## After reading some information at Friends of Science, I got to thinking about how impossible it will be for us to do what so many people are demanding that we do. This is to go to zero CO_{2} emissions by 2050 by getting off of fossil fuels.

So let’s take a look at the size of the problem. People generally have little idea just how much energy we get from fossil fuels. Figure 1 shows the global annual total and fossil energy consumption from 1880 to 2019, and extensions of both trends to the year 2050. I note that my rough estimate of 2050 total annual energy consumption (241 petawatt-hrs/year) is quite close to the World Energy Organization’s business-as-usual 2050 estimate of 244 PWhr/yr.

So if we are going to zero emissions by 2050, we will need to replace about 193 petawatt-hours (10^{15} watt-hours) of fossil fuel energy per year. Since there are 8,766 hours in a year, we need to build and install about 193 PWhrs/year divided by 8766 hrs/year ≈ 22 terawatts (TW, or 10^{12} watts) of energy generating capacity.

Starting from today, January 25, 2021, there are 10,568 days until January 1, 2050. So we need to install, test, commission, and add to the grid about 22 TW / 10568 days ≈ 2.1 gigawatts/day (GW/day, or 10^{9} watts/day) of generating capacity each and every day from now until 2050.

We can do that in a couple of ways. We could go all nuclear. In that case, we’d need to build, commission, and bring on-line a brand-new 2.1 GW nuclear power plant every single day from now until 2050. Easy, right? …

Don’t like nukes? Well, we could use wind power. Now, the wind doesn’t blow all the time. Typical wind “capacity factor”, the percentage of actual energy generated compared to the nameplate capacity, is about 35%. So we’d have to build, install, commission and bring online just under 3,000 medium-sized (2 megawatt, MW = 10^{6} watts) wind turbines every single day from now until 2050. No problemo, right? …

Don’t like wind? Well, we could use solar. Per the NREL, actual delivery from grid-scale solar panel installations on a 24/7/365 basis is on the order of 8.3 watts per square metre depending on location. So we’d have to cover ≈ 96 square miles (250 square kilometres) with solar panels, wire them up, test them, and connect them to the grid every single day from now until 2050. Child’s play, right?

Of course, if we go with wind or solar, they are highly intermittent sources. So we’d still need somewhere between 50% – 90% of the total generating capacity in nuclear, for the all-too-frequent times when the sun isn’t shining and the wind isn’t blowing.

To summarize: to get the world to zero emissions by 2050, our options are to build, commission, and bring on-line either:

**•** One 2.1 gigawatt (GW, 10^{9} watts) nuclear power plant each and every day until 2050, OR

**•** 3000 two-megawatt (MW, 10^{6} watts) wind turbines each and every day until 2050 ** plus** a 2.1 GW nuclear power plant every day and a half until 2050, assuming there’s not one turbine failure for any reason, OR

**•** 96 square miles (250 square kilometres) of solar panels each and every day until 2050 ** plus** a 2.1 GW nuclear power plant every day and a half until 2050, assuming not one of the panels fails or is destroyed by hail or wind.