Wind turbines

Hello, I am trying to find a way to measure the energy generated in a scaled down model using 1 cm fans. They are to be put into a small wind tunnel and I need to see the effect of another object on them. Would anyone know how I could code so that when the fans are connected to the arduino it would be able to let me see how much energy is being produced by the fans being turned by the wind?

Thanks

measure voltage and current