Looking for wind in Africa

Unfavorable wind pattern

Prevailing wind pattern found in the tropics is not very favorable for power generation. Mean wind speed is globally smaller than in Europe and the USA (see the map), except along some coasts (clockwise): North of Senegal, Mauritania, Morocco, Egypt, Somalia, Kenya, South Africa and Namibia. Best spots are predominantly remote, inhabited, and without infrastructures (road and power network).

Global wind speed

Optimistic wind maps

Wind maps, like the one displayed opposite, are created by models based on mathematical equations that describe the physics and dynamics of the atmosphere, calibrated from observational data. The more measurements, the higher the accuracy.

Wind measurement at wind generator height is a scare resource in Africa. Few measurement campaigns were performed, expect at some best spots. In vast areas, in particular the Sahara, calculated mean wind speed entirely relies on atmospheric model calibrated from data measured thousands kilometers away. Such results cannot be seriously used.

Higher vertical and horizontal resolution, as well as few measurements at 40 m were recently used to produce detailed wind maps for Mali and Senegal. Results confirm that global models overestimate wind speed in the Sahara. Wind potential is limited in a narrow band along the coast, where 8 m/s can be found. Wind speed dramatically declines when entering the continent. Best spots in Mali benefits for a mere 5.5 m/s.

Another wrong solution for Africa

Before the national wind map was available, Canadian wind developers supported by the Canadian development cooperation administration convinced the government of Mali to install an hybrid system (small wind turbine & diesel generator) in a remote small town reputed being windy. But the wind people feel is not the one needed for power generation. The wind turbine stands useless most of the time. Inhabitants are frustrated. They were told that the system would produce electricity mainly from wind, but now they have to pay for the fuel. Finally the wind turbine was dismantled and installed in another small town, leaving the diesel generator producing electricity and greenhouse gases. By the way, the same story was repeated in the other town.

Accurate wind map wanted

There is therefore an imperative need in Africa for wind measurements (typically at two thirds of hub height, i.e. 60 m to reach a high of 90 m for the wind turbines) and accurate wind maps. Global maps like the one above, as well as feelings and hearsay, cannot anymore be the only sources of information for decision makers to define investment policy.

Gauthier Dupont
Dupont Energy Consulting GmbH

Advertisements