I'm into alternative energy, but since I work in the oil and gas sector now, I come across different kinds of news. Here's to someday putting my geology training to better use than sucking oil and gas out of the ground! Converting trucks to compressed natural gas, including comments on wellhead filling stations: http://bismarcktribune.com/bakken/b...cle_2b136478-386c-11e4-8fef-001a4bcf887a.html
from the article "Mileage was 1 to 2 gallons per mile better with CNG" Translation please? A liquid measure for a gaseous fuel? Gallons per mile might be used for a jet plane or Canadians on a nostalgia binge. It's fun to note that NG is so cheap it doesn't pay to pipe it to the grid.
I think they either a) converted the energy output into MPG (seen later is a reference to "gallon of gasoline equivalent") or 2) converted the volume of CNG to gallons. One of the reasons they're making headway on the flaring situation (besides state intervention) is that mineral rights owners were suing because they weren't getting royalties for flared gas, which counts as produced under the mineral lease.
Still doesn't compute. This guy makes more sense: What fascinates me the most is the number one question I’m asked: “what kind of gas mileage do you get?” It’s an interesting question because CNG is a gas and therefore there’s no such thing as a gallon of it. That’s hard to explain while screaming out a car window. Though the question is slightly flawed, the answer is fundamentally easy. Compressed natural gas is measured in gasoline gallon equivalents (GGE), which means exactly what it sounds like. One GGE of natural gas produces an equal amount of energy as a gallon of gasoline. Therefore it gets the exact same gas mileage. However, a GGE of natural gas costs significantly less (I pay $1.39). For example, the gas mileage for my 2011 CNG Tahoe is the same as its gasoline counterpart: 21 MPG on the highway. However, if I spend $2.90 (the cost of gasoline in Oklahoma) on CNG, I’ll get over two GGEs and be able to travel around 50 miles. This is true in all cases. So, the next time you’re asked what kind of MPG an NGV gets, you can say: “The same as I would with gasoline, it’s just cheaper to fill up. And cleaner burning, too.” Or I might just yell out my window, “Visit cngnow.com/blog!” link
A better solution for trucks is probably switching them to dimethyl ether (DME). DME can be made from coal and China is already using it to run some of their buses. It is a drop in replacement for propane (you could grill with it) and it has a high cetane number, making it an ideal diesel replacement. The only modification usually required is valve lubrication like you'd use on a gasoline engine, since many diesel engines use slippery diesel fuel for that.
At a defined pressure and temperature, there sure is a gallon of CNG, but I understand the point. Good find on the better explanation. gturner, what's the DME manufacturing process like? Natural gas is coming out of the ground and needs to be distributed and compressed.
For DME you take coal and turn it into producer gas (CO and H2), which you then run through a catalyst. You can convert the gas to methanol and then dehydrate the methanol, or you can combine both catalysts (copper and aluminum) and produce DME directly as 3CO + 3H2 -> CH3OCH3 +CO2. You can also produce it from natural gas or biomass. China is looking at it to go along with LP gas as a cooking fuel, since about a billion Chinese still cook over solid fuels, which is a major indoor pollution hazard. Princeton paper on DME in China, along with cost figures. For some of these alternative fuels, an obvious market would be railroads because they are also their own fuel transport network, and it would be relatively easy to even hook up a liquid hydrogen tank behind a locomotive engine, which you couldn't do for a car or truck.
sorry to belittle the point, but a at 1atm and 0C it would take 950 gallons of natural gas to equal 1 gallon of gasoline in terms of energy content. The equivalency is there, but it really isn't meaningful.* The article linked in the OP stated Mileage was 1 to 2 gallons per mile better with CNG. which is utter nonsense. Granted it wasn't a technical journal but I'd hope the writer of a technical article would have at least junior high level math and science skills or get the energy guys she's writing about to check her facts. *going from memory, but it takes 127CF at 1atm of NG to equal the BTU content of 1 Gallon of gasoline. Check my math as an exercise for the class.
It's compressed, not at standard temperature and pressure. I agree the article could have been clearer, good thing I didn't write it. http://en.wikipedia.org/wiki/Gasoline_gallon_equivalent#Compressed_natural_gas
It should never have been published. "Gallons per mile" is not a measurement of fuel efficiency (maybe in tanks and steamships). Increased gallons per mile being cited as an improvement is a logical fallacy, both because this would infer reduced efficiency and because the use of the measurement "gallons" by itself is meaningless in terms of gasses. As noted in my post above (#5), the efficiency is the same, gallon of gasoline compared with GGE of Natural Gas by definition. The writer should have her Junior Ace Reporter card revoked. The article fails to accurately describe what it is they're burning in their trucks. I think it's "associated petroleum gas" or APG, a mixture that's rather nasty and not marketable at all without refinement and not Natural Gas. This might explain why their trucks have to remain "dual fuel" in order to start running using gasoline and then switch to whatever they extract at the wellhead after they've warmed up (the heavier hydrocarbons in APG will liquefy at frosty temperatures). "Natural Gas," the stuff that's piped to our homes is quite happy igniting at sub zero (F) temperatures. APG goes through several refinement steps and the heavier hydrocarbons are removed (i.e. butane for our cigarette lighters) source: (The "to sales gas pipeline" would be the stuff we burn at home) This raises the question of whether their use is commercially feasible. Even with free APG, I don't see anyone lining up to use it. CNG on the other hand IS natural gas. There is nothing new or exciting about this alternate fuel. Honda is already selling CNG Civics and have for some time. They aren't practical outside of fleet sales as the cost of compressing the gas to a practical pressure for transport and use is prohibitive. The stuff that's piped to our houses, even if you could afford a compressor, isn't suitable for burning in their cars (according to Honda). Even Honda is rather coy not mentioning the usable range of their Civics. At even 2500psi the tanks must be very heavy and thick (think SCUBA tanks). You won't be able to carry the volume of CNG that you could gasoline. A gasoline civic holds about 12 gallons. If they use available interior space to hold CNG tanks maybe they achieve half the range (150miles?) of similar gasoline civics. Consumer Reports found their test CNG Civic priced $8,000 higher than an equivalent gasoline Civic with a range of only 130 miles.
