You can consider a solar panel and a wind power generator to be powered by current sources where the maximum voltage is dependent upon the design of the component.

In the case of a solar panel, the maximum voltage is called Voc for open circuit and the maximum power transfer occurs when the impedance is matched to the load and the source which occurs around 82% of Voc depending on solar input and drops with useful intensity to 70%.

In the case of wind turbine the blade pitch allows the blade tip to go much faster than the wind, due the eddy current effects just as a sailboat goes faster into the wind. Thus with no load the blade angle /diameter ratios determine the upper speed limit and safety brakes are critical.

In all cases the MPT max power transfer is always when the load impedance matches the source impedance. This is also true of batteries but due to the heat rise and electrode warp that will occur, you never match impedance of near true voltage sources, only current sources.

A car AC/DC alternator is considered a field current controlled (mutually coupled) current source which at constant RPM can regulate constant voltage for dynamic loads with proportional field currents. If there was no voltage feedback with no load , the voltage might rise according to its kV/RPM (?) for any given field current. The 3 phase AC is also rectified by. 3ph diode bridge.

So in every case given above these are all current sources. This is not the case with permanent magnet motor/generators which are more constant kV per RPM with no load. Then max power transfer again occurs at matched impedance.

You can consider a solar panel and a wind power generator to be powered by current sources where the maximum voltage is dependent upon the design of the component.

In the case of a solar panel, the maximum voltage is called Voc for open circuit and the maximum power transfer occurs when the impedance is matched to the load and the source which occurs around 82% of Voc depending on solar input and drops with useful intensity to 70%.

In the case of wind turbine the blade pitch allows the blade tip to go much faster than the wind, due the eddy current effects just as a sailboat goes faster into the wind. Thus with no load the blade angle /diameter ratios determine the upper speed limit and safety brakes are critical.

In all cases the MPT max power transfer is always when the load impedance matches the source impedance. This is also true of batteries but due to the heat rise and electrode warp that will occur, you never match impedance of near true voltage sources, only current sources.

A car AC/DC alternator is considered a field current controlled (mutually coupled) current source which at constant RPM can regulate constant voltage for dynamic loads with proportional field currents. If there was no voltage feedback with no load , the voltage might rise according to its kV/RPM (?) for any given field current. The 3 phase AC is also rectified by. 3ph diode bridge.

So in every case given above these are all current sources. This is not the case with permanent magnet motor/generators which are more constant kV per RPM with no load. Then max power transfer again occurs at matched impedance.

Anecdotal

In my 1st job at Bristol Aerospace 1975, our team produced a 1Hp 10m tall window power generator at 5 MPH stall speed using Darrious rotor and Sevonious blades for the Arctic, on a floating automatic weather station transmitting to GOES 1. Speed brakes were tested with guy wire resonances avoided prior to shipping.