Can the U.S. supply it's electrical needs with PV ? I had run some back of the envelope calculation a while back, and had looked them up again when a friend of mine asked me if I had every thought about it.
Yes, I have thought about it, and the numbers I came up with are here.
This is not an exhaustive treatment of alternative energy and all the complicated issues associated with it, such as the grid infrastructure, storage requirements and even the fact that we're all better off with DC voltage rather than AC voltage.
It's just some simple calculations with interesting factoids to demonstrate that WE COULD BE DOING SOMETHING, but we're drilling in the arctic and blowing the tops off of mountains instead.
The first thing you need to know is how much electricity the U.S. uses.
The EIA site is good for answering those kinds of questions. There is a table entitled "Electricity Net Generation: Commercial and Industrial Sectors", and it reads that electricity net generation for 2014 was 144,261 million-kilowatt-hours, or 144terawatt-hrs, which converted to energy is 519 exajoules (144x10^12 joules/sec-hr x60 min/hr x 60sec/min).
So how many watts of solar cells do we need ? Obviously that depends on how much sun you are getting and the intensity of that sun. I'm going to make an assumption that a solar cell will provide it's nominal output for 6 hours out of the day on average. The idea is to put panels where they do the most good, so that seems very reasonable. Although, that assumption is an indicator that there needs to be a discussion about the transmission network.
So 519x10^15/(365*6*60*60) = 65GW of solar panels.
Now the strange thing is, that number looks low to me. However I've been over it a couple of times, and I think it's right. I sure hope so, because if I've lost a couple of decimal points things are going to change drastically.
The WORLD PV manufacturing capacity currently stands at about 36GW as of 2011. However that number is going up and I wouldn't be at all surprised if it's 50% higher in 2015, but regardless, relative to worldwide capacity, things are looking pretty good.
So how much is it all going to cost ? Again i'm going to pull a number out of thin air, and claim the installed cost of solar panels is US$5/W. I also claim that it's definitely on the high side at this point in time.
So we're looking at about 325 billion dollars.
Seriously ? 325 billion and we can replace all of our natural gas and coal fired electric generation ? Really ? 30% of the defense department budget FOR 1 YEAR. sigh
Now, some nattering nabob of negativism is going to complain that you have to put all those solar cells somewhere.
Well to make things simple I'm going to assume that you get 100W/m^2 (1000W/m^2 x 10% efficiency), so we need 650x10^6 m^2, which is a square 25km on as side, i.e. 15 miles on as side.
Wow. That's it ?
Do you realize just how much of that area could be absorbed by the roofs of houses already in cities ? Quite a lot of it, and in my not so humble opinion, a decentralized system is a more robust system.
So there it is. Yes, there's a lot of other things that need to be discussed, in particular storing energy when the sun is not shining, I know that.
Seems to me that the math is quite clear that we could make a substantial dent in our carbon footprint, and we could start doing IT NOW. We just have to not rely on the magical free market fairies to do our work for us.
Isn't this a matter of national security ? why not take 10% of the defense department budget each year and use it to subsidize solar ?
Well, I guess because it's too hard. Easier to blast the tops off of mountains.