This is a continuation of my last diary.
First of all, I would like to point out that the intent of these calculations is not ultimately a realistic analysis. After all, I am not an expert in energy infrastructure or whatnot.
I do, however, think there is value in taking simple models and using them to guide perceptions. For example, as a physics teacher, I often employ simplistic models to introduce ideas. So when I first start discussing force, I use a basic block or whatnot, and ignore things like friction and air resistance. Obviously, not very realistic, but for demonstrating the principle involved, it is still a good way to gain some insight.
In a similar manner, when I previously looked for how many solar panels it would take to power the entire United States, it was more of a starting point to use a simple idea to gain some insight. And, I was quite pleased with the discussions it generated, no pun intended. I feel like I learned a lot.
So even though it is not realistic, for example, the point that was made about how solar is not viable for night-time usage, still, I think it is a good way to translate the generation needed. Maybe it's just me, but I feel that in a lot of peoples' minds, when they think of renewable energy, solar is the first thing that comes to mind.
Hell, it even included a mistake on my part, but as I always tell my students, it's ok to be wrong. It is invigorating to know that there were people who went and fact-checked my post for me, as I was trying to be as transparent as possible with the sources I used.
So, here is another question to tackle.
I found this analysis which is a great read.
One of the things I like about the idea of solar, is just how powerful the Sun really is.
This theoretical potential represents more energy striking the earth’s surface in one and a half hours (480 EJ) than worldwide energy consumption in the year 2001 from all sources combined (430 EJ).
One and a half hours. That's amazing to me.
But, focusing on the United States:
According to this estimate: The solar constant (the solar flux intercepted by the earth) is 1.37 kW/m2. The cross-sectional area of the earth intercepting this flux at any instant is πr2 (where r = 6,378 km is the earth’s radius), but the surface area of the earth over which this flux is averaged over time is 4πr2. Hence, the time-and-space-averaged solar flux striking the outer atmosphere of the earth is (1.37 kW/m2) / 4 = 342.5 W/m2. In addition, enroute to the earth’s surface, about 30% of this flux is scattered, and about 19% is absorbed, by the atmosphere and clouds (Wallace 1977, pp. 320-321). Hence, the average flux striking the earth’s surface is 342.5 W/m2 · (1-0.49) = 174.7 W/m2.
Using the average flux of 175 W/m
2:
From my previous diary, a rough estimate of the United States power usage is approximately 29.3 million GWh of energy (I checked it in google to be sure this time).
Averaged over an entire year, that means the United States uses about 3.4 TeraWatts of power.
If an average of 175 W/m2 strikes the Earth, that means that it would require the amount of sunlight that strikes 19 x 1010 square meters, or 19,000 square kilometers.
That means the amount of sunlight that strikes an area roughly the size of New Jersey in a year would be enough energy to provide all the energy consumption of the United States.
Of course, this is just the amount of Sunlight reaching the Earth, and does not account for the less-than-ideal efficiency of any solar energy conversion technology.
The 2006 paper comes up with a similar result. Assuming a 10% solar energy efficiency conversion, it calculated 185,500 square kilometers would be needed to supply the US with 3.24 TeraWatts of power. At 190,000 square kilometers, we would need roughly the area of South Dakota, instead.
Of course, there's still the possibility of breakthroughs in improving that solar cell efficiency.
Still, the amount of surface area, just shy of 200,000 square kilometers, at just 2% of the land mass of the United States, as noted in the report, is comparable to the amount of area covered by public roads, at 1-1.5%. And if we do it with roads, there's no reason we can't cover a comparative amount of land area with solar panels, attempts to merge the two notwithstanding. It serves as a reminder that a larger footprint for renewable energies is no unreasonable stretch of the imagination.
Finally, imagine if someone could figure out how to float solar panels higher up in our atmosphere, where there is even more power available owing to less deflection by the atmosphere. Such panels could also reduce the amount of sunlight even reaching the Earth to begin with, pretty much the main culprit in the Greenhouse effect.
Of course, anyone else who wants to provide teaching moments, more discussion is highly encouraged.