## 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 https://ourworldindata.org/energy/country/spain).

3. The electrolysis reaction is H_{2}O -> H_{2} plus 0.5 O_{2}

4. Molar masses (molecular „weights“) are H_{2}O = 18 g/mol ; H_{2} = 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 https://www.statista.com/statistics/1218844/irrigation-water-used-agricultural-sector-spain/) . 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…

And see also report in Sustainability & Environment Network 2024.

Copyright Andrew Moore 2024