This page contains selected posts of newsworthy topics related to the subject of this website, on occasion commented on by me.

How much water would a country need to make its primary energy in the form of hydrogen?

I just picked this one up via Linkedin, so I thought I’d have a go at it with the example of Spain given in the question:

Bottom line – well, actually the top line 🙂 with the assumptions made below, the amount of water needed in Spain for the necessary hydrogen per year would be 2.6% of current agricultural use of water in Spain per year. Note, this is based SOLELY on the assumptions and information below: it is not necessarily realistic, but gives some kind of idea…

Here’s a back-of-an-envelope calculation that I’ve just done, assuming the following:

1. We very crudely equate current primary energy consumption in Spain directly 1:1 with equivalent energy from hydrogen. This definitely isn’t 100% accurate, because, for example, hydrogen-fired steel-making uses less MWh per tonne of steel than coal-fired steel making. However, it gives us a reference point from which to refine the calculation.

2. Current annual primary energy consumption in Spain is around 1,600 Terawatts per year (see

3. The electrolysis reaction is H2O -> H2 plus 0.5 O2

4. Molar masses (molecular „weights“) are H2O = 18 g/mol ; H2 = 2 g/mol which means, in terms of mass (weight), we need nine tonnes of water to make one tonne of hydrogen gas.

5. Hydrogen has a gravimetric energy density of 131 MJ/kg (averaged between HHV and LHV, because we don’t know whether we can recuperate the energy of water vapour formation); this is equal to 36 kWh/kg hydrogen gas.

The calculation:

1,600 TWh per year is 1.6 x 10EXP12 kWh per year

Divided by 36 kWh/kg hydrogen gas energy content => 4.4 x10EXP10 kg hydrogen

This equals 44 million tonnes of necessary hydrogen gas.

To make that via electrolysis, the theoretical minimum mass of water is 9 x 44 million tonnes, which = 400 million tonnes of necessary water.

How much are 400 million tonnes of water? – i.e. 400 million cubic meters.

From Statista, I get a value of 15,500 million cubic meters of water used currently in agriculture in Spain per year (see . So, 40 divided by 15,500 gives us a relation to current agricultural usage of water, and it equals 2.6%.

Bottom line: with the assumptions made above, the amount of water needed in Spain for the necessary hydrogen per year would be 2.6% of current agricultural use of water in Spain per year.

On the impacts of mineral and ore mining…

2024, January: United Nations predicts serious environmental and social impacts of raw material mining up to 2060…

January 2024 „Extraction of raw materials to rise by 60% by 2060, says UN report“ — in The Guardian newspaper, UK. Quote from the article „Electric vehicles, for example, use almost 10 times more “critical raw materials” than conventional cars, and reaching net zero transport emissions by 2050 would require increasing critical mineral extraction for them sixfold within 15 years.“

And see also report in Sustainability & Environment Network 2024.

Copyright Andrew Moore 2024