Text written in Basque and translated automatically by Elia without any subsequent editing. SEE ORIGINAL

The supercapacitors

The future of energy is a very important issue that directly affects society and the environment. That’s why they’re doing a lot of research on the subject, but they’re not only looking at how to generate energy, they’re also looking at ways to use it. They are looking for ways to store energy in the CICenergiGUne research center, that is, they are developing storage systems for whatever is needed. We have often heard about advances in batteries, but there is rarely any mention of supercapacitors. They also serve to conserve energy. For example, did you know that there are trams powered by supercapacitors?

The first cable free tram has been installed in Seville. There are sections where there is no catenary and the tram moves thanks to the supercapacitors that it carries on the roof. He travels about 50 miles every day like that. The technology is a pioneer in the world and this has been developed by a company from Gipuzkoa, Trainelec of the CAF group.

MIKEL RODRIGO; Trainelec: This is the equipment that we are using in Seville, Granada, Zaragoza, which allows us to provide a service without catenaries.

The engineers Mikel Rodrigo and Inigo Asegina have participated in the implementation of these trams. The origin of the project in Seville was a special request.

MIKEL RODRIGO; Trainelec: They had a problem in Seville; no, they had two problems. The first was that the tram they had was passing through very touristic areas and it hurt aesthetically and visually the presence of cables and posts there. The second important reason is Holy Week. They would go out with the saints in these places in processions, and because of the danger of hitting the catenary and stopping there, in two weeks of the year the catenary would be removed and the tram would be left without service. That’s where it all started; we were previously working in R&D in this area, creating this team and the opportunity to put it into practice. That's how we pulled out the first tram.

Why use a supercapacitor instead of a battery? Both store energy in the form of electrical charges. Location of Miñao, Álava. At CICenergiGUNE they investigate supercapacitors and batteries.

THE RED THEOPHILE; Zuz. scientific, CICenergiGUNE: The use of one or the other depends on what you want to achieve, if the system requires power, we will use supercapacitors and when the power density is desired, batteries.

When we say energy density we mean duration: the batteries are good for marathon and the supercapacitors are good for the spray. The reason lies in the way in which the energy that each one possesses is accumulated. Batteries do this chemically, while in supercapacitors the charges are physically deposited on the electrodes. These two accumulation paths lead to different modes of operation. Supercapacitors are fast and powerful, but they store less energy. In contrast, physical processes do not deplete the electrodes, or at least much less. Sometimes a marathoner is advisable and sometimes a sprinter is advisable.

IÑIGO ASOBROLAZA; Trainelec: The time you have to recharge it is not very long, it is around 20 seconds: when people get off the tram, when they go up, close the doors, open the doors,...

But that's not all. On catenary routes, the energy generated when the engine brakes is stored by the supercapacitors for acceleration.

MIKEL RODRIGO; Trainelec: According to our calculations and the records we have made, we can extract 30-35%, which is the energy that we can reuse.

In these laboratories, researchers at Energigune are still looking for ways to supercharge supercapacitors. The aim is to increase the power and, above all, to increase the duration. To this end, efforts are made to improve the characteristics of the materials, both electrolytes and the carbon that is the main component of the electrodes.

EIDER GOIKOLEA; researcher, CICenergiGUNE: This would be the active carbon, black, carbon color. This is what we use as active matter, in the electrodes.

With these mini-electrodes, scale capacitors are mounted to scale for testing. One of the aims of the invention is to develop inexpensive ways of synthesizing materials on the one hand.

EIDER GOIKOLEA; researcher, CICenergiGUNE:And on the other hand, to have as much surface as possible facing the material; the larger the surface, the more charge we would absorb, and the more energy we could store at that electrode.

The surface is therefore the key and the surface has a direct relationship with the pores. The pores should be sized appropriately so that they are neither too large nor too small to deposit ions or charges. This is tested here, as different currents are supplied to the capacitor to see how much charge it is able to accumulate. The more, the better the material.

In their quest to achieve this, they are studying all the molecular structures of carbon, from nanotubes to graphene.

JAVIER CARRETERO; researcher, CICenergiGUNE: Graphene has a large surface área and is an ideal material for use as an electrode. In principle it is an unknown material, but with a wide range of possibilities. Research on these materials can be traced back to childhood.

Yes, graphene is very expensive, but imagine: two grams have the same surface area as a football field. And the materials used today are not cheap either.

MIKEL RODRIGO; Trainelec: Today, both the capacitor and the battery, due to the impulse of the automotive industry, prices have fallen sharply, but it is not only the fall in prices, we have capacitors and batteries with higher performance in equal volume and at the same price, more power, more energy,...

Along with the progress, the uses are also increasing. In trains, to expand the emergency exits of aircraft, in port cranes, the focus expands as we investigate. However, the use to which they all aspire is the electric vehicle, and the solution may be that the batteries and supercapacitors work together. The battery would provide autonomy and would last longer, leaving acceleration at the expense of the supercapacitor.

IÑIGO ASOBROLAZA; Trainelec: Many times we oppose them as if there was a struggle between the two, but it is clear that in our sector and in many other sectors, in the future we will go to a hybridization, both the battery and the supercapacitor will work together in different systems.

Another solution may be to unify the best features of both worlds into a single device. Energigunen EnergiGUNE is also working on this path. They are pseudocapacitors that have the capacitor electrode and the battery electrode at the same time.

THE RED THEOPHILE; Zuz. scientific, CICenergiGUNE: In this case, it is important to find a device that is a combination of both the battery and the supercapacitor, which is suitable for hybrid vehicles.

JAVIER CARRETERO; researcher, CICenergiGUNE: In the end, the key is not to stop the battery from being a battery, it is a matter of merging the two areas and filling the gap that is involved.