Image: Each red square illustrates an area that could capture three terawatts of solar energy. Together, the red squares could supply the world’s energy needs

There is no such thing as unlimited growth, so the U.S. government and other governments must understand the connection between energy availability and population growth by integrating sustainability into energy policy and into energy law. The current business-as-usual scenario will not meet the future energy needs of a rapidly growing world.

Also, exponential population growth and increasing energy demands will impact efforts to mitigate climate change. As a result, large amounts of renewable, clean energy will be required to sustain the energy needs of a growing world. However, not even nuclear power can keep up with escalating population growth and the future energy needs of a business-as-usual world in 2050. Solar energy, however, is the only natural energy resource that can keep up with human consumption.

Nathan Lewis provides a gloomy but sobering assessment of the challenges humanity will face in meeting its future energy needs (emphasis added):

Energy is the single most important technological challenge facing humanity today. Nothing else in science or technology comes close in comparison. If we don’t invent the next nano-widget, if we don’t cure cancer in 20 years, like it or not the world will stay the same. But with energy, we are in the middle of doing the biggest experiment that humans will have ever done, and we get to do that experiment exactly once. And there is no tomorrow, because in 20 years that experiment will be cast in stone. If we don’t get this right, we can say as students of physics and chemistry that we know that the world will, on a timescale comparable to modern human history, never be the same.

The currency of the world is not the dollar, it’s the joule.

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Humanity’s current energy consumption rate is 13 trillion thermal watts, or 13 terawatts.

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The United States consumes a quarter of the world’s energy, at a rate of about 3.3 terawatts[.]

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With population and GDP growth conspiring together, we would then obtain a tripling of energy demand by 2050. This is partly mitigated, however, by the fact that we’re using energy more efficiently per unit of GDP. The ratio of energy consumption to GDP has been declining at about 1 percent, globally averaged, per year. The United States actually saves energy at a faster rate, about 2 percent per year. Because we have such a high per-capita energy baseline consumption, it is easier for us to save off that base, whereas the developing countries save less. The “business as usual” scenario assumes that this will continue, and if we project that down, we will achieve an average energy consumption of two kilowatts per person within our lifetimes. (The United States now uses 10 kilowatts per person.) But factor in population growth and conservative economic growth, and we’ll still need twice as much energy as we need now.

In terms of average thermal load, a person on a 2,000-calorie-per-day diet is basically a hundred-watt lightbulb. And in our highly mechanized western agricultural system, the energy embedded in food—to run the farm and grow the food and transport it to the supermarket and put it in the refrigerator—is 10 to 20 times the energy content of the food itself. And the farther you live from the food source, the more embedded energy you consume. If we are 100-watt lightbulbs, this means that just keeping us fed requires one to two kilowatts.

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Ice cores taken near Vostok Station, Antarctica, show that the CO₂ level has been in a narrow band between 200 and 300 parts per million by volume (ppmv) for the last 425,000 years; data from other cores have extended this back to 670,000 years. Current CO₂ levels are about 380 ppmv. “Business as usual” will require 10 trillion watts, 10 terawatts, of carbon-free power, and it never stabilizes CO₂ levels—they just keep going up. So even on that track, we are betting against data that goes back for almost a million straight years, and hoping that this time, we get lucky.

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[U]nfortunately, there is no natural destruction mechanism for carbon dioxide in our atmosphere. Unlike ozone depletion, it will not heal by itself through chemical processes. In our highly oxidizing atmosphere, CO₂ is an end product. The lifetimes of CO₂ in the atmosphere are well known, and the time for 500 to 600 ppmv of CO₂ to decay back to 300 ppmv is between 500 and 5,000 years. Which means that the CO₂ we produce over the next 40 years, and its associated effects, will last for a timescale comparable to modern human history. This is why, within the next 20 years, we either solve this problem or the world will never be the same. How different that world will be, we won’t know until we get there.

If we want to hold CO₂ even to 550 ppmv, even with aggressive energy efficiency we will need as much clean, carbon-free energy within the next 40 years, online, as the entire oil, natural gas, coal, and nuclear industries today combined—10 to 15 terawatts. This is not changing a few lightbulbs in Fresno, this is building an industry comparable to 50 Exxon Mobils. Furthermore, if we wait 30 years, the amount of carbon-free energy we’ll need will be even greater, and needed even faster, because in the meantime we will have put out 30 years of accumulated CO₂ emissions that will not go away for centuries to millennia. So stabilizing at 550 ppmv will then require about 15 to 20 terawatts of carbon-free power in 2050.

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So let’s look at carbon-neutral energy sources. We could go nuclear, which is the only proven technology that we have that could scale to these numbers. We have about 400 nuclear power plants in the world today. To get the 10 terawatts we need to stay on the “business-as-usual” curve, we’d need 10,000 of our current one-gigawatt reactors, and that means we’d have to build one every other day somewhere in the world for the next 50 straight years. I’ve been giving this talk in one version or another for five years—we should have already built on the order of 1,000 new reactors, or double what’s ever been built, just to stay on track. So we’re really behind.

There isn’t enough terrestrial uranium on the planet to build them as once-through reactors. We could get enough uranium from seawater, if we processed the equivalent of 3,000 Niagara Falls 24/7 to do the extraction. Which means that the only credible nuclear-energy source today involves plutonium. That’s never talked about by the politicians, but it’s a fact. Forgive my facetiousness, but on some level we should be thanking North Korea and Iran for doing their part to mitigate global warming. We’d need about 10,000 fast-breeder reactors and, by the way, their commissioned lifetime is only 50 years. That means that after we choose this route, we’re building one of them every other day, or more rapidly, forever.

We don’t have time for the physicists to figure out how to make nuclear fusion reactors—they’ve been saying it will be demonstrated (although not economical) in 35 years, and they’ve been saying that for the last 50. If we assume they’re right this time, then ITER, a multinational demonstration fusion reactor being built in the south of France, will demonstrate break even—that is, it will put out as much energy as it takes to run it—in 35 years, and it will run for all of one week before the entire machine will, by design, disintegrate in the presence of that high-neutron radiation and temperature flux. And in the meantime we would have to build a commercial fission reactor every day for the next 30 years. It’s not going to happen.

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One hundred twenty thousand terawatts of solar power hits the earth . . . It is the only natural energy resource that can keep up with human consumption. Everything else will run up against the stops, soon. In fact, more solar energy hits the earth in one hour than all the energy the world consumes in a year.