NREL Senior Engineer Ken Kelly monitors testing of a Toyota hybrid system drive.
A Better, Cheaper Hybrid
June / July 2009
Volume 7 Number 3
Is electrification the next big thing? Even in Detroit, the answer is a hopeful yes. The auto industry reflects the overall U.S. economy's critical condition with 4th quarter new vehicle sales plunging by more than one-third. But thanks to fresh memories of $4 per gallon gasoline and global warming concerns, sales of hybrid cars dipped just 10 percent.
Now the buzz on this year's auto show circuit is about really new cars—€”plug-in hybrids, gas-electric hybrids, electric cars and more. Toyota still controls 70 percent of the U.S. hybrid market. But nearly every major brand has more than one hybrid design to showcase. Chrysler has two new concepts. Honda has four. Mercedes-Benz has four, including one that would be powered by a fuel cell.
Chevy will begin production of its plug-in electric Volt in 2010, and is working with cities now to prepare charging stations.
Together they suggest a very different transportation lineup in the next decade.
At the National Renewable Energy Laboratory in Golden, Colo., engineers are exploring several ways to improve hybrid performance to such a convincing level that millions of commuters will make the switch. To NREL, that means increasing the vehicles' consumption to 100 mpg or more, improving reliability and reducing costs—€”all while operating with drastically reduced tailpipe emissions.
"The real answer isn't Detroit making the right car but the consumer deciding they want the right car," said Rob Farrington, manager of NREL's advanced vehicles program.
In the Advanced Electronics Laboratory, research engineers are exploring key components of the electric drive systems. Their ground-floor, windowless research unit is about the size of a large suburban garage. There isn't an intact car in sight, however. Instead, researchers are testing key power components at bench stations, including motor controllers, AC to DC converters, and inverters that condition the electrical signal between the power generation unit (a fuel cell or battery) and the electric motor to provide power to various components. No single improvement will make the difference. But combined, the results can help automakers overcome technical barriers that can delay the successful commercialization of advanced vehicles.
"About one-third of the incremental cost of hybrids is in its power electronics," said senior engineer Ken Kelly, task leader for the advanced electronics lab. "We need to process that electricity in ways that are reliable and extend the range of the vehicle. That's what this lab is all about."
On one bench, engineers are testing the performance of a Toyota hybrid system drive. It already works at 90 percent efficiency. But heat is an enemy; the vehicle's efficiency dips as the coolant temperature increases. If it could run cooler, it would run longer. And it could be manufactured using less expensive materials.
Kelly's group is experimenting with heat exchangers made of different layers, including graphite and indium.
"One third of your radiator's capacity is used to cool the vehicle's electronics," Kelly said. "People want to package things smaller and powerfully. That means there is more heat in a small space. So the challenge is growing to get heat from the device to the coolant."
In a separate heat-related experiment, senior engineer Sreekant Narumanchi is exploring advanced materials for the interface between power electronics components. Silicon chips in power electronics typically rest on a metal base plate that conducts heat away from the chip. Coolant flows underneath the plate to carry away the heat. The heat transfer is aided by a very thin layer of "grease" spread between the parts.
"Even though the layers fit together, there are little gaps that cause resistance to the transfer of heat," Narumanchi explained. "The grease is used to close those gaps. It's a much better conductive pathway than air." Automakers don't use conventional grease containing animal fats; typically it's a silicon gel containing aluminum particles and other inorganics. The gels' performance eventually suffers under the heat and pressure generated inside the engine in harsh conditions such as summertime rush-hour traffic.
In extended tests, Narumanchi is precisely examining new gels that include different metals, graphite and even advanced ingredients such as carbon nanotubes. The bench-scale equipment simulates years of high-temperature conditions and temperature cycling over weeks.
"Our target is a material that will perform for 15 years," he said.
Joseph B. Verrengia is a senior administrator in the NREL public affairs office.
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The Evolution of the Electric Car
From what we understand today, electric motor power started in 1834 when Thomas Davenport of New Hampshire built a carriage running on rails that used a non-rechargeable battery. Viable rechargeable batteries did not come into existence till the late 1840s, with the development of the lead acid battery. In England a patent was granted in 1840 for the use of rails as conductors of electric current.
Electric cars started to become popular because they were quieter and ran more smoothly than other cars. After improvements to storage batteries, electric cars started to flourish. However, these were mainly in Europe only. It was not until 1890 that America paid any attention to the growing technology. The first commercial application of an electric car came in 1897 when the Electric Carriage & Wagon Company of Philadelphia built a fleet of New York taxis. Until 1899, electric cars held the land speed record. At the turn of the twentieth century, they were produced by Anthony Electric, Baker Motor Vehicle, Detroit Electric, Woods Motor Vehicle and others and at one point in history outsold gasoline-powered vehicles.
Baker Motor Vehicle Company was a manufacturer electric automobiles in Cleveland, Ohio from 1899 to 1914. The first Baker vehicle was a two seater with a selling price of of $850. One was sold to Thomas Edison as his first car. Edison also designed the nickel-iron batteries used in some Baker electrics. These batteries have extremely long lives, and some are still in use. In 1906 Baker made 800 cars, making them the largest electric vehicle maker in the world at the time
The last Baker cars were made in 1916, but electric industrial trucks continued for a few more years. Baker, Rauch & Lang went on to make the Owen Magnetic under contract.
Founder Walter C. Baker's Torpedo land speed record racer was the first car to have seat belts. The car was capable of over 75 miles per hour.
The early twentieth century was the height for the American electric car. Many factors contributed to the downfall of the electric car, but the final blow seems to be the production of the gasoline car by Henry Ford. His mass-produced cars cost half as much as the average electric car. The electric car was dead until the 1960s.
The 1947 invention of the point-contact transistor marked the beginning of a new era for EV technology. Within a decade, Henney Coachworks had joined forces with National Union Electric Company, the makers of Exide batteries, to produce the first modern electric car based on transistor technology, the Henney Kilowatt, produced in 36-volt and 72-volt configurations. The 72-volt models had a top speed approaching 60 mph and could travel nearly an hour on a single charge. Despite the improved practicality of the Henney Kilowatt over previous electric cars, it was too expensive, and production was terminated in 1961. Even though the Henney Kilowatt never reached mass production volume, their transistor-based electric technology paved the way for modern EVs.
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