So while using a photovoltaic cell may technically be possible, it makes more sense to use a fuel cell.Hope this helps.

In negative curvature the sum of the angles of a triangle are less than 180 degrees, for flat, or Eucledian, they add to exactly 180, and for positive curvature they add to more than 180 degrees.You cannot visualise the actual 4-dimensional shapes but you can easily describe them with math. As the price of petrol increases, I’m confident more money will go into fuel cell research, and any problems will be solved. I suppose most of the combustion energy from burning hydrogen is not instantly emitted from the flame (as UV or any other radiation) but remains in the hot water vapour.

A burning hydrogen flame, for instance, radiates strongly in the 185 to 260 nanometer range and only very weakly in the IR region, while a coal fire emits very weakly in the UV band yet very strongly at IR wavelengths;http://en.wikipedia.org/wiki/UltravioletSo maybe it’s just question of technique toget UV light from burning hydrogen and use itin highly efficient UV cells?And also I thought that in specially designed combustion camera all radiation not absorbedby photocell could be reflected back to heat source. Hydrogen flames do emit IR as well as UV, due to the main product of combustion being water vapor. Luckily, the two are very similar values.I did try to find a spectrum of the photons released by burning hydrogen, but could not find one on google.

I do maintain that this could be used in conjunction with a fuel cell, though. The think the limit is how fast you need to go; I suspect they are built more for economy than for speed. The doughnut shape, called a torus I believe, is the 3-dimensional analogue of 4-dimensional, negatively curved space/time, just like a sphere is the 3D analogue of positively curved space/time and a flat sheet is the 3D analogue of flat space/time.The positively curved is finite but unbounded while the flat and negatively curved are infinite and unbounded.Another 3D example of negative curvature is a saddle, which is equivalent to a section of the inner part of a doughnut.Simple geometric properties. Or find better catalysts for ionising the hydrogen.

I will look into it, but I think it’s 33% of energy absorbed is converted to useful energy. This is why we see the following in the combustion of hydrogen;In addition, the efficiency of even the most modern photovoltaic cells is around 33%, compared to around 50% in a hydrogen fuel cell. Related Discussions:Photovoltaic moduleThermovoltaic car close to reality? »Cold Fusion » that really works?Meaning of anomalous photovoltaic effect?a higher energy output for gasoline?Solar cellsVolcanoes vs young earthersSnow turning black with flameIs combustion endothermic, too?Hydrogen powered cars Originally Posted by Stanley514 I do maintain that this could be used in conjunction with a fuel cell, though. Originally Posted by xspike I just watched a program on documentary channel, where this guy who hardly knew anything bout maths was gettin taught bout prime numbers and other such stuff..They got to a question where the teacher was like « If you get this question right, you’ll get $1million bux » I thought that was a simple question to answer…Well I’ll tell you their answer first, they said it was like a 4D donut. (I won’t bother explaining what a 4D donut is like but I guess a lot of you have heard or something like it..)My simple answer would of been endless for a universe, or a near sphere shape for the end of the material universe.I don’t see how they could come up with anything else, in the donut you could reach the « end » of the universe and if you pass that point you’ll end up on the other side of the universe and you could pretty much travel till you reach the point where you left off on your journey…Where on mine you could reach the end of the material universe which is most likely material which has been thrown further out into space by a recent supernova or even further if your counting how far light as traveled since the first star was born (which would still be traveling today..

What are your thoughts? It may be technically possible to get more power out of a fuel cell, but there is no need to do so in a car. Do you mean burning of hydrogen or gasoline?As I know hydrogen burns with invisible ultraviolet flame.Or you mean thatphotocells are so non-efficient that theywaste much of energy as heat?How do you think efficient could be photovoltaic system for a car?I think if we will create a good thermal isolation,maybe even vacuum isolation,so energy from combustionwill not be able to escape otherwise as radiation,and will make few layers photocells,efficiency could be closer to 100%. Fuel cells are another option (I am not sure which is better).Just my gut feelings – I have not studied the maths or physics behind any of this.

The 4D doughnut shape would have anomalies that we would be able to see. Most people do. The hydrogen around the outside probably burns with an invisible flame.I think the IR in combustion comes from the new bonds formed moving/bending/stretching to de-excite.Another point; the calculation I did before was slightly wrong; I should have used the bond enthalpy for the O-H bond rather than the enthalpy of combustion. For example, how would the 2-dimensional inhabitants on a flat sheet of paper visualise a pencil?Intersect the pencil with the sheet of paper (poke it through) and you get a 2-dimensional circle, ie a cross-section of the pencil. That’s an interesting picture.

We can hoever visualise in 3 or less dimensions. What is main limitation of fuel flow in fuel cell?Is it mostly chemical, like speed of catalysis orrather mechanical problems?I thought that catalysis should happen in milliseconds. I remain skeptical that the color was due to the hydrogen, and not some other combustible material. I think you are confusing the absence of any material thing with the absence of space-time.

