Is air massless

Frequently asked questions about wind power
Small wind power as a city-friendly renewable energy source for Vienna, A. Raberger on behalf of the WUA, 2011 (220-KB-PDF)

Just as the energy from moving water is used to generate energy in hydropower plants, moving air generates energy in wind power plants. The total energy contained in the movement of air is calculated as 1/2 times the product of the moving mass and the square of its speed. However, not all of the kinetic energy can be converted into electricity in a wind power plant. There is only a slight deceleration of the air mass and only this part can be used to generate electricity. The technical challenge with wind turbines is to be seen above all in the uneven flow of wind. It makes considerable demands on the control and regulation technology of the generator and the grid feed - under constantly fluctuating wind conditions - to supply a power grid with precisely defined voltage and frequency. Although these problems are technically well solved, they can sometimes lead to considerable losses in efficiency. It is therefore worth considering temporarily storing peaks that cannot be fed into the power grid at the point of generation and also considering the generation of hydrogen gas as an alternative energy source.

The source of wind power

Different temperature distributions in the air layers of the atmosphere as well as regional temperature differences (sea-land, day-night, etc.) lead to pressure differences and thus to movements of the air. These movements are aimed at compensating for the differences. We perceive these differences as wind. The wind never comes to a standstill, as the earth's orbit around the sun and the earth's rotation ensure that the solar radiation creates constantly changing temperature conditions. These result in a constantly renewed compensatory movement of the air. The cyclical movement of the earth (and subsequently the Coriolis force) and the relatively even flow of energy from the sun are responsible for the fact that stable wind systems and wind situations have developed on earth (trade winds, horse widths, roaring fourties, etc.). So the wind is a movement of air. Air is not massless, but has a mass of 1.293 kg / m under normal conditions3.

© Photo: Freudenau wind power station