**4. Conclusions**

The obtained measurement results showed that the direct connection of the battery to the generator may cause poorer efficiency of the wind microturbine. The solution to this problem may be the use of a simple converter, which can linearize the load characteristics of the wind microturbine. The possibility of changing the pitch of the wind turbine depending on its rotation speed gives some improvement in the efficiency of the wind microturbine. However, in practical implementation, the additional costs of manufacturing the blade pitch adjustment mechanism and its reliability in difficult environmental conditions related to icing should be taken into account. The use of a simple mechanism for adjusting the pitch of the turbine using the centrifugal force of the rotating mass may be beneficial for two-blade microturbines with a high tip speed ratio. Resigning from the third blade in the wind turbine in favor of the blade angle adjustment mechanism, it is possible to achieve a higher rotational speed of the turbine, and thus to use a cheaper generator with a smaller number of pole pairs. The DC brush motor with permanent magnets used in the model as a generator proved its usefulness. The additional resistance to movement caused by the brushes did not cause significant limitations at lower wind speeds. Research has shown that DC motors used in radiator fans from scrap cars can be used in micro wind turbines for recycling. The use of a simple DC/DC converter in this case would allow optimal

adjustment of the load characteristic to achieve the maximum power of the wind turbine in a wide range of wind speeds. The conducted research showed that the built model of the wind microturbine allows us to observe and measure the physical phenomena related to the aerodynamics of the wind turbine and the operation of the electricity generator. Test results that use only simplified mathematical models of the wind turbine often do not take into account the phenomenon of stalling, which is significant when the maximum load power of the wind turbine for a given wind speed is exceeded.

The research model in the presented scale allows you to quickly and cheaply make and test initial prototypes of the designed wind turbine blades using popular 3D printers. In addition, the controller made enables the implementation, in the program memory of the used STM32F1 microcontroller, the developed algorithms for optimal control of the wind microturbine. The computing power of the 32-bit microcontroller is sufficient even for more complex algorithms. The specificity of the operation, construction, and limitations of micro wind turbines is in some aspects completely different than in the case of larger wind turbines, for which numerous scientific studies have already been prepared.

Due to the growing demand for autonomous and portable hybrid micro power plants, combining small photovoltaic panels and wind micro turbines, it is advisable to conduct research on improving the energy efficiency of these devices [6–8].

Further research work will focus on the use of the PMSG permanent magne<sup>t</sup> synchronous generator, the start-up of a wind microturbine with a high tip speed ratio, and algorithms for optimal MPPT control of the wind microturbine.

**Funding:** This research received no external funding.

**Data Availability Statement:** Data sharing is not applicable to this article.

**Conflicts of Interest:** The author declares no conflict of interest.
