Why create green hydrogen using renewable energy? Why not directly use electricity from Renewable sources?

Question

We generate "green hydrogen" using electrolysis of water which is powered by Renewable energy sources like Solar Panels, Wind mills, Hydro power etc.

When we obtain such hydrogen and store it for use later on to generate electricity, the output can be below 30% of the input electricity.

Why even produce such green hydrogen through sheer wastage of electricity produced through renewable means? Why not directly use that electricity to power industries and homes?

People say "hydrogen can be an alternate fuel". I think we can directly make a transition to "electric vehicles" rather than finding "alternate fuels" endlessly until there are no more options left but "electricity"(green, of course)

Answer 1

It's a matter of energy density. Compared to lithium-ion batteries, compressed hydrogen gas stores about 150 times as much energy per kilogram, or twice as much energy per liter.

If you're using the energy immediately after generating it, then yes, direct power makes sense. But if you're storing it for later, or need to use it to power something that can't be plugged in (such as an airplane), then you want to store it in a compact form. Something like gasoline would be a better choice than hydrogen (better volumetric density and easier to handle), but we don't know how to turn electricity into gasoline. We do know how to turn electricity into hydrogen.

Answer 2

Try to use electricity and nitrogen to create ammonia for fertilizer production. I'm sure you see the difficulties in that, as electricity is not an element and thus the only element you have is nitrogen. The element hydrogen is missing. Ammonia requires hydrogen and nitrogen.

Then, try to use electricity to create hydrogen from water (electrolysis) and use that hydrogen and nitrogen to create ammonia for fertilizers. Now you have all the elements you need to make the ammonia molecules.

Similarly, I'm sure that iron production from iron ore is far easier to be done with hydrogen (that takes the oxygen from the iron ore away and makes water as a byproduct) instead of direct electricity. I have heard about plans to make iron using hydrogen to replace coal-based iron production, but have never heard about plans to make iron using direct electricity. However, later on in the steel production chain you might need an electric arc furnace if you need high temperatures, and that actually uses direct electricity and not hydrogen.

Also hydrogen is very easy to store. Salt cavern storage costs about 50 euros per cubic meter. If you can cram hydrogen there at a pressure of 100 bar, it's 0.5 euros per natural cubic meter of hydrogen. A natural cubic meter weighs 0.08988 kg so at density if about 120 MJ/kg (using the lower heating value here) or 33.333 kWh/kg, a natural cubic meter stores approximately 3 kWh. So storage cost is 0.5 EUR / 3 kWh or 0.167 EUR / kWh. The current batteries cost 100 EUR / kWh, nearly three orders of magnitude difference. Even if you take into account that converting hydrogen back to electricity has 50% energy efficiency, hydrogen storage is still 300 times cheaper than lithium ion. Why is this important? Because if you live anywhere far away from the equator, solar power is heavily seasonal. You get lots of it during summer, and practically nothing at winter. Solar power (specifically, photovoltaics, as solar-thermal is very expensive and its cost is not falling exponentially) is projected to become the cheapest electricity production method. Hydrogen allows storing solar power created during summer for consumption during winter. Batteries are way too expensive for seasonal energy storage, although in areas near the equator batteries win for charging during every day and discharging during every night (because batteries have 99% efficiency compared to 75% for hydrogen production and 50% for converting back into electricity or 37.5% for the whole hydrogen chain).

And before you claim that hey let's transport solar power from equatorial deserts long distances, remember that electricity transportation has very large losses and is extremely expensive. Electricity has to be produced near where it's consumed. (Actually you could transport the power as hydrogen using very low losses, having far cheaper transmission pipelines than electricity transmission lines. The trouble is creating that hydrogen in the first place has high losses and converting that hydrogen back into electricity has high losses.)

I agree that whenever electricity is available, it should be consumed immediately. If electricity production all the time matches consumption, then you only use electricity immediately. But production using intermittent renewables never matches the consumption, and that's why you need storage. Batteries win for storage between days, hydrogen wins for storage between seasons.

So what you are missing is failing to realize that renewables are intermittent. If we could produce load-adjustable nuclear power plants cheaply enough then you'd be partially right, hydrogen would not be needed for anything apart from chemical reactions that require hydrogen.

Answer 3

Well, as far as Hydrogen is concerned, the primary reason why it is so sought after is, EASE OF STORAGE and this has already been discussed. Further, transportation and distribution of energy through, say Hydrogen tankers, is much easier, given its high energy density compared to batteries (weight to volume ratio of batteries is quite high) and elimination of after-use disposal problems associated with batteries.

Secondly, the most promising aspect of Hydrogen comes into play when Hydrogen is produced through renewable means. Electricity produced through Solar panels which is then used to produce Green Hydrogen by Electrolyzers is the most viable solution to the world energy problem.