Hybrid and all-electric vehicles are getting a lot of design attention and interest -- with good reason. They offer an alternative to the conventional internal combustion-powered vehicle. Whether there really is an energy advantage is debatable. (See this blistering IEEE Spectrum article.)
For EVs, the recharging is done at fixed stations and takes considerable time. There's no avoiding the realities of power and energy transfer rates and density. But there may be limited, niche situations where electric power can reduce local pollution, such as buses plying well-defined routes. Trials are under way now in South Korea where buses (shown below) recharge from the roadway as they travel. The energy is directed using specially shaped coils.
As they travel, these prototype buses (now in testing) recharge from coils buried in parts of the roadway.
The recharge-on-the-go system eliminates the need to recharge or replace internal batteries, a process that leads to long idle periods.
(Click here for a full-size image.)
There's no need to stop and charge the batteries, swap battery packs, or conduct any of the other activities that reduce vehicle use. You can read reports about these online electric vehicles in The Wall Street Journal (subscription required), IEEE Spectrum, Korea.net, and CTV News. Note that, as it is used here, the term "online" has nothing to do with the Internet.
The system and buses, developed by the Korea Advanced Institute of Science and Technology, are projected to have a 14-year return on investment, but I suspect there are so many unknowable variables and assumptions in this assessment that it is almost meaningless.
The distance from the roadway to the receiving coil is eight inches (20cm), and the bus has 100kW capacity. It's especially interesting that the entire roadway path does not have to be engineered and retrofitted to radiate power. The developers say only 5-15 percent needs to be. The prototype test buses are fairly expensive, but it's hard to say what a true mass-produced version would cost.
Then there's efficiency. Engineers know that is both the area of greatest concern and the largest opportunity to be somewhat selective in the data cited. The people running the Korean trial system say the efficiency rate is 85 percent. That's pretty impressive, but is it just the coil-energy transfer under ideal conditions? What about realistic, less-than-ideal conditions? What about losses in the rest of the power subsystem? It will be interesting to see some solid test data and analysis.
Back in the day when popular science magazines predicted that nuclear power would make electricity so cheap that utilities wouldn't even bother to meter it, there was also lots of discussion about similar powered roadways. Buried wires would provide the energy your car needed without physical attachment (unlike trolleys or electrified tracks). We know that didn't happen for many reasons, and it is highly unlikely to be in our future, but you should never say never, right? Perhaps an updated, limited-focus implementation of that idea would make sense on specific, repeated routes.
What's your view on this approach to EV power? Is it a great idea, delusional, or somewhere in between?