SegwayChat
Home . Old Gallery

Go Back   SegwayChat > Other Topics > Science and Technology

Notices

Science and Technology Science & technology discussions not related to the Segway. This includes discussion of Segway knockoffs and clones.

Old 12-28-2006, 02:34 PM   #1
bystander
Senior Member
bystander is a name known to allbystander is a name known to allbystander is a name known to allbystander is a name known to allbystander is a name known to allbystander is a name known to all
 
Join Date: Mar 2005
Location: Southern California, USA.
Posts: 1,921
5 yr Member
Default Fuel cell laptop

http://www.playfuls.com/news_05645_S...s_a_Month.html

Article states prototype system has 12,000 watt-hour capacity. If adapted to the PT's nominal 800 wh system, it would provide about 300 miles of travel between "fill-ups" (of methanol).

For a PT to travel about 300 miles would cost about 15 kw-hours from the power company, or around $1.50 to $2.50, depending on local cost of electricity. If equivalent amount of methanol is around this price, and the cost of the fuel cell is comparable to the Saphion pack cost, it might make sense to look into a fuel cell conversion. But only if there is a way to make available a rapidly dischargeable power bank for safety overhead purposes.

Although one might use a single fuel cell and single fuel tank, you would want two independent rapid-discharge power banks for safety redundancy, so that has to be figured in the cost.

These power banks would either be supercapacitors, ultracapacitors, or the new nano-scale electrode lithium-phosphate batteries. Sized to run a PT (at full torque) the length of a wide intersection (during a safety shutdown).

If the fuel cell supplies less than 360 watts instantaneously, the power banks will have to be large to accumulate power ahead of time for high torque loads. If one wanted to sustain full PT speed for the 300 miles, the fuel cells must provide 360 watts or more. If cruising at a lower speed, or in stop & go traffic, a lower wattage rating fuel cell can be utilized. I suspect for laptop use, the one mentioned in the link is around 100 watts or less, so it will be more expensive to make one of 300-400 watt capacity.

Another slight worry is regen charge. If the power packs are fully charged by the fuel cell and a protracted down-hill or tail-wind is encountered, there's nowhere for the excess power to go (some fuel cells aren't designed to go into reverse - I don't know if this particular one is or not), so the PT would either have to slow (reduced performance mode), or a extra resistor bank / cooling fan would have to be added to the design somewhere.
bystander is offline  
Old 12-28-2006, 03:47 PM   #2
polo_pro
Advanced Member
polo_pro is a glorious beacon of lightpolo_pro is a glorious beacon of lightpolo_pro is a glorious beacon of lightpolo_pro is a glorious beacon of lightpolo_pro is a glorious beacon of light
 
polo_pro's Avatar
 
Join Date: Aug 2005
Location: Sacramento, CA, USA.
Posts: 2,608
5 yr Member Segway Polo Player
Default Real life long distance gliding data

Quote:
Originally Posted by bystander View Post
http://www.playfuls.com/news_05645_S...s_a_Month.html

Article states prototype system has 12,000 watt-hour capacity. If adapted to the PT's nominal 800 wh system, it would provide about 300 miles of travel between "fill-ups" (of methanol).

For a PT to travel about 300 miles would cost about 15 kw-hours from the power company, or around $1.50 to $2.50, depending on local cost of electricity. If equivalent amount of methanol is around this price, and the cost of the fuel cell is comparable to the Saphion pack cost, it might make sense to look into a fuel cell conversion. But only if there is a way to make available a rapidly dischargeable power bank for safety overhead purposes.

Although one might use a single fuel cell and single fuel tank, you would want two independent rapid-discharge power banks for safety redundancy, so that has to be figured in the cost.

These power banks would either be supercapacitors, ultracapacitors, or the new nano-scale electrode lithium-phosphate batteries. Sized to run a PT (at full torque) the length of a wide intersection (during a safety shutdown).

If the fuel cell supplies less than 360 watts instantaneously, the power banks will have to be large to accumulate power ahead of time for high torque loads. If one wanted to sustain full PT speed for the 300 miles, the fuel cells must provide 360 watts or more. If cruising at a lower speed, or in stop & go traffic, a lower wattage rating fuel cell can be utilized. I suspect for laptop use, the one mentioned in the link is around 100 watts or less, so it will be more expensive to make one of 300-400 watt capacity.

