost down.
There is also the advantage of the backup motors, you could always limp home on one of the motors. I imagine the cheap solution (and most common) will be a single motor driving the wheels thru a limited slip differential, with probably some sort of gearing or electronic reconfiguration of the motor.
Honestly what I like is the simplicity.. imagine opening up the hood and all you see is NOTHING.. just a battery pack or two and 4 sets of wires running to each wheel.
Posted by: Herm Perez | Jan 15, 2008 11:51:03 AM
I saw a breakdown of losses in a car. About 67% was in engine, about 17% was in idling at stop lights and only about 5% was gear losses. If this is the case, you save more with start/stop at lights than doing away with gears.
However, I like the control that you could get with 4 wheel motors in traction control and ABS. If you do not have to build transmissions and differentials, all the better.
Posted by: sjc | Jan 15, 2008 1:02:03 PM
@ Jesse 67,
Your calcs look good. The 1400 Nm was total. Each wheel motor, if our guess is right as to the PML Flightlink model used, was 350 Nm. That's within the limit of traction, unless weight transfer is significant.
@ sjc,
Your numbers are good, and I couldn't agree more with the observation that doing away with the gears isn't too effective in loss reduction.
Regards,
Posted by: Roy | Jan 15, 2008 2:04:33 PM
Roy, sic - The transmission losses you quote (5%) would look even better if you include the differential to come up with the generally accepted ~15%, manual and 17% auto drivetrain losses.
These losses are of course lost after the wopping 67% engine losses ( wich will be vastly better on any battery boosted or hybrid.)
Maybe you got trans L mixed with Idling losses, wich appear very high.
Electric anything hybrids will improve idling losses to 0 for a BEV, unless of course the radio air con are left on.
Posted by: arnold | Jan 21, 2008 1:51:58 AM
Those were the numbers that I saw. If you think that gear loses are higher or lower, the web is a great place to research this.
I do not think that the burden of proof should be only on one person. As a Green Car Congress, everyone should participate.
If I dispute another persons assertions, it is more constructive if I find evidence to the contrary rather than just challenge it.
I once challenged the assertion that pumped hydro was more than 70% efficient. After researching the matter, I found that it WAS more than 70% efficient. It would have done me no good to just say you are wrong and walk away.
Posted by: sjc | Jan 25, 2008 11:01:28 AM
Sure it is appropriate to quote sources and to seek as wide a range of opinion as possible.
When it comes to transmission figures they are very difficult to source as aside from the range of specific vehicle differences, new designs, the fact is that most manufacturers will not supply the figures. So actual dyno test figures are the only resource available.
To obtain the transmission losses from crank minus wheel HP figures is quite an exercise.
Then if this were possible, there are substantial ~10% tolerances between readings adjusted into nearly every dyno manufactures specification.
So If you can find usefull specifications quoted without massive disclaimers you are doing well.
The figures I quote are admittedly older three or four speed trans. Autos wich will definately be lower than lock up clutch and better still with dual clutch semi auto or triptronic boxes. I am also refering to rear wheel drive with drive shaft . Front wheel drives will be substantially better. The rear differential figures however should remain similar at the lower 10 -12% area.
The figure you supply as 5% transmission losses could be very high if taken in the straight through gear ~2%.
There should be no problem with any of these figures if we make allowances for different possible scenarios.
Still working on the idling losses though.
I don't doubt you did research your figures and reported in good faith.
It goes to show how very different outcomes can be generated from the simple act of starting from different perspectives.
Posted by: arnold | Jan 27, 2008 12:35:30 AM
PML Flightlink have already built a car of their own useing their in wheel motors built into a BMW Mini.
This has a 21 Kw battery pack and small generator under the boot/trunk floor.
200 mile range on battery, 80mpg, 0-60mph 4.5, seconds top 150mph, 900 miles range on standard tank. Secret is, there are no mechanical brakes except the parking brake and no transmision. The wheels only weigh 2kg more than a normal wheel and brake assembly. The whole car is only 200kg more than a standard car and can still carry its design load of 4 adults and luggage. The wheels are 24 phase motors and are electric brakes/generators giving 85% energy recovery.
On batteries, a new li silicon battery has just been invented that uses silicon nano wires in the anode, this battery can store 10 time as much energy as a standard li of today and can be charged fast, 10 minutes to 80% and will last 25000 cycles.
So all the technology is in place just needs packaging and Volvo are taking the first steps, but are being carful, they need to take the big step and copy the PML concept car.
The PML car is with Lotus Cars at the moment to make it road legal.
Posted by: Brian | Feb 24, 2008 2:33:39 PM
see this link for the PML mini generator details (250cc 4 stroke) ..
http://www.pmlflightlink.com/archive/mini2.html
and the lightning gt .. uses the hipa drive inwheel motors and some fancey nanatech (recharge in 10 minutes) batteries ..
http://www.lightningcarcompany.co.uk/
does appear the major players are a bunch or pussies .. or really just want us to keep blowing up oil?
why did volvo put a car engine as a generator!?
Posted by: gram | Jul 20, 2008 7:01:57 PM
