Chapter 4.10.1: Feb 2009 Port Alma

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What does a good month of wind production look like?  Queries were run that returned hours and dates where the Hourly Capacity Factor (HCF) was equal to or more than 90%.  Port Alma was picked as a test case because it has the highest number of hours in a single month with hits at or above 90%.  This is the plot of those hours as a percent of time:

You can see 4 dominating towers Dec 2008, Feb and April 2009 and Jan 2010.  And yes, December 2008 had just over 30% of its hours above 90% name plate.  Notice summer is non-existent.  Whether the winter of 2009 is normal or unique remains to be seen, but the winter of 2010 is definitely not as good as 2009 (apparently not in the UK either).   2010 was much warmer in the latter months of winter into spring.

This is the spread of those hours above 90% spread across the day:

The hits are more to the evening hours, but the spread is only 4 percentage points, so for the most part these hits above 90% are evenly spread across the day.

In chart form this is a matrix of months vs daily hours.  Each cell is the number of hits 90% or better (notice summer is blank for the most part):
 

Yr 2008 2009 2010
Mth 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7
1 4 4 10 5 9 8 9 6     1 2 2 3 6 6 3 5 7 5 1  
2 5 4 10 5 7 8 9 5     1 2 3 3 5 7 2 2 10 3 1  
3 3 3 8 5 10 7 8 2       1 3 2 5 9 2 2 9 4 1  
4 2 2 8 4 7 8 8 2       2 2 2 6 7 3 2 6 7 2  
5 3 3 7 4 8 5 7 3       2 3 1 6 7 4 4 9 5 1  
6 5 3 7 4 8 5 8 3       1 3 1 5 6 4 4 8 5    
7 2 4 8 4 9 4 9 2       1 5 1 5 6 4 3 8 7    
8 1 4 10 3 8 6 10 4       2 6 1 6 4 3 2 5 3    
9 1 3 10 3 8 6 11 3       1 6 1 5 6 2 3 6 4    
10 1 4 10 3 7 8 11 3       1 5 2 5 8 2 2 5 5 1  
11 3 3 11 2 7 8 9 3       1 5 2 5 9 2 3 2 6 1  
12 3 3 10 4 8 8 13 3     1 2 5 1 5 10 2 2 3 5 1  
13 3 3 10 5 7 8 11 3     1 2 5 3 6 10 1 3 5 6 1  
14 2 4 9 6 6 9 9 2     1 1 6 3 6 10 1 3 5 5 1  
15 2 3 9 5 7 10 9 3   1 1 1 5 2 6 9 3 3 6 6 1  
16 1 3 9 4 6 9 7 1     1 1 5 2 6 8 3 3 8 8 1  
17 1 4 12 5 7 9 7 2 2   1 1 6 1 5 9 4 4 7 6 2  
18 2 4 11 6 7 7 8 2 1     1 5 2 7 9 2 4 8 5 1  
19 1 4 10 9 8 7 8 3 1     1 4 2 8 8 3 4 5 4 2  
20 2 3 12 8 11 8 7 2     1 1 5 2 7 8 3 5 6 4 1  
21 3 3 12 7 10 6 7 2     1 2 5 3 9 9 3 5 7 2   1
22 2 4 11 7 10 9 7 2 1   2 2 3 3 9 8 1 6 6 3 1 1
23 2 5 11 7 11 9 8 2 1   2 2 1 3 8 9 1 6 7 5 1  
24 4 4 8 7 9 7 7 4     2 2 2 4 6 6 2 6 7 4    

For the purposes of looking at a specific peak period, Feb 2009 was selected.  This is the HCF, along with demand, for all hours in Feb 2009:

As you can see in the bottom graph that the output has distinctive spikes, with dramatic drop offs to virtually nothing.  Note how those spikes fit with demand in the top graph.

This scatter plot matches demand with HCF:

Each dot is an hour.  The yellowed area is when demand is highest and HCF is also highest.  Notice the number of dots (hours) is small.  The red area is when demand is low and HCF is high, that is, when we don’t need the wind.  Those hours are many more than the yellowed area.  The bottom right blue area is when demand is high and output is low to non-existent. About as many hours as the yellowed area.

What is interesting is the complete drop from the 90s to virtually nothing in short order.  It’s worth looking at one of those in detail.  Feb 12 and 13 was chosen.

In 24 hours the output went from 98% HCF to zero.  Notice how it matches up with the demand (right Y Axis).  Watching this progress in a scatter plot looks like this:

This scatter plot of demand (X-Axis) vs Hourly Capacity Factor (Y-Axis) shows how the two moved at the same time.  Each dot is an hour of the day, starting at midnight Feb 12.  Thus at night the output was above 90%, until 7PM, then both the demand and the output drops as the points head to the left.  Demand stabilizes during the night as output drops off the cliff.  Feb 13 morning demand starts to increase, output flat, but starting at 9AM output collapses to zero.

So what does all this mean?  Even though there are periods of very high output, over 90%, most of those hours the demand is not there to use it.   There are more than 3 times the hours where the HCF is at or above 90% when demand is lowest than when demand is highest. 

The “good” periods aren’t so good after all.


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