Posted on 08/19/2006 7:56:28 PM PDT by nicollo
Absolutely!
The present design of gasoline engines, even in the complete absense of frictional losses, would be less than 50% efficient; in any engine where the expansion ratio is no greater than the expansion ratio, more than half the energy of the fuel will either be lost as friction or waste heat to the engine block, or will else go out the tailpipe.
There are many techniques that could overcome the theoretical efficiency limitations of the Otto Cycle engine. I wonder which ones will end up being practical? A few I like:
Very interesting about the amount of energy expended. I used to know how a gasoline engine worked. Diesel has a higher compression with no spark plugs?
What ever happened to the hydrogen fuel cell technology rage?
This is the point everyone seems to miss. Feedback in a dynamic system makes static predictions virtually useless. Price changes are feedback.
How would you calculate that?
(Price / gallon) (Gallon / mile) + (maintenance cost / mile) + (capital cost / mile)
If miles per unit volume is a foolish standard, why are you worried that it takes "more oil" to make a gallon of diesel than a gallon of gasoline? ("More" in volume or mass?)
Okay, a gallon of diesel is denser than a gallon of gasoline. It also contains more BTU's per unit mass, so significantly more BTU's per unit of volume.
But diesel engines are also inherently more efficient than spark-ignition engines, no matter what they burn. Diesels can run at lean fuel-air mixture ratios, even shutting their fuel off entirely to coast. Spark engines can't do that.
A diesel's compression ratio is limited by what the engine can take, structurally, and how much air you can pack into the cylinder. A gas engine's compression ratio is limited by the octane of the fuel; too much compression results in predetonation or "knock". And compression ratio is absolutely related to efficiency.
If diesel efficiency were imaginary, you would see a lot more heavy trucks with gasoline engines. Instead, you see none.
Compare the mileage for my turbo-diesel VW Jetta with its gas engine cousins. The diesel wins every time, and not by a little bit, either. (And it's even fun to drive; I can leave a lot of gas cars in my dust.)
The final win is that diesel engines today can burn biodiesel fuel derived from soybean oil or other vegetable or animal fats. They can burn it in any ratio with petro-diesel up to 100%.
I was just wondering because the electric car was considered to cost so little to run, but if you consider its entire life cycle, it costs more to build and then costs more to dispose of the batteries at the end of its life.
Either way you want to quantify it. When you do fractional distillation of crude oil, gasoline is one of the first products to condense. Later fractions are kerosene, then diesel, heating oil, then tar or paraffin. Due to the high demand for gasoline, the amount of natural gasoline is not enough to supply it. Refiners use catalytic cracking to make shorter hydrocarbon molecules out of the longer molecules in the heavier ends of the refined oil. You can get more gallons of gasoline out of a barrel of crude oil than you can get gallons of diesel fuel. If the purpose is to decrease oil dependency, it is foolish for government regulations to treat MPGGasoline the same as MPGDiesel. Such regulations would cause consumers to increase purchases of diesel powered cars without actually decreasing crude oil consumption.
How much energy is consumed growing crops that would be converted into biodiesel? What about the environmental impact of cultivating more land to produce energy yielding crops?
You can convert distillate fractions (diesel fuel, jet fuel, heating oil) into gasoline instead of selling as distillate, if that's what you mean.
Refiners use cat cracking to convert the heavier fractions to shorter chains to make gasoline, as you point out. Of course, if the demand for the heavier fractions were greater, they wouldn't bother. The heavier fractions they're cracking are exactly the ones that could have gone into diesel.
There are also technologies that can be used to polymerize up the lighter fractions into heavier fractions.
You can essentially convert crude into any distribution of hydrocarbons you want to, depending on how much you want to invest in process chemistry to do it.
Standard #2 diesel fuel has about 15% more BTU per gallon than regular unleaded gasoline. A healthy, modern diesel engine gets well more than 15% more MPG than a gasoline engine for the same application. It also pollutes less while doing it.
If you're talking about petroleum consumption (and not the sunlight that grows the crops), the numbers indicate its about a 3-1 ratio; three gallons of biodiesel out for every gallon in.
What about the environmental impact of cultivating more land to produce energy yielding crops?
As opposed to what? The environmental impact of nuking Iran so they'll leave our oil supply alone?
The future of biodiesel production is going to utilize algae, watered with salt water, in marginal land areas. I've seen numbers that indicate that we could put 20% of the southern California desert to biodiesel production, using salt water from the Gulf of California, and replace our entire current diesel fuel needs.
If Iran were to be nuked, it wouldn't be because of their oil but their nuclear weapons program.
And the reason Iran can afford to build/buy nuclear weapons in the first place is because of their oil revenue.
And the reason their nuclear weapons program is a particular threat to us is their close proximity to the straits of Hormuz, a choke point on the world's oil supply.
In fact, the reason we're next door in Iraq in the first place is to finish the business of 1991. The reason we cared about Saddam attacking Kuwait in 1991 was because (a) Kuwait had oil; and (b) we were afraid Saddam wasn't going to stop at Kuwait but would grab the Saudi oil fields also.
Oil has a lot to do with the situation we're in. That, and the complete foreign policy idiocy of the Clinton administration.
I find the reflexive condemnation of biofuels on FR to be rather silly. It's like a religion with some people on here. Never mind. The free market is going to take care of it, and the higher the price of oil goes the more important biofuels will become.
I'm not condemning them, but you'd have to show me that they can be produced profitably on a rather large scale without subsidies. Biodiesel is probably a better bet than ethanol.
Luv your moniker...In the year 1900, in London, it was calculated that at the current rate of growth of horse drawn traffic, in 20 years the entire city would be covered in a half mile deep pile of horse****, instead, much later, it was covered with a mile deep layer of SMOG from cars....
LOL.....coffee all over keyboard!
It was a mixup. I went into a meeting by mistake, said "Oh, I don't belong here," and they wouldn't let me leave. :-)
Good thing someone didn't invent the internal combustion engine in the 1700's, oil (and gasoline) was really scarce then!lol! And a good point. As if scarcity was a problem in 1900 when there was hardly any use of gasoline. I guess that's part of the allure of hydrogen or bio-diesel, that the sources are everywhere.
As for horses, they certainly were a major source of urban pollution and disease. On top of cruel treatment, the other problem with horses was space for housing them and their hay. The automobile beautifully answered these problems, especially since gasoline was easier to store than hay and, ironically, a lesser source of fires, and because cars could be stacked on top of each other in that marvelous invention, the mult-floor garage. Additionally, cars moved faster and were shorter than horse & carriage, which meant more and better flowing street traffic. The automobile truly opened up cities for better use of space.
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