Um, no... re-read my statement, which included the phrase "desired future state." An engineer makes decisions on the basis of gathering as much information as is possible, subject to constraints of time and budget. He adds in a bit of experience, and the result is called a "decision". That's how I might choose a capacitor: it's not much of a gamble. A gambler decides that, for example, the ICE is bad for a set of reasons. Then he performs an analysis that will tend to confirm his bias. He goes ahead, and makes a decision. The gamble is that his biases are correct or not. If they are not, too bad. If they are, fine, but why bother with any sort of engineering analysis? That's how, in some cases, exceedingly green individuals (or individuals of many other stripes) wander into errors: by doing what "seems sensible" or "feels good" or "looks right": in short, by avoiding the hard work of analysis, and merely gambling.
Bob Lacovara said: "There's a name for a person who shapes their actions on the prediction of a desired future state: it's not 'engineer' but 'gambler'."
This statement seems to reflect an underlying ignorance of the fact that **all** decisions are gambles. Engineers gamble all of the time (as do all people when they formulate a decision). The question isn't whether or not one is gambling when making decisions, but what knowledge and biases they bring to the gambling table and how each affects their likelihood of winning (however "winning" is defined in the given context).
Why not compare the Prius used for commuting to something even larger than an FJ Cruiser? The Prius would look better still. If you don't want to compare the Prius to a tractor trailer, then you might choose a Harley Davidson, a Kawasaki, or a Yamaha or what-you-will. I see guys commuting on those beauties all the time, although it's not for me.
Ok. Let's be fair. You are quite right, who's going to commute in an FJ Cruiser? How about a comparison to a Corolla? Mine gets 28 to 31 mpg going about 60 miles round-trip a day. Toyota's web page says a new one is (base) $15,450, and gets 26/35... adjust the numbers if they don't suit. What does the comparison look like then? BTW, when will the battery in the Prius have to be changed, and what will it cost? My Corolla is an '02, has 113K miles, and I expect another 113K, unless, of course, I buy a second FJ Cruiser to match my other.
These two vehicles, a Prius and an FJ Cruiser, are apples and oranges in a comparison. You note that the idea of the right tool for the right job is a good one: agreed. But there are more variables and requirements on a car choice than just what it costs to buy and run.
Checking with the EPA web site, 103 Prius averaged 49.1 MPG with a range from 35 to 60 MPG. Given a normal distribution of annual miles with 15,000 being the mean, those who drive more, over half of the typical drivers, can save a bundle. For example, let's compare the Prius to the FJ Cruiser:
50 :: 19 MPG combined, EPA standard testing
$22,800 :: $23,400 Toyota 'starting' prices
Right off the bat, the 'hybrid premium' has disappeared. For a commuter car, one that takes one or two people to and from work, typically in an urban or suburban driving experience, the EPA calculates:
$816 :: $2,146 relative fuel costs
Since I'm doing 20,000 miles per year, the savings are even greater. That is why I belong to the 'right tool for the right job' crowd.
The Prius is the natural choice for someone spending most of their miles commuting. In contrast, if someone is driving 15,000 miles a year towing a boat, they should have the FJ Cruiser . . . and an appropriate fuel budget. But we usually call these people "truckers" and unless they inspect or build bridges or water platforms, they seldom are engineers.
I have no problem with engineers who want to play "trucker" with their fun vehicles on the weekend. But trying to commute to and from work in one is the wrong tool for the job . . . like the old Soviet practice of using a hammer to drive screws.
Very provocative yet informative post, just look at the heated debate. Two points:
First, we are not in an energy crisis, we are in a climate change crisis. There is plenty of energy to be had on earth, fossil or non-fossil, the problem is how to extract them without pollution or cause global climate change.
Second, I firmly believe that the cost of a thing tracks pretty well the energy used to produce it. So if a hybrid cost more, the overall energy footprint is higher than a regular car. The the energy saving throughout its life time had better off-set the increase sale price otherwise it makes no sense.
Being a Prius owner and an engineering geek, I've studied the Prius' drive system a bit. It's worth pointing out that there's really no one single factor that gives it its high mileage; it's a combination of many factors.
However, there are two factors that are probably the biggest contributors. One is a high-speed mechanism (i.e., it improves mileage at high speeds), and another is a low-speed mechanism.
At high speeds there's only so much that electrics can do to help. The main thing you can do is just simply reduce aerodynamic drag. The 2010 Prius has a drag ratio of about 0.25 - quite little drag. This is a lot of the reason why, as you mentioned, hybrid versions of pure-gasoline cars often don't get much better highway mileage: The only way to improve that substantially is to change the body design.
At low speeds, the main thing the Prius does is use electric drive as much as possible. That helps because you simply can't create an ICE that burns at 15 miles per hour 1/3 of the fuel as it does at 45 miles per hour. ICEs have a lower limit on how few *gallons per hour* they can consume without shutting off completely. An engine therefore can't rack up very many *miles per gallon* unless without also racking up a fair number of *miles per hour*. In other words, you're not going to get very good mileage in low gear, so you have to simply shut the engine off at low speeds.
After that, yes, keeping the engine in its ideal RPM range, regenerative braking, and so forth also help. After that there are some complicated balancing acts, such as when it makes sense to run the engine just to simply keep it warm, since a cold engine is inefficient.
Something that I think hasn't been done is to try and optimize hybrids for highway driving. They are tuned quite well for say down town Manhattan, but aren't tuned for say open road driving.
The statements concerning conservation of energy is of course correct. However, I do think that there are possibilities out there that haven't been explored. Prime example is thermo-electric generators that capture heat energy from the exhaust and use it to keep the battery charged up. There is, of course, more weight to be hauled around as a result, but it might be possible to improve overall energy efficiency.
Another possibility, at least for short commutes, is to run the car in an all-electric mode. And then on the roof, hood, and trunk, have some of those flexible solar cells, and use them to at least partially recharge the battery. It isn't a magic bullet, but it might be able to bump up the efficiency some.
Exchanging my 30 mpg Toyota Corolla for my 50 mpg (lifetime average over 88,000 miles) Honda Civic Hybrid has saved a lot of gasoline without violating any laws of physics. First, the engine turns off when it isn't needed (that growling SUV behind me at the red light is still gulping gas). Second, the ICE is able to work in a more efficient RPM range and store some energy in the battery for later use. Third this offloading of power enables peak horsepower (ICE + battery) to exceed the power of the ICE alone. Fourth, regenerative braking allows me to recover energy when braking for reuse later. Fifth, the regenerative braking saves wear and tear on my brakes - which have lasted three times longer than on my old Corolla. I earned back the extra cost of my hybrid in gas and brakes years ago. Finally, a calmer driving style reduces speeding tickets and road rage - a benefit that would be great to see on a broader basis.
NASA's Orion Flight Software Production Systems Manager Darrel G. Raines joins Planet Analog Editor Steve Taranovich and Embedded.com Editor Max Maxfield to talk about embedded flight software used in Orion Spacecraft, part of NASA's Mars mission. Live radio show and live chat. Get your questions ready.
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