Electric car are quieter, do not pollute (if they use renewable energy) and can be one of the key elements of sustainable mobility when moving away from fossil fuels. However, of course, they are not free from their own challenges: from the raw materials needed for batteries to the speed of charging, there are still uncertainties to clear on their path to mass adoption. Fortunately, technological advances offer solutions, whether through alternatives to batteries or fast charging systems, improve the efficiency of electric cars. We will tell you more about the latter in this article. Has NASA found the key to fast charging for electric cars?
What you will find in this article:
How long does it take to charge an electric car?
For more than a century, internal combustion engines have reigned supreme due to their long range and speed of refueling. Unless you're waiting in line at the gas station, filling up with gas takes two or three minutes. Electric cars have more nuances. Generally, an electric vehicle (EV) can take between twenty minutes and twelve hours to fully charge. But what factors influence these times?
- Type of charging station: There are several types of charging stations, defined by their power level, ranging from 1 to 3. Home charging stations are generally type 1, while the more powerful types 2 and 3 are reserved for public places.
- Battery type and capacity: Battery capacity varies from 6 kWh for urban cars to 100 kWh for top of the line models, although the average is generally between 40 and 50 kWh.
- Charge level: The initial and final 20% of the battery takes the longest to charge.
- Ambient temperature: Charging speed is reduced at very low temperatures.
Interestingly, NASA exploited this last point with a prototype developed in collaboration with Purdue University. In their case, they chose extreme cooling as their ally.
How to speed up fast charging for an electric car
There is a physical barrier to increasing charging power. It is the same principle that governs the operation of a stove or a hair dryer: electricity passing through a resistance emits thermal radiation. If you've ever noticed the thickness of the “pipe” of fast charging stations, here's your answer: it requires many braided cables to avoid overloading and usually incorporates a coolant. These charging stations generally offer a power of 350 amps.
The new system proposed by NASA can multiply the electrical current carried by the electrical cables of a electric charging station by 4.6 times, operating without problem at 1400 amps. Technically, it could reach 2,500 amps. They used a temperature control system designed to operate in microgravity conditions in space to achieve this. The underlying physical principle is known as subcooled flow boiling. Using this technology, they dissipated up to 24.22 kilowatts of heat.
The prototype was developed by Purdue University, which took NASA's research on subcooled flow boiling and applied it to the field of fast charging for electric cars. In fact, the university laboratory announced another fast charging technology in less than five minutes in 2022.
How does subcooled flow boiling work?
You may be wondering how exactly subcooled flow boiling works. Well this phenomenon happens when a liquid is rapidly heated and begins to boil before reaching its average boiling temperature. If we place a pot of cold water on a ceramic hob or gas stove, the water will gradually heat up. As the water heats up, there comes a point where the surface temperature becomes high enough to form vapor bubbles, even before the entire liquid reaches its boiling temperature.
These steam bubbles that form in colder than normal water are called “boiling cores.” As heat is transferred to the surrounding water, these vapor bubbles expand and break away from the surface. dissipate heat with them.
Subcooled flow occurs when a moving liquid, such as water flowing through a pipe, is cooled below its normal boiling temperature before it begins to boil. This can happen when there is a rapid heat transfer to the liquid or when the liquid is under high pressure conditions.
It should be noted that this technology will initially be intended for space missions and colonization of Mars. In addition, all elements – from the battery to the charging station to the power cable – must be prepared for this level of power. However, who knows how long it will be before we see its application to fast charging of electric cars here on our planet, thus contributing to greater sustainable economy.
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