Wind energy variations
Wind energy production during a day
The vast majority of the installed power of wind turbines in the world is grid connected, i.e. the turbines feed their electricity directly into the public electrical grid.
The graph in the side shows a summer week of electricity output from the 650 MW of wind turbines installed in the Western part of Denmark. The blue curve at the top left shows the power output on 25 June 1997, while the orange curve shows the output the preceding day.
Electrical power consumption was 2,700 MW at the time this curve was printed from the power company control centre. Wind was supplying 270 MW i.e. wind was supplying exactly 10% of the electricity consumption of 3 million people at 13:45 hours when we visited the control centre.
Wind matches daily electricity consumption patterns
At the bottom of the graph it can be seen the power output of the five preceding days. On average, the month of June has the lowest wind power output during the year in Denmark. Some days of fresh winds, however, began in the early morning hours of 24 June.
The typical weather pattern is that winds are low at night and higher during the day, as can be seen from the five days of moderate winds. This means that wind electricity generally fits well into the electricity consumption pattern, i.e. wind electricity tends to be more valuable to the electrical grid systems than if it were being produced at a random level.
Wind matches seasonal electricity consumption patterns
In temperate zones summer winds are generally weak compared to winter winds. Electricity consumption is generally higher in winter than in summer in these regions.
In the cooler areas of the globe, electrical heating is therefore ideal in combination with wind energy, because the cooling of houses varies with the wind speed much like the electricity production of wind turbines vary with wind speeds. In electricity systems that are not based on hydropower and wind there may be good reasons to avoid electrical heating, however:
conventional power plant wastes a lot of heat and thus fuel (at least 60%), i.e. for every unit of useful heat consumed by a household, the power station will waste 1.5 units of heat and fuel.
Annual variation in wind energy
Just like harvest yields vary from year to year in agriculture, you will find that wind patters may vary from year to year. Typically, the variations are less than the changes in agricultural production. In the case of Denmark, you will see that output from wind turbines typically have a variation (a standard deviation) of some 9 to 10%.