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The trick to making gas turbines work is to make it a turbine-hybrid vehicle.. use the turbine to power an electric generator at a more or less constant load to charge a battery bank and use electric motors to drive the wheels. Electric motors have phenomenally good torque curves even at low RPMs.
The problem with the 1960's based turbine vehicles is that they always tried to use mechanical transmissions between the engine and the wheel. Not very efficient to gear down as you point out and hard to throttle them up and down for the demands of city driving. The electric motor battery hybrid model solves that problem and it is MORE thermodynamically efficient than existing hybrids and MORE flexible w.r.t. fuel choice.
Other nice features will be that they are naturally quieter and that the engines will last forever for all intents and purposes. In aviation applications, piston engines require overhaul between 1500 and 2000 hours depending on the model. Turbine engines routinely go 20,000, 30,000 or more hours between overhauls.
The engines will also be safer if you use fuels other than gasoline or alcohol. Kerosene and diesel or bio-diesel are much harder to accidentally ignite.
The hybrid approach I propose also allows these vehicles to function as purely electric rechargeable for short distance daily commutes and they could also double as back up generators for households in the event of natural disaster, terrorism, or other utility failure scenarios. If you had a 50kW to 100kW turbine, it could easily power your house and 10 of your neighbors completely.
The nice thing about turbines is that they don't really care a lot WHAT they burn, you could run them from kerosene, diesel, gasoline, ethanol, methanol, natural gas, rubber bands, plastic spoons (I exaggerate but you get the point). The fuels could be either petro based or from renewable agri sources.
This fuel flexibility feature and the electric hybrid nature of my concept which allows the vehicles to function on shorter runs as pure electrics will force the various energy companies to actually compete against each other and will allow the widest possible variety of energy sources to power our vehicles: traditional petro-chemical, agri-renewable, solar electric, nuclear, hydro, wind, geo-thermal, landfill recovered natural gas - whatever floats your boat...
This approach will truly put the power over energy costs back into the hands of the consumers in a way it simply is not today.
Regarding landfill methane as a fuel source, one thing people don't realize is that our landfills are contributing huge amounts of methane to the atmosphere every year which is actually a far more potent greenhouse gas than CO2. It would be better to convert it to CO2 than to allow it to escape into the atmosphere unburned and then burn something else to create CO2 on top of that so that we could power our vehicles.
As for corn, it is being misused in food stock anyways. It is being used to create corn syrup sweeteners which are making us all fat and causing health problems. It is also being used to feed livestock which is also very inefficient.
Sugar cane seems to be the best solution based on Brazil's experience and right now the gov't subsidizes sugar growers to keep the price artificially high and keep them in business. US sugar prices are 5 times the world market price.
Methanol for fuel cell vehicles can be produced from just about any cellulose source including fast growing tree varieties like hybridized lob-lolly pines.
Further down the road, methanol fuel cell holds great promise and will be even more efficient since it utilizes electro-chemical and not thermodynamic processes. Instead of 40% efficiency of a turbine set up you easily could be seeing up to 70% efficiency for MFC processes.
Hydrogen fuel cells are supposed to be the so called "magic bullet" to global warming but in reality they pose many problems that MFC or turbine-hybrid do not:
Cryogenic fuel handling is something that hardly anyone outside of NASA, the military, and major chemical companies do today. It is hard to imagine average Joe drivers doing it routinely.
Hydrogen is difficult to produce and the only way to produce it without generating greenhouse gases would be through electrolysis powered by nuclear, solar, hydro or wind power.
It takes a lot of energy to liquify the hydrogen and it is difficult to store any significant quantity of it because it is so light, about 1/8th the density of water even in liquid form.
Methanol is very similar to gasoline in terms of handling so distribution infrastructure would be much easier to adapt and/or implement than for hydrogen.
I hope you understand my POV better now..
Douglas J. De Clue Bachelor of Aerospace Engineering, Georgia Tech
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