Daily Archives: September 19, 2018

A new word: curtailment

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[Yesterday: 3 miles on the greenway]

We drove home from Oak Ridge yesterday, so I am back in my regular spot doing my regular stuff.

Before going on this trip I had learned some interesting stuff at the office.  I work at an electric utility and they are looking at moving more and more toward “renewable” energy sources.  The presentation was about battery storage.  It is possible to buy big shipping-container-sized battery units.  It takes a lot of them to do anything serious.  I think he said a unit that size was good for 2 MWh, two hours at one mega-watt output.  I think that is the right figure.  A small coal-fired power plant is 200 MW, so to replace your power plant for a one hour break would require a hundred of them.  That’s not a very impressive figure.  And they are lithium batteries so there are other environmental implications related to production, storage and disposal.  It was an interesting talk.

But the part I wanted to talk about was curtailment.  The guy said that in some power supplier agreements there will be payment to the supplier if the energy is not used.  For example, if you are buying from a wind farm and the wind is blowing strongly, if you don’t take all that you have contracted to take, you may be looking at some serious expenses.  You may even have to pay someone on the grid to take it off of your hands.  He linked that to tax incentives in a way I didn’t quite catch.  Something about, if the wind producer doesn’t produce then his tax incentive is smaller (based on production?) so he’s going to lose money not only because you aren’t buying but because he isn’t producing.  So the rate for the energy you _don’t_ use can be much, much higher than for the energy you do use.

That was a new one on me.  The coal or gas guys, you buy the fuel and you burn it and that’s all.  But now you’re going to pay for what you don’t use.

Ok, starting up a coal power plant is a big process, and their efficiency is best if you are running it near maximum output.  With natural gas it is quicker to start up and the efficiency is not so much an issue.  We have a mix of coal, gas, hydro, wind and a little bit of solar.  The bigger your proportion of renewables, the more this kind of thing becomes a problem.   It is up to the executive-level people to keep all of this stuff in mind as they do load forecasting.

The problems all happen because you can’t economically store electricity.  If you could take all of the wind energy and store it for when you need it, the curtailment issue would go away.  So back to batteries, pumped-storage-hydro and other technologies.  The guy who comes up with a clean, efficient, large scale method of storing electricity will really be making a big breakthrough.


Today’s picture – we stopped in Fort Payne, Alabama and ate at a nice place and did a bit of browsing in an antique store.  Both were in an old mill building that has been re-purposed.  Here is a door which I found interesting.  It hangs on wheels on a descending ramp and it has counter weights.  A self-closing factory door.

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Sep 19, 2018
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