Picture this — a world powered by nothing but wind and solar. Electric vehicles with endless range. Sounds like a dream right? But there’s a problem — to achieve that dream, we’re going to need better ways to store all that energy and distribute it efficiently.
So far, the solution has been batteries, but one technology that’s gained a lot of hype is the Supercapacitor, particularly, supercapacitors that utilize a material called Graphene.
Until recently this technology wasn’t widely available. With graphene supercapacitors gearing up for their commercial debut — it’s worth exploring what they are, how graphene factors in, and what this could mean for both grid energy storage and individual applications.
So, what are Supercapacitors?
I’m glad you asked!
When it comes to energy storage, we typically think of batteries, which rely on chemical reactions between a cathode, an anode, and an electrolyte.
Batteries are great for storing lots of power compared to their weight — their gravimetric energy density, or specific energy. But while batteries have high specific energy, they have lower power density — how much energy they discharge per battery unit.
This is why they’re so great for EVs, where you typically don’t need rapid bursts of power, but steady power for longer range. But, batteries can also take a long time to charge. And those charge/ discharge cycles generate heat which leads to degradation.
So what if we want to store and release energy rapidly? Well, this is where capacitors come in.
Capacitors are similar to batteries in that they are also a way to store energy, but they have some very fundamental differences.
Capacitors have two conductor plates, usually made out of aluminum, separated by a ceramic or glass insulator— called a dielectric,— that collect positive and negative charges. Unlike batteries, which store energy chemically, capacitors store electricity statically — basically capturing static electricity. Because the energy isn’t transferred to another material, it stays electricity, it can move around much more efficiently. How efficiently?
When it comes to power density, Capacitors are roughly 100 to 1,000 times more efficient than batteries. That means if a lithium ion battery has a power density of 100 W/kg, a capacitor would have a power density of roughly 10 to 100,000 W/kg!
Think of a flashbulb in an old camera, which uses lots of energy in a short period of time. Instead of using a battery, the flash uses a capacitor — which draws energy from a battery in a slow, steady flow, but can release super quickly then charge up again rapidly. You can take photos over and over again in rapid succession. There’s no way a battery could do that!
And since capacitors don’t use chemical exchanges, they don’t heat up the way batteries do, meaning they don’t degrade as quickly. A 3V capacitor will stay a 3V capacitor even after hundreds of thousands of cycles.
Now, where capacitors utterly pale in comparison to batteries is in energy density. Tesla’s current Model 3 cells hold about 260 Wh/kg. Whereas dielectric capacitors have energy densities less than 1 Wh/kg.
A standard laptop battery weighs about 1 kg. For a capacitor to store the same amount of energy as my laptop battery, it would need to weigh 260 kg or about 573 lbs!
Now, a supercapacitor sits somewhere between a standard capacitor and a battery.
They use plates and a dielectric, but they also use an electrolyte. Ions build up around the insulator, creating a double layer of charge. The plates are also carbon-coated which increases the surface area.
Supercapacitors also have a much smaller distance between the metal plates — about 10 to 100 thousands times shorter than standard capacitors. That smaller distance leads to a larger electric field. Keep this in mind for later.
Basically, these distinctions mean more energy storage. Compared to a standard capacitor, a supercapacitor can store up to 28 Wh/kg. And while that still doesn’t match a lithium ion battery, it’s getting a lot closer. And in some cases, it may make more sense to use a supercapacitor over a battery.
For example, supercapacitor-powered electric buses are very common in China. The buses may not have anywhere near the range of an EV, but they don’t need it. They can simply go one or two stops, then recharge — in a matter of minutes — then be on their way. Similar to the Gyrobus we covered in an earlier video!
They’re also used in grid level renewables. Supercapacitors show up in wind turbines to help control wind pitch. They’re also great at helping stabilize energy delivery during peak periods.
Anywhere that benefits from large bursts of energy in short periods of time.
And while scale may be an issue for things like phones, batteries, and EVs, for grid storage it’s not. You could have fields full of massive super capacitors out in the middle of a solar or wind farm and it wouldn’t matter.
And since super capacitors are carbon-based, they can take strain off of the supply chain for elements like lithium, nickel, and cobalt. Remember, diversifying our energy storage materials is a good thing!
