Is PV Enough?

An Eccentric Anomaly: Ed Davies's Blog

Specifically, could photovoltaic panels alone provide all the energy needs of the human race.

Obviously it wouldn't be sensible to try; it'd be much better to use a mix of PV, wind, hydro, tidal, geothermal and what have you but still PV is likely to be a significant contributor (mostly because it tends to be sunny where a lot of the people are or will be) so it's at least worthwhile to do a back-of-the-envelope calculation to see if it's plausible.

Towards the end of this century there are expected to be about 11 billion people on the planet, in round numbers the seven billion around now and their immediate replacements plus another billion in Asia and another three billion in Africa.

Currently the average European uses about 5 kW of energy. Americans and Australians use something like twice as much, the rest a lot less. It seems like a reasonable amount to aim for for everybody (though some argue, plausibly, for less).

Note that this is total energy use, not just electricity, so includes use of fossil fuels for heating, manufacturing, transport and so on. On the other hand, primary energy is, I think, a bit more as it includes waste heat from power stations and so on. [[Update: 2018-01-22: nope, I now think that's 5 kW of primary energy. Final energy is more like 2.8 kW/peep so the areas below should be reduced by about 44% which is good news. More discussion. ]] Also, the actual consumption of Europeans is probably a bit higher because of the energy embodied in goods imported from other continents. Still, it gives an idea of the energy needs for a reasonable lifestyle with a modicum of care to avoid waste.

11 billion (11e9) people, 5 kW (5e3 W) each so that's 55e12 watts total needed.

In direct sunlight current PV panels produce about 150 W/m².

According to PVGIS a 1 kW solar panel flat on the ground on a spot in Algeria would produce 1490 kWh per year. Since a (common) year is 8760 hours long that's a fraction better than one sixth of the year.

We're calculating the land area needed so can assume the panels are laid flat. In practice, of course, they're propped up which saves on the panel area needed but doesn't save on land area.

So the total area needed for PV panels would be:

55e12 W / 150 W/m² × 6 = 2.2e12 m² = 2.2e6 km².

How big is that? The square root of 2.2 is just under 1.5 (15² = 225) so that's a square 1500 km on a side. Or about the size of Algeria.

Obviously plastering over just one country would be silly (and a bit rude, really). Ideally we'd have large and small solar farms all over the place with lots of HVDC lines cross connecting things so when it's cloudy somewhere it's likely to be sunny (or windy or wet or hot) elsewhere thereby reducing the storage needed.

Also, it might turn out to be cheaper to use lower efficiency panels needing more area.

Ignoring such details we can say, though, that it would indeed be reasonable to consider providing most of the world's energy needs from PV. I don't know of any other energy source for which that could be said.