Friday, May 27, 2011

Wind Jerks

Are you familiar with the term “Jerk”?

I came across the word a number of times in a fantastic series of comments attached to a very interesting article, CO2 avoidance cost with wind energy in Australia and carbon price implications, so I looked it up on wikipedia:

In physics, jerk, also known as jolt (especially in British English), surge and lurch, is the rate of change of acceleration; that is, the derivative of acceleration with respect to time, the second derivative of velocity, or the third derivative of position.”

Let's look at some jerks in Ontario's electricity system.

Here's a quick graph compiled using the IESO hourly data for price (HOEP), Net exports (from the intertie report), and wind generation. Wednesday night we had a spike in wind production around 10pm, which is just as demand is dying. It may have come a little later than expected, because the price had spiked earlier, or this could have to do with the data being hourly - and shorter time periods would provide a better picture. Regardless, what really sent the price tumbling was the second spike at 2 am Thursday morning.. I've included about a day's data before and after the spikes, and drops, and you can see the variability of the wind doesn't impact the pricing nearly as much as the jerk does:

This was a particularly bad day for Ontario's electricity consumers - those price drops are a call for other markets to feast on our bounty. And they did. In the 24 hours of Thursday, May 26th, 2011, if we assume the hourly intertie totals were sold at the Hourly Ontario Energy Price (HOEP), Ontario paid others about $236,000 to take about 44,200MW of electricity. That amount of electricity costs Ontario's residents about $3.1 million dollars if consumed here.  The highest volume of exports is at the lowest price.

Late in April there was a similar situation as the wind suddenly dropped at about 10PM on a Thursday night - sending the price spiking to over $400/MWh only 5 hours before it would be $-106.10.

Surprisingly, when the price spikes because of a negative wind jerk, exports don't surge at all. In fact the negative pricing is the wee small hours of the 28th may be due to the price spike cancelling out the normally planned exports only 4 hours earlier.


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