These last months were quite busy and this is the reason why I stopped posting on this blog. I moved to Germany for work and now I think it’s time to restart writing.
The region where I live now is Lower Saxony, a very interesting place.
For instance, did you know that the famous mathematician Leibniz worked as a counselor for the Hanover (or Hannover in German) family? Indeed the university in Hannover is dedicated to him.
For me Hannover has always been associated to the neverending war between Austria and Prussia. And also to the rockband Scorpions, they are from Hannover! Indeed the song “Bad boys running wild “ was clearly inspired by the Austrian/ Prussian wars. ( This is not true but I wanted to say something convincing).
Even if Scorpions are amazing, today I will talk about another guy from this region, more precisely from the nice city of Braunschweig. For sure you all know about Carl Friedrich Gauss.
One of his most interesting discoveries is certainly the Gauss Law, which claims that the electrical flux from a closed surface is proportional to the electrical charge contained in the volume that we are analyzing. So what? Well , let’s consider conductors.
A conductor contains free electrons and once it is charged, all the electrons are rearranged so that the field is zero. Of course I am talking only about the field INSIDE the surface. The field outside the surface is not zero, because the conductor is charged. This discovery has a lot of amazing applications because it means that the fields on opposite sides of the same surface are independent.
Let’s make an example. Electrical and hybrid cars are becoming very popular now, aren’t they?
Well, the majority of AC motors need capacitors, to store electrical energy. In Italy we usually refers to capacitors as condensers, which are made of 2 conductors ( metals ) separated by an insulator.
The condenser is totally useless if not connected to a voltage source: once this works we can store electricity between our conductors.
The most common way of storing energy is the use of batteries. Though batteries are very different from capacitors because they just transform chemical energy into electrical energy. I think we can all remeber how old style batteries were made. The main problem was that they needed a solution called electrolyte which was made of sulfuric acid. This solution was required to allow the migration of ions in the electrochemical process. Moreover during the recharge, the process was taking place… in reverse! This used to cause a lot of waste, indeed batteries were not so long lasting. New batteries don’t need liquids any more, luckily for us! For instance, during the recharge of lithium ions- batteries there is a simple transfer of ions from the positive electrode to the negative electrode. Of course the process takes place in the opposite way during the use of batteries. So let’s come back to Gauss: what is the difference between batteries and capacitors?
Batteries contain unbalanced charges internally, so there is an electrical field outside the surface, which does not necessarily contribute to the net flux. So you might ask yourself: who is the winner between capacitors and batteries? The answer as usual is “ it depends” but if you really want to know what works better for electric vehicles I would say “ maybe ultracapacitors .” These devices contain a negative and positive electrode, but they store energy electrostatically. This approach can work well when you need very quick charge/ discharge cycles. Another good news is that the most common material for their electrodes is carbon, so not expensive. On the other hand, batteries are better than ultracapacitors if you need to use a device for a long time after just one single charge.
To simplify: capacitors have high electrical power while batteries have higher specific energy. A lot of companies are already testing ultracapacitors in their vehicles: Tesla, Toyota, Volkswagen, Peugeot just to mention some….
As usual, we cannot be super optimistic and say something like “ Hybrid is the future” or “ We will all drive super cool electric cars within a few years”. For sure will not be able to buy a Tesla by paying it with bitcoins, especially after what Elon Musk has done some days ago… Well, not a big dea! I think the majority of people ( including me) wouldn’t have been able to buy a Tesla anyway. Apart from this, I am glad to see that the transition towards electrical vehicles is on its way and that governments are stimulating their diffusion. Let’s hope that the use of electrical vehicles won’t be just a privilege for a few people and that every family will be supported. Needless to say: the diffusion of electrical vehicles will have a positive impact on air quality and therefore on people’s health. According to the Acea report from september 2020, the percentage of EV in Europe is already 7,2 % .This is great compared to the value in 2019 (2,4 %) but still pretty low. There are a lot of bright ideas about how to make these vehicles more accessible and long lasting, now it’s time to put them in practice. If this conclusion sounds like “ Captain Obvious” to you I will just quote Gauss: “ Theory attracts practice as the magnet attracts iron”. This would have been an amazing motto if he had started his own capacitors company!
Giulia Ioselli
References
Tuning the interlayer spacing of graphene laminate films for efficient pore utilization towards compact capacitive energy storage
Zhuangan Li, Srinivas Gadipelli, Hucheng Li, Christopher A. Howard et al
Nature, 17 February 2020
Techexplorist.com
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