Pushing the Natural Gas Vehicle
As an increasing number of states descend on Detroit to push automakers to focus more effort on natural gas vehicles, the question of success becomes on of refueling, and new innovations, including home fueling stations, could push prices down enough to make this a very competitive market. Some of the latest stories on this ...
It will be interesting to see how GE's plans for a quick fueling system for natural gas vehicles pans out. This is part an ARPA-E funded group of thirteen projects to improve natural gas fueling. If they succeed with any momentum this could revolutionize CNG vehicles. Detroit is likely holding out for this to happen first.
Jalic says: "It will be interesting to see how GE's plans for a quick fueling system for natural gas vehicles pans out. This is part an ARPA-E funded group of thirteen projects to improve natural gas fueling. If they succeed with any momentum this could revolutionize CNG vehicles. Detroit is likely holding out for this to happen first."
Natural gas makes a good motor fuel after it is first converted into a conventional liquid hydrocarbon fuel, such as gasoline, diesel, jet, methanol, etc. All the developed, tried and proven, in-place technology and infrastructure continue to function seemlessly. Large scale compressed natural gas for transportation fuel is just a bad idea. It's just never going to happen because it's too easy to convert NG into methanol.
Very interesting. So how do you think this will play out, and if it has no chance of happening, why the push on Detroit?
Jalic says: "So how do you think this will play out, and if it has no chance of happening, why the push on Detroit?"
Can't say why so many silly things are in the world. Probably some knave will make a profit on the folly of others. Several decades back, the Italian government actually implemented a state sponsored CNG system for private vehicles. Italy had no oil of its own but it had a NG pipeline that ran across to North Africa. On a small market scale, say less than 100,000 small vehicles that travel relatively short distances, it's cheaper to put pressure tanks in cars and install a few high pressure compressors and storage tanks and use CNG directly than to build the methanol synfuel process plants. In the US with over a hundred million vehicles that burn gasoline and diesel the NG to methanol synfuel route has huge economies of scale and is the only rational way to go.
<<Jalic says: “Very interesting. So how do you think this will play out, and if it has no chance of happening, why the push on Detroit?”
My previous response to your question now seems too flippant, so I’ll elaborate a little. Sadly, a really bright man named Don Lancaster passed a few years back. Before he passed, he did the good work to produce a technically objective public service web site that everyone with opinions about alternative energy systems should read. The site is still working.
Don Lancaster: “Two important methods of fairly comparing the value of energy delivery schemes are to ask "How big is it?" and "How much does it weigh?" Although many measurement schemes exist, I feel the fairest and most general are a volumetric energy density in watthours per liter and a gravimetric energy density in watthours per kilogram. There are roughly four liters in a gallon, or 3.785 to be more precise.” Then he provides a valuable comparison chart:
ENERGY DENSITY COMPARISONS
Gasoline 9000 Wh/l 13,500 Wh/Kg
LNG 7216 Wh/l 12,100 Wh/Kg
CNG @ 3600 PSI 2500 Wh/l 14,700 Wh/Kg
Propane 6600 Wh/l 13,900 Wh/Kg
Ethanol 6100 WH/l 7,850 Wh/Kg
Liquid H2 2600 Wh/l 39,000* Wh/Kg
150 Bar H2 405 WH/l 39,000* Wh/Kg
Lithium 250 Wh/l 350 Wh/Kg
Flywheel 210 Wh/l 120 Wh/Kg
Liquid N2 65 Wh/l 55 Wh/Kg
Lead Acid 40 Wh/l 25 Wh/Kg
Compr Air 17 Wh/l 34 Wh/Kg
STP H2 2.7 Wh/l 39,000* Wh/Kg
Whenever one hears promotional propaganda for CNG vehicles, one generally doesn't hear about the many technical negatives. I'll mention several CNG negatives the proponents generally omit.
(1) The energy needed to compress NG to 3,600 psi requires about 10% of the chemical energy in the gas. That’s about the same amount of energy that would be needed to power chemical process to otherwise convert the NG into synthesized conventional fuels. That is to say, we could use the 10% energy to either make gasoline of the NG or to compress it.
(2) Look at Lancaster’s comparison chart and notice 3.6 gallons of CNG @ 3,600 PSI is required to equal the energy of 1 gallon of gasoline (I added the 3,600 PSI CNG line). That means for equal energy storage, at an absolute minimum, the CNG tank volume must be 3.6 times larger than the gasoline tank. To get the same range that a 15-gallon gasoline tank provides, the comparable CNG tank must be 54-gallons. Think of the size of a 55-gallon drum. Well that’s just silly, because passenger cars aren’t nearly large enough to carry that much volume. And there is most of the nub of it. All else being equal, if the CNG tank is the size of a 15-gallon gasoline tank, it only holds the energy equivalent of four gallons of gasoline.
