Stanford system could allow EVs to recharge from the road, while moving
By C.C. Weiss
February 6, 2012
The greatest obstacle standing in the way of electric-vehicle adoption - besides crafty, deceitful right wingers - is limited range. Electric vehicles can only travel 100 miles (161 km) on their best day. Because of the lack of electric charging stations and the amount of time involved in charging a battery, they just can't go as far as gas vehicles. A team of researchers at Stanford University recently made an important discovery in wireless charging technology. Their work could one day help solve the limited-range dilemma.
According to the US Department of Energy's alternative fuel station finder, there are about 5,500 electric charging stations across the United States. That number should balloon into the five figures by the end of this year, but the extra stations will solve only a tiny part of the greater range dilemma. Most of the charging stations built or planned are Level 1 or Level 2 stations. The Alternative Fuels and Advanced Vehicles Data Center estimates that a Level 2 charging station can add about 10 to 20 miles (16 to 32 km) of range to an EV's battery in an hour. Such a little amount of charge in such a long time makes Level II stations impractical for anything much more than emergency fill-ups.
DC fast-charging stations, which make up a very small percentage of today's charging infrastructure, are the more practical solution, but even these are much slower than gas fueling. These stations are powerful enough to deliver 80 to 100 percent of a battery's charge within about half an hour - much better than a Level 1 or 2 station, but still a long time to wait for an extra 75 miles (121 km) of range. Even with these stations, long road trips will be impractical or impossible for many drivers and families.
One of the potential solutions that may make electric vehicle driving easier in the future is highway-integrated wireless-charging equipment. We covered a Korean wireless charging system several years ago, and now researchers at Stanford University have made a breakthrough of their own. The researchers believe that a magnetic resonance system that they developed holds the key to offering a steady wireless charge to moving electric vehicles.
The researchers built on work performed at MIT in 2007, which used magnetic resonance to power a light bulb 6.5 feet (2 meters) away - even while there were objects between the source and receiving coils. Stanford's researchers wanted to see if a similar system could be used to send more power. They aimed to send 10 kW between the source and receiving coil, which they believe would keep a vehicle charged while it moves at highway speeds.
The Stanford team used computers to experiment with the optimal design for a system that could effectively transfer 10 kW to a moving car. They found that a source coil with a 90-degree bend atop a metal plate could transfer the necessary 10 kW to an identical coil equipped to a vehicle 6.5 feet (2 m) away. They achieved transfer efficiency of 97 percent, much higher than other wireless systems, and believe that they can eventually reach higher efficiency by tweaking the design.
While the computer simulation is but a small step toward a road-integrated wireless charging infrastructure, the researchers have filed a patent on their system and plan to move toward laboratory and real-world driving tests. Extrapolated from their simulation, the system would consist of series of electrically charged coils embedded into the asphalt in roads. These coils would constantly charge electric-vehicle batteries during driving.
Study co-author Richard Sassoon, the managing director of the Stanford Global Climate and Energy Project (GCEP), explained to the Stanford Report: "What makes this concept exciting is that you could potentially drive for an unlimited amount of time without having to recharge. You could actually have more energy stored in your battery at the end of your trip than you started with."
Sassoon's quote suggests that the magnetic system would not only help with the range issue, it could virtually solve it. If this technology were one day implemented on interstate and major state highways, it would allow electric vehicles to make longer road trips even more seamlessly than gas vehicles.
The research team has also started collaborating with the engineering department to begin looking at the intricacies and problems related to designing roadways with these coils installed. Of course, they also need to determine that the magnetic system is safe to use in a real world environment and won't result in radiation harmful to humans or electromagnetic interference that could affect vehicular electronics.
You can read the study here, but be forewarned, it's not the lightest read for non-science/math-minded folks.
Source: Stanford NewsShare
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