I read a couple of months ago that if 15% of the Algerian territory would be covered with (photovoltaic) solar panels, their production would be sufficient to supply the worldwide energy demand, on a yearly basis.

After my first reaction of surprise, I took my calculator and had a look on Wikipedia.  Algeria has got a total area of 2.382.000 km², 15% of that is 357.300 km², thus 357.300.000.000 m² (or 3,57 × 10^11 m²).  Common commercially available (photovoltaic) solar panels of 1,73 m × 1,13 m (thus 1,95 m²) generate 400 Wp, thus 204 Wp/m².  And, in the south of Algeria (in the region of the Tenere desert) the solar production is of 3.600 hours equivalent (at Wp constant production) by year.  Thus, gathering all the elements together, we have 3,57 × 10^11 × 204 × 3,6 10^3 = 262.000 TWh/y (262.000.000.000.000.000 kWh/y, or 262 PWh: 262 peta Watt hour).  And since 1 kWh = 3.600 MJ, this is equivalent to 945.000 PJ (peta Joule, or 945 EJ: exa Joule).  This latest conversion is important since the worldwide yearly primary energy consumption (across all types of sources, fossil or not) is expressed in this unit.

The worldwide yearly (in 2019, which most the recent figure available by the time of writing) energy consumption was of around 418 EJ of primary energy (figure depending a little bit on the information source).  It is thus less than the solar electricity production of 15% of the Algerian territory.  The assertion is correct, but we have to challenge it against the final use, because solar power cannot be used in the same way the large majority of the total primary energy consumption is.  Very simply, among others, the sun does not shine during the night, and the whole world can’t be wired till Algeria.  So, transformation, transportation and conversion are necessary, each having a yield that is (of course) below 100%.

To be supplied all around the world, the yearly gross production of 945 EJ, should partly be transmitted locally and further in the region for ‘local’ use, partly transformed in H2 (by hydrolysis) and transported to where H2 is used as feedstock, or itself partly further transformed in methane (CH4) for later (or downwards) electricity generation or heating (dwellings or industrial processes).

If we assume that 50% of the worldwide yearly energy consumption, thus 209 EJ, is used as industrial feedstock, taking into account an electrolysis (+transport consumption) yield of 70%, it will require a solar sourcing need of 298 EJ (209 EJ / 70%).
If we further assume that 25% of the remaining 209 EJ of the worldwide yearly energy consumption will be in the form of electricity, let us say  1/5 in the region (thus just transmitted, with 10% loss) and 4/5 through transformation (in CCGT) of CH4  (obtained by methanation of electrolysed H2), assuming for this latest a global end-to-end yield of 40%, this part will require 12 EJ (1/5 of 25% of 209 EJ / 90%) + 104 EJ (4/5 of 25% of 209 EJ / 40%), thus a solar sourcing need of 116 EJ.
If we finally assume that the remaining 75% of the 209 EJ, is used for heating purposes, requiring the transformation of the solar production in CH4 and its transport, figuring out a global end-to-end yield of 65%, this part will require 241 EJ (75% of 209 EJ / 65%).

The yearly total is thus:

• 298 EJ of gross solar energy to feed 209 EJ needs as feedstock
• 116 EJ of gross solar energy to cover 52 EJ of electricity consumption (direct and through H2-CH4-CCGT generation)
• 241 EJ of gross solar energy to cover the 156 EJ of heating for dwellings and industrial process needs (through h2-CH4 cascade conversion)

thus globally 655 EJ of gross solar production.

Although some yields used above are quite high, they are not futuristic, thus not so far from the actually achievable ones.  Further the today energy demand is also not optimized, and will be lowered in the coming years, due to the improvements made under the constraints of the present energy crisis, or due to the awareness induced by it. So that the demand will drop in the coming years. Additionally, while the assumptions presented above, about the split in the 3 different kind of use is very coarse, their goal is just to give a quite correct approximation of the primary sourcing needs.

Next, the area used in the calculation equals 15% of the Algerian country, but the entire Sahel belt is much larger than that (3.053.000 km² compared to the 357.300 km²), leaving a margin of nearly a tenfold to cover a possible gap.  Very comfortable in comparison with the discrepancies affecting the assumptions about the yields and the split in usages.

Regarding these figures, the question is now why don’t we just realize it ?

Of course, the project is huge, it is indeed as large as the energy transition we have to achieve.  We could start realizing it with the installation of solar panels produced by the existing factories and, in parallel, build local factories to produce new (next) ones, and so on till the production will quench the required installation pace.

The project requires, of course, much more than the installation of solar panels, like the construction of electric lines and of industrial electrolysers and methanisers, the building of port accesses, the construction of pipelines, and of see water desalinisation stations.  These all on the African continent, so that it remains ‘local’ (wired with the production sites), will bring prosperity and wellness for people (provided that the project is realized ethically), that would rapidly join the levels we live in Europe.

The solar power should in first instance be dedicated to quench the local needs in electricity, including the (sometimes deep) water pumping, creating in the same time a vast oasis of shadow.  Conditions probably also favourable to the development of agriculture.

Of course, sourcing all our energy from one unique (even extraordinarily large) region is once again like putting all our eggs in one basket.  A more balanced perspective would be to reduce our consumption by 50% or more and accelerate the deployment of European renewable generation, in parallel with the realization of the Sahel solar project.

In any case this Sahel solar energy factory will require CO2 captured at (European) sites (where the renewable methane will be burned) and streamed back (through pipelines and ships) to the methanation sites (in Africa), so that the process requires a real collaboration (the ones providing energy and the others material that is necessary) to generate a large part of the energy needs.  The dependence is so bidirectional, what will automatically lead to a real and continuous win-win relation.

Considering this huge potential, I hope the presence of the Wagner group (thus Russia) in the Sahel region is not related to that.  It is perhaps seeking far, but who knows ?  For the moment all (collaboration) options are still open, as far as I know.