On 22-Apr-17 12:47 PM, Chris Hogg wrote: ...
As they are working on ways of reducing the cost of producing hydrogen, they have been working on getting the same amount while using less energy. Both claim to have made breakthroughs in doing that. As these are processes with commercial applications, no details have been given, but I assume that the use of catalysts implies that there is some chemical reaction involved as well as pure electrolysis.
All that any catalyst does is speed the reaction up. The amount of energy required for the splitting, per unit, will not change.
You can assume what you like mate, but the fact remains that the binding energy has to be overcome, and that sets a limit on the process. You cant magically create energy out of nothing. The energy you get be recombining hydrogen and oxygen will never exceed what you put in to split them in the first place.
And in fact is usually a whole lot less.
Using electricity to make hydrogen and then burning that to create electricity is a round trip efficiency of probably less than 30% as batteries go, that's crap.
If basic physics wer mandatory like English is supposed to be there wouldn't be as single renewable/alternative energy company in operation.
They all survive because of grants granted by the technically illiterate.
On 23-Apr-17 8:13 AM, harry wrote: ...
Third generation steam locomotives are not typical. They have been specifically designed to use modern technology. The 5AT project failed to get the target funding, but the calculation of drawbar efficiency is given here:
Using 21st century or 19th century materials?
Whatever you want to think, an R&D subsidiary of IAV Gmbh developed a small, lightweight steam engine, using modern technology throughout, that could be fitted into motor vehicles, although they see the initial application as being in auxiliary power units, particularly in third world countries. They claim fuel efficiency as being similar to a diesel engine. It uses catalytic heating to avoid flames, which keeps emissions down to very low levels, and can burn a very wide range of fuels. Steam is viable, even if that does not sit well with your world view.
Technically perhaps ...but economically?
IC engines are good because you don't have to lug the fuel oxidant or the working fluid around. Its in huge supply as atmospheric oxygen and gases respectively.
Once you are building a static installation though, steam predominates and is more efficient, because you can run huge condensers on the back end.
And you have a variety of thermal sources that you can hook up - coal, oil gas, nuclear.
+1000!
It also makes no difference whether you do the process in a number of steps, or in one step, the total energy required to split water into its components will be the same. The idea that you can split water for less energy than you get back when you recombine the products is born out of and fostered by ignorance of the most fundamental laws of chemical thermodynamics.
Freezing points are irrelevant. So are boiling points. It's just gases and absolute temperatures.
+1
From the wiki entry for the Carnot cycle I posted elsewhere in this thread, the theoretical maximum efficiency of a heat engine is given as 1 - Tc/Th, where Tc is the lower temperature and Th is the higher temperature, both in kelvins
A quote from that article:
"Carnot realized that in reality it is not possible to build a thermodynamically reversible engine, so real heat engines are even less efficient than indicated by Equation 3. In addition, real engines that operate along this cycle are rare. Nevertheless, Equation 3 is extremely useful for determining the maximum efficiency that could ever be expected for a given set of thermal reservoirs".
Note that the basis for the formula depends on a relationship between energy and temperature that is not necessarily obeyed if you go through a phase change.
I can't help feeling there's a misunderstanding somewhere along the line. Unless they're being deliberately fraudulent, the researchers you're referring to must know that it's impossible to split water and then get more energy back by burning the products. So either they've been misreported, or you've misunderstood the reports you've read, or you've not explained here what you read, very well, or we've misunderstood you. Links to your original sources might help.
If they're just claiming an improvement in the efficiency of splitting water, from something not very good due to heat generated and wasted during electrolysis, to something that doesn't produce as much heat such as catalysis, that I could believe, but you still wouldn't get more energy out than you put in, and the idea of running a car on water as the fuel is still absurd.
This turns out not to be the case.
You can, for example, use the warm exhaust to preheat the incoming air & fuel.
Andy
FFS Kelvins aren't degrees.
