Coal, natural gas, and CO2

wolfpup :
My hope is that any point of contention between us will not be based upon “snark.” That was never my intention. Disagree as we may, sorry if it comes across as such.

Not on the Ohio river (except on the very short term).

For single cycle. Not for IGCC or NGCC.

I would not put it as the most environmentally friendly. More like third, after wind and solar, in that order. Dams do pretty awful things to the ecology of rivers. Now there are a few hydro generators that do not include a dam. Those actually may be even more eco-friendly than wind, but they make up such a small fraction of total generation that I didn’t count them.

While hydro is saturated in the US and most of Europe and perhaps other places, they are actually building dams in many 3rd world areas right now.

Are there hydro plants on the Ohio? On the main river, that is, not on tributaries?

Yes, many (if not all?) of the navigation dams have been retrofitted with hydroelectric facilities.

“Just different ways to boil water”, right that’s only true for Rankine cycle, ie traditional steam turbine coal plants. Virtually all coal plants in the US are that. But, the key drawback to such a conversion relates to the third mentioned ‘NGCC’, where you fuel a gas turbine with natural gas, then ‘boil water’ in a Rankine cycle using the gas turbine exhaust as a heat source to run a steam turbine. That’s the cheapest way to generate electricity with a new power plant in the current US situation if charging solar and wind for the big new costs of super-grids and/or storage if they were to compose more than maybe 20-some % of output. The standard links saying solar and wind are now cheaper than combined cycle gas plants are on the basis of non stored power, nor do they include the real cost of grid upgrades to ‘wheel’ large amounts of power among distant regions where it’s night v day or whole regions where the wind is/isn’t blowing a particular day.

Anyway the point wrt OP question is the thermal efficiency of converted steam turbine plants burning gas compared to new combined cycle GT plants burning it. The latter is now around 60%. There are 40’s% efficient coal steam turbine plants, but very few in the US and only the very best and newest reach 40. Typically it’s older plants with thermal efficiency half or less that of a new gas plant. So while it’s usually straightforward and pretty cheap to convert the boilers in a steam turbine coal plant to burn natural gas (assuming gas is available in the location, obviously), it’s typically twice the fuel cost of a new combined cycle GT plant. Sometimes those numbers still work, and some of the decline in coal as % of US electric generation is steam turbine plants switching from coal to gas. But often those numbers don’t work, and a good deal of the % change is where new ‘NGCC’ plants have been built to replace relatively old steam turbine coal plants which have been shut down.

Going in the other direction so to speak, new coal plants with thermal efficiency similar to modern gas plants, ie ‘IGCC’ where you gasify coal to fuel a combined cycle plant, cost much more upfront than gas fired ones. They aren’t part of the picture of economically competitive choices given prevailing fuel prices in the US at present.

Yeah, that’s why I said “one of the best” for the environment. But they’re still a heck of a lot better than any sort of fossil fuel plant, and much better than wind or solar in reliability.

Note that most dams have multiple purposes … water supplies, irrigation, flood control, recreation … if it was just hydro-power, the Colorado would still flow into the ocean …

The conversion is all about cost/benefit … how much does a new power plant cost compared to converting an old plant plus upgrading the old plant to current environmental rules … and location is important, aren’t coal fired power plants built near coal mines; we’d want our gas fired power plants built near the wellheads … transporting the filthy stuff has it’s own environmental costs …

It depends. Sometimes it’s cheaper to put the plant near the mine, and sometimes it’s cheaper to put it near where the power will be consumed.

  1. Yes with again a significant part of the cost/benefit being: that a new natural gas fired gas turbine combined cycle plant will have typically twice the thermal efficiency, will burn half as much natural gas as an old coal steam turbine plant converted to gas for a given output, ~2/3’s as much as the most modern coal fired plants in the US if they were converted to gas. The new gas fired plants run on a basically more efficient thermal cycle that’s very expensive in plant cost to adapt to coal as a fuel (via coal gasification).

  2. Per the US eia less than 10% of US coal used for power is fed to ‘mine mouth’ power plants by conveyor. Past that’s it’s a matter of widely varying degree. There are coal plants 1500 miles from the low cost Wyoming/Montana coal fields, cheap coal from there can stand the big add on to delivered cost from a long rail (or rail/great lakes ship) journey. Some surviving east coast power plants use coal imported from Colombia or even Indonesia (yes the US imports coal, though it exports more than it imports). But obviously it’s easier for gas to gain ground in places farther from cheap coal, especially in new shale gas producing areas, than at plants near cheap coal mines. The cost of coal at mine also, obviously, varies very widely per BTU, much more than gas does, since it’s a less homogeneous product. But by the same token if we’re speaking worldwide, nat gas is significantly more expensive in some places than it is in the US.

The State of Texas sued the Obama EPA when it tried to force the State to convert coal plants to natural gas. The conversion is actually easy and economical, and Texas is sitting on enough natural gas to supply the entire world for a century, but we were too damn white to let Obama tell us what to do. Now that Fearless Leader is running things we’re rushing to convert all our coal plants to gas because it’s so much cheaper. It is not the solution to global warming but it helps, and cleans up the air quite a bit, too. West Texans have complained about a couple big Northern Mexican coal plants for decades, Texas gas producers sold the Mexicans on building a pipeline from Texas to Mexico and converting those plants to gas, thus reducing CO2 and ending their contribution to a bad problem with particulate pollution in Texas, what happens? Environnomentalists pitch a fit over building the gas pipeline. Of course since the State is already crisscrossed with thousands of miles of pipelines the suit went nowhere, but it’s just the kind of American stupidity that used to get Mark Twain’s panties in a wad…then, of course, there is the whole conundrum of Texas leading the world in wind energy…