Another slight worry is regen charge. If the power packs are fully charged by the fuel cell and a protracted down-hill or tail-wind is encountered, there's nowhere for the excess power to go (some fuel cells aren't designed to go into reverse - I don't know if this particular one is or not), so the PT would either have to slow (reduced performance mode), or a extra resistor bank / cooling fan would have to be added to the design somewhere.
First let me throw out a few numbers: about 30 charges (some partial) to cover 372 miles. If NiMH cost a dime to charge, I've always thought that Li-Ions should cost about double that. But I've never run the wH numbers (and including loss due to inefficencies in tranfering energy into the battery), so I'm probably basing this next conclusion on this incorrect assumption. So your energy budget for the trip might be upwards of $5 to $6.

As to power draw, here's my thoughts on the matter. There were numerous instances where I drew down the batteries significantly. I don't know the exact details as to how much, but I can say each instance lasted from 2 to 10 minutes. To give you an idea of how big a draw this would be, I'd certainly expect 1 possibly 2 bars to disappear on a set of Li-Ions. I'd usually pick up half a bar on the other side of the hill going down.

Personally, I think these fuel cells are going to be the next generation of batteries, and segways are an easy fit (due to the large volume availalbe to put the fuel cell in). I'll go so far as to say that if Segway INC doesn't mind incorporating volatiles into their power pack, within 3 years they'll be offering a large "power pack" in the shape of 2 mounted Li-Ion battery cases for $3K. As bystander says, there'll be some form of capacitors built into it to handle peak load. As I write this, I'm reminded of the final scene in "Back to the Future" where the good doctor uses a Mr. Fusion...I see similarities as we talk about adapting fuel cells to replace segway batteries.

Last edited by polo_pro; 12-28-2006 at 06:09 PM..
polo_pro is offline  
Old 12-28-2006, 06:05 PM   #3
citivolus
Member
citivolus is on a distinguished road
 
Join Date: Jun 2003
Location: , RI, .
Posts: 562
5 yr Member
Default

The journalists got it wrong again. According to the article, "Samsung claims that the fuel cell offers an energy density of 650Wh/L..." That's fine we know the company's claim. The part they get wrong is when they follow that with "The total energy storage is an impressive 12,000Wh." I don't know about them but when I do the math I get 18.46 L or 1,126.6 cu in. I would believe that the author meant to write 1200Wh otherwise that would be one big laptop inasmuch as one of the biggest standard automotive batteries, a size 95R, measures roughly 15.56 x 6.88 x 7.5 or 802.9 cu in.
Dear journalists, when doing math, the location of the decimal point

That said, the stated 650Wh/L is about 2.5 times the Segway Saphions ~250 Wh/L(1). Using these numbers it becomes an easy extrapolation to make. If you get a 20 mile range now it wouldn't be unreasonable to assume a 50 mile range with appropriate hybrid technology.

Going a bit further, the article says "a mini version of the fuel cell which uses around a coffee cup's worth of fuel, but can still power a laptop for over 15 hours." This makes sense if we assume the real number was supposed to be 1200Wh. I think it is reasonable to figure near 80W for a modern reasonably powerful laptop with plenty of memory. (Not much of a stretch, as my Sony laptop uses 90W doing almost nothing with the energy saver settings turned off.)

Now all the pieces are in place. The boon of the fuel cell comes when you add a second coffee cup of fuel. You get another 1200Wh for each cup full. On a Segway, it would be easy to carry a tank the size of a water bottle that would be good for 100 miles or integrate a simple tank into the CS

I don't know about you, but my coffee cup is closer to 14oz than 8 so YMMV

(1) http://www.powerpulse.net/features/t...hp?paperID=126
__________________
--
swiftly flying
citivolus is offline  
Old 12-28-2006, 06:40 PM   #4
polo_pro
Advanced Member
polo_pro is a glorious beacon of lightpolo_pro is a glorious beacon of lightpolo_pro is a glorious beacon of lightpolo_pro is a glorious beacon of lightpolo_pro is a glorious beacon of light
 
polo_pro's Avatar
 
Join Date: Aug 2005
Location: Sacramento, CA, USA.
Posts: 2,608
5 yr Member Segway Polo Player
Default correction

Quote:
Originally Posted by citivolus View Post
The journalists got it wrong again. According to the article, "Samsung claims that the fuel cell offers an energy density of 650Wh/L..." That's fine we know the company's claim. The part they get wrong is when they follow that with "The total energy storage is an impressive 12,000Wh." I don't know about them but when I do the math I get 18.46 L or 1,126.6 cu in. I would believe that the author meant to write 1200Wh
http://www.dailytech.com/article.aspx?newsid=5487 confirms citivolus.
polo_pro is offline  
Old 12-28-2006, 06:42 PM   #5
bystander
Senior Member
bystander is a name known to allbystander is a name known to allbystander is a name known to allbystander is a name known to allbystander is a name known to allbystander is a name known to all
 
Join Date: Mar 2005
Location: Southern California, USA.
Posts: 1,921
5 yr Member
Default

Re: Math,

My bad. I checked some of the math, but not all of the math.