(3) But to make matters worse, all else is anything but equal. Notice Lancaster’s comparison chart shows each Kg of CNG contains 14,700 Wh of energy, which is comparable to gasoline @ 13,500 Wh. What is not shown is the gasoline tank size and weight is a small percentage of the fuel it contains. The CNG pressure tank must safely contain 3,600 PSI pressurized gas. So the tank must actually be strong enough to contain 7,000 PSI. Unless the tank is fabricated from Krell metal or some other brand of unobtanium, the tank itself must weigh as much or more than its contents. In practical terms, because the tank weight is unavoidable, CNG energy density per unit of weight is very much less than gasoline. That weight doesn’t materially diminish as fuel is withdrawn from the tank; so whenever the vehicle accelerates or brakes, extra energy must be expended to accommodate the constant dead weight of the tank. Obviously that must reduce overall vehicle performance.
(4) Because CNG energy density is so poor, and the pressure tanks so bulky and heavy, most CNG vehicles are actually gasoline powered vehicles that have been designed or modified to also run for a limited range on CNG. In a sense the CNG scheme is similar to the Volt, which can run about 40-miles on batteries, and then the gasoline engine kicks in and powers the car for another 265-miles. When the Volt batteries run down, the vehicle must drag the dead weight of discharged batteries around, except the Volt batteries recover some of the momentum energy through regenerative braking. Obviously production costs of CNG vehicles must be significantly higher than gasoline only vehicles because of the expensive 7,000 PSI pressure tanks.
(5) Because it’s infeasible to transport and distribute NG in the compressed state, each distribution center must have its own high-pressure NG compressor and large-volume high-pressure storage tank. The depreciation and capital cost of that equipment must be borne by the customers or the state.
Many more fair objections might be raised, but from the above you should get a general picture. Gasoline and Diesel offer the best combination of volumetric and gravimetric energy density of all feasible fuels. The infrastructure is already in place for gasoline and diesel vehicles. Hybrid electric/gasoline/diesel vehicles just make a lot more sense than hybrid CNG/gasoline vehicles.
In most instances, CNG vehicles in the US (although not everywhere on earth) are sort of a fraud perpetrated on the innumerate fools by the cunning knaves. All the CNG vehicle systems are heavily subsidized with taxpayer money, so there are always political purposes. Wherever there is a trough full of taxpayer money, greedy hogs will migrate from great distances to thrust their snouts fully to the jowl joints in the abundance of swill.
To be fair to CNG vehicles, one should notice that motorists with CNG hybrid vehicles and natural gas utility services can invest $5,000 into a home NG compressor, and recharge their vehicle tanks with electric grid power driving their uncertain lifespan low-volume NG compressor while they, and their neighbors, try to snooze to the lulling song of the compressor whanging away out in the garage. In effect they would be doing about what plug-in electric hybrid owners do. Their electric bills and their gas bills will increase. I’d guess their combined electric and gas bills to run the compressors would increase more than just the electric bill would increase to directly recharge hybrid Volt batteries. In both cases if they are going to drive over 40-miles they will mostly be burning gasoline.
Last edited by Niccolo5; 07-20-2012 at 08:46 PM.
Collecting road taxes on alternative fuel vehicles
I have a question about electric and natural gas vehicles? When it comes to paying taxes on road use, it was "built in" to the cost of a gallon of gasoline on every purchase. How will the appropriate taxes be collected when cars are recharging at home or using natural gas from the residential lines? Don't think this won't come up at some time. Any suggestions on how it can be implemented?
<<When it comes to paying taxes on road use, it was "built in" to the cost of a gallon of gasoline on every purchase. How will the appropriate taxes be collected when cars are recharging at home or using natural gas from the residential lines? Don't think this won't come up at some time. Any suggestions on how it can be implemented?>>
It’s a bad idea to try to road use tax alternative fuel vehicles. But if the bad idea is to be implemented, probably the least onerous method would be taxing by the mile as indicated on the vehicle odometer during the annual state vehicle inspection procedure. Most states have real time data links to the state’s motor vehicle department. The road tax would then be added to the annual vehicle registration renewal fee. The state could then adjust road tax rates according to class of vehicle. Obviously, a Chevy Cruze puts less wear and tear on roads than a two-ton truck. If you don’t pay the road tax you don’t get a license tag.
Did you know that there are way more natural gas automobiles in Iran than in any other nation? Since natural gas is plentiful in Iran, natural gas cars are easily becoming the very best way of getting around for the residents of that nation despite the raw regime they live under. Source for this article: Iran Natural Gas Cars.
I imagine that natural gas was used to minimize domestic consumption of oil and leave more for exporting. With the sanctions in place and exports falling it would be interesting to know if more people are turing to gasoline cars because of the abundance of oil supply.
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