The Fast Approaching Coal Fired Power Nightmare (Part Two)

Posted on Fri 10/23/2009 by

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PART TWO OF TWO PARTS

THE DREAM NIGHTMARE OF CLEAN COAL

CCS 01

There are three images as part of this post. They are all diagrams and are freely available. I have included them to show how simplified the process has been reduced to. With each image, if you click on that image, it will open in a new and larger window.

Clean Coal. Let’s explain that first. It’s actually Carbon Capture and Sequestration. (CCS) It is also called Carbon Capture and Storage. Politicians don’t understand either what the process is, what it entails, and what it actually means, so rather than explain something that they cannot understand, and then believe that their constituents cannot understand, they give it a totally simplistic and catchy title, ‘Clean Coal‘, thinking that would be easier to sell than actually trying to find out what it is and then explaining that. If they did bother to try and find out, then the hairs on the backs of their collective necks would stand on end as the realisation sinks in that this is just a dream, a dream that if it ever can be realised is so far away into the future that it most probably will never come to fruition. So, to keep up the pretense, they give it that catchy title ‘Clean Coal‘, and then just run with that, thinking that if it actually is just so far away and so unobtainable, people will have forgotten all about it, and what they, in particular, said about it.

So. What is it?

Coal is burned to boil water to steam to drive a turbine to then drive a generator to produce electrical power. During the burning of the coal, basically Carbon, each  Carbon atom then combines with 2 atoms of Oxygen to form Carbon Dioxide. (CO2) The resultant means that each ton of coal burned produces 2.86 tons of CO2, not a gassy thing, but an actual physical weight.

THE CAPTURE.

This CO2 is emitted from those long thin stacks at the power plant. Not that white stuff pouring from the big fat stacks. That’s just cooling steam or water vapor, not that that holds back some media outlets who still show that white stuff in reference to the CO2 emissions. No, the CO2 is colourless and odourless and you cannot see it being emitted from those thin stacks. The Capture part of it is to get these exhaust gases, all of them, as they are actually being emitted. What happens then is that the CO2 is removed from this exhaust before it actually is emitted into the Atmosphere.

THE SEQUESTRATION (STORAGE)CCS 02

That captured CO2 is then stored back into the ground, hence the fancy title, (geo)sequestration, meaning it is sequestered (stored) in the gaps between stable rock formations under the ground.

Sounds pretty simple eh! and a pretty novel idea too, in fact a pretty damn good idea.

Okay then, let’s look at the reality then shall we.

What people fail to realise is just how much coal has to be burned to produce the steam. A large power plant with a Nameplate Capacity of around 2000 MegaWatts (MW) burns on average 6.5 million tons of coal a year, which averages out to around 18,000 tons a day. That varies depending upon the Season and the time, but that average is commonplace for all those large plants. That means that each of those large plants is emitting on average around 52,000 tons of CO2 each day.

So, here’s what now needs to be done.

The exhaust needs to be captured at the same rate as it is being emitted. The CO2 then needs to be extracted from that exhaust at the same rate as it is being emitted. That CO2 then needs to be cooled at the same rate as it being emitted. That CO2 then needs to be liquified for transport at the same rate as it is being emitted. That liquified CO2 then needs to be transported at the same rate as it is being emitted. That CO2 then needs to be pumped back into the ground at the same rate as it is being emitted.

Now it’s starting to look a little more difficult.

Separating the CO2 from the exhaust is not really as simple as it sounds. It involves a complex physical and chemical process. There’s no simple way to explain it, but a similar explanation might be the reverse osmosis process similar to what is being used to turn salt water to fresh water, and that is a complete simplification of a very complex process. Cooling the captured CO2 also would take time. Then, turning the CO2 to a liquid will decrease considerably the volume, but the weight would remain the same. CO2 is incredibly difficult to liquify, and is done by freezing it back past the gaseous stage, and also done under extreme pressure, and once done, it is not very stable in that liquid form. Assuming then that this problem can be resolved, that liquid then has to be pumped down pipelines to the place where it is to then be pumped back into the ground, large electrically powered pumps driving immensely large volumes of liquid CO2 which still has to be kept in the semi frozen liquid state. The deeper you go underground the temperature rises, sometimes to significant levels, so pumping it back into the ground means that it will be heating back up, again turning back to a gas, increasing by a huge amount the volume of the CO2.

All this has to be in a gap between rock formations that will keep the CO2 there forever, so none of it leaks back to the surface in any way.

So, then you are going to need a huge new facility at the plant itself for the capture, separation, cooling, and the liquifying.

CCS 03

Image Credit: Courtesy of the Colorado Geological Survey

Then you are going to have to construct huge pipelines to where the CO2 will be stored. Then a vast new plant at that site to pump it all back into the ground.

It has been calculated that just to achieve this whole overall process, then one third to one half of all the electrical power produced at the plant would be used by this process alone. That means you build a new ‘Clean Coal’ plant of the same 2,000MW Nameplate capacity but only half to two thirds of the electricity is actually available to the end consumers.

