I wrote last week about a
curious fact: even though total CO2 emissions from the US electric
power sector have dropped during the recession, the emissions intensity of the US power supply—that is, the amount of carbon per megawatt hour
produced—actually inched upwards. The decline in total emissions is good news
in the short term. Yet the increase in emissions intensity is worrisome: if
we’re going to keep emissions low once the economy picks up again, emissions
intensity has to keep declining—even if the economy is
stumbling.
Climate Data Due Diligence, rides to the rescue again, with 2 charts that help explain what’s going on.
The first, to the right, shows that carbon intensity at the end of last year moved roughly in tandem with the share of US electricity that came from coal. One possible interpretation: coal remained much cheaper than natural gas last year, so when electricity demand declined, power producers turned down the gas more than they ramped down coal.
The second chart shows
that, for at least one individual coal plant, CO2 emissions per
megawatt-hour inched up (bottom graph) when the plant was run at 50 percent capacity (top graph).
If that’s a common problem, then it might suggest that it would be better to shut one coal plant down entirely, rather than turning several plants down a bit. The reality might be more complicated, and the economics hard to figure out, but it could be worth figuring out if this problem applies to the western grid as well as to the Amos power plant, which is in West Virginia.
So in short, the Climate Data Due Diligence charts suggest that the culprit in the increase in emissions intensity is coal: we’re using way too much of it, even in a recession, and using it less efficiently than we should. So until we start to wring dirty coal plants out of the electricity supply, we’re going to be stuck with CO2 emissions far higher than we need them to be.
This post originally appeared at Sightline’s Daily Score blog.
Comments
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EcoJane Posted 12:51 pm
22 Apr 2009
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garyshu Posted 6:15 am
23 Apr 2009
megawatt-hour inched up (bottom graph) when the plant was run at 50 percent capacity (top graph).
If that’s a common problem, then it might suggest that it
would be better to shut one coal plant down entirely, rather than
turning several plants down a bit. The reality might be more
complicated, and the economics hard to figure out.."Hard to figure out? Not really. In deregulated markets with each plant bidding in their offer curves (i.e. supply curve, for those of the economics persuasion) to an system operator dispatch, if you have a carbon price, this would adjust the curvature of their bids and the dispatch would take care of the rest.RE: "One possible interpretation: coal remained much cheaper than natural gas last year, so when electricity
demand declined, power producers turned down the gas more than they ramped down
coal."There's a couple of ambiguities here that EcoJane hints. Coal indeed remained cheaper than gas, but it's electricity from coal and electricity from natural gas we're comparing. And that's almost always true. Coal usually doesn't get ramped down - that's why it's baseload. It needs to stay hot and fired to be efficient.Finally, looking at one plant is especially bad: sample size of one,
anybody? There could be a number of reasons why its capacity factor
turned down and its intensity went up from poor quality coal shipped in
to needed maintainence. How else can you explain that the Amos' coal plant capacity factor went down while the overall share of electricity from coal went up at the same time?
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