To minimise their impact on the landscape, can we reduce the size of the turbines?

Unfortunately not, because wind turbines must be at least about 80 m in size to become profitable.

The energy that a wind turbine captures in the wind is proportional to the area swept by its blades, i.e. the square of the length of the blades. Therefore, the larger a wind turbine is, the longer its blades will be, and the more electricity it will produce.

The amount of electricity a wind turbine can produce is also proportional to the cube of the wind speed. However, the wind speed varies greatly with the height above the ground. The higher you go, the stronger and more regular the wind becomes, whereas at ground level it is generally weaker and more turbulent because of the relief of the terrain. So the taller a wind turbine is, the more favourable wind conditions it will enjoy, and the more electricity it will produce.

Of course, the taller a wind turbine is, the more expensive it is. But it is not so much the investment cost that counts, but the price per installed capacity (francs/MW). It is this parameter, together with the wind conditions and the local conditions (access, electrical connection, nature of the land), that will determine the cost per kWh of electricity produced, and therefore the break-even point of the installation. The optimum size of a wind turbine evolves with technology. Newly installed or planned wind turbines in Switzerland have a total height (blade tip) of around 150 metres. On the plateau, wind turbines up to 200 metres in height are possible if the site has excellent access. The current trend in the wind energy market is the development of wider and higher wind turbines.

According to the above, mini domestic wind turbines that can be installed on the roof are generally not profitable, as wind conditions on buildings are rarely favourable and the amount of electricity produced over their lifetime does not allow the high investment costs to be recovered. Nevertheless, they may be relevant in specific cases, such as mountain huts that do not have access to the electricity grid.