With all the technology around at the moment and the way it is developing so rapidly, all the above is something that maybe can actually be worked out.

So, what then of the big picture?

Let’s look at the current situation, and I’m purposely doing this, not as a fruitless, redundant, and hypothetical scenario, but to then build a picture of what might be needed in the future.

Currently the U.S. burns just under one billion tons of coal each year, and here’s the link to the EIA site that shows exactly that, the figure at the bottom left column there, and expressed in thousand tons.

So, to produce that amount of electrical power, those coal fired plants are emitting 2.8 Billion tons of CO2 each year. Keep in mind that other methods of electrical power generation  also emit CO2 and this is just from that coal fired sector.

We now have to find a stable geological rock formation capable of holding this amount of CO2. Then we have to construct what can only amount to thousands of miles of pipeline from each and every power plant to that site and then pump it all back into the ground. 2.8 Billion tons each year amounts to 7.7 million tons a day, or 320,000 tons an hour, or 5,400 tons each minute, or nearly 90 tons a second for every second of every minute of every hour of every day.

That’s 2.8 billion tons a year. How large a gap between rock formations will be needed, and how soon, at that rate will it fill. Then, once full, you need to find another formation, construct more pipelines to that, and move all the pumps. 2.8 Billion tons a year.

Now can you see why this is not just a pipe dream, but an absolute nightmare. The cost alone would be so astronomically huge, as to make the whole process completely unviable.

So then, having painted this scenario, let’s then look at the future. We close down all the existing coal fired plants and replace them with new plants that are constructed to this wonderful new ‘Clean Coal’ technology.

This again is a mathematical exercise that can be done. The one saving thing in all this is that those newer plants will be smaller and more efficient, because electrical technology for large plant design has come a long way since the early days of plant construction, keeping in mind that the whole U.S. inventory of coal fired plants has an average age of between 45 and 48 years, and that the usual lifespan of a coal fired power plant is only 50 years.

Those new plants will burn coal more efficiently, meaning less coal, they will produce ‘better’ steam, the multi stage turbines will be a lot smaller and better, as will the generators themselves.

However, the electrical power that they produce will still be an absolute requirement, so for that we will use existing figures.

Currently, from coal fired sources, the U.S. consumes 1.84 Trillion KiloWattHours (KWH) and here’s the link to that stat, at the bottom of the left hand column.

That will still be required for consumer consumption, but keep in mind that part of the power from these new plants will be needed for the CCS process, and for this I’ll be sanguine and take the lower figure of one third.

So now you will need new plants to produce 2.8 Trillion KWH.

There is a specific formula for calculating consumed power from Nameplate Capacity, so we can use the reverse of that formula here to work back from consumed power to that Nameplate Capacity.

That formula is NP X 24 x 365.25 X 1000 X CDF, where NP = Nameplate Capacity, 24, (hours in a day) 365.25, (days in a year) the 1000 to convert from MW to KWH, (one million down to one thousand) CDF being Capacity Delivery Factor.

These new plants will be a lot more efficient than the existing aging inventory, so that CDF might be as high as 85 to 90%, taking into consideration down time, maintenance time and other factors, so I’ll split the difference and use 0.875 (87.5%)

So then using the reverse, 2.8 Trillion KWH converts down to a 366,000MW new Nameplate Capacity.

If a large plant has a capacity of 2,000MW, then from that you can now see that you will need to construct nearly 200 of those large sized plants. In actual fact it will be a lot more than that, because smaller plants will fill the needs in some areas.

Because they will consume less coal, using much improved technology, let’s then say that the much larger power production will only consume the same amount of coal as is currently being used, but when you are talking nearly a billion tons of coal and 2.8 Billion tons of CO2, that figure is still going to be monumentally huge even if they do burn a lot less coal.

Politicians must be aware of the situation with coal fired power, how those renewable plants just cannot supply the power that is needed absolutely and not just the eight hours out of 24 that those renewable sources currently supply at their best output, and how those existing coal fired plants just cannot be closed down in the short term interim, or even in the long term, so this catchphrase of ‘Clean Coal‘ is their way out for the moment, and because it is is just so far off into the future, if at all it can ever be made to work, then what they say now will have been forgotten far off into the future when news comes that it is just not at all economical, and all but a physical impossibility, and as you can quite easily see from the above, this is a process that is so full of hopeful what ifs that something pretty dramatic would need to suddenly come into view to make it work on the scale required.

That being said, you will actually see where something similar to this is already being done. What you need to keep in mind is that what is happening now is on such a monumentally tiny scale as to be totally insignificant. politicians and the media will beat it all up totally out of all proportion in an effort to show that something is being done, but where this is now happening, they are barely doing it with a ton or two tons here and there. Keep in mind the overall picture of 2.8 Billion tons each and every year.

2,800,000,000 tons of CO2 each year.

Read through the process one more time.

This is not only not even a dream, but it just adds to the already frightening nightmare that is closer than you think.