Stripped to the basics a vehicle is just a device that moves by converting stored energy into mechanical energy. In the early days of the automobile it wasn't clear what the stored energy would be and how it would be converted. Experimenters worked with steam engines, a wide variety of two and four cycle internal combustion engines, compressed air and electric motors. There were engineering and usage hints from horse drawn wagons and carriages as well as the bicycle, but infrastructure ranged from poor to nonexistent. There was something of a race to see what would be good enough to begin to define and infrastructure and it was up to the users to invent and evolve usage patterns.
By 1900 three of the main contenders were the internal combustion engine, the steam engine and the electric motor. All were expensive and limited, but new designs were changing and improving rapidly. By 1910 the gasoline engine had matured to the point where it was more efficient, cheaper to manufacture and less temperamental than the steam engine. The electric car had seen considerable use in large cities where its short range wasn't a big issue, but it faded as trip lengths increased, electric starters appeared on gasoline powered cars making them easier to use and the price of gasoline cars dropped.
By the time the Ford Model T arrived it was clear the future was going to be a gasoline fueled internal combustion engine. The innovation that came with the Model T was a dramatic price reduction made possible by standardization and a soup to nuts scale assembly line. Suddenly cars were available to the middle class and the supporting infrastructure from oil refineries to better roads grew sprouted up. So many people had mobility that the distances between where we lived, worked, shopped and played adjusted to fit the hour or so a day we were willing to devote to travel.
Human and family size, road widths, parking spaces and a few other factors fixed the size of the personal car. The cars of the 1950s are functionally not that different from those of today and most of them are built using materials and construction techniques that have slowly evolved.
The efficiency of moving a person around has roughly doubled and cars are now much safer, reliable, easier to use and comfortable. About a billion cars are currently on the road and the developed world is now near or at saturation. There are issues with pollution and global warming and petroleum is becoming more expensive to mine. The question is where do we go from here? What will cars in the US and Europe look like in the next thirty years and what about the next billion that will go into emerging economies?
We need to look at usage models, efficiency and then drill in a bit deeper to get a little insight. Kilowatt-hours of energy used per 100 miles of travel is a common metric used to compare transportation modes.1 Colleen has to provide about 3.3 kWh/100 miles to ride her bike, but her old pickup only gets about 15 miles per gallon so she's using about 225 kWh/100 miles when she's driving.2 The average new American car uses about 147 kWh in 100 miles - a major improvement over the old truck if you're paying three or four dollars a gallon for gasoline. But there is room for improvement.
65 kWH/100 mile gasoline power cars are available, but are not popular as they're considered too small for most buyers and we're not seeing increases in the price of gasoline at the moment. Moving much lower than that with an internal combustion engine is expensive and moving the average family car to that level will be difficult. The low hanging fruit has been harvested so improvements in conventional cars will be incremental.
Pure electrics, on the other hand, represent a major efficiency improvement. The Tesla Model S needs 35 kWh to travel 100 miles and the BMW i3 just 28 when run as a pure electric. (perhaps a tad optimistic numbers as there is weather variation, but consider these will improve over time) But two major issues prevent wide-spread adoption.
Cost prevents an electric car with "good enough" range from being affordable. Automotive grade battery packs are in the $400 to $700 per kilowatt-hour range these days The price is dropping rapidly and many believe it will be in the $150 to $200/kWh range in five years bringing a 100 mile range battery pack for midsize cars down to $7k or less. The cost saving moving from an advanced internal combustion engine coupled with a sophisticated 8 or 9 speed automatic transmission to a simple electric motor with a one or two speed transmission would be close to that figure. A competitively priced 100 mile range electric without subsidies. Two car families may find this attractive. The other niche that would only have a modestly higher price than a normal car might be the 200 mile range family car. Tesla and General Motors are both talking about the "reasonably priced" 200 mile goal within three or four years. Tesla may be very conservative with their battery factory plans.
The issue weight. Current automotive grade lithium batteries store about 150 watt-hours per kilogram while gasoline has an energy density of about 12,800 wh/kg - about 85 times higher. Batteries are very heavy - probably at least 1,100 pounds in a Tesla Model S. Improvements are being made the rate of about five percent per year, but lithium batteries are limited to about twice their current energy density. This isn't quite the problem cost is at the moment, but major improvement will require new chemistries and ultimately may erase the advantage of gasoline. A large amount of research is going into metal air batteries which promise energy densities that, adjusted for power train efficiency, are roughly equivalent to that of gasoline.3
From today's vantage point it looks like cost neutral 100 mile range compacts will be available in five years time. There are numerous advantages to electrics including lower long term maintenance costs and energy costs that may make them very attractive.4
Current electric vehicles are basically a conventional car with a power train transplant. We can, and will, move beyond that and real innovation is possible. Batteries can be distributed around the car and the motor may become several small motors closer to the wheels. It may be possible to build lighter vehicles with equivalent or better crash performance and, without the constraint of large radiators a massive engine better aerodynamics are possible.
