One of the limitations on fast charging is how much current the cable can carry from the charger to the EV.  It’s a problem of heat dissipation.  The more heat, the higher the resistance and the more dangerous the cable becomes.  The usual solution is to get a thicker cable, but that also means a heavier and less wieldy cable.  Or increase the voltage to push more energy down a small cable.  But there are probably valid concerns about just how high a voltage one would want an individual handling.

Researchers at Purdue University tackle the problem in a different way—introducing a simple way to cool a cable.  They have been testing a way to use a special liquid that will boil at low temperatures to keep a cable relatively cool.  The liquid-to-vapor phase change keeps the liquid at safe temperatures and the “bubbling” action provides a way to for the liquid to flow up and down the cable.  No pump is required.   Clever.  The team has demonstrated the effectiveness of this scheme to allow current up to 2400 amps in a relatively lightweight cable.  This is much higher than the 500 to as much as 800 amps in the fastest chargers announced to date.  

It turns out this innovation has been hard to tackle.  But it is based on an old idea.   Many automobiles at the start of the twentieth century were water-cooled but had no water pumps to circulate the water.  Instead, the water moved by convection and ended up in a big radiator where the water boiled and was re-condensed.  The industry came up with the lyrical term “ebullient cooling” for this system.  Eventually as engines became more compact and higher horsepower, a water pump was necessary to boost the flow to ensure enough cooling.  However, lots of farm equipment, mostly stationary engines, continued to use ebullient cooling for decades.  The adaptation for cooling a cable has taken the Purdue team over 37 years to master, but now they think it is ready for prime time.  

Thomas Hall


Gary Simon is the Chair of CleanStart’s Board. A seasoned energy executive and entrepreneur with 45 years of experience in business, government, and non-profits.

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