Tuesday, April 19, 2011

Why is the Car so Inefficient?

In this excerpt I would like to look at what causes the personal automobile to be so inefficient. 
The majority of automobiles on the road are your typical sedan with two seats in the front, three in the back and a trunk.  If you were to look at the cars on the nearest road, you would notice that the majority of vehicles are only transporting 1 person.  The car engine in these cars are designed to be able to move 5 people and belongings in the trunk, this means that the engine would have had to been built larger and with more capacity than if the car was designed only to carry one person and their belongings.  The personal automobile is designed to meet every single possible scenario that one may find themselves in; do I need to take 1, 2, 3, 4, friends/siblings,children,pets along with me; do I need to bring my golf clubs, duffel bag, presentation material; do I need to pick up furniture.  Rather than design cars for the bare minimum for the most common scenario, cars are designed to be able to do everything, and since you will only ever need to move a chair once a year, or pick up a friend once a year, this leads this over design to be a big waste of fuel.  If someone were to truly need a vehicle, they should be able to buy a smart car sized vehicle, and rent an appropriate sized car when needed.  If we are even to begin considering cars in a sustainable world, they need to be built as small and light as possible.

Often cars will be designed with grossly excessive amounts of horsepower than will ever be necessary for a typical commute, all because it is "sexy" or "cool".  The table below compares some of the typical vehicles and their respective fuel economy, carbon footprint and engine size.  As you can see that when you decrease the size of the vehicle along with the size of the engine, your impact on the environment dramatically improves.  When you design a vehicle to transport just a human being as opposed to the blatant excess of a Hummer, you reduce your impact by a factor of 10 and increase your fuel economy by a factor of 16.  Compared to a typical car, your impact is reduced by an factor of 5 and increase you fuel economy by a factor 8.

Traffic Jam
Image Credit: http://blogs.houstonpress.com/

There is the big issue of traffic lights, the dominant form of traffic control at intersections.  If you were to watch a busy intersection you would observe that whenever a certain direction changes red, that 10-30 vehicles will line up.  You will also notice that not one single vehicle will take the fraction of the second that it takes to turn your vehicle off.  It takes 10 seconds of idling to match the fuel spent starting the engine.  Assuming that idling a car for one hour uses 3.78 L of fuel, this works out to be 1.05 mL/s. If you take 10 cars simply sitting at a light for one minute would waste 630mL of fuel, 1260mL for 20, and 1890mL for 30, never mind 100 or 200 vehicles.  I know from my days driving a vehicle that you would be very lucky not to only catch one light for your own trip, in fact you will several lights on your commute, as will the 500,000 other commuters in your city.  This problem is only compounded due to the fact that their is an estimated 600,000,000 vehicles on the planet.  There is a potential for 30,000,000 L of wasted fuel every day with that many vehicles on the planet, all simply due to the fact that people are too lazy to turn off their cars at a light.  The thing is that as always a solution exists, hybrid cars for nearly a decade have been outfitted with a switch that automatically shuts the engine down during idling.  Why has this not been implemented world wide?  Everyday $44,226,000 is being burnt on wasted fuel.  If cars want a place in a sustainable world, legislation needs to be put into place to make this mandatory for every vehicle.

There are a huge swath of energy saving features that should be implemented in every vehicle that could squeeze every the last drop out of every tank.  We could install regenerative brakes and flywheels to capture the energy lost while braking.  We could install motors directly at each wheel, with no loss of power through the transmission which can account for 5% energy losses, but we would rather focus on the color of the car, the material of the seats, and how awesome the stereo system is. 

Another problem with automobiles is a result of the very fuel that they run on, gasoline.  An internal combustion engine only has an efficiency of 15%.  This means that 15% of the energy from the fuel is only used to move your vehicle.  What about the other 85%, approximately 60% of the energy going into your engine is being wasted as heat, other losses are due to friction and inertia.  Cars are wasting 60% of the energy from the fuel in the form of heat, this is heat that is doing nothing, it is not heating steam to turn a generator, this is heat that is simply being released to the environment.  An electric car does not produce as much heat, and therefore can circumvent complicated cooling systems, cooling chemicals, radiators, fans, and wiring. Electric can forgo with many of the harmful chemicals and pollutants that keep a gasoline car running.  As a result, electric cars have less parts to maintain, and fewer fluids to change resulting in lower maintenance costs.  If cars are to have a place in a sustainable world, legislation needs to be in place to ban the prehistoric and inefficient internal combustion engine. 

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