The Future Of Energy Storage - Supercapacitors

With Tesla’s battery day event not too far off, and their acquisition of Maxwell Technologies last years, we thought it was worth taking a closer look at Supercapacitors. Some believe that supercapacitors might be integrated into future EVs. But, what exactly is a supercapacitor? And what makes them so different from batteries? Are they really the future of energy of storage?

Supercapacitors vs. Conventional Batteries

Before we get into depth of whether supercapacitors can really change energy storage all on their own, it’s worth taking a look at what they are and how they’re different from something like lithium ion battery. Both batteries and capacitors are a method of storing energy, but lithium ion batteries rely on chemical reactions to store and release their energy. It’s made up of a positive and negative side, which are called the cathode and anode. These two sides are submerged in a liquid electrolyte and are separated by a micro perforated separator, which only allows ions to pass through, when the battery charges and discharges, the ions flow back and forth between the cathode and anode. During this process the battery is heating up, expanding and contracting. These reactions degrade the battery over time, giving batteries a limited lifespan. 

 

Toyota & Lamborghini have launched hybrid-tech models

 

One benefit of battery technology is a very high specific energy or energy density so that it can store a lot of energy for later use. But capacitors are different; they don’t rely on chemical play in order to function. Instead they store potential energy electrostatically. Capacitors use a dielectric or insulator between their plates to separate the collection of positive and negative charges building on each plate. It’s this separation that allows the device to store energy and quickly release it. It’s basically capturing static electricity. One benefit of this is that a 3MF capacitor now will still be a 3MF capacitor in 15-20 years time, while battery may lose voltage capacity over time and use. And unlike a battery, a capacitor has a much higher power throughput, so it can charge and discharge in a fraction of time but they have a very low specific energy. It’s good for very small bursts of power. And that’s where supercapacitors enter the scene. They start to bridge the gap between battery and capacitor. 

BMW supercharger station

The concept of a “supercapacitor” is not a new thing. In fact, in 1957 the first supercapacitor device was created by “General Electric”, but there aren’t any know commercial applications. In 1966, Standard Oil Co. accidentally discovered the double – layered capacitor when working on fuel cells, but it wasn’t until the late 1970’s that the Japanese company, NEC Corporation began commercially offering the first “supercapacitor” for the computer memory back up. In fact, while we commonly refer to many products as super capacitors or ultracapacitors these two terms are used interchangeably and really depends on what company producing it wants to call it. For the most part it’s really just a trademark thing. 

 

Tesla supercharger

 

In 1990’s, products such as ECOND’s PScap – starter for diesel trains – began hitting the markets and pushing the boundaries of energy storage and capacitor applications. Companies like Maxwell Technologies, Murata and Tecate generally dominate the supercapacitor field. But recently developments in Graphene based capacitors are once again nurturing the growth of supercapacitors efficiency and application.

Supercapacitor vs. Normal Capacitor

First how we need to talk about how a supercapacitor works? And how it’s different than a regular capacitor? Because it’s a kind of cool it’s starting to venture toward a battery’s design and use an electrolyte on either side of an insulator. When current is applied ions build up on either side of the insulator and create a double layer of charge. What makes a supercapacitor truly superior to a normal capacitor or even a battery is the distance between the metal plates. In a normal capacitor the distance is around 10-100 microns. But in a supercapacitor that distance is narrowed to one thousandth of micron and that smaller distance leads to larger electric field i.e. more energy storage. Not to mention, the carbon coated plates on supercapacitors in increase the available surface area for storage capacity by up to 100,000 times. That’s a lot more energy available for use than a normal capacitor. So, what are these power hungry little titans used for? We are just at the beginning of supercapacitor applications. But in general, they’ve been found to have the biggest potential for application in hybrid-transportation. Toyota, Peugeot-Citroen, Mazda and even Lamborghini have all released models of vehicles that use some combination of supercapacitors and conventional Li-ion batteries. Believe it or not, even though Tesla invested $200 million in the purchase of Maxwell Technologies, Elon Musk has said his focus is not expanding the use and development of Maxwell’s supercapacitors for Tesla vehicles but instead in their battery manufacturing technology. However cars like Toyota’s Hybrid-R concept car and Lamborghini’s high powered sedan are using supercapacitors for a very specific role: Power Generation during deceleration. In other words when cars are slowing the energy generated from that action is stored by supercapacitors onboard and later used for acceleration – saving batteries for less strenuous actions than acceleration and deceleration. It’s taking advantage of a supercapacitors superior power throughput.

Supercapacitors in Switzerland

A fantastic example of how effective supercapacitors can be is seen in Switzerland where a fleet of buses will be exposed to charging stations at a variety of stops along their route. Just 15 seconds can top the energy charge off and only a few minutes would suffice for a null charge. With frequent top offs it makes up the lack of energy density and storage. And because supercapacitors draw a lower current over a period of a few minutes at a time, this puts less stress on the grid. However supercapacitors still can’t compete with Li-ion batteries when it comes to that high specific energy and long term energy storage. But despite that some companies are making progress on projects that are poised to make supercapacitors more universally applicable. Graphene – the material actually play a role in the future of capacitors. Companies like NAWA Technologies and Skeleton Technologies have taken supercapacitors to the next level by incorporating Graphene into the coating metal plates. They’ve taken this and expanded the conventional use of supercapacitor into the market like components for e-motorcycles, spacecrafts and wave energy technology. 

Graphene Structure

Graphene provides the next generation of supercapacitors with an interesting array of improvements. In particular, Graphene offers substantially more surface area, giving supercapacitors even more capacity for energy storage. But in addition to that, Graphene is ultra light has unique elasticity and is incredibly strong. In fact NAWA Technologies, Skeleton and other supercapacitor battery companies have already found major application for their Graphene based supercapacitors. Skeleton’s product can be found helping to power major tram systems in big European cities like Warsaw and Mannheim. But it’s not just trams and urban transportation that Skeleton has found use for. They’re working with European space agency on a potential approach for sudden power usage on satellites and spacecraft. As well as developing an ultacapacitor module for use in wind turbines to help manage the blade pitch control.