Why is energy density important in that context? If all other variables were identical between a high density an a low density solution, the high density one would of course be preferable. But if the low density solution is cheaper and relies less on pre-existing long-distance grid infrastructure, why would high density still be considered the most efficient, or possibly the only viable pathway?

IANAE but the general idea from the discipline of urban geography is that industrialization, and also the knowledge economy relies on the economies of scales that come from high density, mixed-used urbanization. These regions rely on extremely high power that must be supplied from scarce land resources.

Hmm. If the target is 1MWh in a year, that seems trivial to deliver in a place like Chad. Insolation in Chad should be right around 6 or 7 kWh per sq metre. [0] Chop off 85% of that, because we can't harvest all of the solar energy that falls on a square metre of land. We can only reliably capture maybe 15 to 20% of it. But even if you harvest that 1.5 kWh for only 4 hours a day, (which is pretty easy in the middle of the Sahara where you should get about 8-12 hours a day), it comes in around 120 kWh per month. Well above the 1MWh per annum target.

So on the distribution side, they have a population of only 13 million, with a geographic size of 1.2 billion sq metres, which lands us at roughly a thousand times the amount of energy they need to meet the 1MWh per annum per Chad citizen. If they were harvesting it that is. (And that's using 20% efficient solar panels alone. No wind, etc.)

Chad's problem is a lack of anything to trade in exchange for the equipment to harness the sun and build the storage and distribution network. (Grid distribution infrastructure, maybe a liquid air storage facility or 3, solar panels etc) But the sun itself provides them more than enough energy to meet that 1MWh per annum per capita target.

[0] https://en.wikipedia.org/wiki/Solar_irradiance

Solar panels themselves are only 10% - 15% efficient at converting solar to electricity. So I think your estimate here is off by a factor of 10.

If you google “solar panel efficiency”, you will instantly find several sources that all indicate that most (cheap!) solar panels are 15% to 20% efficient, which is 50% higher than the number you’re providing. Top end residential solar panels are over 20% efficient, somewhere in the neighborhood of 22%. Specialized/research solar panels can reach efficiencies of over 40%.

Also, energy density is not nearly as important as you seem to fundamentally believe. It’s pretty much all about cost and availability.

In countries that use very little energy per capita, even just a single solar panel (with a small inverter and a lead acid battery) per person (or even per family) is life changing, giving them enough energy to run a small refrigerator, a light bulb, and a place to recharge their smartphone without having to go into town and pay someone.

In deep urban environments, space is definitely at a premium, but I struggle to imagine that many people are excited to set up a dirty diesel plant in the town square when air quality is already bad enough due to heavily polluting vehicles running in the city center, let alone set up a small nuclear plant, even if wealthier countries would allow such a proliferation of nuclear technology and fuels. Once the nuclear fuel is spent, then you have this extremely toxic, dangerous waste that has to be put somewhere, and those people probably have a lot of other things on their minds, so you could just be rad poisoning their town by giving them nuclear if they don’t dispose of the waste properly.

On the other hand, the rooftops are prime locations for solar panels and solar water heaters, and because 175W/m^2 of solar converted electricity is actually a ton of energy, it’s still plenty of power.

Unfortunately, cost and availability are king. Wealthy countries are happy to sell old assets at a steep discount, and so shiny new solar panels have to compete with second hand fossil fuel plants / generators that don’t lend themselves to great air quality.

Solar is an extremely sensible solution. Nuclear is not a clear answer at all for developing countries, unless you happen to have the design for a clean, portable cold fusion reactor in your pocket. Fission has a lot of problems that are manageable, but managing those problems takes significant money.

Your comment about a solar panel and battery reminds me of my van with solar panel and 100ahr lead acid battery and a 2000W inverter.

Things I've done with it. Run a Engel Cooler. Run a microwave. Boil water. Probably 1-2 gallons a day. Charge batteries for power tools. Run a skill saw. Power lights indefinitely.

With just that you're getting close to a middle class lifestyle.

Grandparent estimated capturing 15%-20%, so they’re only off by a factor of 0x-2x from your estimate range.

I'm not going to provide a source, but my understanding is that one square meter can provide roughly 1 KW of electricity at noon on the equator. Looks like that's about 4MW per acre. Five acres for the "traditional" family farm. I bet where I live that irradiation equals 1MW per acre, and of course it varies seasonally. Sounds ridiculous, until you've tried to water any sizable amount of square footage, and contemplated the heat energy required to evaporate all that water which doesn't go into the plants and isn't runoff.

1 KW sounds high to me. Granted I work in higher latitudes (42). Rule of thumb is 1KW for peak solar radiation, which translates 100W from a solar panel (which are 15% - 20% efficiency).

And the sun in eight light minutes away. The sheer power is mind boggling.