Rep.-elect Alexandria Ocasio-Cortez gave a short speech this week to a group of climate-change protesters — 51 of whom were arrested for unlawfully demonstrating — staging a sit-in in the offices of likely new House Speaker Nancy Pelosi. In a video of it, Cortez-Ocasio, who will be representing New York’s 14th District in Congress, can be heard exhorting the protesters to press forward with their efforts.

“We don’t have a choice. We have to get to 100 percent renewable energy,” she insisted, drawing delighted cheers from the protesters. “There is no other option.”

Ocasio-Cortez is only the latest far-left Democrat to push the all-renewable scheme. And just last month, the Intergovernmental Panel on Climate Change declared that, to slash greenhouse-gas emissions, renewables should supply between 70 percent and 85 percent of the world’s electricity by 2050.

There’s no doubt that wind and solar are politically popular, particularly among the millennials who crowded into Pelosi’s office. But the hard facts show that renewables simply cannot provide the massive quantities of energy the world demands.

The fundamental problem is scale. Renewables aren’t growing fast enough to even match the torrid growth in global electricity demand, much less displace significant quantities of hydrocarbons.

Let’s do the math. In 2017, according to the latest data from BP, global electricity production grew by about 522 terawatt-hours. That one-year jump is roughly equal to the historical average.

Between 1997 and 2017, global electricity output climbed an average 571 terawatt-hours per year. Put another way, for the last two decades, the world has been adding one Brazil’s worth of electric consumption (the country used 590 terawatt-hours of juice in 2017) to its total every year.

What would it take to keep up with the growth in global electricity demand by using solar energy? We can answer that by looking at Germany, which has more installed solar-energy capacity than any other country in Europe — about 42,000 megawatts.

In 2017, Germany’s solar projects produced 40 terawatt-hours of electricity. Thus, merely keeping pace with growth in electric demand would require installing 14 times as much photovoltaic capacity as Germany’s entire installed base, and it would have to do so every year.

Prefer to use wind? OK. Let’s look at China, which has far more wind capacity than any other country: about 164,000 megawatts.

To put that in perspective, by itself, China accounts for about 32 percent of global wind capacity. It also has about twice as much wind capacity as the United States.

In 2017, China’s wind sector produced 286 terawatt-hours of electricity. Recall that global electric use is swelling by about 571 terawatt-hours each year.

Thus, just to keep pace with growth in demand, the world would have to install twice as much wind-energy capacity as now exists in all of China, and it would have to do so annually.

And keep in mind that electricity use represents only one facet of ever-growing global energy demand. Oil consumption is also surging.

The International Energy Agency has predicted that, by the end of this year, the world’s demand for oil will hit a record 100 million barrels per day. That would be an increase of about 1.8 million barrels per day over 2017 numbers.

To drive home the argument, compare this year’s uptick in the demand for oil with the world’s solar output: In 2017 — again, according to BP — global solar production totaled the equivalent of about 2 million barrels of oil.

Thus, by the end of this year, just the increase in the world’s oil burning will nearly be as much as the output of every solar-energy generator on the planet.

The punchline here is obvious: If the countries of the world are going to be serious about reducing carbon-dioxide emissions, renewables aren’t enough. Not by a long shot.

If reducing emissions is the goal, then policymakers around the world must get serious about the one form of electricity generation that is scalable and has ultra-low emissions: nuclear energy.

Robert Bryce is a senior fellow at the Manhattan Institute and the producer of the upcoming documentary, “Juice: How Electricity Explains the World.”