Hydrogen has a very wide flammability range with oxygen and I don’t believe it ever burns yellow. However, electrons will more often de-excite in steps, rather than in one go, releasing a number of lower-frequency photons (not ultraviolet). However I’m more than willing to be proven wrong.Interesting words and pictures here:http://books.google.com/books?id=Hju…um=7#PPA165,M1 I can work it out for you;So yes, if the energy is released in a single photon it would be very near ultraviolet radiation, you are correct. In addition, the efficiency of even the most modern photovoltaic cells is around 33% In conventional solar cells there is numberon looses which could be avoided in combustion camera.For example light reflection.If some photon will be reflected incamera it will just get in other photocell (on other side). Related Discussions:Question about: Expansion of the Universe.The shape ot the universe »Shape » of the UniverseUniverse stretching ?The shape of our universe..they saydoes the universe have a boundry?What is the simplest definition for time?The shape of the universeEmbryonic development of mullusks Photovoltaic cells would not be able to use that, and so this solution would be very inefficient, dissipating lots of energy as unused heat.It would make much more sense to use the hydrogen in an ordinary internal-combustion engine (such as contemporary pertol or Diesel engines).

Do you know why fuel cells have such low power density?Is there some hope to increase it? Yes; put the fuel through the cell at a greater rate. Photovoltaic cells would not be able to use that, and so this solution would be very inefficient, dissipating lots of energy as unused heat. Is it in fact the burning of the rubber balloon that the hydrogen was contained in, or is it perhaps not a true-color photo?

I’m just curious because I’ve seen many hydrogen flames, and I’ve seen hydrogen filled ballons exploding but I’ve never seen a yellow flame. I do maintain that this could be used in conjunction with a fuel cell, though. The Hindenburg disaster exhibited a yellow flame and this was attributed to burning of the aluminum paint on the cover, and/or burning diesel fuel.(I was curious enough to google up the source of the photo, which is here http://uw.physics.wisc.edu/~wonders/DemoH.html and was a bit shocked to find this statement on a university physics page: Helium is a special gas called a Nobel Gas The word is noble not Nobel.) The colour of the flame depends very much on the availability of oxygen. I suspect they are built more for economy than for speed But catalysis all the same always happens withthe same speed.How could they slow it downand thus increase fuel economy?In general fuel cells seems to me less fortunate then their metal-air siblings.The latest don’t need any catalyst or bulky membranes.It could be good to see the sameimprovement in fuel cells which work on hydrocarbons.You also may take in account this:http://www.triplepundit.com/pages/nanoantennas-so.phpI also interested to know how could weinsulate combustion camera so energy wouldbe able to escape only as radiation?Is usual glass OK for this purpose?Is it prosorous for IR?

That is the same problem we have with 4D space/time. So while using a photovoltaic cell may technically be possible, it makes more sense to use a fuel cell.Hope this helps. I suppose most of the combustion energy from burning hydrogen is not instantly emitted from the flame (as UV or any other radiation) but remains in the hot water vapour.

In a balloon, oxygen is only present in tiny amounts to the hydrogen in the middle. You could possibly use it as well as a fuel cell.Most of the energy, though, is turned to infrared rather than ultraviolet/visible light. What is main limitation of fuel flow in fuel cell?Is it mostly chemical, like speed of catalysis orrather mechanical problems?I thought that catalysis should happen in milliseconds. I just watched a program on documentary channel, where this guy who hardly knew anything bout maths was gettin taught bout prime numbers and other such stuff..They essaywriterforhire.com
got to a question where the teacher was like « If you get this question right, you’ll get $1million bux » I thought that was a simple question to answer…Well I’ll tell you their answer first, they said it was like a 4D donut. (I won’t bother explaining what a 4D donut is like but I guess a lot of you have heard or something like it..)My simple answer would of been endless for a universe, or a near sphere shape for the end of the material universe.I don’t see how they could come up with anything else, in the donut you could reach the « end » of the universe and if you pass that point you’ll end up on the other side of the universe and you could pretty much travel till you reach the point where you left off on your journey…Where on mine you could reach the end of the material universe which is most likely material which has been thrown further out into space by a recent supernova or even further if your counting how far light as traveled since the first star was born (which would still be traveling today.. at the speed of light).If you could pass that then you’ll reach a part of the universe which has nothing and will go on forever in deep darkness.I think I should of gotten that million dollars.. Originally Posted by Stanley514 Yes; put the fuel through the cell at a greater rate. It is confusing.Welcome to the forum.

Most of the energy, though, is turned to infrared rather than ultraviolet/visible light. Yes; put the fuel through the cell at a greater rate. However, IR and UV are not visible to the human eye so what are we seeing? Usually a yellow flame is associated with burning hydrocarbons.

Do you know why fuel cells have such low power density?Is there some hope to increase it?There exist entire bunch of technologies which convert heat directly to electrics:1)Thermoelectrics2)Pyroelectrics3)Thermovoltaics4)Infrared antennas5)Fuel cellsIt’s strange that non of them works better thaninternal combustion.And especially great problem is power density. The hypersphere (a 4D sphere) works best for an expanding universe. But the pencil’s length is in a dimension that the paper’s inhabitants cannot visualise.