Electric cars are becoming attractive. Two drivers for development are (1) concerns about excessive carbon emissions and (2) the political and economic fallout associated with imported petroleum. Investment dollars for electrics have risen, but what’s coming onto the market still doesn’t match the convenience and low price of petroleum-based cars. How far away are good electric cars.
Current electrics: the good and the bad
Electric cars are already very good in most ways. Electric motors are powerful and are lighter, cheaper, and more reliable than gasoline engines. Finding enough electricity is not a problem: the current energy grid already has enough excess capacity to replace about half of the gasoline-powered light vehicles on the road in the U.S. with electrics (or 73% replacement with plug-in hybrids). Moreover, clean energy (e.g., wind power) is now becoming close in price to the cheapest legacy dirty energy (coal), and is far cheaper than gasoline for powering a car. Per mile, the energy costs to power an electric are about one fifth that of a gasoline-powered car.
The problem with electric cars are the batteries, which don’t deliver. Batteries don’t power a car far enough for cheap enough. Costs will come down, leaving two parts to the problem: battery energy density and charging time. Consider gasoline, a potent fuel that packs 12 kilowatt-hours per kilogram (kWh/kg). Compare that to the latest high-tech batteries in use for transportation, which hold only 0.14 kWh/kg, and you'll see the problem.
Gasoline’s high energy density explains how 14 gallons, or about 40 kilograms, powers a car for 400 miles, even though 75% of the energy in gasoline isn’t even used in a car. It would take a 1000kg battery to replace a 14 gallon (40kg) tank of gasoline. But that’s too heavy for a car and, it turns out, expensive too ($30,000). Moreover, batteries take four hours to charge, which could leave a driver stranded. An empty gas tank means an inconvenience of just a few minutes at a filling station.
Current batteries can cheaply offer a range of 50 miles, which could be useful for some transportation segments, but isn't sufficient for most buyers of a primary car.
How far away are good batteries?
A ballpark target for a good battery is one that holds 1kWh/kg, or a seven-fold improvement over the current technology. What would it take to get there? Consider recent developments in battery density.
Large improvements are anticipated for the future. The government of Japan (through NEDO) has set targets to improve energy density three-fold in a seven year project.
Focusing on technologies that have actually been implemented, the latest Li-ion batteries used in the Tesla roadster hold about 0.14 kWh/kg compared with the 0.03kWh/kg for lead-acid batteries used in electric cars just ten years ago. Some batteries in existence push that figure to around 0.3 kWh/kg, but aren’t ready for use in a car.
A repeat of this five-fold improvement would make the electric car attractive, and electric car manufacturers are banking on major improvements in battery technology energy density and cost.
Investment in batteries
Investment in battery technology is growing with the market. For the near term, the real market is in conventional hybrid and plug-in hybrid cars. The hybrid car market, led by the Toyota Prius, is now at over 300,000 cars sold per year and is driving demand for batteries. The Fisker Karma and Chevy Volt are plug-in hybrid cars that will be available in 2010, to be followed by a slew of other models under development. For purely electric cars, Tesla Motors leads the news with a luxury sports car already in production. Building on its success with the first model, the company is developing a newer model and announced it’s plan for an IPO in January.
Among battery manufacturers, there are several players developing and selling batteries. A123 Systems made big headlines with their IPO in September. The demand for high-performance batteries for all applications, including transportation, is increasing dramatically.
Recent breakthroughs in battery technology are pushing energy density figures higher, but these developments are still in the laboratory. Materials costs, safety, and several performance parameters are important to any technology. Lithium batteries may turn out to be inherently expensive, but promise nice improvements. Innovations focus both on the electrolyte and the composition of the electrodes. Many non-lithium-based batteries are also in the laboratory.
The list of lithium ion technologies is long (e.g., see here), and include several variations on the lithium ion battery: lithium polymer (currently over 0.2kWh/kg), lithium air, zebra, thin film batteries, lithium iron phosphate, the long-lived lithium-manganese spinel, lithium vanadium oxide, lithium sulphur (currently at 0.25kWh/kg), (silicon) nanowire, and others. Other enticing technology experiments include zinc–air batteries and several different innovations for electrode nanostructures. Claims have been made that sodium-ion batteries promise 0.4 kWh/kg, though there are practical disadvantages inherent to this technology.
Ultracapacitors are a less developed, battery-like technology that charge in a few minutes, which might solve the charging problem, and store power more efficiently. Ultracapacitors currently hold only 0.03 kWh/kg, though this is expected to improve. Also, combining an ultracapacitor with a battery could yield a significant improvement in cost and energy density. For the future of ultracapacitors, new materials such as carbon nanotubes are predicted to yield order-of-magnitude improvements.
Most technologies won’t make it out of the lab, and it’s too early to generate a short list of winners. The point is that breakthroughs have yielded order-of-magnitude improvements over the past decades and are expected to continue. Meanwhile, investment dollars (and yen) are pouring in to ensure that they do.
The road ahead for electrics
A realistic timeline for an electric vehicle that can economically meet the needs of most private individuals is 10 to 20 years and will depend on battery technology. Targets set under programs by NEDO in Japan hint at a 2020 to 2030 timeline for a cheap, fully commercializable electric car battery. These timelines are similar to what has been set by federal EPA mandates for a significant adoption of biofuels, which will continue to struggle to compete in a petroleum market.
While current batteries still fall short, electric cars are otherwise much better than current cars. Solve the battery technology problem and there will be a clear path to clean transportation, carbon reductions, and energy independence.
