Manufacturing Hydrogen

deckart

What is/are the process(es) to manufacture hydrogen? The reason I ask is I'm curious as to the amount of energy required to get and store hydrogen. And, if the process itself makes it an energy source worth the expense of manufacturing.

Q_Goest

The vast majority of hydrogen made today is done by steam reforming of natural gas.

thearny

I believe there are certain bacteria that manufacture hydrogen. Can't really see that steam reforming and hydrolising water are sustainable.

Astronuc

One would have to do a cost comparison of different energy sources.

There are applications for which hydrogen is essentially! One process is ammonia production, which can also be used as a fuel - the ammonia is cracked to form N₂ and 3H₂.

Steam reforming of natural gas is the most practical process given the large (but not inexhaustible) supply currently. Hydrogen is then purified and stored as a compressed gas or cryogenically. So to evaluate the cost, one must know the cost of natural gas being converted to hydrogen, the cost of the energy used to do the convertion, and the energy required to compress and store the gas. Cryogenic storage also requires that energy be removed from the hydrogen.

Converting the hydrogen to ammonia should also be considered.

At some point, hydrogen may be the most available fuel - once natural gas is depleted. So other processes are being investigated, but one must determine the processes which can produce hydrogen in millions of kgs, or millions of cubic meters.

A world in which transportation has a significant role in the economy requires a transportable (and storable) fuel.

luckycharms

Go to the DOE hydrogen website and they have all kinds of facts and figures. Production, storage, and usage are three different beasts.

Basically, hydrogen production is an economics problem, storage is a technological problem, and usage is somewhere in between. We know how to produce H2, we just can't do it cheaply enough to compete with fossil fuels or without using them in the first place. Storing it (in a non-Hindenburg fashion) is something that really hasn't been figured out from a technology standpoint so we can't really begin to consider economics. We know how to use it, in a fuel cell for example, but they need to be improved both technologically and economically.

russ_watters

But how large is large? If we start powering all of our cars from natural gas, I'm not sure "large" will be very large for very long.

Also, doesn't steam rerforming, then burning create exactly the same pollutants that straight burning the methane does? If so, it doesn't really fit the goal of the "hydrogen economy".

I think the end-game of the hydrogen economy is going to have to be water->hydrogen-> water and the energy source is going to have to come from somewhere else (the hydrogen won't be an energy source, just a carrier).

Astronuc

Well after all, fossil fuels are nothing more than solar energy stored in chemical form.

So one could produce hydrogen from solar power - PV or solar dynamic. Essentially an endless supply of energy for the next few billion years!

russ_watters

What we need is something that is renewable on human timescales. Certainly, but I'm not sure the economics of that will ever work. My money's on nuclear.

Ivan Seeking

There is a plant going up in Nevada, or at least it should be by now, that is designed to crack methane using concentrated solar, ultimately yielding hydrogen, I think oxygen, and ultra-pure carbon as marketable products. So there are carbon dioxide emission free processes coming along for methane as a hydrogen supply. Next, if we can tap the vast reserves of methane trapped in ocean clathrates, supplies could last for 500 years or more. Presently, the best well to wheels efficiency [for autos] is found in the methane -> hydrogen -> fuel cell -> electric motor fuel chain.
http://www.physicsforums.com/showthread.php?t=29373

Astronuc

Well there is Fischer-Tropsch synthesis which takes CO₂ + H₂ --> light alkanes and alkenes -> heavier alkanes and alkenes.

Presumably there are fast growing plants (perhaps phtyoplankton or phyto-bacteria) which also takes CO₂ + H₂ and produces cellulose or sugar or other compounds of C, H and O.

It would also help to increase fuel efficiency or otherwise reduce wasteful use of hydrocarbons.

Using solar energy, which isn't necessarily stored, and which is always available somewhere on the earth, makes the most sense.

Ivan Seeking

Here we go
http://www.eere.energy.gov/hydrogena...ewandowski.pdf

scott1

Isn't there one way where you can frezze oxygen to it's liguid(or soild)state and wait tell starts vaporize and that gass that starts to varproize is hydrogen?Or is that helium?

russ_watters

Huh? Oxygen is oxygen. Liquid or gas. Are you for real?

scott1

Sorry I ment air.I'll edit that
Can a mod edit that for me for some reason it let me edit it

pallidin

Sure, one could probably extract hydrogen from air using some type of advanced freezing/controlled thawing, but could you imagine the costs!!!
Also, I suppose one could even design a centrifuge that would seperate the various densities of air-gases. But again, imagine the costs-vs-the volume of hydrogen obtained.

Ivan Seeking

Air is mainly O₂ and N₂ - no H.

We can get hydrogen from H₂O because it has [an H] hydrogen as part of the molecule.

Natural gas - Methane - is CH₄, which is why we look to methane as a source of hydrogen.

Astronuc

Air has been liquified for about 100 years. Primarily it was done for the oxygen, however, it other gases were collected as well.

Interesting history at - http://www.boc.com/aboutus/history/index.asp (click on History on right to get decade index)

BOC is one of the largest companies producing industrial gas. Others are Linde (formerly part of Union Carbide) and Air Liquide.

Lecture by Heike Kamerlingh Onnes -
nobelprize.org/physics/laureates/1913/onnes-lecture.pdf

From Linde Engineering - the history of air liquefaction -
http://www.linde-process-engineering...on_history.php

As Ivan Seeking mentioned, air is primarily N₂ and O₂ - ~78% and 21%, respectively. The hydrogen in the air is in the form of water vapor, which is removed in the initial stages of compression of the air before it is cooled, because water freezes at 273 K.

Ultimately, once fossil fuels are depleted, hydrogen will be produced mainly from dissociation of water (H₂O). Hydrogen production in a nuclear power plant is one consideration, as well as from solar power.