Charging an electric car as fast as filling a tank of gas

January 20, 2016 by Anne-Muriel Brouet
Charging an electric car as fast as filling a tank of gas

Electric cars will only be truly competitive when it doesn't take longer to charge them than it does to fill a gas tank. The storage capacity of batteries is improving exponentially, but the power grid is the weak link: how could it possibly charge thousands of cars at the same time? This is especially problematic in the case of ultra-fast charging, which requires more than 10 times more power. EPFL researchers have found the solution: intermediate storage.

It only takes a minute and a half to put enough fuel into the tank of a diesel car to run for around 1,000 kilometers. After being charged for the same amount of time, the best will only go six kilometers. The only way to make the charging process faster is to increase the flow going in. But such a quick charge would require 4.5 MW of power – equivalent to 4,500 washing machines. This would bring down the .

Low or medium voltage

"We came up with a system of intermediate storage," said Alfred Rufer, a researcher in EPFL's Industrial Electronics Lab. "With this buffer storage, charging stations can be disconnected from the grid while still providing a high charge level for cars." And this can be done using the low-voltage grid (used for residential electricity needs) or the medium-voltage grid (used for regional power distribution), which significantly reduces the required investment.

Intermediate storage is achieved using a lithium iron battery the size of a shipping container, which is constantly charging at a low level of power from the grid. When a car needs a quick charge, the buffer battery promptly transfers the stored electricity to the vehicle. The grid is not even used.

Charging an electric car as fast as filling a tank of gas

To prove the system works, the researchers at the EPFL Energy Center and Industrial Electronics Lab built a demonstrator together with their partners from the Swiss Federal Laboratories for Materials Science and Technology (EMPA), the Swiss Federal Institute of Technology in Zurich (ETHZ) and the Bern University of Applied Sciences. The demonstrator is a trailer holding the intermediate storage battery. It draws power from the low-voltage grid and, in the space of 15 minutes, provides the 20 to 30 kWh needed to charge a standard electric car battery. "Our aim was to get under the psychological threshold of a half hour. But there is room for improvement," said Massimiliano Capezzali, deputy director of the Energy Center, who coordinated the project.

Determining the capacity of tomorrow's charging stations

What is also interesting about this concept is that it can be used to determine how much capacity future charging stations will need. Gas stations from the last century will gradually give way to electric . And just as owners had to assess how big their fuel tanks needed to be, future suppliers of electric energy will have to estimate the needed capacity for their buffer storage. To help them in their task, the researchers developed an equation that factors in a number of parameters, including traffic statistics on a given stretch of road, the estimated number of electric cars, the charging capacity of the batteries, users' charging needs, and so on.

The simulations, which are based on actual figures from French-speaking Switzerland, show that the scenario is entirely realistic. A station able to quickly charge 200 cars per day would need intermediate storage capacity of 2.2 MWh. This is the same order of magnitude as the energy consumed by one home in one year. In volume terms, it corresponds roughly to four shipping containers. "Electric cars will change our habits. It's clear that, in the future, several types of charging systems – such as slow charging at home and ultra-fast for long-distance travel – will co-exist," said Dr. Capezzali.

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10 comments

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gkam
2.6 / 5 (5) Jan 20, 2016
Fast charging puts stresses on everything. The gas pump is equivalent to five Megawatts - try putting that into your car without melting. Instead, most folk will have inductive chargers at home, and the big ones like this will probably be used for larger vehicles such as buses. Most vehicles do not run 24/7, and can be charged when not running in their parking place.

Ours gets charged at night.
Lord_jag
4 / 5 (4) Jan 20, 2016
Electric cars won't require you hold your hand on the freezing nozzle while you're stainding out in the -25 and windchill. Just plug it in and go inside to enjoy a nice cup of coffee. Make me comfortable for a half hour and I won't mind waiting. I'll take that over standing outside for 10 minutes any day.
Lord_jag
4 / 5 (4) Jan 20, 2016
What gas car can be refueled in 2 minutes as shown in the picture?? Maybe from the moment the gas starts flowing until you get to $20.

