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Sustainable Energy

How Can Electric Vehicles Go Farther Without More Batteries?

In hopes of decreasing the “range anxiety” that might inhibit the market for electric cars, researchers are looking for ways to squeeze more miles out the vehicles without significantly increasing their cost.

Some electric vehicles can go as far on a charge as a traditional car travels on a tank of gas. But they come at a steep price. The top-of-the-line Tesla Model S, which can go around 265 miles per charge (according to the U.S. Environmental Protection Agency), has a base price of $80,000; a Nissan Leaf with base price of $29,000 can travel only around 84 miles per charge. That’s because the Tesla has a bigger pack of batteries.

Tesla’s Model S charging.

Given that adding batteries to electric cars (or putting in bigger ones) can quickly drive up the price far beyond what the average consumer can afford, researchers are also pursuing other ways to extend the range. Here are some examples.

Compact Moto

A new motor developed by the Nanyang Technological University and the German Aerospace Centre could increase the range of electric vehicles by 15 to 20 percent. The increase is possible partly because this unit weighs less than traditional motors. It also is more efficient because the air-conditioning compressor can use energy regenerated from braking. This design would benefit drivers in tropical cities like Singapore, where the car’s air conditioning can eat up as much as half the battery power, the researchers say. The technology is in early stages; the team is applying for funding to make a prototype to test in Germany.

Predicting Range

North Carolina State University researchers think that better data analysis can help the drivers of electric cars plug in less frequently. Many owners of electric cars may not be driving as far as possible because they worry they’ll run out of power before reaching a suitable outlet. They get cues about their remaining range from a readout on the dashboard, but software in today’s cars might be underestimating the figure. That software estimates the range based on the amount of energy the car has consumed over a certain time period, says Habiballah Rahimi-Eichi of North Carolina State, who thinks he and his colleagues have developed a more accurate approach. The researchers have developed software that analyzes how much energy it will take to reach a driver’s destination when real-time conditions like traffic, weather, driving behavior, and the remaining charge in the battery are taken into account. Rahimi-Eichi (the lead author of a paper describing the software) and Mo-Yuen Chow presented the research at an Institute of Electrical and Electronics Engineers conference in November.

Refined Routing

A new navigation tool from engineers at the University of California, Riverside, could cut electric vehicles’ energy consumption in half on certain routes. The researchers are using real-time information about traffic flow and factoring in road type and grade to calculate the most battery-friendly trip. They say that in some simulations, they can get a car to use between 25 and 51 percent less energy than it would have if the driver determined a route on the basis of the shortest travel distance or the shortest travel time. The research is outlined in a report presented to the California Energy Commission.

Power Panels

Australian and U.S. researchers have developed body panels that can power cars. These flexible-film supercapacitors are made of graphene electrodes with a gel electrolyte between them. The material can be embedded within the frame of the car to provide quick jolts of power when the car accelerates, and they can be recharged within minutes with energy from braking. At first the technology could be used in addition to lithium-ion batteries in cars, as an extra power supply.

The team hopes that one day a car could be entirely powered by supercapacitors that could store more energy than a lithium-ion battery and run for more than 300 miles. But first the researchers would need to find the right materials to increase the charge that these supercapacitors can store, says Nunzio Motta, a principal research fellow at Australia’s Queensland University of Technology. The scientists must also find a new way to produce the graphene films quickly enough for mass production, he adds. The research was published in the Journal of Power Sources and Nanotechnology.

The Takeaway:

Batteries are the most expensive part of an electric vehicle, so making them cheaper will remain the most cost-effective way to extend the range. (Researchers are also pursuing several methods of increasing batteries’ power and lengthening their life span; see a previous Question of the Week, “Can We Get Better Batteries?”) Tesla Motors is building a “gigafactory” to ramp up lithium battery production and estimates it can halve the cost of its $70,000 Model S. Even so, that cheaper car would have a range of only 200 miles.

Thanks to Brendan Raftery for the idea. Do you have a big question? Send suggestions to questionoftheweek@technologyreview.com.

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