Energy density for SLA, Li and Gasoline

[gmouchawar]

Here are some interesting numbers from Design News magazine cover from 04.28.08

Lead Acid battery 50 W-hr/kg
Lithium Ion 150 W-hr/kg
Gasoline 12,722 W-hr/kg

Lithium is better than SLA by 3x but doesn't come close to the energy trapped in Gasoline.
Even if you consider that electric motors are 80% efficient and ICE is 25% efficient the spread is large.
Perhaps this should lower the expectation of a pure electric 400 Mi per charge electric car.
a 25 MPG car consumes ~4lbs (1 gallon) to go 25Miles. At 25% efficiency that is still 12,722 W-hr as useful work and 3 times that thrown away as heat.
To do that with an electric car you need ~100 kg of Li battery, assuming 84% efficiency.
Still batteries are good for ebikes. 3kg or 6 lb Li battery is good for 1 hr of 450 W.
On my EV Global ebike that is ~11 Miles on flats with battery alone. It takes 9kg or 18 lbs to do the same with SLAs.

 

[PaulM]

Here's an interesting plot I found on wikipedia:

Looks like liquid hydrogen is the way to go, just need a big tank but it won't weigh very much.

 

[dogman dan]

Shorter range electric cars, like 100 mile range will be very practical when the technology gets to where a 10-15 minuite charge is possible. After about 100 miles most folks are ready for a break close to that long anyway. Even out here in the west, few stretches of road are more than 80 miles between towns. But if you need 8 hours to charge, you need at least 300 mile range to get anywhere on the highway. Commuters that need more than 100 mile range, live too far out and need a train.

 

[snowcrow]

Shorter range electric cars, like 100 mile range will be very practical when the technology gets to where a 10-15 minuite charge is possible. After about 100 miles most folks are ready for a break close to that long anyway. Even out here in the west, few stretches of road are more than 80 miles between towns. But if you need 8 hours to charge, you need at least 300 mile range to get anywhere on the highway. Commuters that need more than 100 mile range, live too far out and need a train.

I take it you havn't seen the "Tesla Roadster" yet

• 100% electric
  0 to 60 in 3.9 seconds
  14,000 rpm redline
  244 miles per charge
  3.5 hour charge time (DOD)

http://www.teslamotors.com/

If I had the money I'd be buying one!!!!!!!!

Stock Shares

• GM 2.65
  F 1.87
  TM 67.89 !!!!

I've been doing my homework 8)

Blessings, Snow Crow

 

[dogman dan]

I wish I'd see a Tesla in the local junkyard, so I could raid it for the A123"s If you can afford a Tesla nothing us normal foks care about applies. Just solve all problems with money. Tesla battery dead? Just take the humvee. Travel more than 100 miles in a jet. I just meant that for people who commute for several hours in the morning and several hours in the evening, a good transit system would be nice. I have been there and done that, and it did suck, I changed the oil in my bug twice a week! Driving that far in a car everyday had better be in a company vehicle.

 

[TylerDurden]

Mass transit has issues, but it's handy to read the news on the way to work and back. Now, you can download podcasts and listen to the day's events too.

 

[John in CR]

No matter what mode of transit you use, commuting hours in the morning to work and again in the afternoon back home is a waste of life and resources regardless of how well you make use of that time. Find a job closer to home, or move closer to work and get a life. Call it just 3 hours out of a waking day of 16hrs and do the math yourself.

While I don't disagree with the point of the original post, he is comparing apples and oranges. The batteries need to be compared to the gas tank not the gasoline in terms of cost, and then except in terms of maximum range without refueling, you've gotta compare the cost of refueling and battery life in a truly meaningful analysis. Anyone would have a difficult time arguing that electricity isn't the most dense and cheapest form of energy widely available.

What the original post does highlight is the need for a new type of vehicle that is far less massive than current cars. Look at ebikes at one extreme and hummers at the other. Somewhere in the middle, but far closer to ebikes is the right answer. The Jetson's had it right and even though we can't fly our daily commutes, there's no real reason our vehicles can't be as light as George Jetson's "car" looks. At that point lithium chemistry batteries begin to make economic sense already, and the world has yet to tap into readily available and cheap lithium reserves. They may not be sufficient for batteries for everything, but it's surely a significant start until a far better battery or capacitor is developed.

John

 

[safe]

Going by the chart Ethanol is very good.

At least with Ethanol it's possible to create it using farming techniques which can be done on a large scale. But they have to separate corn out of the equation. They need to focus Ethanol production onto lands that food crops do not do well. By dividing the crops onto the lands on which they belong it makes the whole system make more sense. The crop subsidy programs for Ethanol now are just screwing up the food system and driving up food prices which ultimately acts like a "tax" on the public. So in effect we are first "taxed" in the form of the subsidy to the farmer and then "taxed" again as we pay a higher price for the food.

Electric power can be produced by many means and so if we instead go with electric vehicles it allows for unlimited growth of electrical power. The bigger the power network (and more diverse) the better. And the more localization (like solar or wind) the better still.

Our thinking should be based on the pragmatic wisdom of what is most protected from potential failure. The more redundencies you have the "safer" you are.

Let's be "safe" and go electric... it's the most conservative option... :lol:

Just hope an enemy never drops an EMP weapon over our heads.

 

[TylerDurden]

...a waste of life and resources regardless of how well you make use of that time...

If you use the time well, it is not a waste, eh?

Mass transit works well in high density areas and is much more efficient than most single-occupancy transport for lower density areas.

Moderate distance between workplace and housing is to be expected, extensive distance is usually unnecessary.

 

[Joey]

Things get more interesting in the energy density comparison between batteries and gasoline if you consider motor efficiency, and include the anticipated 8x-10x energy density improvement expected for Lithium-Ion batteries based on the silicon nanowire technology under development at Stanford University. Commercialization of this technology is projected to occur within 5 years.

Gasoline: 12,722 W-h/kg x 0.25 ICE efficiency = 3180.5 W-h/kg effective 1/1 energy density ratio compared to gasoline considering motor efficiency
Present Li-Ion: 150 W-h/kg x 0.80 e-motor efficiency = 120.0 W-h/kg effective 1/26.5
Nanowire Li-Ion (8x): 1,200 W-h/kg x 0.80 e-motor efficiency = 960.0 W-h/kg effective 1/3.3
Nanowire Li-Ion (10x): 1,500 W-h/kg x 0.80 e-motor efficiency = 1200.0 W-h/kg effective 1/2.65

Taking into account motor efficiency, and an expected 8x-10x improvement in Li-Ion battery energy density, we'll soon be at about 1/3 the effective energy density of gasoline. Since there is probably a 2x spread in fuel consumption among ICE vehicles sold for personal use, a 3x factor in energy density spread between ICE and Li-nanowire doesn't seem all that bothersome. Also considering that Li-Ion battery technology is in its infancy (lead-acid has been around more than a century), the future looks even brighter.

-- Joey

 

[gmouchawar]

Agree with Joey. That is the kind of leap that is required for a pure electric car. Till then a hybrid car and an ebike or a 30Mi range electrics are what we have to settle for.
I look forward to that day though, and I am glad there is a light at the end of the tunnel.
I am optimistic about our future but it may be our kids that will get the benifits of it and not us.
Till then we have to deal with stronger herricanes, tornados and wild fires.

 

[Fumesucker]

The motor and drive train in an EV weigh less and are more compact than an equivalent ICE, this leaves more weight proportionally for batteries in the vehicle than fuel in the ICE.

Not sure how much effect his has, but it wouldn't surprise me to see it add another 20% or so range.