At the menu no windenergy, three notes (in Dutch) about double bass have been added being: Modulaties, Gelijkzwevend stemmen contrabas and Lak bijwerken contrabas.

On 7-10-2015, the VIRYA-1.65 with the Chinese axial flux generator as described in public report KD 595, has been installed. This windmill has a 2-bladed stainless steel rotor with a design tip speed ratio of 5.5. For the head, the slightly modified head of the VIRYA-1.8 is used. The modification includes a smaller and lighter 2 mm aluminium vane blade and clamps and sheets for mounting of the generator shaft. The 2 m long stainless steel tower pipe is connected to the 12 m free standing 3-legs tower of the VIRYA-4.2 windmill, such creating a total tower height of about 14 m. The generator is loaded by a voltage controller and dump load which is adjusted at a voltage of 13.5 V, such simulating a 12 V battery load.

The added oil seal resulted in a friction torque of the generator of about 0.13 Nm and this torque gives a starting wind speed of about 3.5 m/s. It could be seen that about this wind speed is required for about half a minute to make the rotor accelerate up to a rather high rotational speed. However, once the rotor is rotating, it keeps running even at very low wind speeds. The rotor is running unloaded as long as a voltage of 13.5 V isn’t reached. An unloaded rotor makes some noice because the angle of attack isn’t optimal. The noice is reduced at higher wind speeds when the generator load reduces the tip speed ratio to values closer to the design tip speed ratio. During the first hour of rotation it was checked if vibrations caused by the gyroscopic moment could be felt in the tower foot but nothing was felt. There wasn’t much wind during the first hour so the generated power was nothing or very low. The tower is provided with a cup anemometer at a height of 10 m but the wind speed can not yet be read because the control box needs a 230 V, 50 Hz power supply and this isn’t available in the shed where the electronics of the windmill are installed.

Photo VIRYA-1.65 

The prototype of the VIRYA-2.2S has been tested for more than 12 years on the testfield of Kragten Design in Sint-Oedenrode which is certainly long enough to prove that it is a good design. The windmill is dismounted because the starting wind speed was increased. It appeared that the oil seal at the generator shaft was worn and that water had penetrated in the front bearing resulting in too much friction. Both generator bearings were replaced by new bearings with rubber seals. The oil seal was replaced by a spring loaded type with dust lip. The steel Permaglide head bearings were replaced by bronze Permaglide head bearings. As the rotor, the generator shaft, the head and the tower pipe are made out of stainless steel, this windmill is now as good as new. It can start a second live and it is expected that it will work well for many years. The steel 6 m low lattice tower has to be re-painted. The concrete foundation size 50 * 50 * 50 cm has still to be dug out but a larger foundation size 70 * 70 * 50 cm is better for soft grounds.

The prototype of the VIRYA-2.2S is for sale for a fixed price of € 1000 excluding 21 % VAT. A detailed specification is given in the folder of the VIRYA-2.2S which can be found at the menu VIRYA-folders. A control box with short-circuit switch, rectifier, voltage controller and dump load for 24 V battery charging is included in the price. Buying the prototype, doesn’t mean that one gets a licence for manufacture of more VIRYA-2.2S windmills for free.