Quite often in discussions about global warming, “green” energy and so forth, it is mentioned that the solar power reaching the earth is for all practical purposes unlimited. More precisely, the number which is tossed around is that there is about 10,000 times as much solar power reaching the earth as our current power consumption. We also tend to think of the total power produced by the sun (not just what hits the earth) as “infinite”. Compared to what we use today, it might as well be infinite.
But here is some sobering math that might just wake you up, if it doesn't put you to sleep. :)
First lets confirm that factor of 10,000. Current global energy consumption (2008) is about 474 exajoules/year. The total solar power reaching earth is 174 petawatts. Doing the math:
(174 petawatts) / (474 exajoules/year) = 11584
So the 10,000 multiplier is about right. 10,000 is really big. How could we ever use that much more energy than we do now? (rather, how could we ever use that much power -- the rate at which we consume the energy and how fast the energy is supplied are what we are talking about, and the correct term for both of those is “power”).
It seems like a lot. It seems like we could “never” need so much power. Now for the sobering math. Over the past century or so, we can estimate the growth rate of global energy consumption. It is about .5% annual growth in energy consumption. It has been close to 2% recently. Lets take the smaller number. Assuming we continue at that rate, how long before we would be using all the solar power reaching the earth? Rounded off we have:
#years .5% energy growth = log(11584)/log(1.005) = 1876 yearsNow, almost two thousand years is still a long time... but it is far from an eternity... just 19 centuries is a time-span we can easily grasp. It brings into perspective just how rapidly our energy use is increasing. The solar supply is far far from unlimited, and nothing else we have comes close. If our energy consumption grows at the 2% number, then here is that calculation again:
# years = log(11584) / log(1.02) = 473 yearsLess than 500 years! Given that 2/3rds of the worlds population are scrambling to get to the level of technology, industrialization, quality of life that we have in the U.S, and given the the U.S. by far uses the most energy per capita, we can be sure that the growth in global demand for energy is not going to level off any time soon. The only thing that will slow down the growth in consumption is if the energy is simply not available. High demand for a scarce resource means trouble.
Now here is something I think is even more sobering. The total power output of the sun is 3.86x1026 watts. At the above growth rates, how soon would we be using that much energy?
# years at .5% growth = log(3.86x1026watts / 474 exajoules/year) / log(1.005)
= 4,805 years
# years at 2% growth = log(3.86x1026watts / 474 exajoules/year) / log(1.005)
At our current rate of growth of energy consumption we will need the entire energy output of the sun to sustain our civilization within about 1000 to 5000 years! All the power output of the sun. Let that sink in. All the power output of the Sun.= 1210 years
No amount of earthbound energy, no amount of oil, no number of nuclear reactors, no amount of solar panels can so much as scratch the surface of the power output of the Sun. The sun is a giant fusion reactor, about 300,000 times the mass of the earth. Nuclear reactors (fusion or fission) on earth will never produce a significant amount of power as compared to the sun (This does not mean they won’t play an extremely important role in the near to mid-term).
It is also unrealistic to suppose we’ll be able to grab every drop of sunlight even with some crazy science-fiction technology. We won’t be able to get all the solar power reaching the earth even if we blanket the planet with solar panels. Getting all the power of the sun will require satellites in solar (not earth) orbit... it would take so many satellites we’d have to strip the earth of pretty much all useful material just to build them and launch them into space -- perhaps we could consume the entire moon for this purpose. This means that the time estimates before we saturate the available energy are actually quite a bit shorter.
Now you might say “500 years, 1000 years, 5000 years... that’s too far in the future to worry about.” What our descendents do when the energy from the Sun is not enough will be their problem, true. But the point is that our demand for energy is increasing so fast, it is going to outstrip everything we can possibly get our hands on, unless we can research and develop new sources very quickly. Competition for scarce energy resources is going to shape our near and long term future. There are only three possibilities:
(1) War! War that makes WWII look like a pillow fight folks. Not an acceptable option, I should hope.
(2) Conservation. This will be forced on us by simple reality. But not without huge conflict -- see #1 above. Remember half the world is impoverished and scrambling to reach our quality of life, unless we set an example by cutting back massively, they are not going to voluntarily sit in poverty.
(3) Research. Develop new sources of energy, especially solar power, as fast as we possibly can. This means research research research.
What can you do? Individual conservation (recycling and whatnot) is a good gesture, but cannot possibly fix the long term problem -- you won't convince enough of the rest of the world to do it with you, and there will always be others willing to consume what you do not. We’re just not going to convince enough people to conserve before shortages force them to do without. But you can do the following three things.
(3) Invest. Seriously. Invest spare cash into energy research. Nowadays anyone can invest via simple internet sites like E-trade. If you have a retirement account that lets you choose investments, make a heavy allocation specifically towards energy research and development. Any company researching new energy or developing energy technologies. There are plenty of mutual funds focusing on energy R&D. It does not take an expert in energy or investment to do this. Even invest in the dreaded “big oil” -- even at the risk of repeating the Gulf Coast disaster, the looming energy shortage means we’re stuck with “big oil” in the near term. Investment in any research and development in products that make more efficient use of energy is also good -- electric cars and so forth.
(2) Talk. Make people aware that the sheer magnitude of the problem of “not enough energy” trumps even “global warming”. It trumps worries about supposedly “unsafe” nuclear power (which is arguably far safer in terms of long term health effect than oil or coal, and also does not cause global warming). You are a participant in the global conversation. You are one drop in the bucket of “public opinion” and “political will”.
(1) Vote. And contact your representatives. Demand massive investment into energy research. New energy of all kinds really does need to be today’s “Apollo Program”, but on an even more massive scale. Demand a repeal of regulations blocking nuclear power. And since we're stuck with oil for the time being, we must also research so-called geo-engineering methods to prevent or mitigate global effects such as climate change in the face of continued use of fossil fuels.
skg rightly points out that the exponential growth in power usage must slow down or even halt, so that my projections are not likely to come to pass, with which I completely agree. If we are unable to collect that amount of solar power, we won't be consuming it either. But that is precisely my point -- our insatiable demand for more energy is going to hit a brick wall of limited supply very very soon, unless we are able to science & engineer our way out of the dilemma. There is simply no other way.