Supercapacitors

[DGDanforth]

Elon has done work with supercapacitors and has said they will be the future of electrical storage.

The future is here now, at least according to a UK company Superdielectrics Ltd. (SDL).
SDL is a spinoff of the Universities of Bristol and Surrey, UK.

The claim is their dielectrics can attain an energy density greater than that of lithium-ion,
50% greater!

Not only that but now Rolls-Royce has invested with them. Here is the press announcement
Rolls-Royce links up with UK-based Superdielectrics to explore potential of very high energy storage technology

If their claims bear out under scrutiny and further testing then this is a game changer and Elon should get in the game!
Everything changes.

 

[CoastalCruiser]

I keep wondering if capacitor technology would evolve enough to make it worth another look since Musk rejected the tech all those years ago in college. Perhaps at least evolved enough to make for a decent substitute for the 12v accessory battery in a BEV?

The [highly PR based] press release does indicate that a breakthrough has been made. The key phrase in that release though (excerpted below) is "prospect" and "potentially". The question as always is; When will it be ready for the market?"

"The University of Bristol estimates that these newly discovered materials have dielectric property values which are 1,000-10,000 times greater than conventional electrolyte solutions. This breakthrough offers the prospect of a new energy storage technology that is superior to existing battery technology. Superdielectrics Ltd’s technology is not limited by rare or expensive elements and potentially has a higher energy density than both Lead Acid and Lithium-ion batteries."

 

[ItsNotAboutTheMoney]

Add it to the list of things that you'll have forgotten about by the time it comes to market (if it ever does).

 

[DGDanforth]

Agreed.
However, Rolls-Royce is not going to accept anything that does not work. I trust that they will do rigorous testing.

I would like to enlist a commitment from Elon that as technology advances Tesla will upgrade existing battery packs, at no cost to the current owner. For low cost supercapacitors labor should be more than covered by the difference in materials cost and the recycling of the old into powerpacks. For other technologies (lithium-air, lithium-metal, lithium-sulfur) the cost difference might not be as clear.

I keep wondering if capacitor technology would evolve enough to make it worth another look since Musk rejected the tech all those years ago in college. Perhaps at least evolved enough to make for a decent substitute for the 12v accessory battery in a BEV?

The [highly PR based] press release does indicate that a breakthrough has been made. The key phrase in that release though (excerpted below) is "prospect" and "potentially". The question as always is; When will it be ready for the market?"

"The University of Bristol estimates that these newly discovered materials have dielectric property values which are 1,000-10,000 times greater than conventional electrolyte solutions. This breakthrough offers the prospect of a new energy storage technology that is superior to existing battery technology. Superdielectrics Ltd’s technology is not limited by rare or expensive elements and potentially has a higher energy density than both Lead Acid and Lithium-ion batteries."

 

[BillO]

”potentially has a higher energy density than both Lead Acid and Lithium-ion batteries."

I gotta say this phrase really makes me question the whole thing. Maybe it came from a reporter and not the company, but lead acid and lithium ion do not have anything like a similar energy density. Comparing them this way makes the author sound like they don’t know anything about the technology...

 

[BillO]

Check out this article - UK supercapacitor results suggest challenge to battery technologies
Says this tech may be able to reach 180 wh/kg. Since current li-on is around 240 wh/kg I would say this isn’t the breakthrough everyone is looking for...

 

[DGDanforth]

Wikipedia says for Lithium ion 100–265 W·h/kg

Charge and discharge times for the supercapacitor are far greater than for battery and
it is non flammable, conditions one would definitely want in an electric vehicle.

Check out this article - UK supercapacitor results suggest challenge to battery technologies
Says this tech may be able to reach 180 wh/kg. Since current li-on is around 240 wh/kg I would say this isn’t the breakthrough everyone is looking for...

 

[DGDanforth]

When writing to a general audience one uses familiar benchmarks. That is not claiming the energy densities of lead acid and lithium ion are similar.

I gotta say this phrase really makes me question the whole thing. Maybe it came from a reporter and not the company, but lead acid and lithium ion do not have anything like a similar energy density. Comparing them this way makes the author sound like they don’t know anything about the technology...

 

[deonb]

“My top advice really for anyone who says they’ve got some breakthrough battery technology is please send us a sample cell, okay. Don’t send us PowerPoint, okay, just send us one cell that works with all appropriate caveats, that would be great. That sorts out the nonsense and the claims that aren’t actually true.”