I've timed it. Filling a tank, all 60 liters, including opening the gas door, swiping your card, waiting for it to authorize, putting it all away, waiting for the receipt.... From the moment you open the car door to the moment you close it again is 10 minutes minimum.

Or an electric, you pull up, plug it in and go inside for a coffee. No fuss, no effort, no danger of a spark igniting the gas vapors and bursting your car into flames.
Mayday
5 / 5 (2) Jan 20, 2016
IMO, electrics will remain niche for quite some time. A frequent trip to visit my family is 300 miles one way. I live in a housing complex where all vehicles are outdoors and seldom in the same parking space two days in a row. In the coming blizzard, many vehicles will be stuck in traffic for hours in below freezing temps. Rapid charge at the local fuel station is a must. And no one has yet designed an electric car with safe back up or dead battery option -- a small gas or NG motor that can reliably get me somewhere safe. Love the idea, but so far, only for a few. When one can safely be my only car, without a garage, I'm in.
Eikka
2 / 5 (4) Jan 21, 2016
In volume terms, it corresponds roughly to four shipping containers.


And four shipping containers corresponds in volume to the entire gas station.

http://www.homedi...tainers/

The other problem with "intermediate storage" is the efficiency. Charging a battery is at best 85% efficient because of the need to convert voltages and balance the cells, and the embedded energy or ESOEI of the battery represents another 10% loss in efficiency, which means roughly a quarter of the energy is lost.

That makes the electric car pretty much identical in efficiency to a fuel cell vehicle running on biogas - with the difference that the biogas car is more easily refueled and has greater range, and it's lighter, cheaper, it has better heating, a range of options for fuel if CNG is not available...

If you get stranded in an electric car, you have to tow. If you get stranded in a CNG car, you can hook up a propane tank and go.
Eikka
2 / 5 (4) Jan 21, 2016
Electric cars won't require you hold your hand on the freezing nozzle while you're stainding out in the -25 and windchill.


There's a little locking lever in the handle. You stick the nozzle in, cock the lever and sit back in the car, then wait for the pump to stop.
Lord_jag
3.7 / 5 (3) Jan 21, 2016
There's a little locking lever in the handle. .

These ones?
http://www.ocregi...ger.html
"There are as many as 3,000 stations statewide that don't have latches on their pumps, according to the California Service Station and Automotive Repair Association, an industry advocate."

I haven't seen a pump with a lock in years.
Zzzzzzzz
5 / 5 (1) Jan 24, 2016
Getting back in the car while the gas is pumped can be very dangerous. Electrical charges can build up and discharge with a spark. Similarly filling a portable container in a pickup bed instead of on the ground can end up with the same kind of result.
I have filled cans in the back of my truck many times and lived to tell the tale, but about seven years ago saw a fire start that way. The resulting fire is large and agressive, and always kills the person making the mistake. It's rare enough, but since that I time I always put the cans on the ground. Nationally several people are killed each year by filling cans not on the ground, or by getting in & out of the car while the gas is pumping.
Zzzzzzzz
5 / 5 (1) Jan 24, 2016
Getting back in the car while the gas is pumped can be very dangerous. Electrical charges can build up and discharge with a spark. Similarly filling a portable container in a pickup bed instead of on the ground can end up with the same kind of result.
I have filled cans in the back of my truck many times and lived to tell the tale, but about seven years ago saw a fire start that way. The resulting fire is large and agressive, and always kills the person making the mistake. It's rare enough, but since that I time I always put the cans on the ground. Nationally several people are killed each year by filling cans not on the ground, or by getting in & out of the car while the gas is pumping.
greenonions
5 / 5 (1) Jan 24, 2016
Eikka
which means roughly a quarter of the energy is lost.
Perhaps - but if the vast majority of your charging is done at home. at work, or with a public charger that does not use storage - that is pretty irrelevant. We have owned a Leaf for about 3 months now. Wife uses it for her 25 mile round trip commute - and we run around some evenings and weekends. ALL of our charging is done on a level 1 home charger. It is working out fine. We need a gas car as backup - as the range is still not there - but give it a few years - and it will get there. So as the smart grid evolves - storage - as mentioned in this article, and home storage, and charging at home/work - will all be part of the evolving story. Poor Eikka - still stuck under the desk there.

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