What exactly is the “wind speed” you mentioned? This is the key to answering your question. Is it the wind speed at a specific point, or the overall, approximate, general wind speed?
If we talk about global wind speed: no need to do experiments, energy cannot be generated or disappear out of thin air. Wind energy generates electrical energy, so this part of the energy cannot be generated from nothing. the rarefied air. It is converted from the kinetic energy of the wind. The overall wind speed will naturally decrease after passing through the generator fan blades.
If it is a single point, then it is obvious that the flow at most points has decreased, and the flow at some points (a very small part compared to the majority ) accelerated.
That's all. If the airflow to your air outlet has been exhausted, then in theory itcan be used to generate electricity. If you're using a fan to blow air to generate electricity, then no, because. there will be a loss with each energy transformation.
In addition, because the density of air is very low, the energy carried by the wind per unit volume is very low. Therefore, to obtain relatively large power, a large diameter wind turbine must be used. Only in this way can benefits be produced, and the energy conversion limit of wind turbines is only 0.59, less than 0.6. Generally, large wind turbines are actually 0.5, so wind power generation must be increased to gain benefits.