Article lent by Purdue University.
WEST LAFAYETTE, Indiana – Purdue University engineers have invented a new, patent-pending charging station cable that can fully recharge certain electric vehicles in less than five minutes – about as long as it takes to fill up a gas tank.
Today, chargers are limited in how fast they can charge an electric car’s battery due to the danger of overheating. To charge an electric car faster, a higher current must be run through the charging cable. The higher the current, the greater the amount of heat that must be removed to keep the charging cable running. The cooling systems that chargers currently use only remove so much heat.
Using an alternative cooling method, Purdue researchers have designed a charging cable that can deliver a current of 4.6 times as fast as the fastest available EV chargers on the market today by removing up to 24.22 kilowatts of heat. The project was funded by a research and development alliance between Ford Motor Co. and Purdue.
The charging time for electric cars can vary greatly today, from 20 minutes at a station along a road to hours using a charging station at home. Waiting times and the location of the charger are both mentioned as major sources of anxiety for people considering owning electric cars.
“My lab specializes in coming up with solutions for situations where the amount of heat produced is far beyond the capabilities of today’s technologies to remove,” said Issam Mudawar, Purdues Betty Ruth and Milton B. Hollander family professor in mechanical engineering.
“Ford is committed to making the transition to electrification easy,” said Matt Stover, director of charging, energy services and business development at Ford. “We are pleased to support Purdue’s research, which has the potential to make ownership of electric cars and commercial fleet more appealing and accessible.”
Although the prototype has not been tested on electric cars yet, Mudawar and his students demonstrated in the laboratory that their prototype can hold a current of over 2,400 amps – far beyond the minimum requirement of 1,400 amps that would be needed to reduce the charging time of large commercial electric cars to five minutes. The most advanced chargers in the industry only supply currents up to 520 amps, and most chargers available to consumers support currents of less than 150 amps.
Ultimately, the charging time will depend on the power output values of the power supply and charging cable and the power input value of the EV battery. To achieve a charge of less than five minutes, all three components must be rated at 2,500 amps.
The prototype also mimics all the features of a real-world charging station: it includes a pump, a pipe with the same diameter as an actual charging cable, the same controls and instrumentation, and it has the same flow rates and temperatures.
Mudawar’s laboratory intends to collaborate with manufacturers of electric cars or charging cables to test the prototype of electric cars within the next two years. The test will determine more details about charging speeds for specific models of electric cars. A video about the project is available on YouTube.
Removing more heat to shorten EV charging time
EV charging stations and other types of electronics rely on liquid cooling systems to remove heat from their wires. Increasing the current through a charging cable using this method would require larger conductive wires and more liquid coolant, making the cable heavier and difficult for customers to handle.
For the past 37 years, Mudawar has been developing ways to cool electronics more efficiently by taking advantage of how liquid traps heat when boiled to a steam. By capturing heat in both liquid and vapor form, a liquid-to-vapor cooling system can remove at least 10 times more heat than pure liquid cooling.
These cooling advantages make it possible to use a smaller wire diameter inside the charging cable and at the same time divert a higher current. Research articles on the team’s experimental demonstration of the charging cable prototype and the cooling method it uses have been published in the International Journal of Heat and Mass Transfer.
Despite decades of research into liquid-to-vapor cooling, no industry has begun using these systems, however, because studies such as those conducted by Mudawar’s laboratory are necessary to understand how best to implement the technology.
“The industry has a gap in the knowledge and expertise needed to switch from pure liquid cooling to liquid phase shift cooling. How do you design the system? What type of equations do you use to optimize it? But we have this knowledge through our extensive research,” Mudawar said. .
In addition to electric cars: aircraft and spacecraft
Based on what Mudawar and his students observed from experimental demonstrations of their prototype, liquid-to-vapor cooling is so efficient at removing large amounts of heat that electric cars could be charged in far less than five minutes using this technology.
“The industry does not really need electric cars to charge faster than five minutes, but we think we can increase the power even more by changing both the state of the incoming liquid and the design of the cooling space around the conductor wires in the charging cable,” said Mudawar. .
The prototype’s ability to remove far more heat than other chargers was not a surprise to Mudawar. “My lab has developed solutions that use liquid phase change technology for many applications, including in aerospace and defense. We knew how skilled the technology is,” he said.
Similar to the prototype of the EV charging cable, the systems designed by Mudawar’s laboratory for aircraft allow aircraft electronics to dissipate large amounts of heat, increasing their performance. Mudawar also has projects funded by NASA to increase the cooling capacity of rocket engines and spacecraft.
The researchers have filed a patent application for their charging cable invention through the Purdue Research Foundation Office of Technology Commercialization and are looking for additional industry partners to continue the development of the technology.
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