Wind supply and electricity demand

In The Financial Post on Thursday, 4 August 2011, there was an article entitled ‘Energy Rules Change in the Wind’.  I pull out one passage for examination – namely: ‘The Liberals seem not at all upset that wind power is unavailable when needed, as seen during Ontario's relatively warm July, when wind was producing at only 12.6% of capacity.’

First, I wondered about the figure of 12.6% capacity factor in July.  I immediately went to the IESO website on wind, and found data available for the first 27 days of July.  My final figures are listed below.

Windfarm	Nameplate capacity (MW)	Average hourly production, first 27 days of July 2011 (MW)	Capacity factor (percentage)
Amaranth	199.5	26.9	13.5
Dillon	78	11.5	14.8
Gosfield	50	6.67	13.3
Kingsbridge	39.6	4.41	11.1
Port Alma 1	101.2	13.9	13.8
Port Alma 2	101	15.7	15.6
Port Burwell	99	11.3	11.4
Prince	189	26.5	14.0
Ripley South	76	9.27	12.2
Spence	98.9	13.6	13.7
Underwood	181.5	25.0	13.8
Wolfe Island	197.8	26.0	13.2
TOTAL - Ontario	1,411.5	190.7	13.5

My calculated figure of 13.5% is quite close to the author’s.

I also wondered how the wind plants performed – solely during July 2011 – during those times that it was ‘needed’.  I thus looked at three periods:  when time-of-use prices were ‘on-peak’ (i.e., non-holiday weekdays between 11am and 5pm); when Ontario demand was highest; and when Ontario prices were highest.  The table below gives some data regarding the capacity factor (in percentage terms) for each.

Windfarm	OEB on-peak periods         (114 hours)	Top 100 hourly demand periods (21,174 MW to 25,450 MW)	Top 100 hourly price (HOEP) periods ($39.55/MWh to $184.38/MWh)
Amaranth	14.1	22.9	19.2
Dillon	14.9	19.9	16.4
Gosfield	9.63	16.4	12.7
Kingsbridge	11.4	14.6	10.9
Port Alma 1	13.8	18.1	14.4
Port Alma 2	14.1	21.1	17.1
Port Burwell	12.3	17.0	12.9
Prince	7.80	9.35	11.1
Ripley South	11.0	15.6	12.4
Spence	13.1	17.4	13.3
Underwood	13.6	18.7	15.6
Wolfe Island	12.4	22.4	18.9
TOTAL - Ontario	12.4	18.2	15.3

Interestingly, the capacity factor goes up for two of the three ‘critical periods’ above.  More about this can be found in some work we did previously.