If you can't beat stop-and-go traffic in India and China, you might as well join it, but only if you're driving a hybrid car. The resulting fuel savings of about 50 percent are greater than what drivers experience in the United States and could make a big difference in countries experiencing a rapid growth in the number of cars on the road, according to recent U.S. Department of Energy research.
Hybrid cars offer 47 to 48 percent in fuel savings over conventional cars in India, according to two new papers by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory. The simulations also showed that Chinese drivers could reap 53 to 55 percent in fuel savings by taking the wheel of a hybrid. The fuel savings come from three factors—regenerative braking, turning off the engine in a stopped or low-power condition, and the hybrid electric motor and batteries allowing the engine to operate at higher efficiency.
"We weighed the importance of these three mechanisms against each other for the Indian vehicles, and found that the ability to increase engine efficiency was the most important reason, second was regenerative braking, then engine shutdown," Samveg Saxena, a researcher in the Grid Integration Group at Lawrence Berkeley National Laboratory and a coauthor on the new studies, said in a press release.
The simulated results for India and China compare favorably to hybrid car fuel savings of about 40 percent when driving in typical U.S. traffic conditions.
U.S. fuel efficiency ratings use drive cycles that include about 55 percent city driving and 45 percent highway driving, but those cycles are different in India and China. To accurately reflect the situations there, researchers had to simulate the drive cycles for New Delhi and Pune in India and compare the results to the Modified Indian Drive Cycle, the test used for India's official fuel economy rating. For China, the researchers simulated drive cycles in 11 cities and tested three possible hybrid powertrains.
"With the official fuel economy test procedure currently used in India, fuel savings for hybrids are fairly grossly underestimated, showing only a 29 percent savings over conventional vehicles," said Anand Gopal, a senior scientific engineering associate in the International Energy Studies Group at at Lawrence Berkeley National Laboratory, and lead author on the studies. "The test cycle is not representative of driving conditions in India, so that's sending the wrong signal to the consumer."
(The Modified Indian Drive Cycle is based on the European Drive Cycle with the maximum speed reduced to 90 kilometers per hour. The European Drive Cycle includes four repeated urban driving cycles and a highway driving cycle. But researchers have shown that the Modified Indian Drive Cycle does not match up well with real-world driving patterns. For instance, the average speed for driving tests carried out in Pune were 16 percent lower than the average speed in the official drive cycle. The average acceleration and deceleration in the Pune drive cycle were 120 percent higher and 133 percent higher, respectively.)
Gopal and his colleagues used their powertrain simulation model, named Autonomie, to create hypothetical hybrid versions of top-selling conventional cars—the Maruti Alto in India and the Buick Excelle in China. The results for India are detailed in the January issue of the journal Applied Energy, and those for China have been accepted for publication in the International Journal of Powertrains.
Such results may not surprise anyone, but both India and China may have to take additional action if they want to encourage drivers to buy hybrid cars—vehicles currently viewed as higher-end products. Hybrids also won't solve the road congestion problems and epic traffic jams that currently plague drivers in both countries. For that governments will have to expand road infrastructure, improve public transit options or take steps to alter driver behavior. But for now, many Chinese commuters have voted with their wallets by snapping up millions of electric bikes as a cheaper, more agile form of transportation.
Jeremy Hsu has been working as a science and technology journalist in New York City since 2008. He has written on subjects as diverse as supercomputing and wearable electronics for IEEE Spectrum. When he’s not trying to wrap his head around the latest quantum computing news for Spectrum, he also contributes to a variety of publications such as Scientific American, Discover, Popular Science, and others. He is a graduate of New York University’s Science, Health & Environmental Reporting Program.