Urban WindConditions

By Mate Hebenstreit

The number of domestic scale windturbines increasing, due to theavailability of such small andrelatively cheap devices.

VAWTTipically1-5 kW

Or traditional horizontalaxis turbines, in a1-50 kW range.

How the different city structures alter te wind

Steep changes in terrain,such as tall buildingscause turbulence in the air flowon both the base and the topof the structure,which results in power loss.

To avoid turbulent flows, we must place the turbines in respect to this figure,which shows the

Zone of maximum turbulent flow:

The distance between the wind turbine and the obstacle causing the turbulance (10H+),must be at least 10 times largerthan the height of the obstacle.

How the different city structures alter te wind

Of course as if in open land, it is better to put the wind turbines on a greater height, but it is also important to put them at least 10 meter above the highest point of the roof and also other obstacles and buildings within a 100 meters.

These rules are hard to keep up with, in a cost-

effective perspective.

Measurements

• We used two anemometers. (AIRX, UNITEK)

• Our reference point was the location marked by AIRX arrow.

• We did measurements in two week cycles on locations 1-4.

During the reference measurements, it turned out that the UNITEK instrument measures only 80% of the wind velocity of what the other device was showing, so we had to correct the values according to this difference.

Wind-map

In the city environment, streets act like channels for the wind, as shown on the picture above.It’s important to be aware of these wind-maps in order to maximize efficiency trough proper turbine placement.

Conclusion „We need to able to locate the best

spots for these expensive

devices, to get a fair amount of energy for our

money.”

Thank you for your attention!