Recently several studies have come out comparing how green electric cars are vs hybrids and conventional vehicles. The conclusions are usually mixed, largely depending on how local electricity is generated - electrics do very well in places like Idaho, where most electricity is hydroelectric and poorly in North Dakota, which relies on coal.1
Real life is much more complex and sorting out life cycle emissions, energy mining emissions (difficult petroleum sources like tar sands are becoming increasingly important), and so on are extremely difficult to project so most examples tend to be special cases that may not be very close to your situation. What is communicated is a sound-bite .. like "hybrids are greener than plug-in electrics" .. even though that is not generally true.
It turns out these comparisons are not only misleading, but aren't getting at the right questions.
clip once meant to run or fly swiftly. This became applied to clippers - the fast sailing ships that began to dominate the long range routes in the 1840s. For a few decades they ruled the seas. Steam power was a competing technology, well proven in stationary and rail applications, but problematic on the sea due to (early on) low efficiencies of the engine and a poor understanding of propellers. Steam was used for some ships, but its use on clippers began as a powered winch to raise and lower the sails.
It turns out things changed - steam engines became efficient, propeller design advanced and not having to depend on the wind was a feature. People starting rethinking what a ship was and what it was supposed to do.
Electric cars have been around for well over a century, but have been hampered by the poor energy storage capabilities of batteries compared to fossil fuels. The advent of laptop computers pushed lithium-ion battery technology and made electrics sort of practical for some applications. While there is the promise of dramatic improvements it is reasonable to sort out what a car is and what it means to move us around.
It is very easy to get lost in a thicket of calculations. When I was looking at the efficiency of Colleen on her bicycle we started to talk about what it means to move a person around. She weighs about 170 pounds and her bike comes in around 30. An interesting metric is the ratio of her weight and the bike's weight and her weight. In this case it is (170 +30)/170 or about 1.18. Using this she can get the equivalent of about 1,000 mpg of "gasoline".
She has an old pickup that weighs about 4,000 pounds with her and a few gallons of gasoline. Looking at our total load to payload ratio we now get 4,0000/170 ... about 23.5. Colleen on her bike wastes much less energy as the combination is focused on carrying her around rather than the truck. Her bike is a good match for her weight. Her truck is an ok match for its weight - but why carry all of that around?
That which I am writing about so tediously, may be obvious to someone whose mind is less decrepit.
At the time I was writing a series of notes and giving some talks on energy. They were aimed at a general audience, but weren't connecting - my writing isn't exactly good. There were too many technical issues that needed explanation - or so I thought. Colleen was helping me with comments and came up with some simple ways of looking at the issues. Here is a simple, but accurate enough way of looking at things:2
° a car is about 25% efficient (best case) .. when you burn a gallon of gasoline, about a quart is used to move you and the car around. The rest is mostly waste heat.
° a car weighs about 25 times more than an average person .. of the quart used to move you and the car around, something like an ounce is used to move you.
° a single passenger car is only about 1% efficient
now for the electric car
° about 80% of the energy stored in the car's battery is used to move the car - something like three times better than a gasoline powered car
° the weight of the car isn't that different from a gasoline powered car.
° a single passenger electric car is about 3% efficient
A good case for car pooling! But also for making lighter vehicles. It vehicle efficiency in urban and most suburban driving is stop and go - the cost of accelerating a vehicle depends on its mass. A light car is going to be much better than a heavy one. Very small, but safe, urban cars have been built at well under 1,000 pounds. Now imagine Colleen in a car that weighs 1,000 pounds with her. If it is electric 80 cents of her energy dollar goes into moving her and the car around. Multiply this by her weight over the total weight moved (.17) and you get something that is over 13 times as "efficient" as the single passenger gasoline powered car. A remarkable improvement.3 And if she used a 50 pound electric bike the number would be 0.8 * (170/220) - over 62 times as good as the single passenger car!
The point is electric cars, by virtue of their electric motors, are more than three times as efficient as a similar gasoline powered car. That number is likely to improve slightly. The poor energy density of batteries and their high cost makes electric cars mostly impractical.
Bikes are incredibly efficient as are ebikes. Very small cars are very efficient. A shift to bicycles and small vehicles may require a different infrastructure. Bikes need bike paths, places to park and relative safety. Communities in Denmark and the Netherlands are showing an efficient and inexpensive transport mode for short distances (up to about 10 km).
Crystal balls are usually faulty, but perhaps conventional electrified cars are the steam powered winches on the old clipper ships. The ground transportation that will evolve will almost undoubtedly electrified, but highly computerized and part of a new infrastructure that may even impact urban and suburban planning as the gasoline car mostly created the suburbs.
At the same time other technologies are developing. Vehicle sharing (car and bike) schemes are growing, car to car communications, sensor equipped roadways, autonomous vehicles, electric cars, using car batteries for grid storage. Even how the cars (or whatever they will be called) are manufactured will become a big issue that will see enormous change.
These other technologies are developing both with and independent of the other technologies. They will stitch together producing something new and perhaps unimagined. It is likely these paths will be different around the world. At some point "good enough" states will form and become difficult to dislodge - just as the state of transportation that developed in the decade after WWII became very rigid in the US.
It is fun to speculate on scenarios, but assigning likelihoods is a very non-trivial task. The only thing I feel very comfortable about is small, light, electric and autonomous or at least semiautonomous seem very likely in the next three decades.
So much will change.
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1 a not entirely up to date listing from EPA's eGRID (pdf)
2 lots of footnotes are implied here, but reasonably good for the argument
3 This isn't a true efficiency, but rather a figure of merit for comparing types of transport.
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recipe corner
Sometimes you need a proper ice cream sandwich. I don't eat many, but they are fun to give away. First you need to find or make a good vanilla ice cream. Then the cookie.
I usually make a chocolate chip, but gingersnaps work well - the cookies aren't that big in diameter, so the sandwiches aren't huge 600 calorie monsters. Gingersnaps are good warm, but I like refrigerating them for ice cream sandwiches - add the ice cream and freeze the sandwiches.
Gingersnaps
Ingredients
° 280g all purpose flour
° 1-1/2 tsp baking soda
° 1/2 tsp non-iodized salt
° 2 tsp ground cinnamon
° 1-1/2 tsp ground ginger
° 1/2 tsp finely ground fresh black pepper
° 150 g unsalted butter softened to room temperature (you can used salted, but leave out the salt above)
° 130 g white cane sugar
° 1/2 tsp vanilla extract (I soak beans in rum for months)
° 80 g light molasses
° 1 large egg at room temperature - I use pasteurized eggs so I can taste the dough and play with the flavor a bit using this recipe as a guide, but modifying
Technique
° pre-heat your oven to 350°F , rack in the middle
° mix the dry stuff before the butter in a large enough bowl
° in a separate big enough bowl beat in the butter until fluffy and add the sugar, beating until it is smooth. Stir in the egg, vanilla and molasses
° add the dry ingredients slowly and beat until smooth
° roll into logs and wrap tightly in plastic wrap and freeze for a few hours until they are firm. You can also refrigerate overnight.
° slice into rounds about 3/8" thick and bake until brown - about ten to twelve minutes for me. Optionally sprinkle one side with some sugar - if you can find big sugar crystals, extra points.
° let them cool on a rack
Steve, you might also like to look at the Lit Motors C-1. It's an enclosed two wheeler, so has the energy dynamics of a motorcycle, while maintaining the conveniences of a car. Energy wise, we're looking at an 8.5kwh battery pack giving 320km of range. That is far far more energy efficient than a Tesla.
Plus, they look badass.
Posted by: Oliver Bruce | 10/27/2013 at 06:55 AM