And it must be absolute temperature for the equations to work.
Just consider what the results would look like for Tin-Tout/Tout if Tout was negative.
Andy
Perhaps these researchers are of the same ilk as the Cold Fusion ones, or that autism/vaccination [1] twerp.
Of course, all the dim lightbulbs can't understand why you couldn't e.g. just put water in your car instead of petrol. They haven't grasped that water is already burnt.
Yes they are. Each one equal a degree C, but the scale starts at absolute zero rather than at the melting point of ice.
Actually Tin-Tout/Tin. Which equals 1 - Tout/Tin.
And the reason its degrees K is because the kinetic energy in a gas is proportional to its temperature in K. Just look up thermal efficiency in Winky.
[1] I see the anti-vax twerps are still on the go, with outbreaks of measles as a result.
Well, assuming by "Kelvins" you meant Degrees Kelvin and by "degrees" you meant degrees Celcius, they are! If the standard atmospheric pressure had been a higher value than it's currently assumed, those degrees Celcius would simply have been a larger sized increment across the arbitrary 100 degrees Mr Celcius had chosen to span the freezing and boiling points of pure water and a smaller starting volume of gas than the 273cc's worth at zero degrees Celcius would have been determined as the basis for establishing where absolute zero would be in the (now) larger scale units of degrees Celcius.
Anyhow, putting that aside, degrees Kelvin are directly based on degrees Celcius no matter that there is an element of arbitrariness in the Celcius scale. The difference is merely in where the zero point is set on the scales. In the case of degrees Kelvin, this was based on an Absolute Zero derived from the behaviour of gases which all exhibited the same expansion coefficient throughout their gas phase, allowing the Absolute Zero point to be extrapolated beyond the limits set by each particular gas's liquifaction points at NTP.
My bad, I just assumed that mere temperature differences would suffice. :-(
Obviously, I *didn't* consider negative temperatures, just temperature differences. :-(
Mother nature has beaten us to this 'trick' as can be seen in the anatomy of penguins' feet where the veins and arteries in their legs run side by side so as to allow the veins to recover heat from the arteries before it gets lost by contact with the ice upon which they roost or walk. The feet themselves are little more than bones, ligaments and tendons acting as remote controlled low temperature tolerant appendages.
In the case of the flash boiler, the hot combustion products are routed in a contra-flow to the direction of the feed water flow from the condenser and the boiler unit itself is extremely well insulated to minimise unproductive heat loss through the casing.
Getting back to the original question, most electric vehicle designs eliminate the mechanical variable ratio gearbox, electing instead to use high power handling switching converters to control the motor speed instead. Even when a design uses a fixed gear ratio box to better match the loading on the drive motor, electronic drive voltage control is still the method by which modern electric road vehicles are speed regulated.
In an ideal setup, you would have hub motors in each wheel which could be arranged as a series wired pair on each axle to provide a built in differential and halving of the current required to drive each axle's worth of hub motors.
However, in order to maximise efficiency and power to weight performance of electric traction motors, you get the best performance using a high rpm motor[1] which basically precludes direct drive hub motor designs unless you're prepared to sacrifice top end performance for improved battery economy at more modest urban traffic speeds (you replace mechanical transmission losses with much lower electric cabling losses).
[1] High rpm on account it uses less turns of heavier gauge copper in its windings, meaning reduced I squared R losses.
But needs more current to achieve the same magnetic moment.
No, what counts is magnetic reversals per second, times the iron mass.
You can achieve that with a lot of poles, or a lot of RPM.
Copper losses turn out to be pretty much independent of the configuration, and are a more a function of as you say RPM BUT its not 'RPM' that matters, its 'poles per second'.
The effect is negligible and leads ot all sorts of control problems. The specific heat of air is low.
I looked up water-fuelled cars on wiki. The whole business is riddled with fraudulent claims. I suspect nightjar has been suckered by one such.
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