Experimental Methodologies for the Measurement of Wind Turbines Performance

Wind Turbines are one of the most promising technologies to exploit renewable energy sources, and maybe the one which is the closest to achieve grid parity. Many modeling and experimental research activities are carried out in order to continuously improve devices performance. Another promising sector is small scale turbines, below 100kW installed power, for small installation, domestic use, and to be installed on ships. Moving within this scenario, a 1,5 kW turbine was tested inside a wind tunnel, and the following were measured: forces applied to the tower, angular speed, electric power output, mechanical power involved, and stress induced on the blades. Moreover, the cut in rotor speed and the turbine’s efficiency came as outputs of the activity. After some simple forecast calculations, to establish expected maximum values of physical quantities, the experiment was designed. The method used for acquiring all the values at one time involves a wi-fi device, attached to the rotor, in order to acquire signals coming from strain-gauges placed on the blades, avoiding long and cumbersome transmission lines towards the DAQ, coupled to anemometers, load cells, and a wattmeter. Coordination of operators during the tests had a crucial role in carrying out the procedure correctly. Since the main objects of study were blades, rotor and electric generator, the tower has been replaced with a robust support structure, designed to host and protect load cells and signal conditioners from accidental damage, thus permitting a correct measurement of axial force applied to the rotor and reacting momentum of the generator. The wi-fi device was linked to the rotor, in order to affect its mass and inertia characteristics as less as possible. This required the design of a proper linking structure, which was light and well balanced despite being mechanically resistant. Measured quantities are useful to evaluate the turbine’s performance (efficiency, power curve, cut in speed), and also to validate some fem and multi physics predictive models, that are currently under development, as possible tools for general wind turbines design. The outputs of these tests satisfy the need for a wide range of experimental data. This way of designing tests, the physical quantities involved and the schedule of experiments can be suggested as a valuable operative procedure.