If you are willing to consider new niches there are some interesting possibilities. Many European cities and suburbs have speed limits of 40 km/h (25 mph) or less.. While most Americans would consider a 25 mph speed limit a burden, it would make bicycles more practical and open up niches for very different vehicles. A back of the envelope shows a two passenger 1,100 pound, 100 mile range electric car is possible without resorting to exotic materials. The battery pack could be about 10 kWh making the total cost very low. And there are even ways to manufacture it without resorting to a billion dollar factory.
Very small electric cars may be the first practical self driving platform. They would probably be confined to small areas that could be well mapped with embedded naviation aids. Driver controls could be eliminated reducing cost and making it easier to improve crash protection. It would probably make more sense to have a city or company own the cars - they would be a bridge between mass transit and a private car or taxi. There are a number of problems to work out and even discover, so trials are necessary. Google appears to be moving down that path and there are indications several other companies are doing the same thing.5
We're witnessing an exciting time. The advent of new materials, improving batteries, very different production techniques with different scaling characteristics, networked vehicles and self driving technologies. These changes are arriving along with middle class growth in emerging nations and new cities where moving people, pollution and efficiency are issues.
The automobile gave us suburbs - perhaps we'll see major change in what a city is.
I've run over my hour and haven't touched many issues. Automotive electrification may well become universal in the next decade for example. Beyond the car it makes sense to talk about energy storage - something fundamental to energy use and a very hot topic these days. My guess is Musk is at least as interested in it as he is in the electric car.
Jheri asked a question in the comments that I should comment on in the main body:
How much extra should you spend if greenhouse gases are important to you? I think I know that they aren't a good carbon investment.
While I think government stimulus makes sense to encourage battery development, buying a electric car only to be green is a poor use of money. There are much cheaper ways to keep more greenhouse gases from the atmosphere using the price differential. That said there are other reasons for buying one, although I'm waiting a few years myself.
The question often comes up about how clean the electric source is. No emissions means nothing from plug to wheel and people are often interested in power plant to wheel. If the power comes from a green source you're in good shape, but grid power is a mixture and you have to look at the mix. The worst cases in the US are the Intermountain West and North Central which have a heavy reliance on coal. For every kWh of fuel burned you get about 0.3 to 0.35 kWh of electricity at your plug and then you need to factor in the charger. For the bad areas you are close to or just a little worse than breaking even given similar cars. Everyone else emits less. But it is important to note an internal combustion engine emits far more than just carbon dioxide and keeping that out of your local environment is a good thing. Particulates from fossil fuel power plants in North America are better managed than those from a car.
The bottom line is get an electric car if the other features are important to you and lower your greenhouse gas emissions from other areas in your life for much less money.
1 You could use any distance or unit of energy. In the US we tend to think in terms of a gallon of gasoline, but that is about 33.7 kWh. Megajoules are commonly used as an unit of energy at the scale of a car, but we'll stick with kWh.
The simple conversion is 3370/mpg = kWh/100 miles.
2 More detail here, but note her bike has a comfortable upright riding position that happens to be common on European commuter bikes. This position and the large amount of frontal area she presents because she is tall gives her a somewhat lower efficiency than a smaller rider in a tucked position on a bike with higher pressure tires. A road bike is probably closer to 2.5 kWh/100 miles.
3 Progress has been very slow. It is fairly easy to make a single use metal air battery, but there are serious problems when the battery is rechargeable. Even if one was announced tomorrow it would probably take five to seven years from lab to production.
There has been some progress with an aluminum-air battery that is not rechargeable. The idea is to install it in a car where the main battery is lithium and only use it for long trips. It would store enough energy for about 2,000 miles and would be swapped for a rebuilt battery when it expired. The economics aren't practical yet, but the approach is under active investigation.
4 There is almost no brake wear as the motor is used as a generator to move about half of the energy used to slow the car back into the battery. The motor has one moving part, very low vibration and no complex pollution system. It is possible that a drive train could go a half million miles with only tiny amounts of regular maintenance - a bit of oil on the bearings every year or so. Tires would be the other item and, at around eight or ten years, the battery pack would be replaced with one that is much less expensive with a higher energy density. The car would get better with age. Most car dealers make much of their profit in the repair shop, so this will be a major issue.
A 33 mpg car can go 100 miles on three gallons of gasoline - $9 to $12 at current prices. A similar electric needs about 30 kWh. If you charge at night some utilities are offering power for around ten cents per kWh .. so $3 for the same distance.
5 Google is getting the lion's share of publicity because they have been issuing a lot of press releases. Most of the other companies known to be working on this are not in the habit of pre-announcement at Google's level.
Avocado's are inexpensive these days. This is a modification of an old Bittman recipe.
Avocado and Peanut Salad
° 1/3 cup rice vinegar
° 50 g white cane sugar
° pinch of salt
° 2 tbl freshly grated ginger root
° 2 medium avocados pitted and sliced
° 1/4 to 1/2 cup salted roasted peanuts chopped
° make a dressing by heating the vinegar, sugar, salt and 2 tbl water in a small pan over medium heat. Cook until the sugar dissolves
° add the ginger and cook until the dressing thickens (about five minutes)
° remove from heat, cool, cover and chill for at least an hour
° arrange the avocado slices on a plates, drizzle with the dressing and sprinkle on the peanuts.