In an early post I charted how the monthly demands in the PJM grid which manages the supply of electricity to Pennsylvania and neighboring states. The chart shows that when our electricity supplies are the greatest, in the summer, you can depend on the fact that wind speeds are appreciably lower causing marked decrease in electricity generation from wind. What this means is that it does not matter how many wind turbines you build for a grid, you will ALWAYS have 100% duplication of the installed wind MW by traditional sources, (nat gas, coal, nuclear or hydo) because you can expect the wind to completely die on almost a daily basis for a period of time. My early posts prove that beyond doubt. See the youtube video I created to show how completely unreliable North Dakota wind is, touted as the #1 wind in the country. note: Basin Electric from ND removed their weekly wind chart updates right after I posted that youtube video.
Today we look at how the wind output is not in sync with the users demand. The line is an hourly demand curve I found for the PJM customers. It is quite typical of how electricity demand varies throughout the day. Demand is lowest at about 4am, then begins to rise as civilization wakes up between 5-6am, rises throughout the morning, levels off and then decreases as business and industry closes at 6pm. It sharply declines after 9pm as we shut off our electricity and prepare for bed. You can view daily updated curves for California here and Ontario here. The problem with wind in Pennsylvania and many locations worldwide is that wind speeds tend to run in exact opposite to the consumer and business demand. The green curve I plotted a PJM hourly output spreadsheet for 2008 found here. If wind output was equal throughout the day it would be about 4% of the total daily output for each hour. You can easily see that wind output varies by about 35% from the low at 3.4% to a high of 4.6%.(those % are the hourly contribution of daily output). When we need the wind the most it is not there, and when we need it less at night, it is blowing more. This created a very interesting scenario for base load coal and for some natural gas plants. Many of the larger plants run at 100% all day long. I would think that for many power grids, with a large amount of wind installed, if the wind output is large, there is more wind power than is needed because demand is low and nuclear, some nat gas and base coal are always running at 100%. This scenario is also more likely during the shoulder seasons of spring and fall, when our air conditioning and heat is off, yet the wind output is higher because seasonally there is more wind in the seasons when we don't need it! This is even more likely to occur on a weekend when many industries are closed. Our total electricity demand is 1/3 residential, 1/3 business and 1/3 commercial or industry. Do you get it?
The demand affects price. Many grid pays their electrical power plants less for power created during the night because supply is there but demand is less. So when a state created a Renewable Energy Standard forcing the grid and their customers to purchase wind power at a certain price, at any time of the day, then we are paying much, much more for night wind than we would for coal or other traditional. The chart to the right shows you power is more expensive during the summer and less expensive in March and October when wind output is at its' highest. You can see that in the Alberta daily wind charts where there is a rough in of hourly price data for electricity, also discussed on the above referenced youtube video.
I can promise you, if they had the choice your electrical company would never consider putting up turbines and then forcing you to buy the power. Wind power always costs more. Usually those costs are hidden in Federal and state tax subsidies and by the fact that wind is only a small percentage of total electricity generation, even though in many locations they are putting up turbines everywhere, destroying our precious landscape, scenic beauty and natural habitat.