We Need Solar Now

I just watched Colbert Report, and his guest was James Kunstler. I consider myself an environmentalist, and knew about peak oil but I hadn't heard it discussed in quite such stark terms before (at least not on TV). Mr. Kunstler stated that peak oil has come and gone--that we produced less oil last year than we did two years ago, and that the decline is going to continue. In short, he scared the crap out of me, so I did some research. I don't know if he is quite right about peak oil having passed--there is some data, at least, which seems to show that the world oil supply is still stable (See inset). Nonetheless, it is clear that we have a finite supply of oil, and we will likely soon reach declining production.

Mr. Kunstler also stated that all alternatives combined (solar, wind, geothermal, nuclear, etc.) are insufficient to meet current energy demands. What he didn't say, but which is even scarier, is that energy demand is definitely growing. This is especially true in rapidly developing and large economies such as China and India, but also to a lesser extent throughout the world. Again, though, I am not sure Mr. Kunstler has his facts straight. I remembered reading recently that more solar energy hits the Earth's surface every hour than the entire population uses in a year. This has been often repeated--a couple sources are here and here. While repetition is not proof of veracity, I'll assume for now it's true.

Well, what about solar then? Say that the United States wanted to generate enough energy through solar capture to power the entire planet--how much land mass would have to be covered?

I did some calculations.* The Earth's surface is about 510,065,600 sq. km. The United States covers about 9,826,630 sq. km., or a little less than 2% of the Earth's surface. So, if it takes just an hour for enough energy to reach the Earth's surface to power the planet, it should take about 50 hours for enough to reach just the US. Now, solar panels aren't all that efficient. Modern photo-voltaic cells range from 14%-19% efficient, according to wikipedia. Using an average of that, 16.5%, or about 1/6, it turns out that if the entire surface of the US were covered in photovoltaic cells, it would take about 50 * 6 = 300 hours to gather enough energy to power the planet for a year. There are 8,760 hours in a year, so it stands to reason that only 300/8,760 = 3.4% of the United States would have to be covered in photovoltaic cells to produce enough energy for the whole planet, year round.

Of course, photovoltaic cells aren't cheap(although nanosolar powersheets may change that), and it takes a couple years for them to produce enough energy to offset their production costs. However, there are methods like thermal solar that have higher efficiencies (up to 30%) and are less expensive than photovoltaics. Still, even with the hurdles that exist, why aren't we doing more?

* I started off with the assumption that sunlight reaches the US on average with the same intensity as it does everywhere else, which of course isn't true--but it's good enough for a rough estimate. I'm also assuming that the 1 hour assertion holds true any time of day, which is only true if you're using the whole earth, but not just one country where there is sometimes night. Nonetheless, the math holds since we're still talking about the proportion of solar energy the US receives.