- Elon

 

[deonb]

I would like to enlist a commitment from Elon that as technology advances Tesla will upgrade existing battery packs, at no cost to the current owner.

Why on earth do you think Elon owes you that?

Do you also want a commitment from Apple that as phone technology advances that you will keep getting a new iPhone at no cost to you?

 

[DGDanforth]

“My top advice really for anyone who says they’ve got some breakthrough battery technology is please send us a sample cell, okay. Don’t send us PowerPoint, okay, just send us one cell that works with all appropriate caveats, that would be great. That sorts out the nonsense and the claims that aren’t actually true.”

- Elon

I agree with Elon.
It seems that Rolls Royce, however, has stolen the show and opted to be the one to evaluate the technology.

 

[DGDanforth]

Why on earth do you think Elon owes you that?

Do you also want a commitment from Apple that as phone technology advances that you will keep getting a new iPhone at no cost to you?

Not the same case. Phone technology and battery technology are different. If a massively cheaper supercapacitor does hit the market then I would expect phone companies will adopt it. But a phone is far cheaper than a car so replacing the battery rather than buying a new phone does not make much sense. But replacing the battery of a car does make sense since the battery is modular and easily swapped while retaining the car body unchanged.

 

[jeffro01]

Not the same case. Phone technology and battery technology are different. If a massively cheaper supercapacitor does hit the market then I would expect phone companies will adopt it. But a phone is far cheaper than a car so replacing the battery rather than buying a new phone does not make much sense. But replacing the battery of a car does make sense since the battery is modular and easily swapped while retaining the car body unchanged.

You do realize Tesla isn't running a charity? It's a for-profit business and there's nothing profitable about giving away the most expensive part of the car... Come on...

Jeff

 

[deonb]

But replacing the battery of a car does make sense since the battery is modular and easily swapped while retaining the car body unchanged.

Replacing the battery I have no problem with. Why would they need to do it for free though?

 

[BillO]

Wikipedia says for Lithium ion 100–265 W·h/kg

Charge and discharge times for the supercapacitor are far greater than for battery and
it is non flammable, conditions one would definitely want in an electric vehicle.

Yes, true. However supercapacitors (or any capacitor) don’t hold a charge very long, certainly not like a lion battery. That wouldn’t work too well for an EV. Also,the voltage of a capacitor tends to drop very rapidly as it discharges, compared to a battery. This is hard to manage.

 

[DGDanforth]

My worry is the retention time which is not mentioned in any of the reports I have read. High charge and discharge rates mean nothing if the energy leaks away in a few seconds or a day.

 

[DGDanforth]

You do realize Tesla isn't running a charity? It's a for-profit business and there's nothing profitable about giving away the most expensive part of the car... Come on...

Jeff

They still make a profit when the cost of the supercapacitor is far less than the cost of the battery. The battery is repackaged as a powerpack and resold.

 

[DGDanforth]

Replacing the battery I have no problem with. Why would they need to do it for free though?

They make a profit by the cost difference between supercapacitor and battery.

 

[mongo]

Also,the voltage of a capacitor tends to drop very rapidly as it discharges, compared to a battery. This is hard to manage.

Indeed, one might even say the voltage drops linearly based on current draw.
Much worse curve for content power draw, the lower the voltage the higher the current the faster the voltage drop the higher the current....

Lithium batteries are great in that their voltage does not change much verses their SOC, so the power electronics can always run in buck (step down) mode.

A supercap system would either need enough capacitance to keep the voltage high at 0% effective SOC, or use a boost/buck converter for the power stage.
For example: A 100kWh capacitor bank with a voltage range of 350V to 400V (similar to the Tesla pack) would need to be 20,282 Farads. At 350V, it is still holding 345kWh of energy.

 

[DGDanforth]

For example: A 100kWh capacitor bank with a voltage range of 350V to 400V (similar to the Tesla pack) would need to be 20,282 Farads. At 350V, it is still holding 345kWh of energy.

Based on E = 1/2 CV^2 I find the capacitance necessary for an energy of 100kWh at 400V to be 4500 F.

When the voltage drops to 350V the remaining energy is 76.56 kWh.

A Tesla model S gets about 3 miles per kWh and its range is about 300 miles. Driving at 60 miles per hour takes 5 hours to cover 300 miles.

Assuming a constant power output from the supercapacitor the 300 miles and the time 5 hours will be the same as for the battery (energy is energy). Note the voltage of the supercapacitor drops as the square root of the time.