Oil prices falling: http://qz.com/278945/oil-prices-have-plunged-through-another-psychological-barrier/ I now see my complete brain fart with "gallons per mile"--I must have switched it around in my head the dozen times or so that I read it. Glad I started this thread, thanks steve2^4!
From the linked article: That's completely backwards. Prices are falling because the global economy is back in the tank and demand has accordingly shrunk.
Both statements are true. The price is depressed by slack demand, but low prices can stimulate production by lowering the cost of a major input. Of course, it's not so simple as any of that, but just the same, low prices can definitely prime the pump, so to speak.
Oil prices dropping more. http://www.businessweek.com/news/2014-12-12/crude-oil-extends-drop-below-60-as-iea-cuts-forecast Saudi Arabia is trying to cut off shale oil production in the US and elsewhere. Shale oil costs more per well to produce, so it's only economically viable at higher oil prices. This has been hurting smaller operators for a few months now, but the majors are starting to cut back projections as well. http://www.nytimes.com/2014/12/09/b...ow-and-companies-start-to-retrench-.html?_r=0 Not sure what this will mean for everyone in the industry. It will probably slow down new drilling first, which means fewer rig workers needed...
I'm not arguing that. It's just that when the whole economy tanks, people are all , even though we all know it will get better again, someday.
The bottom line: no matter the technique for producing X amount of energy it still takes energy to produce it. It's six of one/half dozen of the other. As energy consumers increase (via growing economies) we will still get further and further behind. Demand needs to lessen ACROSS THE GLOBE. Will we as a planet do this? Hell no - but it's what we have to do before the planet says "sorry - no can do" and kicks us back to the stone-age.
Energy's not a zero-sum game, @oldfella1962. Well, it is, but not on any scale humans need to worry about. We've got plenty of energy left in fossil fuels--we keep finding new ways to get 'em out of the ground--and there's still a very abundant supply of nuclear fuel. Within a few decades, we will crack fusion, and then our energy problems will vanish. Huge amounts of energy will be available very cheaply. Demand lessen? No. People 100 years from now will use much more energy than you or I do, even though their devices will be much more efficient.
And in response to the Russians raising interest rates to 17% in response to the nose-dive of the ruble, the ruble continues to nose-dive and the Russian stock market crashes some more. A basket case Russia with lots and lots of nukes and a strong-arm lunatic running the place is not a comforting thought.
I think we should start a cash for efficient cars program and offer incentives for buying a 2015 Ford Excursion (zombie edition) in order to stabilize the world oil market and avoid nuclear armageddon.
I've been looking into an approximated Ericsson Cycle engine, which can almost reach Carnot efficiency by isothermal compression and expansion. It's not been used in piston engines because it's too hard to cool the gas as it compresses via the side walls, but if you compress the gas in small increments you can cool it in between stages. If you use an axial compressor you just put regenerators in between stages so that you final temperature is similar to ambient. Since the gas doesn't heat up, it's much easier to compress, boosting efficiency. On the expansion side you keep injecting heat in between expansion stages, so the exhaust gas temperature is the same as the combustion temperature. Then the exhaust gas is run through another regenerator or recuperator so that it's heat is transferred to the still cool, compressed air about to enter the combustion chamber. You could think of it as a Brayton cycle with massive amounts of regeneration and reheat, but unlike the Brayton cycle, the efficiency isn't dependent on compression ratio, only the ratio of combustion versus exit temperature. Anyway, I was thinking of compressing the gas in small increments using pistons, which are cheap and efficient, with each stage feeding a large air tank or finned-pipe that feeds into the next stage, letting the gas cool back to ambient after each stage. But to run the efficiency way up I'd want extremely high combustion temperatures, possibly using pure oxygen from pressure-swing adsorption. But that runs into issues with turbine entry temperatures (even advanced blades couldn't take it), and lubricating expansion pistons at those temperatures is problematic, not to mention the problem of having the pistons melt. But suppose I used something like a kiln for the expansion chamber, insulated with 3600F or better refractory (such as various cerium oxide castable refractories such as you'd find in a glass plant). So the refractory-lined kiln is the cylinder and cylinder head of a piston expansion stage. But instead of using a piston (which can't work because it would just grind through the refractory, and couldn't be lubricated anyway, I nearly fill the kiln with a molten metal, with an outflow at the bottom. Then the piston is actually the surface of a molten lake, and as the combustion gas forces the surface down, the liquid outflow is used to do work, either driving a turbine or pushing up a column of liquid somewhere else. The exhaust from the piston cycle is then reheated (fuel injection) and the cycle repeated several times, since the goal is isothermal expansion for maximum efficiency. That should allow combustion temperatures to soar into the range of high-temperature refractories - 2000C or higher, and allow the engine efficiency to pass 80 percent.