OT- MIT engineers create an energy-storing supercapacitor from ancient materials

[Mitch Alsup]

The supercapacitor may work but the author must be an English major. His description of a capacitor is wrong. A capacitor consists of two conductive surfaces separated by a thin insulating barrier.

When voltage is applied to the conductors, an electric field is created and a charge develops across the barrier. The charge remains even after the applied voltage is removed.

The charge remains after the supplying voltage is removed--the charge is a direct consequence of (and proportional to) the voltage being held by the capacitor.

The capacitance is proportional to the surface area but inversely proportional to the separation between the two conductors. While a large surface area is required, it is the thickness of the dielectric layer separating the two conductors that makes it a supercapacitor.

 

[RJSakowski]

My curiosity regarding supercapacitors was piqued by this post so I went to DigiKey to what is currently available. The largest listed was a 13,500 farad made by Power Responder. I was surprised to see that energy densities are approachiung that of lead acid batteries in both kwh/kg and kwh/l. The 13,500 farad capacitor lists for $120 and can store 16.5 wh of useful energy for a cost of $7.3/wh. My deep cycle lead acid battery can store about 1 kwh of useful energy at a cost of about $.10/wh.

It will be a long time before I am replacing my traditional lead acid battery with a supercapacitor.

 

[dabear3428]

My curiosity regarding supercapacitors was piqued by this post so I went to DigiKey to what is currently available. The largest listed was a 13,500 farad made by Power Responder. I was surprised to see that energy densities are approachiung that of lead acid batteries in both kwh/kg and kwh/l. The 13,500 farad capacitor lists for $120 and can store 16.5 wh of useful energy for a cost of $7.3/wh. My deep cycle lead acid battery can store about 1 kwh of useful energy at a cost of about $.10/wh.

It will be a long time before I am replacing my traditional lead acid battery with a supercapacitor.

as with most studies and groundbreaking scientific discoveries i start to doubt the veracity of the story when i see them stating things like 10KWH as the typical home daily power needs, most homes need 5 to 6 times that. if you then start looking at how much concrete would be needed to accommodate that power demand you begin to realize that these people are not in touch with reality.

 

[homebrewed]

The problem with supercapacitors is their low breakdown voltage. While 13,500 farads certainly is impressive, its just good up to a maximum of 4 volts. You would need to stack three of them to get 12V. That drops the effective capacitance to 4,500 farads.

One capacitor can store 108,000 joules but because the stored energy is proportional to v-squared the stacked set can store 324,000 joules. But at $360 for that, a lead-acid still wins out.

 

[dabear3428]

they calculate that "just" 45 cubic yards of concrete would be needed for 10kwh of storage lol and one of the larger contributors to green house gas is concrete production lol. you have to wonder what they are thinking, oh wait i know lets follow the money "with sponsorship by the Concrete Advancement Foundation" lol. reminds me of the great corn to gas debacle, it was really great for the corn farmers and the ethynyl refineries but very bad for carbon into the atmosphere.

we are not in a huge hurry to install 10 deep cycle batteries to hold 10kWhs of energy but we are going to run out and install 45 yards of concrete? just for reference in my area a 1800sf house would only need about 22 yards of concrete for a foundation.

 

[RJSakowski]

The problem with supercapacitors is their low breakdown voltage. While 13,500 farads certainly is impressive, its just good up to a maximum of 4 volts. You would need to stack three of them to get 12V. That drops the effective capacitance to 4,500 farads.

One capacitor can store 108,000 joules but because the stored energy is proportional to v-squared the stacked set can store 324,000 joules. But at $360 for that, a lead-acid still wins out.

Add to that, that current supercapacitor technology has a 2.5 volt minimum voltage which limits the amount of useful stored energy.

The manufacturer's data sheet states an energy capacity of 16.5 wh for the capacitor.. To store a typical day's worth of energy for a household would require 600 of the suckers @$120 a pop.

 

[dabear3428]

Add to that, that current supercapacitor technology has a 2.5 volt minimum voltage which limits the amount of useful stored energy.

The manufacturer's data sheet states an energy capacity of 16.5 wh for the capacitor.. To store a typical day's worth of energy for a household would require 600 of the suckers @$120 a pop.

most homes in my area run about 2000kWh per month 2000/30 == 66.6kWh per day 16.5 wh X 600 == 9.9kWh so in my calc we are looking at 4036 of those $120 per pop, even if i'm off by a factor of 2 that is a lot of pop!

 

[rabler]

The supercapacitor may work but the author must be an English major. His description of a capacitor is wrong. A capacitor consists of two conductive surfaces separated by a thin insulating barrier.

Yep, typical university press release. Someone in the public relations office wrote it. It was called the "communications" office for us, reported directly to the university president. Never mind if they get their facts straight. Woe to the mere faculty/staff member that talked to any press/media, or posted a website that didn't comply with their guidelines.

 

[RJSakowski]

Yep, typical university press release. Someone in the public relations office wrote it. It was called the "communications" office for us, reported directly to the university president. Never mind if they get their facts straight. Woe to the mere faculty/staff member that talked to any press/media, or posted a website that didn't comply with their guidelines.

I thought that it might be something lost in the interpretation so I looked for additional releases. One that I found was actually a publication for a scientific journal. There were a lot of equations but not much in the way of an explanation as to how they intended to scale up the minuscule proof of concept that they had.

What bothered me about the whole thing was that I could see their explanation as to how the carbon structure could make one electrode but I failed to see how the dielectric barrier was formed. The only explanation that I could see was that the carbon was hydrophobic so the electrolyte could create a conductive path to it. Then the electrolyte, in conjunction with a conductive outer shell would for the other conductor. The other concern that I had is that salt solutions and Portland cement don't play well with each other. In order to form a conductive electrode, the concrete would have to be virtually saturated with the salt solution.

 

[WobblyHand]

Yep, typical university press release. Someone in the public relations office wrote it. It was called the "communications" office for us, reported directly to the university president. Never mind if they get their facts straight. Woe to the mere faculty/staff member that talked to any press/media, or posted a website that didn't comply with their guidelines.

Pity, they fell into the "lets publish before thinking this all through" trap. You know, review by peers, what a concept. Everyone wants to blow their own horn, even universities.

I wouldn't want them to be tarred by the same fake stuff as the "superconductor" LK-99 is turning out to be. One guy admitted to a fake video... https://www.tomshardware.com/news/lk-99-video-fraud-taken-down Not sure if LK-99 is real or not at this point. Peer review is ongoing. Even Nature Magazine has been snookered on fake findings.