And this is where graphene comes in! But before we dive into that, we can’t wait to tell you about today’s sponsor!…
Graphene comes from Graphite, that stuff inside pencils. Graphite is an allotrope of carbon — having the same number of atoms but arranged differently, giving it distinct properties.
Graphite typically has a three dimensional “crystalline” structure. Graphene has a single, 2 dimensional layer only one atom thick connected in a hexagonal, honeycomb shape.
Why does this matter?
The structure allows for the atoms to form strong covalent bonds. As a result, graphene boasts a tensile strength of 130 gigapascals — 100 times stronger than steel! Yet it also remains incredibly flexible.
This unique atomic structure also allows the electrons to move around more freely, making graphene insanely good at conducting both heat and electricity.
Because graphene is so thin, AND so conductive, it’s an excellent candidate to take supercapacitors to the next level!
So remember earlier, when we said supercapacitors can have shorter gaps between their plates, allowing for more static charge?
Well, typically, as we mentioned, those plates are made out of aluminum. Now, while aluminum may seem thin to our eyes — when we scale down, we can see… It’s definitely thick! Now compare that to graphene, which has a thickness of only 1 Atom! Now, in the same amount of space, we can fit hundreds of thousands more of those gaps, which in turn means more energy storage!
The main reason we haven’t seen graphene supercapacitors before is that age-old issue of making them economically sound to mass produce.
And this is where Skeleton Technologies is making seismic leaps forward.
This European tech company has found a way to break that cost barrier. How did they do it? By using what’s called “curved graphene,” which essentially uses crumpled up sheets of graphene.
The exact process is a pretty heavily guarded company secret, but suffice it to say, it has brought the cost down so much so that they’re just about ready to hit the market.
How does their technology stack up? Their current 3V ultracapacitor has a specific energy of 11.1 Wh/kg with a specific power of 28.4 kW/kg. Now, again, that may not sound like a lot, especially compared to a battery, but the company says by using graphene, they’ve improved their technology by about 72%!
Now — you won’t see these supercapacitors replacing your lithium ion batteries any time soon. So in that sense, they may not totally change the energy game the way some have prophesied.
But, that doesn’t mean they can’t have a major impact on many of the technologies you’re using today!
Skeleton Technologies offers KERS systems for electric trains throughout Europe that can recover up to 30% of electricity depending on whether the train is used as a long-distance train or a full stop commuter train. This could mean cheaper shipping and public transportation!
Supercapacitors could also be used to power your EVs 12-Volt Board that runs lights, power autonomous driving, AC, even your cars start-stop function.
Taking the load off your car’s battery could theoretically increase range between 10-15%. For a Model S with 400 miles of range — that could add another 60 miles — 20 miles more than the Average American’s daily commute!
Supercapacitors could also help with rapid acceleration — like the Tesla Model S’s “Ludicrous” mode. Typically, to achieve those quick bursts of power, you need a larger battery pack. But doing so also stresses the battery, which is why Tesla doesn’t recommend using Ludicrous mode all the time.
Pairing a supercapacitor with a Tesla battery could help your vehicle accelerate quickly without that added battery strain, preserving its lifespan!
But the applications don’t end with vehicles.
As we mentioned, supercapacitors are already used in grid-level renewables. But what about your home solar?
Intermittency can wreak havoc on batteries as fluctuating output can interrupt battery charging and discharging. High energy demands in short periods of time can seriously impact the life of a home battery.
Installing a supercapacitor to run in parallel with a home battery system could help reduce stress on a battery by allowing sufficient energy in a short amount of time, and leveling those peak power requirements.
Supercapacitors could also make home solar systems more efficient, allowing storage of more precious sunlight in a shorter window of time. One study suggests that adding a small, fast-responding storage device to your solar system could increase energy efficiency as much as 83% on a sunny day and up to 114% on a cloudy day!
This could also help reduce the battery size since supercapacitors can share some of the power load. This could bring down home battery system costs while also increasing battery life, making home energy storage systems more cost effective in the long run.
So, will graphene supercapacitors be the game changing technology they were projected to be? Well, the jury is still out on that. But they may prove worth it in different ways.
So much of the technology we cover on this channel tends to be five, ten, sometimes 20 or 30 years away from hitting the market. Thanks to Skeleton Technologies, Graphene Supercapacitors are here now!
