Graph 1: The blue line is the load or electricity used/demanded from this customers of this California Utility. Study the blue line and notice how the least demand occurs at 4-5am, rises throughout the day and peaks about 5pm then trends down and then dives as people go to bed at about 10pm.
Now study the green line which is the contribution of wind power on a summer day. As you can clearly see the electricity Load and the wind Power run almost contradictory to each other. As people wake up and need electricity the wind dies down from it's nightly blow. Then as people leave work and business's close throughout the day, the wind picks up again in the evening.
Each evening the grid manager turns down the electricity generating power plants because he knows the demand will lessen throughout the evening. If the plant is a coal generating plants burning tons of coal per day, do you think the engineer can turn down the coal fire even to compensate for both lower customer demand and increased wind power availability? Instead, the Utility is forced to buy this evening/night electricity because they need the renewable energy credits, the coal fire continues to burn because it is going to be needed again in the morning.
Isn't it clear this is a zero sum game?
This graph just confirms the above and shows you how you can absolutely depend that wind energy will be undependable. Each day at the peak of customer electricity demand, that is the lowest point of wind energy availability for that day.
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