July 29, 2002
Efficiencies, Or Lack Thereof: Part 2
Last week I indulged a fit of environmental conscience and explored some areas of food and water efficiency that my household, among millions, is not exactly up to snuff on. This week Iím going to pick on my favourite subject: the automobile.
There have been a lot of hot days this summer, and for some reason this got me thinking about sources of heat. In general, heat is waste energy. It may be produced to be useful emanating from your furnace in the middle of a February cold snap, but in the great majority of other instances, heat is a waste product.
Driving is such an example. By exploding a noxious liquid inside a hollowed-out chunk of metal, you can propel yourself and the steel and glass surrounding you down the road. This alone produces a lot of waste heat Ė the agreed-upon statistic is that only 15% of the energy contained in gasoline is actually used to move you and your vehicle down the road. The rest? You guessed it Ė waste heat.
The problem is, it doesnít end there. Say Iím driving in my truck at neighbourhood speeds, and I come to a stoplight. I apply the brakes, and stop. Where did all the momentum energy that my truck and I had go? The brakes turned it into waste head and dissipated it. Same thing if Iím driving toward Toronto at highway speeds and suddenly come upon a traffic jam Ė I brake and dissipate the momentum energy into waste heat.
In the first case, I would have dissipated approximately 200,000J of energy. In the second case, it would be about 800,000J instead. To put that into a framework that is more understandable, each time I stop from neighbourhood speeds I could bring 2L of ice water to the boiling point. In the case of highway speeds to a dead stop, that would be 8L of ice water boiling.
My truck is ungodly in its heft, Iíll admit. Something more civilized like a Honda Civic or a hatchback of some sort would weight just over half as much as the beast I call transportation, so youíd produce just over half of that amount of heat. Half or not, itís still going to add up. Think of all the vehicles out on the road in your neighbourhood, city, province, country, continent Ė and youíll quickly see that automobiles alone could boil off Lake Erie in short order.
Just because Iím a geek letís do some quick math. Each year in the United States, Honda, Toyota, and Ford compete to see who can sell the most Accords, Camrys, or Tauruses. Generally, they each sell about 400,000 of each, every year. First Iíll guesstimate an average weight of 3300lbs each. Next Iíll give each of those 1.2 million drivers a ridiculously short drive to and from work that consists of only 10 stops from neighbourhood speeds, and only 3 stops from highway speed. All told, the amount of energy dissipated from just stopping these vehicles during an average day would boil over 45 billion litres of the Atlantic ocean each and every day. In less than a month one cubic kilometer of ice-cold water could be brought up to boiling. Thatís a LOT of waste heat, and Iím not including 40 ton transport trucks or any other vehicles already on the road Ė of which there are millions.
Just as a comparison, if a big dude on a bicycle were to stop from 40km/h (a fair clip on a bike Iíd say) heíd produce only 6200J, which might be enough to warm a small cup of tea by 30įC.
Before you tell me that Iím blowing things way out of proportion because Iím assuming that all this braking is slowing vehicles down, Iím actually not. It doesnít matter whether I let my truck coast down from 110km/h to a standstill without ever touching the brakes, lock the wheels up and come screeching to a halt, or just normally apply the brakes until Iím at a standstill. In each case, some part of the vehicle is creating heat out of the momentum energy that the vehicle has, and is bleeding it off. It doesnít matter if itís slow or quick, the same amount of energy is dissipated in heat. It could be heat from the brakes, heat from the driveshaft shearing through the differential oil, or the heat produced when the tires are mercilessly scraped across the asphalt. It will be the same amount of energy total.
So, we know that there is buttloads of energy being blithely wasted each and every day (actually, every second of every hour) across the world. The big question is: Can we do anything about it?
Yes, there is. Thereís not a lot we can do, but there is something each of us can do right now: conserve momentum. Thatís right, the very same thing that race car drivers do out on the track we need to do on the road. Some of you may be staring blankly and wondering what the heck this ďmomentumĒ thing is, and how on earth you can conserve it. To put it in simpler terms, conserve speed. By keeping as much forward speed as possible in any given situation (within safe limits, of course Ė please continue to brake instead of hitting pedestrians and concrete embankments) youíll be conserving momentum. This will have the effect of not bleeding off as much energy over the course of your drive, and an efficiency gain will be realized.
