1) heating the reagents still requires burning fuel (or heat from a nuclear reactor). First case can make the whole process ecologically useless (CO2 is been produced during heating) and the second case increase the risk of a nuclear accident. Using electrical current for heating isn't an ecological solution.
It has been assumed that reaching the required temperature could be done using solar ovens, or electricity from photovoltaïc cells.
Concerning storage, you are right to point out this issue. New processes are being tested right now (including for cars tanks, that should be able to store at least 7 kg of H2 for an autonomy of 500 km): hydrogen can be stored in the molecular cavities of water ice, with an efficiency at least equivalent to the one of metallic alloys. Tetrahydrofuran is needed to stabilize the hydrogen hydrates formed, at a pressure of only 100 atmospheres instead of 2500 normally.
[QUOTE]JY_French said this in post #17 : It has been assumed that reaching the required temperature could be done using solar ovens, or electricity from photovoltaïc cells.
They're likely not effective. Otherwise different solar power plant would have been already built but it's not so.
Concerning storage, you are right to point out this issue. New processes are being tested right now (including for cars tanks, that should be able to store at least 7 kg of H2 for an autonomy of 500 km): hydrogen can be stored in the molecular cavities of water ice, with an efficiency at least equivalent to the one of metallic alloys. Tetrahydrofuran is needed to stabilize the hydrogen hydrates formed, at a pressure of only 100 atmospheres instead of 2500
normally.
Yes there are many methods in the R&D stage But I think carbon nanotubes look much more effecient. Water ice tanks look not more capacital then alloy tanks, they must be freezed not stay in the solid form.
And how long is their lifetime?
nikiTa said this in post #11 : And how many wars do we need to fabricate to sustain the gluttony?
Global conflict over oil...we're just starting to see the surface of this dependence on fossil fuels.
This is starting to surface, Nikita and its starting to scare us all.
You must turn on, tune in and drop out.
Timothy Leary
I reserve the right to be ignorant. That's the Western way of life. The Spy who came in from the cold
Mama always said life was like a box a chocolates, never know what you're gonna get.
It's interesting (funny) when people with no knowledge or training in engineering, mathematics, thermodynamics, or any other field that might lend some credibility to their statements try to come across as educated and informed about technology so far outside their understanding. Remember your statements on this forum when you are tempted to purchase a StarRotor powerplant in leiu of your 50cc moped engine. Normally, skeptics motivate me, but the basic presumption is that their negative remarks are backed by a resume in the field. You remarks really don't do much for me. Have fun on your moped!
Of course it's always good to be skeptical, but there are some valid reasons to believe the StarRotor motor would be significantly more efficient as well as a much simpler engine than the standard gasoline engine. The advantages of a StarRotor Brayton Cycle Engine (SBCE) over the standard Otto Cycle Engine (OCE) used in most automobiles are:
1. A SBCE can use a regenerator to recover exhaust heat and improve efficiency whereas an OCE can't.
2. The SBCE expander (power output stage) allows gas to expand to near atmospheric pressure for better recovery of energy before release, whereas an OCE exhaust gas is still under considerable pressure when released to the atmosphere (hence the muffler).
3. The StarRotor compressor and expander is more efficient at low speeds than a turbine and thus doesn’t need a large speed reducer gear set for use in an automobile. It also allows efficient operation over a wide speed range as compared to a turbine which generally operate efficiently only at one speed.
4. Hot gas in a SBCE is in contact with only a small metal area that carries away combustion heat before it does its work. An OCE has large metal area in the combustion chamber which absorbs significant heart and reduces efficiency. Thus an OCE also requires a large cooling system whereas a SBCE will requires little or none.
4. A SBCE can change engine speed by changing the port timing and compression ratio. This allows more efficient operation at low power levels than throttling the input in an OCE which lowers the effective compression pressure and thus significantly lowers the efficiency. Although lower compression pressure does lower the efficiency of the SBCE as well, it's not as much as with the OCE. For example at an effective ratio of 2 the theoretical Brayton Cycle efficiency is still about 35% whereas the Otto Cycle is only about 27%. And that doesn't include any effects of regeneration that would further improve the Brayton Cycle efficiency.
5. A SBCE has lower friction from having only a few parts that operate in pure rotation with no reciprocating or sliding parts, no pistons, camshafts, or valves.
6. A SBCE can use water injection at the compressor input to further improve its efficiency. This has only a minor effect on OCE efficiency where it's mostly used to minimize detonation at high boost pressures in supercharged engines.
7. An SBCE can burn just about any liquid or gaseous fuel. It doesn’t require high octane gasoline.
8. It is a continuous combustion engine so the fuel burning can be optimized for high efficiency and low emissions.
The big question is, of course, can they actually build on that will work as theory would suggest?
P.S. Perhaps I should clarify that the efficiency I'm referrring to in my discussion of the StarRotor engine is the ratio of mechanical energy output to fuel heat energy input, not how efficiently the fuel is burned. Fuel is burned with near 100% efficiency with both engines.
This brings up a second point. No matter what fuel you want to use. whether petroleum based, alcohol, hydrogen, or swamp gas, the higher the engine efficiency, the less of it you'll have to burn to go a mile. And if the StarRotor engine is as efficient as claimed then imagine how far you could go with a hybrid StarRotor auto. It should be well over 100MPG.
04-04-2005 06:33 PM
