Hybrids, Batteries, and Electric Cars
A point frequently lost in the excited talk about fuel cell vehicles is that a fuel cell is simply a device that allows for the controlled oxidation (burning) of Hydrogen, but that Hydrogen is not freely available. In fact, Hydrogen is tied up in water (H2O) and in fossil fuels (natural gas is CH4, for example), and to get pure Hydrogen into your fuel cell you need to first expend energy to separate it from the Oxygen in water or the Carbon in fossil fuels. Then you get that energy back in the fuel cell when you recombine the Hydrogen with Oxygen from the air. So, in a sense, fuel cells use Hydrogen as a battery. Because the Hydrogen is not freely available in atomic or molecular form, it is not a fuel, per se. We would use it as a carrier the same way a more conventional battery carries electricity that is produced through some other process (coal burning, hydroelectric, solar, wind). The problem with Hydrogen as the energy carrier is that we do not have the infrastructure to produce, transport, and store Hydrogen, while with conventional batteries the power is transported over the existing electric grid. One simply has to plug the battery in, and power is delivered to the storage device. The problem is, those plug-in cars aren’t available anymore.
The other problem is that the energy density of a Lithium-ion battery is about 200 times less than that of gasoline. That is, for 1 kg of gasoline you can go about 200 times farther than with a fully-charged 1 kg Li-ion battery. So purely electric cars typically have had a limited range compared to their gasoline counterparts, and less passenger and cargo space to make room for a big, heavy set of batteries. The great things about hybrids is that they give consumers the option of the long drive with the gasoline engine, and the electric motor is there to reduce gasoline consumption. However, carmakers have made their hybrids without a large battery and without the option to charge the battery through a power outlet. The Prius comes with a battery pack that, fully charged, could power the car for about 2 miles. 70 kg of additional batteries could give the car a 30-mile electric-only range. That may not seem like much, but it is the average distance driven by Americans each day. Since the Prius and other hybrids have the gas engine also, once those 30 miles have been driven the car would get the same fuel economy as a standard hybrid. Hopefully Toyota and Honda will start selling plug-in versions of their hybrids soon. In the meantime, some groups are doing conversions of the Prius to make them plug-in hybrids. If you’re driving 10-15 miles to work (or less), a plug-in hybrid would use almost no gasoline for a typically daily commute, but would be ready to go the long haul with the standard hybrid technology.
The energy to charge up those batteries comes from the electric power grid. A little over half of the U.S.’s electricity comes from burning coal, which is a pretty dirty prospect. Nevertheless, the electric motor makes the electric powered car, even on a coal-supplied electric grid, cleaner than conventional internal combustion engine cars. Calcars’ approach is to convert Priuses to make them operational plug-in hybrids to exert some pressure on the automakers to do this themselves. While the batteries are expensive, mass production, a growing market, and continued technical advances should bring these prices down and make plug-in hybrids an available and economical option - with any luck, by the time I need my next car.
Here is one company’s FAQ page with interesting details on their plug-in version of the Toyota Prius.