Chargers for electric vehicles could be getting much smaller and more energy-efficient, if technology developed by scientists at North Carolina State University reaches consumers. The system may also allow for considerably quicker charging times.
In a regular 50-kilowatt vehicle charger, a 1,000-kg (2,205-lb) distribution transformer draws power from a utility medium-voltage line, then reduces the voltage to 480 volts so it can be used by a 200 to 600-kg (441 to 1,323-lb) fast charger. That charger in turn converts the AC voltage to DC, making it compatible with the vehicle's battery.
By contrast, NC State's new 50-kW medium voltage fast charger (MVFC) performs the tasks of both the transformer and the fast charger, as it takes power directly from a medium-voltage line and converts it for use in a battery. Made possible by the use of wide bandgap semiconductor devices, this design results in a charger that juices vehicles up just as quickly as a regular model, but is only one tenth the size – it weighs about 100 kg (220 lb), and can simply be mounted on a wall or pole.
Besides being smaller and lighter than its conventional counterparts, the MVFC is also more energy-efficient, losing less power in the form of heat. Whereas the efficiency level of regular chargers tops out at 93 percent (meaning seven percent of the power is lost as heat), the NC State prototype reportedly manages 97.5 percent.
The researchers now plan on building a 1-megawatt five-port charger, that could deliver a maximum of 350 kilowatts per port. It will draw power from a utility line that is directly connected to a solid-state transformer, which in turn feeds a local DC microgrid. Multiple vehicles could be charged by the device simultaneously (although presumably not all five at the 350-kW maximum), plus the university claims that the charging of a single vehicle should be up to seven times faster than is currently possible with a 50-kw charger.
Industry partners are now being sought to help bring the technology to market.
Source: North Carolina State University
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