18.46 liters would fit nicely in a five gallon water bottle one might see sitting on a water cooler. Can't imagine a tank that size on a PT though. Especially filled with a flammable liquid. Might have a difficult time checking that through an airport, eh?

I erroneously assumed the 650 wh / L figure was for the converter itself, the tank being separate. Meaning that the fuel cell reactor takes up a liter of space for every 650 watt-hours of capacity.

I'm still looking around for a corroborating story or source to confirm or deny some of these assumptions.

Here's a source that states the energy density of methanol is around 4800 wh / L. If Samsung is only getting 650 wh / L out of it, that's only around 14% effeciency, with 86% waste heat. Not the performance of a typical fuel cell? Although elsewhere on the page it mentions that some type of menthanol fuel cells demonstrate < 20% effeciency.

http://www.millenniumcell.com/fw/mai...ntages-28.html

However, if the laptop uses 75 watts an hour for eight hours a day, for 20 work days in a month, that multiplies out to 75 x 8 x 20 = 12000.

If the power budget is only 1200 watt-hours, then for the laptop to last the same amount of time (160 hours), it must consume only 7.5 watts per hour. Is this a realistic figure?

Last edited by bystander; 12-28-2006 at 07:12 PM..
bystander is offline  
Old 12-28-2006, 08:38 PM   #6
citivolus
Member
citivolus is on a distinguished road
 
Join Date: Jun 2003
Location: , RI, .
Posts: 562
5 yr Member
Default

The ratings given should be taken with a grain of salt and don't try to do too much with it unless the application has a similar power consumption. I say that because energy density is an often abused term. Engines don't have an energy density and I don't really see how a fuel cell can either. Essentially a fuel cell is closer to an engine driven generator than a battery. Granted, the fuel cell cuts out the auxiliary mechanical conversion but the overall energy conversion is the same. When Samsung puts an energy density number on a fuel cell, I assume they are starting from a point of fixed volume that includes a specific amount of fuel.

When looking at fuel cells as just a "box," it almost looks like a battery, but when making the more accurate engine comparison, the difference becomes clear. Consider a basic automobile type engine that has a volume of 8 liters including radiator and other required accessories. Further assume that it converts fuel energy at 20% efficiency. Pair that engine with a 2 liter fuel tank and you would get 9600Wh of energy taking up 10 liters for 960Wh/L. Include the conversion efficiency and that drops to 192Wh/L. Looks pretty bad but it doesn't mean anything because if we now take the same engine and pair it with an 92 liter tank and the numbers now show 441,600Wh of energy in 100 liters for 4416Wh/L and likewise the 20% conversion drops this to 883.2Wh/L.

With the Samsung unit, we don't know the actual energy conversion efficiency of the fuel cell. We also don't know the maximum power output of the fuel cell to judge its utility in other applications. We only know approximate average power output.

The trick is to minimize the size of the converter (engine-generator) portion of the fuel cell while still providing the necessary power to operate the desired device and maximize the tank portion to provide long run time.

Quote:
it must consume only 7.5 watts per hour. Is this a realistic figure?
No, the screen would use that much power and probably more, all by itself.
__________________
--
swiftly flying
citivolus is offline  
Old 12-28-2006, 09:11 PM   #7
bystander
Senior Member
bystander is a name known to allbystander is a name known to allbystander is a name known to allbystander is a name known to allbystander is a name known to allbystander is a name known to all
 
Join Date: Mar 2005
Location: Southern California, USA.
Posts: 1,921
5 yr Member
Default

But we do know the type of methanol converter, it's Direct Methanol Fuel Cell (DMFC), which typically has an power conversion efficiency of less than 20%.

And trying to make out other figures from this Samsung press release site (in the Korean language), the converter itself may be rated at 20 watts.

And this site that playfuls.com cited says the converter's maximum is 20 watts, and the run-time is 8 hours (no mention of a month)

http://www.akihabaranews.com/news-13...Sense+Q35.html

I guess one "source" typoed the "1200" into "12,000", then another "source" made the calculation without checking the first source's facts and then added the "for a month" claim.

If the converter is only 20 watts, it needs to be scaled up about 20 times to be keep the battery size minimized on something the size of a PT. And the fuel conversion efficency isn't much different than an internal combustion engine. So I guess the whole thing isn't very practical at this time. Oh well... Sorry for the false alarm.
bystander is offline  
 


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 01:56 AM.
Copyright © 2002-2023 SegwayChat.org.
All rights reserved. Not affiliated with Segway Inc.

FreshBlue vBulletin skin by
VayaDesign
Powered by vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
SegwayChat Archive