June 13, 2009
Posted by Jonathan
It has to be a kilometer tall, with a 1.5 mile radius of "greenhouse canopy", just to power 200,000 homes only for 50 years? AND with a cost of 1Billion dollars/tower? And...??? Are you kidding me? How can you think this is a good idea?
Sometimes people fascinate me. Really.
I got that message after posting about solar updraft towers a few days ago.
I thought, and still think, that solar updraft towers as power plants are a great idea.
But I do think it's good to take differing perspectives into account, and so I decided to look into this.
What I've found (as you'll read below) has convinced me that solar updraft towers are not only a great idea, but one that we should be pressing our energy utilities to act on, or creating solutions to ourselves.
Here's what I mean:
We currently use coal to generate significant amounts of electricity, right?
Coal is cheap. It's "easy" to come by, and easy to use to generate power. (RIght?)
This is an aerial shot of one of the largest open pit mines in the world, the Black Thunder Coal Mine in Wyoming.
I learned from here, that "In 2004, Black Thunder became the first coal mine in the US to ship a cumulative 1,000Mst (907Mt) over its 27-year life to date." and that "The combined operation is now producing coal at a rate of around 91Mt/y, equivalent to about 10% of total US coal production."
I had no idea what those measurements meant.
Turns out it was easier than I thought. It's 901 Million Tons total, or 91 Million Tons/year.
So the first complaint/rebuttal offered by this individual was It has to be a kilometer tall?
Well, how much concrete would be needed to build a solar updraft tower?
I know that in the world trade towers, 425,000 cubic yards of concrete were used. (It's unfortunately an easy number to look up.)
1 cubic yard of concrete = 3,000 pounds (approx.) source
Less concrete would likely be needed for this kind of tower, but let's assume it's the right amount of concrete.
We would need 6,375,000 tons of raw material per tower. (I realize as well that there would be steel and other materials to build a solar updraft tower, but we'll just go with the base material for now.)
Not comparing apples to apples here (at all) but go out on a limb with me for a second and say we were to make towers out of the material that has been extracted already (coal instead of concrete). From what has already been taken out of the ground there in 27 years (as of 2004), we could have built 151 towers. (907Million tons/yr. divided by 6 Million tons/material per tower). Coal's not as dense as the material needed to make concrete, so let's round that number down to 100 towers, just to give flex room in my figures.
So I realize that's not apples to apples, but it gives a good base for understanding. From one (albeit large) mine, the raw material could have constructed 100 or more towers.
The next complaint offered by this person was It has to have a 1.5 mile radius of "greenhouse canopy"?
Well, just how big is that footprint?
The image below shows how many of these 1.5 mile radius greenhouse canopies could fit into the surface area of just the Black Thunder Coal Mine. (I left the scale on the map so you could see I was accurate to a 1.5 mile radius.)
I'll save you the time in counting.
It's 16 (or more).
So, for the same space used by this one coal mine over 27 years, we could build 16+ towers.
For the same (or similar amount) of raw material extracted from the earth by this one coal mine over 27 years, we could build 100+ towers.
The next issue offered by this person was this expense would be *just* to power 200,000 homes *only* for 50 years/tower?
Well, how much coal is needed for 50 years of powering 200,000 homes?
In 27 years, 907 million tons came out of the Black Thunder mine.
They say that met about 10% of the nation's energy needs.
If that number is accurate, this means that in 25 years, the US used about 10 billion tons of coal. If energy consumption remained the same (which it won't because consumption is increasing, but it's easy for purposes of the example), the US would use 20 Billion tons of coal in 50 years.
According to the US DOE, it currently costs about $36 to mine a ton of coal and deliver it to a utility.
20 Billion tons of coal * $36/ton = 720 Billion dollars to get coal to utilities over 50 years.
That's 720 solar updraft towers that can be built for the same amount of money.
But the utilities have costs to building and maintaining power plants for turning coal into electricity.
According to the DOE, "Each ton of coal consumed at an electric power plant produces about 2000 kilowatt hours of electricity."
According to APPVoices, a traditional coal power plant costs approximately $1,300 per kilowatt hour of generation capacity. Therefore, a 500 megawatt plant costs about $650 million. (Integrated Gasification Combined Cycle plants and Fluidized Bed plants are more expensive at more than $1,400 per kilowatt hour, or more than $700 million for a 500 megawatt plant.)
We're going to use the lower number of those numbers, $1,300 per kilowatt hour of generation capacity.
This means that (in 50 years) 20 billion tons of coal produced around 40 trillion kilowatt hours of electricity.
40 trillion kilowatt hours * $1300/kilowatt hour, is a a total cost (just in production of electricity from coal) of 520 trillion dollars (over 50 years).
Assuming each tower would cost 1 Billion dollars, we could *only* build 520,000 towers for what it would cost (at the current price of coal), to power the United States for 50 years.
(I know coal was less expensive in the past, but it will likely cost more in the future, especially with the dropping value of the dollar. So just stick with the example here.)
A single tower could power 200,000 homes. The US Census Bureau reports 126,316,181 housing units as of 2006. That equates to 632 of these towers to power the entire US. Let's round that up to 640.
(Significantly more than $640 Billion was spent in the Iraq war, 20 billion was spent so GM could go into bankruptcy, but I digress...)
After the first 50 towers were built, construction efficiency would increase and as a result costs would decrease. But let's assume that didn't happen.
Compare these numbers next to each other.
$520,072,000,000,000
$ 640,000,000,000
For the same space used by one coal mine over 27 years, we could build 16+ towers.
For the same (or similar amount) of raw material extracted from the earth by this one coal mine over 27 years, we could build 100+ towers.
For the same costs as the entire coal industry over 50 years, we could build 520,000 towers.
For the same electricity production as the entire coal industry (to power the United States over 50 years), we could save more than 520 TRILLION dollars.
Is my math flawed? Am I missing something here? Please let me know if I am.
Even if my numbers are way off, and there are all sorts of unaccounted for expenses in building the solar updraft towers, the cost to power the United States for the next 50 years is so much better when looking at the solution proposed by solar updraft towers.
And this ignores the real costs of coal.
Coal cleanup (after mines are carved into the earth)
Coal pollution (health challenges)
Trucking/Equipment pollution and oil price fluctuations
Continue reading "Open Pit Mines (coal) vs. Solar Updraft Towers" »
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