The RURERG research group also operates a small wind turbine test site in Rafina, 45 minutes by car from the NTUA. The test site allows for outdoor measurements of the power and energy production of household small wind turbines for grid connected and battery charging applications. The facilities of the test site are in accordance to the IEC international standard 61400-12-1: Power Performance Measurements of electricity producing wind turbines, and specifically of Annex H which refers to small wind turbine testing.
The test site
The test site’s infrastructure allows for the installation and testing of small wind turbines ranging from 1.2m to 7.6m rotor diameter in off-grid (battery charging) or grid tied operation. The wind turbines are installed at a hub height of 12m above ground on a galvanized metal tower of appropriate diameter and thickness, while the tower is supported by two sets of guy ropes (one at 6m and another at 12m) with four galvanized steel ropes in each set, at an angle of 90 degrees between each one. The guy ropes are safely anchored to concrete blocks at ground level. The specifications of the steel wire ropes and of the concrete blocks are such as to withstand wind gusts of up to 40m/s when the largest 7.6m rotor diameter small wind turbine is facing the wind.
Meteorological data collection
For the collection of the necessary meteorological data the following sensors are used (temperature, wind speed, wind direction, air pressure, humidity), which are placed on a separate meteorological mast, 9m away from the installed small wind turbine. The positioning of the sensors is specified in the IEC 61400-12-1 standard, while the horizontal positioning of the anemometer is determined by the rotor diameter of the small wind turbine under test and can be adjusted accordingly.
Electrical data collection
For the collection of the necessary electrical data the following sensors are used and are placed close to the turbine’s load. Three AC voltages and AC currents are logged before the rectifier, with the ability to also measure revolutions per minute (RPM) through the AC signal frequency. After the rectifier, the DC voltage and DC current flowing in the battery bank are recorded for battery charging applications or the DC voltage and DC current flowing through the grid-tie inverter for grid connected applications. In this way the power curve of the turbine can be plotted along with all other relevant data, including losses in the cable connecting the turbine to its load, while the distance of the turbine to the load meets the standards set by IEC 61400-12-1.
Data is logged through software and a data acquisition card. Logged data are stored locally on a PC and sent at the end of each day to the SmartRue data base in NTUA. Further on, real time data observation is possible on site or remotely.