I was catching up on episodes of The Daily Show that I have fallen behind on over the last couple of weeks, when I came across an interview from the other week that I thought was a little interesting. Jon Stewart was interviewing a Harvard physics professor about her new book, and he was trying to ask some relevant science questions, but you could tell he was in a little over his head. I give Jon an A for his effort, he tried ask what he felt were legitimate questions about how science is used to shape government policy; however, his guest was less than helpful with her answers.
The question that was asked that I'll take the time to address is the one about why we are still using internal combustion engines when it seems like there are so many better alternatives. Why we continue to use fossil fuels when we have developed more environmentally friendly alternatives is a simple question with a complex answer. The basic answer to the question is that we continue to utilize fossil fuels to power our cars is because we do not have a better alternative that is cost-effective on a commercial scale. The two most promoted alternatives to fossil fuels are fuel cells or plug-in electric cars.
The biggest challenge that we face to realizing a plug-in electric car is battery technology. Currently there are two high profile plug-in all electric cars, the Tesla and the Nissan Leaf. While each car utilizes a slightly different battery design, they are both basically lithium-ion batteries, similar to the batteries that are in your laptop or cell phone. While the amount of electricity that can be stored is pretty much dependent on how big the battery is, what limits the use of rechargeable batteries is the time that it takes to recharge them. Right now it takes between 4-8 hours to fully recharge the car, depending on the voltage of the recharging outlet, the higher the voltage the less time it takes.
While this time is fine for recharging the car at home at the end of the day, it does not work if the car is being used on a long trip, say from Atlanta, GA to Nashville, TN. This is a trip of about 250 miles, and is within the maximum range of 300 miles that the Tesla claims. The recharge problem comes in we get stuck in traffic or don't start the trip with a full charge. In order to recharge any battery quickly we would have to add a lot of electrons in a short time, this leads to the generation of significant amounts of heat. Automotive engineers call this build up of heat a thermal event, you and I call it a fire.
In order to solve this problem of heating researchers are experimenting with new materials for batteries as well as new structures for how the battery is constructed. These early results show a lot of promise for decreasing the amount of heat that is generated when the battery is recharged. If these new technologies work as well at full scale as they work in the lab then we would be able to recharge a battery large enough to power a car in 10-15 minutes. While it seems like this solves the problem, there is a more subtle and practical problem to consider. In order to recharge the battery in that time we would need to have a wire that is about 5" in diameter. Imagine trying to pick up a copper wire that is as about the size of a cantaloupe. Even if we can solve the recharge time for a battery from a heat dissipation stand-point, we then have to figure out a way to get the electrons into the battery that is practical, try picking up a wire that will weigh several hundred pounds.
Fuel cells provide a more practical alternative to powering our cars. In a fuel cell we use a type of chemical reaction called an oxidation-reduction reaction to generate electricity. The particular fuel cell that is commonly promoted is the hydrogen fuel cell. The biggest advantage is that the "waste" from a hydrogen fuel cell is clean water and heat. The problem with the hydrogen fuel cell as an alternative to fossil fuel is where do we get our hydrogen from? Currently, we get almost all of the hydrogen that we use by processing natural gas and other fossil fuels. Until we can develop a better source for hydrogen, using a hydrogen fuel cell does not get us away from fossil fuels. While it is possible to get hydrogen by splitting water molecules into hydrogen and oxygen, this requires a tremendous amount of energy. A better alternative would be a fuel cell based on methanol.
Methanol has a couple of advantages over hydrogen. Since methanol is a liquid, we can use much of the same infrastructure that we currently use to transport gasoline. Methanol is also the product of fermenting cellulose; this is bulk of most plants. By fermenting the cellulose into methanol, it would be more economical than using ethanol, because we do not eat cellulose. This would convert what is currently a large source of waste into a fuel source. While there are currently drawbacks to the methanol fuel cell, research is currently underway to develop materials to make these fuel cells more efficient.
Hopefully in the not too distant future we will be able to do away with our use of fossil fuels to power our cars, but for the time being we are stuck with oil.
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