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Splitting water is a very energy inefficient process so if you want hydrogen that badly, you’d better make sure you have a large surplus of electrical power generated from other sources. But yes you can use e.g. a lot of hydroelectric power plus the water itself to make hydrogen fuel. Perfect for Norway or perhaps places where the sun shines continuously

The Japanese have apparently been very serious about hydrogen for the past couple of years, and it’s probably no coincidence that Japan is also big in hydroelectric power generation.

Last Edited by Silvaire at 31 May 04:27

Nuclear fusion would be great for making hydrogen…

Shoreham EGKA, United Kingdom

LeSving wrote:

What hydrogen has as an advantage is incredibly high energy density (kWh/kg), almost 3x that of gasoline, about 200x that of current battery technology.

But that’s pretty much irrelevant, because to get high energy density per volume you either have to store it cryogenically (which is very awkward, and not at all user friendly) or compress it to such tremendous pressures that the vessel that holds it has to be incredibly heavy and you’ll have very few choices on what shape the tank can be (basically, you’re stuck with cylinders with thick walls…which will still leak the hydrogen anyway, and become embrittled and as such have a short lifetime compared to cylinders storing other high pressure gases). This isn’t helped by hydrogen having such a low molecular weight, which means its energy density per litre (very poor) dominates over its energy density per kg (which is nearly irrelevant).

Gasoline has an energy density of 9.5kWh per litre, liquid hydrogen (basically as dense as you’re going ever make it) only 2.7kWh per litre, and only 1.4kWh per litre when compressed to a pressure of 690 bar (10,000 psi). At standard temperature and pressure, hydrogen’s energy density is absolutely pathetic at only 0.003kWh per litre.

Electrolysis is a complete non-starter unless you need hydrogen for some industrial process and it just so happens it’s the most convenient way to make it. Otherwise it’s far better to use the energy from renewables by putting it on the grid where it can be used rather more efficiently than turning into hydrogen which is awful as an energy storage medium. If you need to store energy from a renewable source, there are far better ways to do it, such as flow batteries (some of which have very high energy densities, and are orders of magnitude more efficient).

If we do develop a cheap efficient way of making hydrogen, I bet the first thing done to it if it’s to be used for energy storage for transportation – will be to tack on a bunch of carbon atoms.

Last Edited by alioth at 31 May 08:59
Andreas IOM

LeSving wrote:

Regarding global warming. I took the picture below less than 2 hours ago when walking in the woods with my wife (tomorrow it’s June 1)

What is your point? That global warming is a hoax because there was some snow on June 1st? Surely you know better than that!

ESKC (Uppsala/Sundbro), Sweden

Funny to see all this chat here. I’m currently running a 4 year project on solar water splitting

EIWT, Ireland

And I bet if you’re successful, someone’s project will be how to add to this project an economic way to tack on a bunch of carbon atoms to what you produce – because let’s face it – raw hydrogen is NEVER going to be a useful transport fuel.

Andreas IOM

alioth wrote:

But that’s pretty much irrelevant

No, it’s not. Take a look at the Japan paper referenced by Silvaire. Hydrogen is packed full of (green) energy per kg no matter how you look at it, and no matter how you store and distribute it.

IMO the main point is there simply is no free lunch. I’m sure at least 50% of the European population have been led to believe that “going green” is simply a matter of building enough solar plants and wind power plants, and all will be well. All the free energy in the world, “if only the politicians would act, and the gas and oil companies would stop working against it”. This is what children learn in schools these days.

Although wind and solar is a part of the solution, it’s only a small part, the simplest part, and by far the cheapest part. Without the other, difficult and expensive part, solar and wind is worth nothing. Hydrogen is a key component in the solution, there is nothing else that realistically can replace it. Maybe batteries will increase their power density by a factor 10-100, but that is much farther from a solution (even on a purely theoretical level) than using hydrogen. Nuclear will solve lots of problems, unfortunately it’s popularity is not the best, except in France and Finland.

Airborne_Again wrote:

What is your point?

To show one of the many effects of global warming of course


LeSving wrote:

Hydrogen is packed full of (green) energy per kg no matter how you look at it, and no matter how you store and distribute it.

But per kg is pretty useless when each kg takes up such a huge volume and the gas is difficult to store and handle.

For grid storage, flow batteries will be about 1000 times more easily managed and more practical than using hydrogen (which requires costly rare catalysts for both electrolysis and use in fuel cells, and electrolysis is tragically inefficient). They are based on liquids that are not particularly hazardous and don’t need to be compressed to ludicrous pressures. For transport – especially air transport – forget it – it’s not going to replace liquid fuels because even if you compress it to 10,000 psi it is vastly less energy dense per litre (and even less so, when you consider you can no longer make the fuel tank simply the shape of a wing D section) and due to the weight of the high pressure tank it’s also going to simultaneously lose a lot of energy density per kg (a modern composite high pressure tank, designed for 500 bar (we actually need nearly 700 bar) with a 250L capacity weighs 495lbs, or 225kg). No one is going to trade a safe, easily maintained and managed way of storing fuel (fuels that are liquid at room temperature) for a dangerous, heavy, high pressure system that has an energy density per litre less than 1/3rd of avgas. (A Bonanza for example carries around 300L of avgas, the equivalent in hydrogen would be at least 900L of high pressure tanks, the maths just doesn’t work for hydrogen and air transport once you realise what you need to store a gas at 10,000 psi with the consequently heavy gas cylinders)

Last Edited by alioth at 31 May 12:54
Andreas IOM

Maybe there will be a useful competition between Japan (now committed to Hydrogen for transportable energy) and the EU, with its politics of the moment focused on electric propulsion and batteries. North America can then (as always) use both as appropriate, plus fossil fuels for applications where highest power density storage is really required – like flying. It’ll be interesting to watch other people spending their money

There is regardless no chance that I’ll own or fly anything in my lifetime (a few decades given a bit of luck) that isn’t AVGAS powered.

Last Edited by Silvaire at 31 May 14:05

Silvaire wrote:

There is regardless no chance that I’ll own or fly anything in my lifetime (a few decades given a bit of luck) that isn’t AVGAS powered.

With a bit of luck you wouldn’t get tempted by a nice turboprop?

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