Toyota lowers hybrid car emissions with SiC power semiconductors

Last updated on March 21st, 2018

Toyota has recently announced that it is having success in using a rather new technology called “silicon carbide”  (SiC) power semiconductors in its hugely successful hybrid cars such as the Prius, Lexus, Camry, Highlander, and others.  This technology will reduce emissions by increasing the efficiency of the energy conversion processes in Toyota’s hybrid cars.

The new technology will be used in the complex computer-driven power controllers which govern the different phases of power conversion involved in charging the batteries of the hybrid car. Choosing the mix of gas and electric which is most efficient.  There is a great deal of energy loss in the various phases of converting mechanical to electrical energy and vice versa, and the SiC power semiconductors replace earlier, less efficient components used in the power conversion processes.

Toyota, which is conducting practical tests on the new components now, is optimistic that the use of the SiC power semiconductors will result in a significant decrease in the energy loss in, for example, charging the batteries from the braking energy.

Toyota is universally recognized as the premier pioneer of using “hybrid” technology to improve the efficiency of gasoline-powered automobiles.

Hybrid cars, like the Toyota Prius, are using several of technologies designed to reduce the energy loss which is unavoidable in converting gasoline into power for a moving vehicle.  Toyota’s take on this technology is one of many methods to combine internal combustion engines, like the typical automotive engine, with electric motors, braking energy recapture, and other techniques.

I recently bought a 2007 Toyota Highlander Hybrid, a largish crossover SUV which is available with several drivetrains, including the hybrid drivetrain of my car.

This is a big, heavy car.  The hybrid drivetrain adds about 35hp to the mix when accelerating, it can drive the car by itself at low speeds (giving a weird experience), and it gives a combined 26-27mpg as compared to perhaps 20-21mpg for a comparable gas-only car from 2007.  And it gets about the same mileage in town as on the highway.  The acceleration to 60mph is one second faster than for the standard Highlander.

The drivetrain is very smooth, and it is fascinating to watch the dashboard energy diagram, which is a submenu of the trip computer.  The diagram shows a wheel, an engine, and a battery.  Arrows, updated in real time, show when the car is running on gas alone, electricity alone, together, or when the battery is being charged by the regenerative braking energy subsystem or when going downhill.  You can test the system in different real-world scenarios and see directly what the average mpg is at different speeds, and how the system optimizes usage to achieve that.

The hybrid system saves energy and emissions by stopping the motor at stoplights and while you are waiting in line at your local Burger Lord. And the energy used in braking is partially recaptured by a system of motor generators which are governed by the power control system.  The superior capabilities of the SiC power semiconductors will add several percents of efficiency to the battery charging process.  Several presents (and it may be considerably more when the product development process is complete) do not sound like much, but it is through incremental advances like this, year in and year out, that Toyota has developed the most efficient hybrid system presently available.

Hybrid technologies are only now making their breakthrough in the automotive world.  However, similar technologies have been in use for decades in trains, cranes, and other heavy applications.  Hybrid technologies have proven their ability to save much energy and it seems likely that most or all cars will be using some form of hybrid technology ten years from now.

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