Here are some practical ways you can do this. First, I think rolling stops should be legalized. Donít put a stop sign where you could put a merge lane or a yield sign with a good view of oncoming traffic. By keeping your speed up, thatís less energy you have to waste, both slowing down and getting back up to speed again.
Second, everyone should learn to enjoy high-speed cornering. Just like rolling stops, the less you have to slow down the less you have to speed up again. There are production vehicles that can take the industry standard 700ft cone slalom test at well over legal speeds, so thereís no reason you shouldnít be able to manoeuvre a family sedan around a sedate neighbourhood corner at a measly 50km/h or so. Youíll slide before you flip (unless you own an SUV), so give it a whirl.
These are all stop-measure gaps, unfortunately. You could be the most diligent and efficient driver, maintaining your momentum for all youíre worth, but the fact of the matter is that unless youíre especially skilled or live in the middle of nowhere, youíre eventually going to run into some sort of traffic control Ė namely, stoplights or stop signs. There is only one way around this, and Iíve mentioned it (in a previous article I canít find right now): automated driving.
Last I mentioned automated driving I was talking simply from a userís perspective. Get in, tell the car where to go, and you donít have to do anything. This time, Iím thinking from an efficiency standpoint. If automated driving can become universal, there will be lots of efficiencies to gain.
Why do we have traffic lights? The simple answer is to make sure people donít run into each other in intersections. The more complex answer for major cities is to most optimally control the traffic flow through and throughout a municipal roadway complex. However, if the controls of our vehicles are in the digital hands of computers that can rapidly communicate with each other, why would we keep traffic lights around, which are specifically designed for human use?
Whatís more, once we ditch traffic lights there isnít any good reason why any vehicle should have to stop at intersections. As long as all the vehicles are properly spaced and co-ordinated, I can envision two streams of vehicles flowing through each other, at normal speeds and without any collisions.
I see two ways to make this work. First would be to treat traffic like little packets of vehicles, and weave them in and around each other at speed. One block of traffic would go through, and just as it ends another packet comes through another way. The second way would be essentially the same, but on a vehicular level. The latter would be quite hard, as youíd need the exact exterior dimensions of each vehicle. Put down a tailgate, or load some lumber into your trunk and suddenly youíre getting clipped.
Have you ever watched a parade where the Shriners come out on their little scooters or go-karts and they weave in and out of each other? Iíve seen it done with police motorcycles and RCMP horses as well. What Iím proposing would be the same effect, but on a city-wide scale. Each vehicle would just zip merrily along with other vehicle whooshing past them in front and in back, always looking like theyíre about to collide but never doing so. Such a system would mean you could start from your departure point, get up to speed, and never slow down except for hills, sharp turns, and to stop at your destination. No stopping in between at all. Wouldnít that be great?
While Iím wishing I may as well ask for a great body, to win the lottery, and be able to do the New York Times Saturday crossword puzzle in under 5 minutes. After all, Iím only asking that automated driving technology be perfected and implemented across the board and our cities to be redesigned accordingly. Of course, we could always skip the technology and its implementation and just train each and every driver to be as good as the Shriners, but at highway speeds. If I had that much faith in humanity, Iíd probably be dead right now.
So, the only thing I can really hope for is that more people buy a Honda Insight or Civic Hybrid, or a Toyota Prius. These vehicles make getting better mileage a game, and give drivers some sort of drive to figure out how to be more efficient in their vehicles. To figure out mileage in my truck I have to jot down the odometer reading and amount of gas Iíve filled up with at each filling and get a calculator. These hybrids tell you what mileage youíre getting that very instant.
So, what is the moral of todayís lesson? There is no problem that canít be solved with a sufficiently unlimited budget. While Iím waiting for pigs to fly and my abs to appear chiseled, I think Iíll go and enjoy the ocean before it gets boiled off.
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