In an effort to improve energy efficiency and reduce carbon emissions, carmakers have turned to electrification, both in the form of hybrids, as well as battery electrics and fuel cell electrics. Electronics, and the software that inevitably accompanies them these days, provide a much broader and more flexible creative palette for designers compared to the legacy mechanical systems that are still showing a surprising amount of efficiency improvement. As Mike Robinson , GM’s VP of Sustainability and Global Regulatory Affairs recently said, “climate change, energy security, and congestion challenge our environment and our industry, but we see value in the disruption.” Indeed, the industry has certainly responded with a substantial wave of innovative products.
Electronics, which have truly exploded into every facet of modern life, have primarily focused on functionality first, followed by cost, with efficiency lagging somewhere down the line. That leaves a lot of opportunity on the table as carmakers not only realize the inherent efficiency benefits that come from electrification, but also invest in further improving the efficiency of some of the key electronic components.
That’s exactly what Toyota has been doing in their Central R&D Labs, and in collaboration with electrical supplier Denso. An early result of this research is a new Power Control Unit (PCU), the chip that manages the exchange of power between the motor, the battery and the regenerative braking system found in hybrids. According to a recent announcement, this relatively small change could improve the fuel economy of the already efficient hybrids, by as much as 10%,
While electric power-trains are far more efficient that internal combustion engines , there are power losses, usually given off as heat. Approximately 20% of those losses take place in the power electronics. Researchers at Stanford and elsewhere are investigating ways of recovering waste heat in cars using thermoelectric generators that can turn it back into power. Given that any such modification will be less than 100% efficient, avoiding the heat loss in the first place is probably the best bet.
Toyota’s modification will also reduce the weight of the PCU from around 40 pounds, to less than nine pounds. This, in turn, will further improve fuel economy through a process called mass decompounding. In essence, lighter vehicle components require a lighter chassis to support them, which, in turn requires a smaller engine to accelerate. That smaller engine is also lighter, which requires an even lighter chassis, and so on.
The smaller unit could possibly extend the range of vehicles that could be hybridized, to include smaller cars.
The new PCU will be made from silicon carbide, a semiconductor material that has lower resistance and, compared to conventional silicon-only devices, reduced power loss when switching on and off, particularly at high frequency. This, in turns requires smaller circuit elements like capacitors and inductors to stabilize the system.
Improvements of up to 5% have already been demonstrated in prototypes. The company expects to have these new units on the market by 2020. Test vehicles will be on the roads in Japan within a year.
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