Methods and Devices for Wind Energy Conversion

*Janis Viba, Vitaly Beresnevich and Martins Irbe*

### **Abstract**

The chapter deals with the analysis and optimization of the operational safety and efficiency of wind energy conversion equipment. The newly proposed method of wind energy conversion involves flat blades or space prisms that perform translation motion due to the interaction with air flow. Air flow interactions with 2D moving prisms (convex, concave) are studied by computer simulation. Optimization of prism shape is made using as criteria maximum of generating force and power. Theoretical results obtained are used in the designing of new devices for energy extraction from airflow. Models of wind energy conversion devices equipped with one vibrating blade are developed (quasi translatory blade's motion model; model with vibrating blade equipped with crank mechanism). The operation of the system due to the action of air flow is simulated with computer programs. Possibilities to obtain energy with generators of different characteristics, using mechatronic control, have been studied. The effect of wind flow with a constant speed and also with a harmonic or polyharmonic component is considered. Partial parametric optimization of the electromechanical system has been performed. The serviceability and main advantages of the proposed methods and devices are confirmed by experiments with physical models in a wind tunnel.

**Keywords:** air flow, vibrating blade, energy conversion, computer simulation, experiments

### **1. Introduction**

Various types of methods and devices are used for energy extraction from airflow. The operation principle of existing wind energy conversion systems is mainly based on air flow action on blades mounted on a special wheel and further transformation of air flow kinetic energy into the mechanical energy of wheel rotation [1, 2]. But as it turned out in practice, such a design does not provide the desired position of the blade against the air flow in relation to the rotating wheel. Its position is only optimal at certain wheel angles.

The interaction between the rotating plate and the air flow under different aerodynamic conditions is analyzed in [3]. The special orientation of a plana-shaped object during movement is realized in [4, 5]. The main disadvantage of these devices lies in a large number of blades. For example, it has been argued in [6] that turbine operating power efficiency decreases with an increasing number of active blades. This means that the front (airflow side) blades prevent airflow from accessing the rear blades.

Consequently, the interaction of the rear blades with the air flow differs significantly in the direction and size from the interaction of the front blades. This is because air vortices are generated in the system. Besides, it is known that increased efficiency of existing equipment can be achieved by increasing the radial grooves of the blades. However, such a solution has a negative effect on the use of wind turbines, as the final speed of the blade rotation increases and the generated noise becomes higher. In addition, it becomes possible to kill birds and other living things with a rotating flat blade.

This chapter discusses some new methods for describing wind interactions with rigid bodies and provides recommendations for wind energy conversion based on the use of flat blade translational motion excited by air flow.
