None of this would be an issue, of course, if EV battery packs weren't so big in the first place. The packs, often weighing more than 400 pounds, can have trouble releasing their heat, because they're so much bigger than laptop or cellphone batteries. That's why most electric car makers are employing complex active cooling systems that cellphones don't need.
"Can you put cooling channels" in an EV battery pack, Sadoway asked. "Sure. But they may not hit the price point you want."
Researchers are working on new chemistries that could supplant the lithium-ion formula, but such batteries are still a long way from production. Lithium-sulfur, which is said to have higher energy and better heat characteristics, could reach production for small products, such as laptops, in the next 10 years. Lithium-air, long talked about as a high-energy replacement for lithium-ion, might be two or three decades from widespread use, Cairns said. Batteries based on other metals, such as magnesium, are also under consideration.
The bottom line is that today's technology of choice may be facing challenges ahead. Automakers are relying on a steep drop in battery cost to help electric car sales take off. And additional safety constraints aren't going to help them reach their cost targets, especially since cost was already an issue before the Volt fires.
"My position is that we must get beyond lithium-ion for vehicles," Cairns said. "The lithium-ion systems of today are inherently too expensive and too low in energy for electric vehicles. If we use lithium-ion as we now know it, the EV will always be a specialty vehicle."
For a deep look a GM's Chevy Volt, we recommend you go to the Drive for Innovation site and follow the cross-country journey of EE Life editorial director Brian Fuller. In the trip sponsored by Avnet Express, Fuller is taking the fire-engine-red Volt to innovation hubs across America, interviewing engineers, entrepreneurs, innovators, and students as he blogs his way across the country.
Many good comments by various folks! Here are my responses to a few:
Alexander: fuel cells are still ridiculously far from being a cost-effective automotive power source (using ANY fuel, but hydrogen is easiest to implement as far as fuel cells go). They are also still very low power density - so they need to be large if you want realistic horsepower. I think we will see some applications in fixed installations long before any automotive applications.
Jerry: I agree completely - while a "miracle" breakthrough battery would be nice...there are many things that can be done to reduce the energy needed to move the car and therefore make it easier to have a practical and cost-effective EV. see: http://www.edison2.com/blog/month/january-2012 These guys won the "automotive X-Prize" usign an ethanol burning engine...but now have an interesting prototype EV version. 114 mile range on 10.5 KWh's. However, I'll also point out that the low weight and drag of their design also gives awesome performance using fuel-burning engines too.
After researching all the related issues deeply, I find myself scratching my head about what problem the EV zealots think they are solving. First, modern engines are more efficient than most articles say - the Prius is ~38% efficient, and future versions will certainly acheive over 40%. That is higher efficiency than the average coal power plant, and in fact higher than the USA average grid efficiency (coal & natural gas to electricity conversion). The "elephant in the closet" is that EV's do not save energy vs. fuel burning cars (although they do shift from oil fuel to coal+natural gas).
A much more practical solution is to create a liquid synthetic fuel that will supercede gasoline, but leverage all the existing infastructure and vehicle technology. In the short-term, this could be synthesized from coal and natural gas (cut out the "middle man" of the power plants). Longer-term, solar-synthesized fuels or biofuels would create a renewable fuel that has all the conveniences of gasoline without the huge trade-offs of EV's.
Chuck, thanks so much for the link. I want to cover this topic more from the materials standpoint, since there seems to be a lot of research going on, and I want to make sure I focus on what's most useful to our readers.
Actually, lithium-ion is today's leader, which is why all the automakers are using it. Lithium-sulfur and lithium-air, two long-range contenders, are so far off that not much has been written about them yet. Here's a starting point on the challenges of Lithium-ion.
The question of money is a really important one. My feeling is that we need more battery research -- lots more. Lithium-ion has an energy density that's about 1/80th that of gasoline. We don't need to build a battery with an energy density that matches gasoline's, but it would be nice to get closer. And that isn't going to happen by tweaking lithium-ion. The only real answer that I can see is research.
Chuck, I remember GaAs. It was the material of choice for not only Cray processors but some really high-speed networking chips way back when only huge companies could afford them, and could afford the associated cost. Although it didn't win out as the material of choice, I think it helped spur forward-thinking innovation of the type you mention by showing that at least those speeds were possible, and forming a competitive alternative.
Silicon has won out over several other materials for various specialty chips, most lately active PV solar cell wafers, primarily because it's so cheap and abundant, and because it got there first in manufacturing, that chip makers have been highly motivated to make it keep working so they can keep getting ROI for their enormous fab cost outlays.
Battery materials, OTOH, appear to be so complicated and diverse that I don't think this model applies. It sounds like many different approaches need a lot of money and innovative thinking thrown at them.
Ann: Indeed, changes in materials really have historially messed things up for electronics manufacturers. Consider the great Seymour Cray: He believed he could get past all the technical difficulties associated with gallium arsenide and build supercomputers with it. If anyone could have done it, it would have been him. But he's gone (unfortunately) and silicon is still the material of choice.
That's a really good point, Ann. If we're going to make a competitive vehicle battery, we're going to need a "battery miracle," as Gates has said. And I think the only way we'll get there is to heavily fund forward-thinking battery research. This is a really sticky, difficult problem and I don't believe it will get solved without a concerted effort.
Chuck, thanks for the link to Gates' talk on Moore's "Law" (Moore himself said it was only an observation). Aside from pointing out how we have misunderstood Moore's statement, Gates also mentions briefly that batteries have "deep physical limits" to improvement, and that the problem may not be economically solvable. I just hope throwing lots of money at it in 50 different startups may result in something useful.
As a LEAF owner I am disappointed that zero analysis of the Nissan battery design was mentioned. While Tesla was critical of the LEAF battery cooling system (there isn't one) the choice of keeping a system simple by avoiding the need for cooling and hence the need for coolants not only improves the cost, it also provides an improvement in safety and reliability with a simpler system.
A half century ago, cars were still built by people, not robots. Even on some of the countryís longest assembly lines, human workers installed windows, doors, hoods, engines, windshields, and batteries, with no robotic aid.
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