What Causes Wind

As long as there is sunlight, there will be wind. The wind is a by-product of solar energy. Approximately 2% of the sun’s energy reaching the earth is converted into wind energy. The surface of the earth heats and cools unevenly, creating atmospheric pressure zones that make air flow from high- to low-pressure areas.

Trade winds on a tropical island are fairly dependable, providing a nearly constant wind flow throughout the day and night. Unfortunately, we have no trade winds in our part of the world, and weather systems move through every few days. With alternating stormy and fair weather, wind speeds can range from gale force to total calm within a 24-hour period. An Iowa wind turbine owner must cope with these large variations. Daily and seasonal changes are important considerations for applications where electricity use is time-dependent.

Seasonal winds in Iowa are strongest in winter and early spring and weakest in summer. Daily winds generally are strongest during the afternoon and lightest during the early morning. To make the most efficient use of the energy supplied by the wind turbine (assuming little is to be fed into the utility grid), users should adjust their energy consumption to match the availability of the wind. Weather forecasts are valuable in planning for high and low wind periods.

Wind direction is also variable, although the strongest winds generally prevail out of the southwest to northwest. Knowledge of the prevailing wind direction is important for siting the wind turbine in the least obstructed setting possible.